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Senior Design I Documentation - University of Central Florida

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1. Figure MPL3115A2 Figure MPL3115A2 Figure MPL3115A2 Smart Pressure pin connections block diagram Sensor MPL3115A2 Features 1 95V to 3 6V Supply Ability to log data up to Fully compensated voltage internally 12 days using the FIFO internally regulated by LDO 1 6V to 3 6V digital 1 second to 9 hour data Able to program events interface supply voltage acquisition rate Direct reading I C digital output Autonomous data compensated pressure of interface operates up to acquisition 20 bit measurement 400 kHz This sensor is also able to be sampled which makes it a great contender for our design choice If bought in bulk one must purchase 10 000 at a time However each smart pressure sensor individually costs 1 43 61 Group 14 Senior Design 1 Although this pressure sensor offers a large amount of information it measures more data than needed for this project including the altitude and temperature Because of these extra unneeded capabilities this sensor is more costly and thus will not be the first choice in the project design 3 4 Evoked electromyography e Records the compound action potential caused by stimulation of a peripheral nerve surface electrodes are employed to record overall electrical activity of the muscles e Patents 4 291 705 and 4 595 018 e EMG signal amplitude is typically in the range of 3 uV to 5 000 uV the duration about 3 ms to 15 ms and the frequency
2. Here is a look at some of the pros and cons that are important for the decision of this project PROS CONS Fully Embedded v3 0 Profiles Expensive 32 USD Bluetooth v3 0 EDR Small Flash Memory Integrated Antenna Weak Wall Penetration 128 bit AES Encryption Cluttered 2 4GHz Band 48kb RAM FCC Certified Micro sized 11 6mm x 13 5mm Table 2 6 4 Pros and Cons for STBT2632C2A Bluetooth from Microchip 2 6 C 802 15 4 ZigBee When it comes to low powered wireless communication ZigBee is a smart choice because it was specifically designed as a low powered mesh networking protocol 50 Group 14 Senior Design 1 standard to monitor sensor data in buildings where the data might potentially traverse multiple hops before it reaches its destination The advantages of using a ZigBee device is that it has a unified standard for data transfer so you are assure to have compatibility amongst similar devices that use this protocol ZigBee can be used for point to point communication which is what this project will be focused on and also for point to multipoint communication Below CC2531 This USB enable true SoC is made by Texas Instruments This module is intended for IEEE802 15 4 ZigBee and RF4CE applications and is primarily used in personal area networks This chip is a combination of an RF Transceiver with an enhanced 8051 microcontroller This device has programmable flash memory 8KB of RAM and
3. schematic of ACH 01 series Pending approval by Measurement Specialties Inc ACH 01 Series Features wide frequency response low transverse sensitivity excellent phase response 3V to 40V supply low noise very high resonance frequency low cost excellent Linearity ultra low power Mounting method plays a critical role in the overall performance of any accelerometer Erroneous results can be given if an accelerometer is improperly mounted Therefore Measurement Specialties Inc MSI recommends an adhesive mounting method for proper performance of the ACH 01 It calls for the 55 Group 14 Senior Design 1 surface to be flat and the area where the ACH 01 is to be mounted should be thoroughly cleaned then add the adhesive To keep the product cost low the project design will probably use a ceramic substrate as the mounting base DIRECTION OF ACCELERATION FASTEN CABLE TO CERAMIC SUBSTRATE MOUNTING SURFACE MOUNTING SURFACE Figure 3 1 4 mounting method for the ACH 01 series Pending approval by Measurement Specialties Inc The table below is all the product qualifications for the ACH 01 series as listed on the Measurement Specialties Inc website Wide Frequency Range Wide Dynamic Range High Sensitivity Low Noise JFET Buffer Ta ad a feet Qa ae j Sgrams Rewing ead Adesso Figure 3 1 5 Table of the product qualifications of ACH 01 se
4. S S2 2 a 2 F Q oO ue O z uwy y 5 ee g orgs A ISSF Fi2QN OSE oz sOOOF HSA a2z22O05 agegoess o cEkrRg5AD 5eegedgoss v 9SeeoZzae Irz SO a OFF K Eo lt 5 5 2 a SSSsEztzz z ZO S86 SEN FERETE FRITE N NNN NNN wow i gt 3 64 63 62 61 60 86 56 57 86 55 54 53 52 51 50 46 1 4 7 6 5 4E 3 2 1 0 Ogongo go BRODDDLOLSLESLSSS Q RESRT5AH Y5eeee se Vaesseees OORREED FA0GQaK ogus REEERE 222a EsRRF re R sse2265 geaaaaae TORE RAK BZ SRrereer aaan a 9 a So 5 a 8 PJ 2 TMS 47C 460 450 4c 83L 42 CC430F613x LAES 407 3q 38c 37L 360 350 aq o P4 0 S2 PJ 1 TDUTCLK PJ 0 TDO GUARD R_BIAS AVCC_RF AVCC_RF RF_N RF_P AVCC_RF AVCC_RF RF_XOUT RF_XIN P5 2 S0 P5 3 S1 vss Exposed die attached pad Figure 2 4 5 CC430F5137 Pin Configuration Courtesy of Texas Instruments 2 4 C FPGA An FPGA board is an integrated logic circuit that is intended to be programmed by a customer just like a microcontroller but where it differs is in variety of applications that it can be used for FPGAs are often used to prototype integrated circuits and once the design of the circuit is set the design is then transferred to a 39 Group 14 Senior Design 1 hardware chip for faster performance and better power consumption They are simple an array of logic blocks connected together to perform a designated function FPGAs can be used to design many different logic functions instead of a c
5. blood pressure better and it protects the brain Inhalation anesthetics are rarely used alone in recent clinical practice As a result in most surgeries today intravenous anesthetic agents are used for induction of anesthesia and then followed by inhaled anesthetic agents 2 1 C Inhalation Anesthetics There are several inhalation anesthetics today but with each there are both positives and negatives Halothane has a pleasant smell and causes patients to lose consciousness but provides little pain relief and can be easily overadministered Very rarely it can be toxic to the liver in adults Because of its good odor it was a top choice when giving general anesthetics to children until the introduction of sevofluorane in the 1990s which has caused its use to decline Enflurane is known for producing a rapid onset of anesthesia and a faster recovery It is less potent than some of the others and acts as an enhancer of paralyzing agents On the other hand it is not used in patients with kidney failure and has been found to increase intracranial pressure and the risk of seizures Isoflurane can induce irregular heart rhythms but is good because it is not toxic to the liver It is often used in combination with intravenous anesthetics for anesthesia induction Nitrous oxide also known as laughing gas is used with other drugs such as thiopental to produce surgical anesthesia It is regarded as the safest inhalation anesthetic because it does not
6. muscles by applying a tetanic stimulation This will induce a transient 19 Group 14 Senior Design 1 exaggerated release of acetylcholine that is sent to the end motor nerve Once this happens even if there was no discernible twitch before there will usually be a brief but noticeable muscle contraction afterwards First the anesthesiologist applies a tetanic stimulation of usually 50 Hz for 5 seconds and then observes the post tetanic response to single twitch stimulation which is given at 1 Hz starting 3 seconds after the end of the tetanic stimulation During truly intense blockade there will still be no response however when the intense neuromuscular blockade begins to wear off but before response can be seen by the TOF the first response to post tetanic stimulation occurs The PTC method is mainly used to assess the degree of neuromuscular blockade if no response is displayed to the TOF Intense block Deep block Surgical block ICR AA A AA A Response NE ONE E N E 0 1 0 3 1 PTC and no of TOF responses 0 0 8 Figure 2 2 9 Stimulation and responses to TOF nerve stimulation 50 Hz tetanic nerve stimulation for 5 sec TE and 1 0 Hz post tetanic twitch stimulation PTS during 4 levels of neuromuscular blockade picture from Ch 47 Neuromuscular Monitoring PDF Double Burst Stimulation DBS The goal of double burst stimulation was to establish a stimulation pattern that was even more sensit
7. w an ob bod b ea A n A aia E th i L r l r L r L Pin Connections Figure MPL115A Figure MPL115A Figure MPL115A block diagram pressure sensor pin connections with SPI Interface MPL115A Features Digitized pressure Monotonic pressure Surface mount outputs Has 1 kPa accuracy Integrated ADC 2 375 to 5 5 volt supply SPI or I C Interface Additionally this pressure sensor is able to be sampled which allows for getting a small quantity to test which makes it an excellent competitor in the design 60 Group 14 Senior Design 1 choice If bought in bulk they offer 10 000 at a time however each one only costing 1 05 The MPL3115A2 Xtrinsic Smart Pressure Sensor by Freescale is another option that has been used for monitoring neuromuscluar blockade during anesthesia in the past It is employes a MEMS pressure sensor with an I C interface to provide accurate Pressure Altitude and Temperature data The outputs of the sensor are digitized by a high resolution 24 bit ADC Typical active supply current is 40 uA per peasurement second for a stable 30 cm output resolution It is great for measurement with its small size at just 5 0 mm x 3 0 mm x 1 1 mm Reference Regulator CAP SCL Sense Pressure Amy Sensor P Digital Signal MUX ADC Processing and Control INT1 Temp Clock Oscillator Trim Logic
8. 7 ilz_ _y ae D 1N12000 vA Figure 4 1 2 Now back to a less grim topic the transformer The transformer being used is center tapped which means that halfway along the secondary coil a lead is placed for various reasons in this circuit it will be used as the common output to the diode bridge while the outside two are used as positive lines This can be done because the two outside lines are wired in series with their own diodes preventing current from leaking back when that lead is actually negative relative 91 Group 14 Senior Design 1 to the common Using a center tapped transformer provides the circuit with its first voltage step down even if the transformer has the same number of turns on both coils this is because the common is halfway through the secondary winding effectively creating a virtual ground This leaves the outside two taps to be 180 out of phase with each other relative to the virtual ground Thus using two diodes to prevent the outside taps from exerting their negative sweep on the diode bridge the AC signal is effectively completely rectified At this point the diode bridge comes in as can be seen above the bridge is wired in such as was as the diodes look like they re pointing in the direction of the current This is how the bridge works allowing current to flow in their forward active direction and preventing it from ever flowing in the opposite direction The post rectification part of the circuit otherwise
9. Description of How It Works Even in present day after all the years of research the exact mechanism of general anesthesia is not yet fully understood There are many hypotheses that have been made and studied to explain exactly why general anesthesia occurs The first known as the Meyer Overton theory suggests that anesthesia happens when enough molecules of an inhalation anesthetic dissolves in the lipid cell membrane saying the higher the solubility of anesthetics is in oil the greater its potency Another hypothesis called the Protein Receptor Theory explains that the anesthetic strength is based on its capability to inhibit enzymes activity of proteins in the central nervous system Another belief brought about in 1961 by Linus Pauling suggests that receptor function is inhibited when anesthetic molecules bind with water molecules forming clathrates The interesting part about general anesthesia to this day is that no one is sure how it precisely works Even with the abundant number of studies of patients individual brain cells to try and better understand how general anesthesia works they have only been able to observe and understand what anesthetics do Exactly how the anesthetic does it is still not understood since the drug apparently does not bind to any receptor on the cell surface and does not affect the release of neurotransmitters which are chemicals that transmit nerve impulses from the nerve cells All that is known is t
10. MSP430F5418AIPN sof Dvss2 AVSS P7 0 XIN P7 1 XOUT DVSS1 DVCC1 P1 0 TAOCLK ACLK 49 VCORE 48 P4 5 TB0 5 47 P4 4 TB0 4 46 P4 3 TB0 3 45 P4 2 TB0 2 44 P4 1 TB0 1 P1 1 TA0 0 43 P4 0 TB0 0 P1 2 TA0 1 42 P3 7 UCB1SIMO UCB1SDA P1 3 TA0 2 41 P3 6 UCBISTE UCAICLK 34 35 36 cI ME nv CHNy OnHyvorvratawos of Bae Tha a PLOLOTTzZOHOHRIDEIDGRH O EES SEEESRB lt 29 93922 8H STENSKA sojos cee HERES 5222388 2 RESE565 FEFFTF 2832828 5388338 aS25 3 Qa ots AagnmMann aa Qa Figure 2 4 2 MSP430F5438A Pin Setup Courtesy of Texas Instruments MSP430F5329 This Texas Instruments microcontroller is very similar to the above TI chip but has its subtle differences This device runs on 1 8V to 3 6V and has a very fast wake up from low power mode of 3 5us The device has a very powerful 16 bit RISC CPU with 16 bit registers and a system clock up to 25MHz Among other features that are important to this project are 12 bit AD converter two universal serial communication interfaces hardware multiplier and real time clock module This chip is relatively small in size and has 63 I O pins which plenty enough for this type of project This chip has 128KB of Flash memory 10240 Bytes of SRAM and four 16 bit timers This MCU would be a good choice for the finger sensor since it has enough RAM and memory for the given application Typically this device is used in applications like analog and d
11. Once all pieces of the device have been tested individually and with their related components the final hurdle comes with a full assembly test For this section the test will be run as though an anesthetist were performing routine checks this should test the full range of functions and provide feedback about the functionality of the entire device The initial requirement for this section is to fully assemble the device under the impression that everything will work once it is assembled Once fully assembled the first test will be a simple power on If at the push of the power button nothing pops or smokes or sizzles then it can be assumed that nothing was miss wired upon assembly just in case a thorough check with a multimeter is necessary to ensure that all components are getting the power they need If everything appears to be working properly move on to section 5 8 B If there is an issue with the power feeding to a specific part then the issue can take two roads Is the component being fed zero volts or is there a partial voltage Assuming that all of the previous power tests have succeeded the problem here is most likely that something was miswired Disconnect the faulty piece check the wiring diagram and reassemble it This should fix the problem For components like voltage regulators there should be no partial voltages because they are hardwired to the power source If this is the case then it is highly probably that the component was
12. RAM Accepts 3 3V Regulated and 3V Battery Power Supplied Up to WPA2 Authentication Table 2 6 2 Pros and Cons for RN171 WiFi Module from Microchip 2 6 B Bluetooth Bluetooth is commonly used on small portable electronics It is mostly used to exchange data over short distances This wireless technology is fast and highly secure The range of each device depends on the power class of each device Some devices are capable of transmitting data from up to 100 meters but most operate at approximately 10 meters 48 Group 14 Senior Design 1 The devices that were looked at for this project are mostly similar but a few important features to the project make a difference in choosing or not choosing the module for the design Some advantages to consider are low power requirement many options for short range communication simple connection The following are some disadvantages of using Bluetooth short transfer distance need to pair the devices weak wall penetration and interference in the 2 4GHz band Here are some of the devices that were researched as potential parts for the design RN42 This Microchip Bluetooth module has a class 2 radio and therefore can deliver up to 3Mbps data rate for distances up to 20 meters which makes it a perfect solution for this project This device support multiple interface protocols making it a complete embedded Bluetooth solution that is simple to design and in addition to all th
13. an input mechanical force into an electrical output signal The force sensor has a variable resistance as a function of applied pressure These devices are used in mechanomyography MMG and measure the strength of muscle response to stimulation of the peripheral nerve Although it is highly implemented in clinical research there are 57 Group 14 Senior Design 1 several disadvantages to using mechanomyography and the force sensors to measure the output Cons e cumbersome and costly to implement e requires patient s hand and thumb be restrained e may result in nerve or tissue damage if thumb is not positioned properly with respect to the transducer linkage due to the necessarily rigid connection thereto Tekscan has offered a new set of force sensors known as FlexiForce sensors that are ultra thin and flexible printed circuits which can be easily integrated into force measurement applications These FlexiForce sensors are a versatile and durable piezoresistive force sensor that has been made in several different shapes and sizes For these sensors the resistance is inversely proportional to applied force Benefits of FlexiForce Sensors e greater flexibility e superior linearity and accuracy e offers a website with expert technical guidance for questions e wide range of forces e sensor output is not a function of loading area e has different sensing area sizes e may be less accurate than needed because these are FS
14. and respiratory depression Propofol is the most recently developed intravenous anesthetic to the medical world It offers a rapid induction and short duration of action just like the thiopental but recovery occurs more quickly and with much fewer side effects The biggest advantage of propofol is that it is metabolized in the liver and excreted in the urine which allows it to be used for long duration of anesthesia As a result it is rapidly replacing thiopental as an intravenous induction agent 2 1 E Precautions There are many precautions that must be taken place when a patient is planning to receive general anesthesia A complete medical history including a history of allergies in family members is very important to have This is because patients may have a potentially fatal allergic response to anesthesia known as malignant Group 14 Senior Design 1 hyperthermia even if there is no previous personal history of reaction General anesthesia is only given by board certified professionals These professionals known as anesthesiologists consider many factors when deciding what combination of anesthetic medication to use such as a patients age weight allergies to medications medical history and general health General anesthetics cause hypotension or lowering of the blood pressure a response that has the ability to lead to death and therefore requires close monitoring and special drugs to reverse it in emergency situations 2 1 F
15. blockade drip has been administered to maintain sufficient levels of paralysis Once selected the first setting that is presented to the user is the time frame for every pulse This can be as short as every half second to as long as once every four hours If these extremes are intended to be used it might be wiser to use 112 Group 14 Senior Design 1 another pulse types to perform this function A reasonable time frame is once a minute for surgeries less than two hours and once every five to ten minutes for those greater than that A second option will be presented once the timing has been decided though it can be skipped if no changes are required Because the supramaximal stimulation varies patient to patient it is given as an option to change the current strength If this option is skipped then it will automatically be set to 50mA the greatest current that the device will manage Once these two options have been set the done button can be pressed to apply the setting and return to the pulse screen 6 1 C Tetanic When this setting is selected there will be no options This is because this has only one purpose and is operator time limited When pushed a 50mA 100Hz pulse is issued to the patient to create a full muscle contraction This is done to see if once the hand is contracted the muscles have enough control back to maintain contraction This is normally the last test before fully reversing the neuromuscular blockade and remo
16. board provides very simple hardware interfacing with the TFT panel by just using the flat ribbon cable of the display More detailed features and specifications of the Solomon SSD1963 controller that are relevant to this project will be discussed in the next section of this document W a Pe o S4v 8 ios 0080 41X00 Figure 2 5 1 Newhaven TFT Controller board w SSD1963 Graphics Controller Courtesy of Newhaven Display International SSD1963 This Solomon display controller is a market leader in this display category and is widely used in many displays It has 1215KB of embedded 42 Group 14 Senior Design 1 display SRAM and frame buffer This particular display controller supports screens up to 864 x 480 pixels at 24bpp Below are the important display features for the project listed by Solomon on their website e Support for TFT 18 24 bit generic RGB interface panels e Support for 8 bit serial RGB interface e 8 9 16 18 24 bit MCU interface e Hardware display mirroring e Hardware rotation of 0 90 180 270 degree e Programmable brightness contrast and saturation control e Dynamic Backlight Control DBC e Deep sleep mode for power saving e Built in Clock Generator The figure below shows a simple design overview of this graphics controller and shows the I O pins that will be used to interface this controlled with a TFT display Because this is a widely used controller for the type of display that will be used in thi
17. circuit will be in the diagram below with values removed for reference Figure 3 6 2 3 6 C Design summary Now that a decision has been made about how to power the device the actual design must be taken in to consideration Because this project will be entered in Texas Instrument s Analog Design Competition initial part searching began with them and as it turns out they make all the IC this project will need The chosen regulators are listed in the following chart with a schematic of their proposed wiring Part Vin Vout li Max lo Max For Part Bridge lt 200V N A 35A N A Rectifying GBPC3502W Diode lt 200V N A 30A N A Power Uni NTSJ30120CTG Inductor N A N A 25A N A 2mH Smoothing RB8522 25 2M0 V Reg 9 26V 3V3 N A 1A uC RF LED PT5103A V Reg 9 38V 5V NA 1 5A Res Touch PT78ST105H Table 3 6 3 85 Group 14 Senior Design 1 12VReg Figure 3 6 3 3 7 Patient Medical Safety Concerns The main goal as stated earlier is that the Paralytic Twitch Sensor device be ready to use in the operating room In order for the device to be used in the operating room the group needs to follow the guidelines that are set for the operating rooms when deciding on what parts to use for the project 3 7 A Sterilization Concerns The main concerns that the group has is obtaining a sensor that both works well but also follows the steri
18. correct device When all fails the last option is to check the software that runs your display and make sure there is not simple syntax error For more detailed software testing please refer to section 5 8 Due to the simplicity of the design and interfacing of the wireless display the only other options are failed external parts that will need to be checked individually and the test for each of those are described in this chapter 5 6 Wireless When testing wireless communication the firs functionality that should be checked is connection communication between the two given devices because if does not work then there not a lot that can be done The first step would be to check every pin to make sure there is no loose contacts of unsoldered pins and also make sure that the pins are connected to the right wires For example check the power pins to make sure the wireless device receives power In addition to the above tests checking the device antenna for proper connection might avoid many headaches If the above fails the next option would be to check 107 Group 14 Senior Design 1 if the chip was programmed properly Sending a simple data bit to the wireless module and trying to detect it can be as simple as plugging in your debugging dongle and running a few lines of code One other very rare cause of wireless data transmission failure can be the interference of other wireless devices in the area This brings up another test case that is very
19. crucial test case the test for error detection and correct in wireless transmission Every wireless network is prone to errors in bit transmissions and each device has its own algorithm to detect and correct errors As with other devices software error can really make things a nightmare As a rule of thumb have two different people check the syntax of the code and by doing that most of the simple error will get filtered out and then the logic of the program can be checked to make sure everything makes sense At this time majority of the basic check should have revealed the problem and luckily fixed right there on the spot 5 7 PCB The testing of the PCB outside of the components already covered will be limited The first test because it will be made by someone else it to make sure that all the connections and pins are present when it arrives If nothing looks terribly wrong then continue to test by hooking up the one power supply line and the ground This can be done with relatively low voltage as this test is just for continuity Once continuity has been established and obvious shorts have been identified the board can be assembled After assembly or even piece by piece the board should be rechecked for shorts and faulty wiring 5 8 Software Software testing is probably one of the most time consuming processes that one goes through when designing a real world application The device might not work because of a simple semicolon omission
20. design document Please get back to me as soon as you can Thanks Sergey Cheban House OBS KATT House bntypeg __ _ eas bee SUBMIT c LS Research permission pending Required Fields Email Inquiry First Name Sergey Last Name Cheban ce seriy knights ucf edu Country United States City Orlando State Province Florida Zip Postal Code Company University of Central Florida Industry Medical iv Comment or Question Email we will keep your email completely private Group 14 Senior Design 1 Thanks Sergey Cheban jHi I am a student at University of Central Florida Our group jis working on a senior design project and would like to get lyour permission to used your schematics diagrams and material lof that sort for the parts we will be using in our design document Please get back to me as soon as you can Submit d Solomon Systech permission pending Group 14 Senior Design 1 B Send Y Spelling Attach gt f Security i Save From Sergey Cheban lt ce seriy ucf gmail com gt CE SERIY UCF x To amp sales solomon systech com en Permission to Use Material AAA Hi I am a student at University of Central Florida Our group is working on a senior design project and would like to get your permission to used your schematics diagrams and material of that sort for the parts w
21. enough programmable memory and processor power to handle a single sensor and be able to transmit data without significant delay to the wireless screen 3 4 Wireless This section of the design chapter will go over the wireless RF transceivers that have been researched and will review the pin descriptions applications schematics and features in much more detail This will allow picking the best wireless module for the wireless display From section 3 3 above it is know that the wireless module on the thumb sensor end will be built in into the microcontroller so in this section we will only look at the wireless module for the display and the best module will be picked 3 4 A 802 15 4 ZibBee As mentioned earlier at this time it s only needed to look at the detailed design of an RF wireless transceiver for the wireless display only since the wireless design 74 Group 14 Senior Design 1 of the thumb sensor is taken care of by using an SoC chip with a built in wireless module CC2531 This Texas Instruments SoC chip is intended to be used in personal area networks Like many other device from a manufacturer like TI this device lives up to its name This is a widely used chip in the low powered applications field This device is a really convenient solution for many applications but because the wireless display has its own controller the built in MCU is not going to be utilized for this project s scale None the less it is better to
22. has various operating modes that it supports This device is well suited to be used in ultralow power requirement designs The ZigBee protocol stack that this device supports simplifies the data transfer for any similar project design Below are some of the features of this device that are relevant to this project Provided by TI RF Chip e 2 4 GHz IEEE 802 15 4 Compliant RF Transceiver e Excellent Receiver Sensitivity and Robustness to Interference e Programmable Output Power Up to 4 5dBm e Few External Components e Only a Single Crystal Needed for Asynchronous Networks e 6 mm x 6 mm Chip Size Microcontroller e Low Power 8051 MCU Core With Code Prefetching e 256 KB or 128 KB In System Programmable Flash e 8 KB RAM With Retention in All Power Modes e Hardware Debug Support 51 Group 14 Senior Design 1 PROS CONS Low Voltage 2V 3 6V External Components Needed 128KB Programmable Flash Only Two UARTs Integrated Antenna Slower Data Rates than Bluetooth 128 bit AES Encryption Cluttered 2 4GHz Band Very Small 6mm x 6mm FCC Certified ZigBee Protocol Standard Table 2 6 5 Pros and Cons for CC2531 from Texas Instruments 52 Group 14 Senior Design 1 Chapter 3 Design Sensors Because visual and tactile assessment of neuromuscular function is unreliable there has been an emerging interest in the development devices that will offer quantitative measurements T
23. is inserted for the exact same reason R5 is a relatively small high wattage resister on the order of 10Q that is in place to prevent a short circuit to ground then the MOSFET is active It was experimentally found in Multisim that C3 should be around 470uF to give the desired charge current but when referencing the current design of the neuromuscular stimulator it was found that a capacitor as big as 2mF might be needed This capacitors associated resistor is what is known as a bleeder because its only purpose is to discharge the capacitor when it is not in use R3 will most likely be on the order of 10MQ R10 is the current set in this design which was discussed before its value will depend on the specific current the anesthesiologist is looking for Most likely this will not be a single resistor but an analog switch wired to several different resistors to allow for discrete current values And R11 is the final resistor but as mentioned before this is simply a place holder for the skin resistance of the patient 3 3 Controllers This section of the design paper will go into more detailed design of the microcontrollers that were researched and will look at the pin configurations of each MCU and how each pin will be used in the design of this project and how the other parts will interface with the microcontroller The last subsection of section 3 3 will reveal a microcontroller of choice and will explain why a particular controller was chos
24. known as the DC side will be wired to that the current always flows in to its positive side and out of its negative The rectified AC signal will be wired to the other two poles of the diode bridge once the DC side has been hooked up it is actually irrelevant which lead goes to which pole here it is chosen in the simplest manner with the common on the bottom vA kt 820uH jer e 25yF T25yF DC f Figure 4 1 3 After the diode bridge an inductor is added in series to the circuit while two capacitors flank it branched between the DC and DC This capacitor inductor section of the circuit serves to smooth out the ripple that is left by rectification Ideally all ripple will be removed but a ripple of less than ten percent is reasonable for this purpose this is because gt 85 precise DC DC converters will be used as necessary to regulate this new DC voltage to levels useful to the ICs of the project 92 Group 14 Senior Design 1 And with the mention of the regulators now would be an ideal time to introduce their circuitry connection Because of the ample power now available to the rest of the circuit several voltage regulators can be used in parallel without any worry of brownouts or occurrences where the voltage falls to low to be useful in individual components A wiring diagram is provided below to show the method in which these will be connected DC A Note Care should be taken when looking at voltage
25. master output slave input SEL SPI select active low Yes IRQ Interrupt request signal active high Yes XTAL1 Crystal pin or external clock supply Yes XTAL2 Crystal pin Yes EVDD External supply voltage analog domain AVDD Regulated 1 8V supply voltage analog domain AVSS Pins 30 31 32 Analog ground AVSS Paddle Analog ground Exposed Paddle of QFN package Table 3 4 2 AT86RF230 Pin Description Information from Atmel 3 4 B Final Design Choice Through careful analysis and in depth research of the device s specifications the final design choice for the RF module is the Atmel AT86RF230 low voltage chip This chip was chosen because it does not require a lot of power and was recommended by a lot of application designers in the field of low powered networks and it supports many standards like 802 15 4 ZigBee RF4CE SP100 and a few others 78 Group 14 Senior Design 1 3 5 Wireless Display When it comes to a wireless display it was decided in the research section of this document that the best display technology for this project would be a TFT resistive display In section 2 5 D there were two displays that were discussed and compared and it was clear from then that the display of choice would be the lItead Studio ITDB02 4 3 a 4 3 inch LCD TFT display that has a built in graphics controller and also a micro SD card slot for memory expansion This is the display of choice without any questions unless it goes out of stock from
26. neuromuscular blockade In the single twitch mode of stimulation single supramaximal electrical stimuli are applied to a peripheral motor nerve at frequencies ranging from 1 0 Hz once every second to 0 1 Hz once every 10 seconds It is important to note that the twitch can fade after high frequency stimulation As soon as a stimulation frequency of 0 15 Hz is exceeded fade or fatigue of the muscle response can be observed As a result a frequency of 0 1 Hz is generally used Because 1 Hz stimulation shortens the time necessary to determine supramaximal stimulation this frequency has proven to be most useful to use at the onset of neuromuscular block Using a single twitch at 1 Hz 1 twitch every second it is possible to establish the level at which a supramaximal stimulus is obtained The onset of neuromuscular block can then be observed using a single twitch at 0 1Hz 1 twitch every 10s The disadvantage to single twitch stimulation is that it can only be used to measure the extent of muscle response when it is compared to a reference value as a stand alone stimulation pattern it has no clinical relevance 0 1 1 0 Hz AAAA Response Non dep i block 2 16 Group 14 Senior Design 1 Figure 2 2 6 Pattern of electrical stimulation and evoked muscle responses to single twitch nerve stimulation at frequencies of 0 1 to 1 0 Hz after injection of non depolarizing neuromuscular blocking drugs arrow picture fr
27. order for the measurement to be accurate This design monitors the smaller movement used in the contraction of the muscles that lie underneath the skin instead of the larger movement of the thumb in order to get its reading It also stimulates the 29 Group 14 Senior Design 1 peripheral motor nerve instead of the ulna nerve that the more common sensors like the accelerometer or the anesthesiologists hand needs This also has a processer within the device that is capable of making a visual representation of the response of the neuromuscular block caused by the anesthesia 2 3 E Electromyography Electromyography EMG evaluates the electrical activity or potential of the skeletal muscles Using the surface electrodes the anesthesiologist can obtain the results needed through non invasive means While stimulating the nerves that control the muscles that need to be measured the devices can measure the activity of these nerves without having to see or feel the force of the twitch 2 3 F Shortcomings After looking at all of the different methods that have been implemented in the past few years it became apparent that each one of them has their own shortcoming The first method with the visual and the actual use of the anesthesiologist s finger has quite a few issues The device that supplies the current to the nerve only runs on a nine volt battery meaning that the anesthesiologist would need to bring in extra batteries to make sure the devic
28. regulated voltage at the output it also requires that the potentiometer be exposed or easily accessed so that it can be modified after manufacturing The issue will eventually arise that the potentiometer has modified itself turning either up or down in such a way that it prevent normal operation or even worse destroys the device due to power overload Seeing that all analog manually adjustable devices will eventually need to be tuned it was proposed to find a solid state solution to this regulation problem Upon further research it was found that a voltage regulator or converter can 84 Group 14 Senior Design 1 found to fit any application imaginable and as such seems to be the obvious choice In addition as an added safety feature it was suggestion that the device be decoupled from the wall unit to prevent any unfortunate accidental shocks caused by a faulty circuit component Decoupling this device can actually serve two purposes it can prevent catastrophic failure from hurting the patient and it can also perform an initial step down to the voltage Fortunately a simple transformer will provide both of these functions in one component Transformers of all kinds are also widely available and as such will be relatively inexpensive to purchase especially in the situation of mass production For this the chosen setup the circuit will need a diode bridge a capacitor a transformer and the chosen voltage regulator The basics of this
29. strain force SA The bending strain is what is being calculated in this test because that is the strain that is ultimately going to create the force that will tell us whether or not the sensor is relaying the information that is needed To create a baseline the sensor will be bent to simulate the movement of the thumb the group can then easily relate the bending strain which is also a moment strain that would help determine the relationship between the amount of bending and the amount of force that caused it Then to test it using the group s volunteer the strain sensor will be checked to see that the force of the thumb movement can accurately be found using this sensor The last sensor that the group researched and has to test is the Piezoelectric sensor Essentially this sensor should be tested in a form that is relatively similar to the force sensor The sensor will be placed on the thumb of the group member that volunteered their thumb for this process the same one will do all of them so that comparisons will be able to be performed accurately without worrying about error due to different forces from different group member s thumbs The output voltages will be measured when the thumb is moving so that the voltages can be related to the force that is being exerted by the muscles in the thumb 106 Group 14 Senior Design 1 The main reason for testing these sensors is to make sure that they are accurate enough to measure the force but not t
30. the date of this design paper to the beginning of next semester when the parts are going to be ordered 3 5 A TFT LCD Display Since the display choice is already know it would be proper to jump straight into the design aspects and how it will integrate with the project application Although this display only supports up to 65K colors at a resolution of 272 x 480 pixels it will be more than sufficient to graph the data from the sensor on the XY axis Because this particular display does not have a lot of documentation just like other screens of this type it will require a lot of on the go design decisions Let s take a look at the pin configuration of this display in figure 3 5 1 below e0e006 60 6000060080 Figure 3 5 1 ITDB02 4 3 Pin Configuration Courtesy of Itead Studio Given the above pin configuration let s look at what each pin is supposed to be connected to and its description Many of the same screen have similar pin configurations so it should be familiar to a lot of designers 79 Group 14 Senior Design 1 PIN NAME PIN DESCRIPTION USED GND Ground Yes VCC 5V power supply pin Yes NC No connection RS Data Command selection Yes WR Write signal enable low active Yes RD Read signal enable low active Yes DB8 DB15 Data Bus Yes CS Chip selection low level active Yes NC No connection LED Backlight Yes NC No connection DBO DB7
31. the evoked contractile response Mechanomyography MMG Mechanomyography is the only approach that directly measures muscle force which best reflects the degree of relaxation of a given muscle For correct and reproducible data of the evoked tension it is required that the muscle contraction be isometric To do this the palm of the hand is turned upward and restrained in this position The thumb movement is then measured after the resting tension of 2 3 N to the thumb is applied When the ulnar nerve is stimulated the thumb acts on a force displacement transducer This transducer should be attached in such a way that the force development or tension of the thumb is applied exactly along the length axis of the transducer The force of contraction is then converted into an electrical signal which is amplified displayed and recorded Mechanomyography requires the most stringent preparation and precautions making it far from ideal for routine clinical use The preload and abduction of the thumb are critical to the measurement s accuracy Just a slight adjustment in the position of the hand can change the preload and or the degree of abduction and 21 Group 14 Senior Design 1 thus disproportionately affecting the results of the force development Therefore the arm and hand should be rigidly fixed This method must also be taken with caution so as to prevent overloading of the transducer Moreover reaction to the supramaximal stimula
32. the members of the team possessed the basics of power management It was also decided that leaving the power to an unpredictable battery source was unwise so an AC source would be used The first step in using an AC source for a DC project is to convert the first to the second A standard extension cable will be used to go from wall plug to device Once it reaches the device it will be connected using a standard screw terminal to guarantee a secure attachment but still maintain the ability to be replaced should the wire break or be damaged in the future Once plugged in to the terminals the hot wire will be connected in series with a current limited resettable fuse This fuse will be limited to seventy five percent of the nominal current rating of the components it directly connects to This device will provide a safety mechanism to prevent accidental shorting from annihilating the rest of the components The neutral and ground will also be used in the circuit to provide the negative and an emergency ground Should any component decide to short out all of its power will be redirected to ground instead of across the patient 120 Vrms 60 Hz HDR2X3 Figure 4 1 1 Figure 4 1 1 shows these pieces and how they shall be connected It can be seen that a switch is also built in to the design this is to disconnect the main power from the device Consider it an On Off as well as a second to last resort to cut power to the device shoul
33. the third stage or the surgical stage the skeletal muscles relax the patients breathing becomes regular and eye movements stop Additionally the patient s pupillary gaze is central and the pupils are constricted This is the target depth of surgical anesthesia The fourth stage or medullary paralysis occurs if the respiratory centers in the medulla oblongata of the brain that control breathing and other vital functions cease to function Death can result if the patient cannot be revived quickly This stage should never be reached Because it can happen from an overdose of anesthetics careful control of the amounts administered to a patient prevents this occurrence It is common today to use a combination of intravenous drugs and inhaled anesthetic gases during general anesthesia a practice called balanced anesthesia This method is used because it takes advantage of the beneficial effects of each anesthetic agent to reach surgical anesthesia stage three The biggest benefit of general anesthetic inhalants is that it allows an anesthesiologist Group 14 Senior Design 1 to quickly modify the amount of the anesthesia given to a patient by simply adjusting the concentration of the anesthetic in the oxygen Intravenously injected anesthetic produces a fixed degree of anesthesia and cannot be changed as quickly and must be reversed by administration of another drug However intravenous anesthetics still remain popular because it controls the
34. to look deeper into the design of this chip and figure out what each pin is supposed to be connected to and its function The following figure shows the pin configuration for this chip left and a simple RF to PCB interfacing schematic 76 Group 14 Senior Design 1 right also right below it is the description of each pin and its function in table 3 4 2 AT86RF230 17 10 111213 14 15 16 SGF 88808 sausages w O Figure 3 4 2 AT86RF230 Pin Configuration Left and Simplified RF Front End Schematic Right Courtesy of Atmel To make thing clearer and to better understand what each pin is designed for let s look at the pin descriptions for the above chip 77 Group 14 Senior Design 1 PIN NAME PIN DESCRIPTION USED AVSS Pins 1 2 and 27 Analog ground AVSS Pin 3 Ground for RF signals Yes RFP Differential RF signal Yes RFN Differential RF signal Yes AVSS Pin 6 Ground for RF signals Yes TST Continuous Transmission Test Mode active high Yes RST Chip reset active low Yes DVSS Pins 9 10 Nd 12 16 18 21 Digital ground Yes SLP_TR Controls sleep transmit start and receive states Vise active high eee rede Regulated 1 8V supply voltage digital domain Yes DEVDD External supply voltage digital domain Yes CLKM Master clock signal output Yes SCLK SPI clock Yes MISO SPI data output master input slave output Yes MOSI SPI data input
35. to the current that is applied in the above example However instead of the anesthesiologist monitoring the force with their hands or just visually a force transducer is used in their place The force transducers in these designs require the patient s arm to be restrained in order for the reading to be accurate The transducer will register the force when the twitch is present and records the data for the anesthesiologist to see the strength of the twitches 2 3 C Accelerometers The use of accelerometers being used to measure the force of the twitches is one of the more common methods being implemented today This method uses either a biaxial or a triaxial accelerometer that is placed on the thumb of the patient being monitored When the nerve is stimulated the twitch is created which is monitored by the accelerometer and using the well known force equation you can relate the acceleration to the force of the actual twitch This method has also been used on the face in order to monitor the eye when the thumb or the foot is covered and are unable to be monitored 2 3 D Piezoelectric Sensor The flexible piezoelectric sensors that are produced in sheets also were one of the sensors that were used in previous designs This sensor is used in U S Patent No 5 131 401 Method and Apparatus for Monitoring Neuromuscular blockage where the sensor is placed on the palm of the patient s hand This method does not require the arm to be restrained in
36. too many losses and very probably too much heat it was almost immediately written off for more efficient designs Knowing that resistors were a poor choice but liking the idea of a handmade voltage converter team decided to attempt a simplistic transistor design that would rectify the voltage and then step it down as needed Towards that end the diode bridge will again be utilized before connecting its output to the input of the a very simplistic following circuit This circuit utilizes 2 2222 DC Reg two transistors and a potentiometer as well as various resistors to produce the reduced voltage Various other resistors can be used to set a minimum or maximum regulated voltage Again DC a2 even here the problem of severe inefficiency occurs With this design though the inefficiency 2N2222 comes up from two things first from the 4 potentiometer and second from the wasted power at 50 anything other than the highest voltage The apparent nature of the second issue makes it simpler to describe first Because of the simplicity of the circuit any voltage that isn t needed is drained straight to ground instead of potentially storing it for when a higher voltage is required this goes a long way towards unnecessarily wasting power The potentiometer on the other hand leads to a cons outweighing the pros problem While having the potentiometer control the voltage level gives the circuit the ability to precisely tune the
37. was making sure that all of the research that was needed was completed The research portion of this project allowed the group members to become familiar or more familiar with the different technologies that need to be implemented and utilized within our design This has allowed the group to expand their knowledge of engineering design and research phases in the work place Learning to work together and as a team has proved to have its ups and downs but in the end it made the learning more enjoyable as well as important Now that there is an added pressure of other members counting on the parts that certain individuals have researched and worked on makes it that much more important to know what you are talking about Senior design has allowed the group to come together as a team The group has come to realize each individual member for everything that they bring to the team and it has allowed us to accomplish what is set before the group and we are ready to conquer senior design II Once the research is finished the move to senior design II with the obtaining of parts and actually building the pieces will be smoother The main and most important part of this design came down to the sensors That s what most of the research time went into it was also the part of the design that our sensors spent the most time harping on how important a good sensor is to the implementation of the group s design The sensor is what initiated the need for this new des
38. will be able to create a constant current anywhere from 2mA to 30mA which given its name will be able to sustain that current given the variations in human skin resistance Once this is managed the group will need to design or find a sensor that is capable of measuring the force that was created once the twitch occurs The sensor will need to be low power to accommodate our limited power supply and be sensitive enough to respond to the lesser strengths of the exceptionally young Group 14 Senior Design 1 and elderly The sensor will also need to be cheap enough to dispose of at the end of use or capable of being cleaned as to avoid cross contamination as the device is used on multiple patients Having these qualities the group will then be able to incorporate them into a controller that will trigger the current pulse and check the response It will need to be able to read very quickly so that the group gets reasonably accurate data from the short pulses that will be delivered This is necessary so that the sensor doesn t give a false negative for the remaining twitches that are needed to be measured The group also will need the data to be displayed on a screen that is easily accessible and readable by the anesthesiologists that are using the device It should also be safe to use in the operating room as that is where it will be implemented in most cases Upon the finishing the above requirements that the group feels are necessary there are
39. 5 Ib 110 N 0 100 Ib 440 N gh 0 100 Ib 440 N Temperature Output variance up Output variance upto Output variance up Output variance up Sensitivity to 0 2 per degree F 0 16 per degree F to 0 2 per degree F to 0 2 per degree F Pricing Type Price 4 pack Resulting Individual Price A201 series trimmed 2 in 77 19 25 A301 series 65 16 25 A401 series 78 19 50 59 Group 14 Senior Design 1 3 3 Pressure Sensors Here are some examples that were researched and found as a possible uses for a pressure sensor that could be used The MPL115A by Freescale is a simple barometer with a digital SPI output for cost effective applications It has a MEMS pressure sensor with a conditioning integrated circuit to provide accurate pressure data from 50 to 115 kPa It has low current consumption of 5 uA during Active mode and 1 uA during Sleep mode which is beneficial when aiming for a low power application An integrated ADC converts pressure sensor readings and digitized temperature to digitized outputs through a SPI port It also offers factory calibration data which is stored internally in an on board ROM The host microcontroller is able to execute a compensation algorithm utilizing the raw sensor output and calibration data to find Compensated Absolute Pressure The MPL115A are ideal with their small size at 5 0 mm x 3 0 mm x 1 2 mm N L4outlijotlito4 oo
40. 50mA The only way to know whether a stimulation sequence is doing anything at a specific current level is to first know what current is being used and second to obtain baseline measurements before the neuromuscular blockade is administered With more advanced circuitry a baseline can automatically be calculate at the beginning of surgery with quantifiable levels of paralysis with this particular circuit all that is available is a rough guess by the anesthetist in charge Once they ve made their guess they must also make a guess as to which current level they are using because this circuit provides no way of measuring it even with calculations provided by the microcontroller The final problem and possibly the biggest with such a simplistic circuit is the issue of voltage given that its source is a nine volt battery some sort of step up circuitry will need to be provided to overcome the exceedingly high resistance of human skin 3 2 B Active Circuit Designs Ve With these flaws of the resistive network in mind the next circuit set g to be analyzed is the transistor based constant current circuit The first of two simple transistor circuits is shown to the left It can easily be seen from this circuit that there is minimal difference between it and the resistive circuit discussed above Due to this limited too difference it suffers from most of the same issues as the resistive R2 network minus the possibility of slightly more accurate curr
41. Acquire PCB and Test 5 Feb 13 15 Feb 13 10 Acquire Display and Controls 10 Feb 13 20 Feb 13 10 Test Microcontroller with Display 20 Feb 13 25 Feb 13 5 and Sensors Assemble First Prototype 1 Mar 13 7 Mar 13 7 Test First Prototype 7 Mar 13 14 Mar 13 7 Fix Prototype Issues 14 Mar 13 24 Mar 13 14 Housing for Final Prototype 20 Mar 13 24 Mar 13 4 Assemble Final Prototype 25 Mar 13 28 Mar 13 3 Fix Final Prototype Issues 28 Mar 13 8 Apr 13 12 Test Final Prototype 8 Apr 11 16 Apr 13 8 Final Documentations 1 Mar 13 18 Apr 13 49 Figure 7 2 2 119 Group 14 Senior Design 1 7 3 Closing Comments The Paralytic Twitch Sensor device that the group has been working on throughout senior design and will continue to work on through senior design II will allow for future ease in monitoring patients in the operating rooms when they are under the effects of neuromuscular blocking drugs This device will allow the anesthesiologist to monitor the patients more effectively because not only will they be able to have a sensor that will measure the force for them the device will hopefully work under the most difficult circumstances These are the ones where the anesthesiologist was unable to get to the patient in the previous designs because they had to monitor the patient s reactions to the current with their hands Now they should be able to apply the sensors of this device even if the arm is tucked to the side of the patient The main focus of senior design
42. CU will not be discussed in detail Some of the main features are 32KB of flash memory 4KB of RAM two timers A D converter and 32 I O pins The most important and catching part of this device is the combination of both the microcontroller and a transceiver For this project this chip is an ideal solution considering its small size that will save space on the PCB board This board can be programmed using C which is a widely used programming language and familiar to many students and beginner programmers Because this board has a slower rate transceiver it is currently the second choice chip 38 Group 14 Senior Design 1 PROS CONS True SoC chip 32 I O pins might not be enough Wake from stand by in about 5us Small number of A D converters Small in size 9 x 9 mm Slow data rates of the RF module Real time clock Free IDE Table 2 4 5 Pros and Cons for TI CF430F5137 Microcontroller P1 7 PM_UCAOCLK PM_UCBOSTE RO3 gt P1 6 PM_UCAOTXD PM_UCAOSIMO R13 LCDREF gt P1 5 PM_UCAORXD PM_UCAOSOMI R23_ gt LCDCAP R33 gt como gt PS5 7 COM1 S26 gt PS 6 COM2 S25 gt P5 5ICOM3 S24 gt P5 4 S23 gt VCORE gt bvcc gt P1 4 PM_UCBOCLK PM_UCAOSTE S22 gt P1 3 PM_UCBOSIMO PM_UCBOSDA S21 gt P1 2 PM_UCBOSOMI PM_UCBOSCL S20 gt P1 1 PM_RFGDO2 S19 gt ORME IONSIS fa 7 18 19 20 21 22 23 24 25 26 27 28 29 30 E RRO DANAE i oi u t o uy lt lt z cs amp
43. Data Bus Yes T_CLK Touch clock Yes T_CS Touch chip selection Yes T_DIN Touch data input Yes T_BUSY Touch status Yes T_DOUT Touch data output Yes T_IRQ Touch interrupt Yes SD_SO SD MISO master input slave output Yes SD_SCK SD SCK Yes SD_Sl SD MOSI master output slave input SD_NSS SD NSS Yes NC No connection NC No connection Table 3 5 1 ITDB02 4 3 Pin Description Information from Itead Studio 3 6 Power Supply For the last section of the project a power supply must be chosen to withstand the demand and accuracy required The current device uses a simple nine volt battery that through manipulation supplies the required current levels of anywhere between 1mA and 100 mA Other possible power supplies are larger rechargeable and non rechargeable batteries and as a last resort using an AC wall socket directly Before getting in to what power supply would most aptly suit the needs of the project it is prudent to examine loosely what its needs will be at peaks times Planning for peak usage guarantees that any and all power needs will be met when running under normal conditions In point of fact taking the peak power requirements and adding a certain percentage would be particularly useful if we intend to avoid brownouts In normal circumstances brownouts will not damage 80 Group 14 Senior Design 1 any of the components intended for the stimulator but they can and probably will cause the controller to
44. Following the issue of recharging or replacing batteries it was decided to just remove the battery from the equation entirely As has been mentioned 82 Group 14 Senior Design 1 previously Dr Looke arranged a viewing of the current neuromuscular device in action in an operating room From the visits made by individual members of the team it was observed that not only are there plenty of AC outlets available but using a battery wasn t even necessary to smooth operation With that information and the exclusion of a standard battery source a new design was formed that used the available wall outlets to the advantage of the project This decision removed the overly strenuous requirement to conserve every electron possible as well as giving the project the ability to grow beyond its original definition The question now becomes how to convert the 110VAC wall outlet in to a manageable voltage for the stimulator to distribute as necessary Fortunately for this project the low power nature of the device allows for several different AC power supply designs With many options available it became necessary to consider other requirements when choosing an appropriate component such as individual and bulk pricing and simplicity of design Once these were taken in to consideration choices were limited to the following categories an RC network an AC DC step down circuit using transistors or a DC DC step down IC Each of these will be considered in t
45. GROUP 14 Paralytic Twitch Sensor Senior Design 1 Ryan Cannon Kristine Rudzik Serge Cheban Kelly Boone Group Sponsors Dr Thomas Looke Dr Zhihua Qu Group 14 Senior Design 1 TABLE OF CONTENTS Chapter 1 Introduction SECTION 1 1 NARRATIVE 1 1 a Executive Summary 1 1 6 Motivation SECTION 1 2 PROJECT SPECIFICATIONS SECTION 1 3 SPONSOR GROUP Chapter 2 Research SECTION 2 1 REQUIRED MEDICAL KNOWLEDGE SECTION 2 2 RELATED PROJECTS amp SHORTCOMINGS SECTION 2 3 BIOMEDICAL ENGINEERING BACKGROUND OLD SECTION 2 3 PREFERRED DESIGN ROUTES SECTION 2 4 CONTROLLERS 2 4 a Microcontrollers 2 4 b Microcontroller w Transceiver 2 4 c FPGA SECTION 2 5 WIRELESS DISPLAY 2 5 a Capacitive vs Resistive 2 5 6 Graphics Display Controller 2 5 c TFT Display Unit 2 5 d Display w built in Controller SECTION 2 6 WIRELESS 2 6 a WiFi 2 6 6 Bluetooth 2 6 c ZigBee 2 6 d HIPAA Regulations Chapter 3 Design SECTION 3 1 SENSORS 3 1 a Piezoelectric Sensors 3 1 6 Force Sensors 3 1 Pressure Sensors 3 1 d Evoked Electromyography 3 1 e Accelerometers SECTION 3 2 CONSTANT CURRENT CIRCUITRY 3 2 a Passive Circuit 3 2 6 Active Circuit 3 2 c Purchased Circuit Group 14 Senior Design 1 3 2 d Safety Considerations 3 2 e Final Design Choice SECTION 3 3 CONTROLLERS 3 3 a Microcontroller 3 3 b Final Design Choice SECTION 3 4 WIRELESS 3 4 a 802 15 4 ZigBee 3 4 b Final Design Choice SECTION 3 5 WIRELESS DISPLAY 3 4
46. Microchip copyrighted material solely for educational non profit purposes falling under the fair use exception of the U S Copyright Act of 1976 then you do not need Microchip s written permission For example Microchip s permission is not required when using copyrighted material in 1 an academic report thesis or dissertation 2 classroom handouts or textbook or 3 a presentation or article that is solely educational in nature e g technical article published in a magazine Please note that offering Microchip copyrighted material at a trade show or industry conference for the purpose of promoting product sales does require Microchip s permission
47. P1_0 7 Digital I O Ports 1 1 through 1 7 Yes P2 0 2 Digital I O Ports 2 1 through 2 2 Yes P2_ 3 XOSC32K_Q2 Port 2 3 32 768 XOSC Yes P2_4 XOSC32K_Q1 Port 2 4 32 768 XOSC Yes RBIAS Analog I O External precision bias resistor for reference current RESET_N Reset active low Yes RF N Negative RF input signal to LNA during RX yae T Negative RF output signal from PA during TX RF P Positive RF input signal to LNA during RX Yes E Positive RF output signal from PA during TX USB_N USB differential data minus D Yes USB_P USB differential data minus D Yes XOSC_Q1 ao crystal oscillator pin 1 or external clock XOSC_Q2 32 MHz crystal oscillator pin 2 Yes Table 3 4 1 CC2531 Pin Description Information from Texas Instruments Because this chip most likely won t be used in the project design no further design development will be done The information given above is sufficient enough to make a decision on the wireless module and to further design this device if the need arises or if this part is actually used in the application AT86RF230 This RF transceiver is manufactured my Atmel and supports the IEEE 802 15 4 and ZigBee protocols that are important to this project s wireless design The selling point of this device is its low voltage power requirements In addition to this it has an industry leading link budget of 104dB In order to make a knowledgeable decision on the best wireless module for the display it is best
48. Rs Force Sensitive Resistors Below are the ones that could possibly be used and the specs of each provided by the Tekscan website The HT201 model was not included in possible sensor options because the design does not require a high temperature sensor 58 Group 14 Senior Design 1 Peo ented tit FEIF e ernn Figure A301 Figure A401 Figure A201 Model A201 MODEL is as A301 MODEL A401 MODEL Spec Sheet Spec Sheet Spec Sheet Spec Sheet PHYSICAL PROPERTIES Thickness 0 008 in 203 mm 7 75 in 197 mm 6 in 152 mm 4 in 102 mm 2 in 61mm Length 1 in 25 4 mm 2 24 in 56 8 mm 0 55 in 14 mm a J 0 375 in diameter 1 0 in diameter Sensing Area 0 375 in diameter 9 53 mm 9 53 mm 25 4 mm Connector 3 pin male square pin 2 pin male square pin TYPICAL PERFORMANCE Error Repeatability lt 2 5 of full scale lt 3 5 of full scale lt 2 5 of full scale lt 2 5 of full scale Hysteresis lt 4 5 of full scale lt 3 6 of full scale lt 4 5 of full scale lt 4 5 of full scale lt 5 per logarithmic lt 3 3 per logarithmic lt 5 per logarithmic lt 5 per logarithmic time scale time scale time scale time scale Operating 15 F to 140 F 15 F to 400 F 15 F to 140 F 15 F to 140 F Temperatures 9 C to 60 C 9 C to 204 C 9 C to 60 C 9 C to 60 C 0 1 Ib 4 4 N ne 0 1 Ib 4 4 N Force Ranges _ 0 25 Ib 110 N Pach We oe 0 25 Ib 110 N 0 2
49. SoC Single on Chip Solution that combines both the microcontroller and an 2 4GHz RF wireless 36 Group 14 Senior Design 1 transceiver in one chip which makes it a very convenient and potentially implementable chip choice for this project This chip has a 2 4GHz IEEE 802 15 4 compliant RF transceiver with a link of 103 5dBm 32 bit MAC symbol counter temperature sensor 128 bit AES encryption and high data rates up to 2Mb s The microcontroller included with this chip has 128KB of Flash memory 16MHz operating frequency 16KB SRAM 4096 EEPROM Bytes 38 I O pins and its operating voltage Vcc is from 1 8V to 3 6V Although this chip is very convenient for use in this project and is very small in size it has its disadvantages in small I O pin count and small number of analog peripherals and most likely won t be used for this project due to these issues Due to projects constantly changing design and requirements this SoC chip still remains our top backup choice With that said this microcontroller could be a very good chip to use with the thumb sensor that needs to be as small as possible and the transceiver can be used to send the sensor data to the wireless LCD display for graphing Although the wireless LCD display is a secondary option that will be exercised if time permits PROS CONS 128 bit AES encryption Only one USCI_A port 128KB of flash memory Small number of I O ports Low operating voltage 1 8 to 3 6 Volts Onl
50. TAL2 Output of the inverting 16MHz crystal oscillator Yes amplifier AREF Reference voltage output of the A D Converter TST Programming and test mode enable pin Yes CLKI Input to the clock system Yes Table 3 3 1 Pin Description for Atmega128RFA1 Information from Atmel The table above gives a better understanding of what each pin on this chip is responsible for and if it is going to be used at all The build section of this chapter will go into more details on how each pin is going to be interfaces with other devices in the design e g sensors antenna and power supply Now that the pin description is clear let s take a look at a basic application schematic provided by 71 Group 14 Senior Design 1 Atmel This application schematic was closely studied and it was concluded that it closely matches the applications requirements for this project so it will be used as reference design that will be built upon to further develop the interfacing between a wireless RF module power supply and the antenna Optional 32 kHz Crystal 2 V 3 6 V Power Supply er Antenna 50 9 j z Deo D amp T C253 CC2531 P2 DIE ATTACH PAD XOSC_Q2 23 C262 XOSC_Q1 22 Figure 3 3 1 Basic Application Schematic Courtesy of Atmel PIC24FJ64GA310 This Microchip MCU was designed to be used for extremely low powered applications and is very well suited for this project Although this chip is a little large
51. a TFT LCD Display SECTION 3 6 POWER SUPPLY 3 6 a Battery 3 6 b A C Supply 3 6 c Final Design Choice SECTION 3 7 PATIENT MEDICAL SAFETY CONCERNS 3 7 a Sterilization Concerns 3 7 6 Reuseability 3 7 c Patient Variability SECTION 3 8 ALTERNATIVE Chapter 4 Build SECTION 4 1 POWER SUPPLY SECTION 4 2 CONSTANT CURRENT CIRCUIT SECTION 4 3 SENSORS 4 3 a Accelerometer Eye 4 3 b Force Sensor SECTION 4 4 LCD 4 4 a Programming SECTION 4 5 WIRELESS 4 5 a Programming SECTION 4 6 PCB SECTION 4 7 CODING 4 7 a Pulse Control 4 7 6 Sensor Polling SECTION 4 8 CASING SECTION 4 9 ISSUES RESOLUTIONS Chapter 5 Test Plan SECTION 5 1 POWER SOURCE SECTION 5 2 CURRENT SOURCE CIRCUITRY SECTION 5 3 SENSORS Group 14 Senior Design 1 SECTION 5 4 LCD SECTION 5 5 WIRELESS SECTION 5 6 PCB SECTION 5 7 SOFTWARE SECTION 5 8 FULL ASSEMBLY Chapter 6 User Manual SECTION 6 1 DEVICE OPERATION UNDER NORMAL CONDITIONS SECTION 6 2 TROUBLE SHOOTING SECTION 6 3 ACCEPTABLE ALTERNATIVES Chapter 7 Administrative Content SECTION 7 1 BUDGET SECTION 7 2 MILESTONES SECTION 7 3 PROJECT SUMMARY amp CONCLUSION Chapter 8 Appendix A Schematics Chapter 9 Appendix B References Chapter 10 Appendix C Permissions Group 14 Senior Design 1 Chapter 1 Introduction 1 1 A Executive Summary In an increasingly technological world the method for monitoring patients while under anesthesia is becoming dated The inspiration for this project began when D
52. a ear ae SF PL wf wf A Pd Fi 4 oa Ca re oo aw 8 afa P 5 s P s Pye o a E J M a C r rP i tf F 3 o af m a oa OS Cg G gt Z y oy Figure 2 2 3 The EL500 paired electrodes Picture from http Awww biopac com disposable paired electrode foam 25pairs These types of electrodes can prove to be quite costly however when bought in large quantities For 25 pairs of electrodes the BIOPAC Systems Inc website lists the price to be 42 without tax That is 1 68 per electrode pair or the price per patient For the EL500 series one would also use the LEAD110 series electrode leads as well Although for testing many electrodes will not be used in the larger aspect for hospitals with thousands of patients it is important to be efficient while also not wasting money As seen however the price of two electrodes more than doubles for each patient when using the paired electrodes Therefore testing will be done with the individual electrodes 2 3 Related Projects amp Shortcomings In coming up with this design time was spent browsing through other designs that have worked in the past to see what can be improved on as well as what technology can still be used in the new design Problems that were found by the group and by others who have researched these devices were not overlooked but were taken into consideration so that as a group these problems could be solved and the end product would be better than t
53. accelerometer Acceleromyography is frequently used today because it is easy to apply can be used with data processing devices and is relatively inexpensive The TOF Watch is one detached monitor based on measurement of acceleration that is commercially available today One feature that the TOF Watch has made available is the hand adapter to keep the thumb in place It still allows the entire arm to be restricted in place like other recording devices do but it allows for more reliable measurements Originally accelerometers required that the thumb move freely but to measure a preload at least in research studies However it was realized that accurate readings were not being measured because the thumb did not return exactly to its starting position during a TOF sequence and as a result 23 Group 14 Senior Design 1 its resting extension changed before the next TOF stimulation This preload has proven to be very beneficial because it allows the thumb to always return back to its exact starting position Thus measurements are less prone to error Another main reason to add this feature to neuromuscular monitoring is because repositioning of the patient during operation is actually quite a common practice such as lowering their head or turning them on their side With these shifts it can alter the patient s thumb position making the measurements useless at that point With this project the goal will be not to have anything that is rest
54. additional specifications that would be nice to add to the project but are not imperative to the device to make it work that the group decided would be nice to add if the time was there These specifications are completely optional and will not be worked on until the necessary specifications and requirements are met If there is time at the end the group will try to implement as many of these additional requirements in an effort to create the ideal project within the allotted timeframe of senior design Il First the group would like the final project to be rather inexpensive as the goal is to mass produce the device and use it in the hospital operating rooms Also if possible the group would like to make the device capable of wirelessly transmitting data so that the display does not need to be directly connected to the device and can be placed anywhere within the operating room It would also be a great feature to have if the anesthesiologist were to be working on a research study for new advancements in medicine and needed to have the data from multiple cases on their personal device so they can look over them during and after the study It would also be nice if the group was able to make the device run on battery to keep the number of wires in the operating room to a minimum but also this would allow the device to be used during the test of local anesthetics as well These local anesthetics are administered to the patients in the areas outside of th
55. attached to an LCD screen The screen will display the results of the twitches so the anesthesiologist will know whether or not more medication is needed or that the body is responding just as it needs to for that point of the surgery process A wireless option will also be integrated to allow for the transmission of the data to a computer or a tablet for the anesthesiologist to use for future studies It will also allow them to keep an accurate history of past performances The end product will be a lightweight portable device that is able to run on battery for shorter surgeries but also capable of being plugged into an outlet when a longer surgery is needed Low cost is also an ideal for the sensor as the 1 Group 14 Senior Design 1 hospital is leaning towards disposable instruments that come in contact with the body The Paralytic Twitch Sensor will be useful in operating rooms where the anesthesia is being administered as well as in the recovery rooms so that the doctors do not pull out essential tubes too early to keep the risk of complications from the anesthesia to a minimum 1 1 B Motivation The motivation for this project lies mostly with the medical part of the Paralytic Twitch Sensor itself Two members within the group have personal ties to this project although for very different reasons The first Ryan is fascinated by this project because of chronic medical conditions that have already required major surgeries and will req
56. ay when the voltage is measured when the thumb is lowered the group can compare that to a force that would be outputted at that voltage The next sensor that will be tested is the accelerometer To create a baseline for this sensor the group will see if it will read the correct value for gravity in each one of the three directions Once the group sees that a correct reading is obtained then the volunteer can attach the accelerometer to their thumb Then they can create the twitch motion and using the force equation that relates the two the force can be calculated Once the baseline is set then the volunteer can have the accelerometer placed on their thumb and replicate the movement that would happen when the current is supplied Then the group would see if the acceleration would match the force found in by the other sensors If it is off by a large amount then as a group it would be decided that the accelerometer lived up to the research that was conducted and therefore is not a good enough sensor to use in this device For the accelerometer the group will also need to test out how the accelerometer will be placed on the eyelid and test whether or not that is a plausible design to measure the twitch of the eyelid with the accelerometer To test the strain stress sensor the group will again be testing something other than force This time the test is on the strain put on the sensor by the movement of the thumb Strain is related to force by the equation
57. chematic of the 40 pin LCD interface will be given below This schematic was provided by ltead Studio for the use in the design of applications like this project 8 IRQ DATAL 2 NC DATA2 LCD 0 15 BO Oo ww pu knee ees omo FE ooo009 8 40PIN _INTERFACE Figure 4 4 1 40 Pin LCD Interface Schematic Courtesy of Itead Studio 4 4 A Programming Here is the outline of the functions that will be used to program and control the display of sensor data on the LCD module These functions are subject to change during the course of prototyping phase of this project 99 Group 14 Senior Design 1 Function Name Function Description Function calculates the X coordinate value when pressed on the screen Function calculates the Y coordinate value when pressed on the screen Functions takes in two parameters the touch input and a task based on where you pressed and returns the command as an integer Function will return the input data Double getInputData data coordinate from the touch screen if the user changes any parameters Function will graph the data from the sensor Table 4 4 2 Outline of Function for the Wireless Display Double getXCoordinate touch_input Double getYCoordinate touch_input Int getInputCommand touch_input task Void graphData array_of_doubles 4 5 Wireless Figure 4 5 1 is a schematic diagram provided my Atmel that shows how a typical antenna
58. ct components to achieve a specific task PIC24FJ64GA310 This Microchip microcontroller is a very low powered chip that is designed for extremely low power consumption applications that run on battery power This device has many low power features including a low voltage sleep mode where the device state RAM is maintained by only using 340 nA of current and also a Vbat pin that allows the microcontroller to transition to battery power when Vdd is turned off or removed In addition to all this the MCU has a 480 segment LCD Driver that can be very useful for this project when displaying sensor data from the patient This chip has a 16 bit MIPS CPU with 64KB Flash along with 8192 RAM bytes that operates at 32MHz The chips operating voltage is a typical 2V to 3 6V range that many of the competing chips have This chip is fairly large with 100 pin count along with 85 I O pins to interface the chip with your design For digital communication the chip has 4 UART 2 SPI and 2 l2C peripherals As for analog peripherals this chip has a 12 bit A D converter 3 comparators and five 16 bit timers There are a few variations of this chip within the chip family with fewer pin counts and different RAM size 32KB 64KB and 128KB 32 Group 14 Senior Design 1 PROS CONS Samples Available Relatively large in size 14 x 14 mm 85 I O Pins No D A converter built in Free IDE for students No LCD Driver for TFT Displays V
59. d it experience catastrophic failure 90 Group 14 Senior Design 1 The next piece of the power supply will be the actual manipulation of voltage that gives the circuit ability to create a constant DC signal The lead from the switch will be connected to one end of a transformer while the neutral is connected to the other This transformer performs two functions for the circuit first it allows for an isolation of the circuit from the wall outlet and second it provides and initial voltage step down Isolation is critical when dealing with any kind of power grid because there exists the potential that if any piece of the grid fails to work properly it will propagate a power surge down the line and through any device While a power surge is unlikely in a hospital setting it is better to be safe than sorry this leads to a second reason for power isolation patient safety In the unlikely event that something went wrong with the device maybe a power surge fried something a possibility exists that instead of frying in the off position a component will be permanently on This can lead to major issues if say the component stuck in the on position happens to be the switch allowing current to flow through the patient A continuous unregulated current flowing through a human can do extensive damage in a short period of time with a worst case scenario being the loss of use of the body part being electrocuted S mA
60. d t02 i4 iadt02i4p279 paf Train of Four Monitoring PDF located in Dropbox Articles recent http neuromonitoring files wordpress com 201 1 02 neuro musc blockers slp train of four monitoring 1 pdf http ionphysiology com ssep 20settings htm http www mainlinemedical com mm bluestar enterprises hand adapter htm Electrodes http www biopac com disposable paired electrode foam 25pairs http faculty smcm edu wihatch courses 436web 436resources bsl_ hardware gu ide pdf http www wisegeek com what is an ecg electrode htm Group 14 Senior Design 1 Sensors Piezoelectric Comparison with M NMT C Motamed K Kirov X Combes and P Duvaldestin 2003 Comparison between the Datex Ohmeda M NMT module and a force displacement transducer for monitoring neuromuscular blockade European Journal of Anaesthesiology 20 pp 467 469 doi 10 1017 S0265021503000735 Force Sensors http www meas spec com product t_product aspx id 5123 http www tekscan com flexible force sensors Pressure Sensors http www freescale com webapp sps site application jsp code APLANAMON MCU and Wireless Research http embedded lab com blog p 3557 http www scriobd com doc 98700331 Wireless Radio Frequency Module Using P IC Microcontroller http www mikroe com products view 285 book pic microcontrollers programming in c order http www engscope com pic24 tutorial 1 introduction http newbiehack com MicrocontrollerIntroducti
61. de REPEAT Instruction Hardware Traps Configuration Word Mismatch OST PLL Lock nstruction Set 76 Base Instructions Multiple Addressing Mode Variations 64 Pin TQFP and QFN Figure 3 3 1 Features for PIC24FJ64GA306 MCU Courtesy of Microchip Now let s look at the recommended minimum connections to get the chip operating These recommended connections are provided on by Microchip the device maker These are the values of the components used in figure 3 3 2 C1 through C6 is 0 1uF and 20V ceramic C7 is 10uF with 6 3V or greater tantalum or ceramic R1 is 10kOhm and R2 is 1000Ohm to 4700hm Since this is a critical design point for this project the schematic in figure 3 3 2 will be used to start basic testing for the MCU 73 Group 14 Senior Design 1 PIC24FJXXXX Figure 3 3 2 Minimum Connection Recommendation for PIC24FJ MCUs 3 3 B Final Design Choice After a lot of research and design trials the MCU of choice for this project is the Atmel Atmega128RFA1 Because this is a single System on Chip solution the design of RF transceiver and microcontroller is already taken care of for the designer Instead of acquiring two separate modules one for the MCU and a separate module for the RF transceiver it is much simpler and cost effective to use this Atmel SoC system In addition to all this you will be saving energy consumption because most of the SoC chips use up a lot less power than any two given devices This chip has
62. disposable hydrogel electrode picture from http www fis uc pt data 20062007 apontamentos apnt_134_5 pdf There are two general types of disposable electrodes that can be used for the stimulation in neuromuscular monitoring There is the basic single Ag AgCl adhesive electrode that is pre gelled and is high chloride for quick accurate readings The other type of electrode is the paired Ag AgCl electrodes These electrodes have been specially made for neuromuscular monitoring As stated previously electrode placement is vital to the accuracy of the monitoring results It was stated that electrodes should be between 3 to 6 centimeters apart Therefore paired electrodes one positive and one negative have been made commercially available that offer a fixed distance for quicker setup One option that could be used for the single Ag AgCl disposable electrodes is the EL503 series by BIOPAC Systems Inc These snap electrodes do not contain any latex They are easy and convenient because they are adhesive pre gelled and designed for one use only 26 Group 14 Senior Design 1 i A o KE a A o 5 W TaT os he 4 in a rs b ps aps a a4 sae a Oto ar m2 2m 2 Figure 2 2 2 EL503 single surface electrodes picture from http www biopac com disposable electrode 100 For a pack of 100 individual electrodes the BIOPAC Systems Inc website lists the price to be 38 without tax When realizing that each patient needs tw
63. e will last through the entire surgery There also is not an indicator as to whether or not there is juice in the battery so they could assume that they are applying 30 mA of current through the nerves when in fact they are not sending anything which would result in a false negative Also the only way to choose how much current is being supplied would have to be a guess because there is only a dial on the side of the device that allows you to choose the current that is being supplied There is no indication as to how much current is being supplied so it really could be supplying 30 mA or 25 mA of current There is no way of being completely positive that you are using the same amount of current every time the device is applied The anesthesiologist may miss the actual twitch and assume that the neuromuscular blockage medicine is still working properly This method requires the anesthesiologist to be confident with his knowledge of the medicine and the patient s charts They have to keep track of the time since they have administered the anesthesia in order to know when they need to give more If they are too late in checking to see if they are waking up then the surgeon is going to let the anesthesiologist that the patient is moving under their knives 30 Group 14 Senior Design 1 Also when our individual team members shadowed Dr Looke in the operating room the conditions that the anesthesiologists work under became apparent In the operating
64. e best cases make it seem like the variations in patients very a great deal more than just the age and their overall fitness Thats why the biggest factor that shows that this Paralytic Twitch Sensor is needed is the fact that each patient is different when it comes to anesthesia medicine response Even in the most ideal cases where the patient is young healthy and fit there really is no real way of conclusively telling whether or not the medicine will work as it is prescribed The reason that this is so unknown is that the chemical makeup of these drugs reacts differently to each person s body chemistry as does other medications However in the situations that these drugs are used the anesthesiologist needs to be able to have some way of monitoring the drugs because it is imperative that the body of the patient is paralyzed while the surgeon is working Monitoring these patients starts to become really important once the surgery starts The risks from the anesthesia depend on patient s age health and how they respond personally to the medicine The anesthesiologist can know the drug like the back of their hand and can have studied the patients records yet still not know when to give an additional dosage of the medicine The records that the anesthesiologist will go over are very important It is important that the patient answers all the questions honestly This in depth history is important so that the 88 Group 14 Senior Design 1 anes
65. e can make them sterile The electrodes are the easiest part of the design of the device to make reusable Not that the electrodes are reusable but they can be easily disposed of after they are used so that the anesthesiologists do not need to worry about having to disinfect them making it easier for them to use making the reusability of the device that much better 87 Group 14 Senior Design 1 The sensor is the part of the device that may be a little more difficult to create ease in the eyes of the anesthesiologist in reusing them From what the group could tell from the research conducted the best bet is to either invest in the top notch sensors and have only a few on hand at the hospital and then at the end of the day having the sensors sterilized so that they will be ready for the next wave of surgeries or creating something or just having a rubber glove between the patients hand and the sensor so that there is nothing on the device that is touching the patient This may increase the reusability of the device and make it easier to use The devices reusability and the ease of its use becomes a major concern for the group because this is the main reason why this project was taken on Anesthesiologists are not using the devices that they have now because of the fact they are not very reusable and they are not user friendly 3 7 C Patient Variability The fact that these anesthetics that are given to patients are so unpredictable in even th
66. e operating room where there are not outlets readily available so a battery operated device would be able to serve multiple functions 1 3 Sponsor Group Group 14 Senior Design 1 The sponsor and mastermind behind this project idea is Dr Looke Without his presentation to the senior design class at the beginning of the semester this project would have never taken form This was not an idea that was in any of the group member s initial designs Dr Looke is an anesthesiologist in the Orlando area The reason that he came to the class to present this idea is because his undergraduate study was in the field of electrical engineering so he knew that this was a device that would be able to be created based on his past experiences in the engineering industry Dr Looke helped guide the group with the medical research and answered any of the lingering questions that individual group members had when trying to relate the medical and the engineering worlds He also sponsored each member of the group to allow for the visit of the operating room in the hospital in Winter Park This experience helped the group see where the major problems were with the old design of the current source and why the monitoring by the senses of sight and touch were not always an accurate way of obtaining information Not only that but they were not completely reliable to give a reading at all The group s other sponsor is Dr Zhihua Qu His background in robotics will help t
67. e will be using in our design document Please get back to me as soon as you can Body Text Variable Width gt an ae eg m O Thank you Serge C e STmicroelectronics permission pending B Send Spelling Q Attach gt f Security mp Save gt From Sergey Cheban lt ce seriy ucf gmail com gt CESERIY UCF v To amp AME_West_Inquiries list st com Subject Permission to use content BodyText Variable Width gt e AAIAAA Hi am a student at University of Central Florida Our group is working on a senior design project and would like to get your permission to used your schematics diagrams and materials of that sort for the parts we will be using in our design and be able to use them in the design document Please get back to me as soon as you can 1 AOR Thank you Serge C f Texas Instruments Tl further grants permission to non profit educational institutions specifically K 12 universities and community colleges to download reproduce display and distribute the information on these pages solely for use in the classroom This permission is conditioned on not modifying the information retaining all copyright notices and including on all reproduced information the following credit line Courtesy of Texas Instruments Please send us a note describing your use of this information under the permission granted in this paragraph Send the note a
68. ectronic devices Acceleromyography AMG Acceleromyography measures acceleration of a given end organ such as the thumb It is a technique based on Newton s second law FORCE MASS X ACCELERATION If mass is constant acceleration is therefore directly proportional to force Thus after nerve stimulation one can measure not only the evoked force but also acceleration Acceleromyography is based on the piezoelectric effect which derives from the phenomenon that electrical charges can be present on the surface of certain materials mostly crystals Their electrical current is induced by acceleration of the piezoelectric element or the acceleration transducer Once acceleration is measured deductions are made to provide information about the force of the stimulated muscle Thus acceleromyography can be performed on muscles that can be easily measured after stimulation Evoked stimulation is usually performed on the ulnar nerve and the acceleration is then measured with a piezo electrode that is fixed to the thumb Alternatively it can also be applied to the nerve muscle unit of the posterior tibial nerve or the facial nerve with the orbicularis oculi muscle Acceleromyography uses a piezoelectric ceramic wafer with electrodes on both sides This signal can then be analyzed and displayed on a recording system For accurate and reliable measurements the thumb may only move in a strictly horizontal direction if measuring with a single axis
69. een to the device Any damage to the line has the ability to ruin the entire thing If this does not resolve the issue then there is nothing else to be tried If it appears that the stimulation circuitry is not working properly the first step in correcting this is to ensure that the electrodes are as close as possible to the nerve area If they are where they should be use the tetanic shock to see if movement is observed Because of the intention of this mode the patient should have complete contraction of the muscle group If this is not the case then it is likely that the pads will need to be removed and replaced in their correct position If no contraction is seen from the patient entirely then the patient should be disconnected from the device Trusting that the device will not harm the user it is suggested now to apply the device to a portion of skin and try the tetanic pulse that way This will give the user definite feedback as to whether or not the device is working If it is and the patient exhibited no reaction to it then s stronger pulse strength will need to be selected or a weaker nerve muscle combination will need to be selected This concludes the troubleshooting section 114 Group 14 Senior Design 1 6 3 C Acceptable Alternatives This section is added to the user manual in the even that a particular part cannot be found in time to be used in surgery There are a few generic pieces that can be swapped out and used from othe
70. en for the project 3 3 A Microcontroller For this project there were two categories of microcontrollers that were researched and considered for the design One being a single chip that just has an MCU built into it and nothing else and the second category of microcontrollers was SoCs System on Chip that had the RF wireless module built in into the same chip making it a very lucrative choice for the MCU of choice Based on the research that was done on these two types of chips the top two parts that fit the project better were chosen to go look into design specific and how each can be used for this project The two that were chosen are Atmel Atmegai28RFA1 MCU with built in RF transceiver and Microchip PIC24FJ64GA310 MCU ATmega128RFA1 This microcontroller is made by Atmel and features a built in RF transceiver which solves a problem of MCU and Transceiver interfacing in the design This chip has a lot of example code right inside the spec sheet and you 69 Group 14 Senior Design 1 don t have to look around much to find most of examples need for this project This is why this MCU will be the most likely choice for the project design For more detailed features list and description refer to section 2 4 A of this document Table 3 3 1 below lists all the available pins on this chip and their descriptions Relevant Features e 1635 Powerful Instructions Most Single Clock Cycle Execution e 32 8 bit General Purpose Registers e U
71. en it comes to wireless communication and data transmission The organization that regulates all of this is FCC Federal Communications Commission The following research section will look into some different types of wireless communication options available and compare them to see which is more suitable for this project This includes but is not limited to Bluetooth WiFi and ZigBee 2 6 A WiFi This is a very popular technology that is being used in almost every personal electronic device WiFi uses high speed internet connection to exchange data wirelessly using radio waves over a computer network WiFi is based on IEEE 802 11 standards Some things to consider for WiFi are WiFi is readily available in most locations reliable error correction and fast data transfer rates There are disadvantages though and some of them are too much for the scale of this 46 Group 14 Senior Design 1 project design need extra components for connection interference in this RF band CC3000 TIWI SL This TiWi SL module from LS Research utilizes Texas Instruments SimpleLink WiFi CC3000 technology To be clear this not a TI product but simply uses Texas Instruments SimpleLink technology This kind of solution simplifies the design and implementation of a wireless internet connection SafeLink minimizes microcontroller requirements on the software side reduces development time lowers cost saves space on the PCB and requires less RF expert
72. ent tuning by the adjustment of R1 and R2 though the actual current values are still unknown sm RLoad IH 64 Group 14 Senior Design 1 VCC The second basic transistor circuit a current mirror is 4 p shown left Because of the definition of the circuit it ha ae provides a way to accurately set the current through the two BJTs by accurately setting their base currents Assuming that these two BuTs are identical this means a Me that the current through the left and right one match regardless of the value of RLoad Obviously this logic will T need to be modified for the real world and its finite sources but the idea works What is does not do is the same as the previous two designs give the actual current value step the voltage up or self adjust for variations in patients For a self adjusting constant current circuit to be built it is necessary to use a more advanced circuit containing OpAmps This circuit Figure 3 2 1 uses just a single OpAmp with a voltage divider to bias the positive input and a negative feedback system to create the adjustment feature needed This negative feedback voltage is determined by the resistor Rset placed between it and ground the bigger the resistor the smaller the maximum allowed current DC lt E Grnd lt lt Figure 3 2 1 With this in mind Rset can be replaced by an electronically controlled switch that chooses between several di
73. enter a reset sequence Any reset sequence while being used on a patient will ruin the data collected up to that point and will possibly render using the device during that operation pointless The table that follows will give a visual of expected maximum power requirements for each of the main parts of the device Part Min V Max V Min I Max I Manufacturer LCD 3V 3 6V 20mA 30 3mA Newhaven Display Res Touch Controller 2 5V 5V 60uA 17mA Microchip RF Transceiver 2 4V 3 6V 2uA 23mA _ Microchip PIC uC 2 2V 4V 80uA 300mA Microchip Table 3 6 1 From this table it can easily be calculated that a minimum of 5V and 370mA needs to be available to the device at all times just to maintain the main components In addition to these things the actual neuromuscular stimulation circuitry will need upwards of 100mA just to perform its limited duties Thus for caution s sake stimulator will be designed to maintain 5V at a maximum current draw of 1A Due to the unpredictable nature of human interaction the stimulation circuitry will have an unpredictable effect on the circuitry and because of this it is necessary to plan for double the calculated current draw With these numbers in mind we move on to choosing an appropriate power supply 3 6 A Battery Power As mentioned before one of the bigger reasons that this device and its cousins aren t more commonly used is because of the difficult
74. equence instruction and to enter low power mode This is probably not the expected shutdown that the operated was looking for but once this mode has been entered the power switch can be thrown off without the worry of damaging the device in any way Returning to the pulse sequences it is necessary to discuss their settings before actually using them On power down all of the previous users setting will have been erased and because of this new settings will now need to be decided upon Some of these settings will modify themselves for the different pulse types 111 Group 14 Senior Design 1 but the majority will need to be manually modified upon first use To do this from the home screen touch the pulse button on the LCD This will bring up the new menu of the types of pulses and settings Go to settings and you ll be shown an individual setting at a time with the ability to scroll through to the setting that the user is looking for We now go through the settings for the individual pulse types 6 1 A Train of Four For this setting the device will issue four pulses of 200us duration at a frequency of 2 pulses per second This is the setting most commonly used to test whether the patient has begun to wear through the original bolus injection of sedative The options available for this setting begin with the current strength A setting of preselected values from 1mA to 50mA are available choose one The next setting will be whether to make
75. eries to get the voltage to a reasonable level but in doing so the weight of the device becomes unreasonable Also if chaining D cell batteries were the primary option it would be simpler and safer to purchase a laptop battery and use it instead Failing to find a sufficient disposable battery the next step was looking in to higher power rechargeable batteries One reasonable suggestion was to use a small standard laptop battery such as the one used by the Asus Eee These batteries can have anywhere between 4400 to 7200 mAh for the standard and extended battery pack respectively with a nominal 10 8 volts Considering these new parameters a device could easily be made to work exceptionally well even when considering a less than optimally efficient design Unfortunately the main drawback to this new choice in power will obviously be its cumbersome size Even the reasonably small Asus Eee s battery has rough dimensions of 1 x2 x8 far too large to strap to someone s arm Another significant drawback to using any kind of battery is the simple fact that at some point is will die With your standard alkaline battery you can just throw it away and buy a new one but a rechargeable battery must be plugged it in for upwards of three hours to obtain a full charge And even then they eventually need to be replaced as batteries have a preset number of charges they can take before the individual cells begin to die 3 6 B AC Power Supple
76. ery low power consumption Five 16 bit timers Sample code and libraries available C compiler optimized instruction set Fail safe clock monitor JTAG programming interface Table 2 4 1 Pros and Cons for TI CF430F5137 Microcontroller 100 Pin TQFP 100m SEGE YPMO4 AVDIN CTEDAICNE2 RES SEGSVUCTEDSICNB2IRG15 I 1 87 9 SEG2Z7 PMO 11 CNSS RFO G3YCNSTIRCS EET 8 68 E RP2ISEG1SRTCCICNSUR ANI RPIG1USEGSYPMCS2ICN4MRCS 9 EG4SPMBE 1 CN44IRA15 ANI7ICIINDIRP2USEGOUPMASICN IRGS ET 10 66 E RPDESEGAYPMAZICNEURATS VicAP AN 18 0 TINCIRP2B PMASICNARGT L 11 es ves VLCAPZIANTYC2INDIRPINPMAVCNIORGE _ 12 PIC24FJXXXGA310 64 OSCOICLKONCN2URC15 MCR E 13 63 _ OSCICLKICN2YRC12 ANQO C2INCIRP2TISEG UPMAZICNIVRGS T 44 voo vss CJ 15 61 E TOOCN3SRAS vo C 16 60 E TOYPMA2T CNSTIRAS ONAN a 5 5 F p 3 E i 4 RRRARSRB MOUUUUDD TH t 6665 86 ny 1E a f AN ISIRP2NSEGNREF OC TE OSIP MAWON 12 RB Figure 2 4 1 PIC24FJ64GA310 Pin Configuration Courtesy of Microchip 33 Group 14 Senior Design 1 MSP430F5438A This Texas Instruments microcontroller is of ultralow power family of chips that could be used for a variety of applications The architecture of this chip and its low power mode is optimized to achieve great battery life in portable applications This device has a 16 bit RISC CPU Architecture with 16 bit registers up to 25MHz system clock extended memo
77. everything back in to a low power state If everything flashed to the LCD properly then normal operation can begin There will also be a power indicated on the front of the device that lets the user know that the device is power up On the front of the device will be a small resume button that needs to be pushed to wake up the device once pushed the LCD will light up and wait for and entered command When connected to a patient the first command that should be entered is the baseline test this allows the device to get a basic reading of the patient s reaction to the ToF With the baseline test there will be multiple iterations of the ToF to make sure that the patient s appendage is returning to the home position Without this check to make sure that the patient s muscles are behaving as normal the device runs the risk of getting a good reading the first time and now getting another good reading until it is physically reset by someone in the room After the baseline tests have finished running there are three different operation modes that the device can be set to ToF Twitch Custom and Tetanic These will be discussed individually in the following If none of the modes are desired or the device is not to be used at this time then it can be told to shut down and will do so in a matter of seconds Although because of the nature of its build even when the device has been instructed to shut down the best that it can manage is an end s
78. f patient extremity or an expensive sensor requiring precise orientation and or rigid attachment to the patient Piezoelectric Force used in kinemyography consists of a molded plastic device which mirrors the contour of the outstretched thumb and index finger measures the bend of a mechanosensor in a piezo electric ceramic wafer current examples are the ParaGraph and the AS 5 M NMT very versatile and mobile but not nearly as accurate as a piezoelectric accelerometer Pizeoelectric Accelerometers Used in acceleromyography AMG Just as reliable and accurate as the quantitative measuring methods used in mechanomyography MMG and electromyography EMG Usually utilizes a disposable adhesively affixed transducer Easier application less hassle A possible option for an accelerometer that has been researched is shown below ACH 01 Series 54 Group 14 Senior Design 1 The use of piezoelectric polymer film in the ACH 01 by Measurement Specialties Inc provides many cost performance advantages that allow it to be used ina wide range of applications where the use of traditional accelerometer technology is impractical 1 000 700 025 SQUARE PINS GND i poem ie v 10 TYP _ CENTER LINE i Lo jej e F ACH 01 02 with Pins Figure 3 1 1 ACH 01 piezoelectric Figure 3 1 2 block diagram with pins of Accelerometer ACH 01 series Ne pe nao get lies T Q1 Equivalent to 2N4117 Figure 3 1 3
79. f the body that the sensor is going to be connected to so that the device follows the guidelines for health and safety within the operating room The best part about having a glove or protective covering is that it will keep the sensor from actually touching the patient but at the same time the sensors that the group is looking at will work with something underneath it The sensor will still be able to measure the force of the twitch even with a glove or something else over the hand to keep it sterile 3 7 B Reusability The sterilization concerns are closely related to finding a sensor that is reusable if needed The most important part of this Paralytic Twitch Sensor is the sensor itself But the device itself also has to be reusable It has to be able to work in the operating room This is a device that is being created to help the anesthesiologists with the work that they do So it is important that they have a device that is both reusable and functional Each part of the device has to be used on a daily basis This is being created mainly for use in the operating rooms and therefore it needs to be able to be sterile and capable of being used multiple times without having to worry about overheating The only two parts that really cause any concern for the reusability requirement are the electrodes and sensors because those are the parts of the device that touch the patient and therefore special consideration has to go into those parts and how w
80. failure This is what happens when the anesthesia has ended and the patient is in the recovery room The breathing tube is taken out and due to the fact that there is still some neuromuscular blocking drugs in the patients system the muscles within the respiratory system are still weak This causes the patient to struggle with the task of taking normal breathes In these cases doctors either have to reinsert the breathing tube to help assist with the breathing until the drugs have completely left the body or the anesthesiologist has to treat the patient with another drug that will either counter act the effects of the blocking drug or blocks the memory sensors in the brain so that the patient starts to breathe normal and does not have to remember the short breathes that they are taking so that it will have less of a negative response in the patient This is not something that doctors want to do to the patient The other major issue with these anesthetics lie with the fact that if too much of the drug is administered at one time there is no way to monitor the amount that is in a patient The anesthesiologists rely on the patient being on the edge of alertness in order to make sure that when the surgery is over that there is not a major time difference between when the surgery is over and when the patient finally wakes up This is also done to be sure that the patient is not being charged with additional medicine that is not truly needed The operating roo
81. faulty to begin with and loading it has caused it to fail In this scenario there will also most likely be a considerable amount of heat and possibly smoke coming from the part Assuming that all components are getting their proper voltages at this point it is time to move on to the startup sequence 109 Group 14 Senior Design 1 5 9 B Functional Power Up At power up the turn on sequence should initiate Here the test is not for the content of the sequence but simply to see if it happen because the sequence has already been tested previous sections it is known to work but with everything wired up it is not known whether there will be a low power failure due to some miscalculated circuit section Assuming the LCD works move on the section 5 8 B if it does not then the first thing to check will be the wires of every component from the power to the LCD making sure that everyone is where it needs to be and that they are securely fastened Failing to find the issue there the next component to check is the AC DC converter Starting with it check the voltages of every component directly linked from the DC source to the screen Components will include the following five volt regulator LCD controller and microcontroller Because all of the individual components up to this point have been tested individually if they are getting the power they require then the next part of the test is a rebuild Most commonly on first assembly if everything was
82. fferent resistor values Because the delivery system will be controlled by a microcontroller already adding this feature gives the device the current select ability it needs in addition to the auto adjust feature allowed by the OpAmp In an effort to be thorough the team has come across many more homemade circuits that can effectively produce at least the required current levels but none of them will be thoroughly discussed here The reasoning for leaving them out is the shear unpredictability of the circuits take the camera flash shocker for 65 Group 14 Senior Design 1 instance This particular circuit harvested from a disposable camera is more than capable of providing a shock with enough current to create a feasible device But for this single advantage it actually lacks everything the other circuits provide intentional repeatability with the same values designable safety features controllable current etc Because of these flaws these circuits were almost immediately ruled out regardless of the simplicity of adding them to this project s design 3 2 C Voltage Booster Returning to the OpAmp circuit while it has alleviated two of the problems ailing all the previous circuits it leaves one major problem The voltage levels for this circuit still need to be stepped up to reasonably high DC levels to create the current required To do this there are a couple of available option buy or design a DC DC boost converter bu
83. frequency is 75Hz Also shown in the diagram is a simple on off switch to deliver the built up charge to the patient or the resistor on the right 67 Group 14 Senior Design 1 vcc lt Figure 3 2 2 3 2 D Final Design Choice Now that a specific design has been chosen for the constant current source and a boost converter has been chosen the two can be linked together for a fully functioning neuromuscular stimulating circuit shown below At this point parts and specific values can also be decided lt lt vcc Figure 3 2 3 For the first part of the circuit the 555 timer must be properly timed so that it creates the current shunting necessary for proper function of the second part This is achieved by the following equations that determine the values of R1 R2 and C1 C2 can simply be 10uF as it just needs to be capacitively coupled to ground F In2 C R1 2 R2 1 Ta In2 R1 R2 C T In2 R2 C With these three equations it can readily be found that the following values give a frequency of 75Hz with an 87 duty cycle R1 300kQ R2 50kQ C1 47nF 68 Group 14 Senior Design 1 These numbers can be tweaked to individually tune each parameter of the above equations Because the MOSFET Q1 is assumed to have ideal characteristics and the timer is assumed to not sync any current the resistor R4 must be inserted to siphon off excess charge that could possibly cause a false signal R12
84. h a material that can store electrical charge so when you touch the screen that charge that is on that surface gets transferred to your body and the location at which the touch occurred loses some charge and that location gets sent to the 40 Group 14 Senior Design 1 device and the touch is registered That is the basic principle of how capacitive screens work Resistive touch screens on the other hand work a little different the screen is made up of a normal glass panel and this panel is coated with three layers a conductive and resistive layer and these two layers are covered by a third scratch resistant layer When you press on the screen the conductive and resistive layers touch each other and an electrical field is created giving out a charge This charge is then registered and the point of contact is sent to the display driver for processing Now that the basic operation principles are understood one can look at the pros and cons of each display technology to the related project and make proper decisions Capacitive PROS CONS Very sensitive to touch More expensive Good visibility in sunlight Only works with finger touches Multi finger touch support Very fragile Not prone to dust particles Table 2 5 1 Pros and Cons for Capacitive LCD Displays Resistive PROS CONS Mature and reliable technology Not as accurate as capacitive Easy to use can use hard objects e g pen nails Low b
85. h a current that is usually about 20 to 25 above that necessary for a maximal response This electrical stimulus is said to be supramaximal and can be reached with a current of usually 50 60 mA in most patients during anesthesia Since nerve stimulation can be painful this technique should only be performed on the anesthetized patient During recovery on the other hand the patient may be awake enough to experience the discomfort therefore some researchers advocate stimulation with submaximal 12 Group 14 Senior Design 1 current during recovery Submaximal stimulation is current between 10 mA and 30 mA depending on the stimulated nerve It is much less painful and better tolerated on an awake patient However testing has shown that submaximal current is much less accurate and gives a very widespread range 900 Plateau ea l 750 4 675 Supramaximal stimulation 30mA fa 600 525 3 450 375 300 225 150 75 Threshold to 20 30 40 50 6 amp 0 Current mA Figure 2 2 2 Displays the plateau effect after supramaximal stimulation has been reached usually at about 30 mA picture from book 2 2 B Monitoring Sites An ideal stimulation site is one that is easily accessible in the operating room and where the corresponding neuromuscular response can be identified clearly and unmistakably One caution is to avoid any direct muscle stimulation positioning is a very important factor in proper stimulation of the respective motor ne
86. h is shown connected from Pin 1 to Vpp A second 100 nF capacitor connected from Pin 2 to Pin 3 is used to bypass the internal regulator The functions threshold and the timing of 95 Group 14 Senior Design 1 the interrupt pin INT1 and INT2 are user programmable through the I C interface The Vpop power supply connection can range from 1 95V to 3 6V Connected to Pin 7 is the I C serial data and to Pin 8 is the I C serial clock Figure Pin connections for the MPL3115A2 pressure sensor Below is the table of the functions for each pin shown above Then a figure of the MPL3115A2 circuit board Pressure Interrupt 2 Pressure Interrupt 1 IC Serial Data I C Serial Clock Figure Pin descriptions for the MPL3115A2 pressure sensor 96 Group 14 Senior Design 1 MPL3115A2 circuit board 4 3 B FlexiForce Sensors The following is a recommended way to integrate the FlexiForce sensor into an application In this case it is driven by a 5V DC excitation voltage It then produces an analog output using an inverting operational amplifier arrangement that is based on the sensor resistance and a fixed reference resistance Rr Once this measurement is found an alalog to digital converter can be used to change this voltage to a digital output In this circuit the sensitivity of the sensor can be adjusted in one of two ways by changing the reference resistance Rp and or the drive voltage VT The sensor can become le
87. hapter 7 Administrative Content 7 1 Budget As with any good idea there is always a price tag that comes along with it The aim of the group is to keep this design cost effective there will not be any skimping on the sensors or any other part for that matter just to save a few dollars here and there The table below shows the estimated amount of money that the group is expecting to spend on this project in order to obtain a product that is completely functional When this budget was created the group did it s to try and overshoot as much as we could in estimating how many of what parts would be needed just in case there was something that broke or needed to be replaced with a different part because the one that is on the table is not going to work out anymore This table is just a ballpark figure as to how much we can expect to spend in the course of the project and to the groups dismay it has already increased from what was initially put in the document that was submitted in September The group is planning on applying to the TI competition which will allow the group to get 200 in credit that can be spent on any parts that need to be acquired through TI This does not mean that the group is not going to try and see if TI will give extra samples to us It never hurts to try The rest of the budget is being supplied by Dr Looke He has approved a budget of just under 800 so there should be little out of pocket expenses for the members of the grou
88. hat anesthetics appear to shut off the brain from external stimuli nerve impulses are not generated the brain becomes unconscious does not store memories does not register pain impulses from other areas of the body and does not control involuntary reflexes In recent studies scientists have cloned forms of receptors to gain knowledge of the proteins involved in neuronal excitability Despite decades of research however the efforts to explain the mechanism of how general anesthetics produce a loss of consciousness still remains a mystery Group 14 Senior Design 1 2 1 G Side Effects In all patients including the healthiest there can be large differences in the sensitivity that they have to the neuromuscular blocking drugs This sensitivity can be increased by disease hypothermia or a disturbed acid balance and altered liver and kidney functions The patient s response to these drugs is unpredictable The correct amount of the drug can be administered yet it can be an overdose or an under dose depending on the patient The lack of predictability of the effectiveness of these anesthetics for the different patients is why the patients need to be monitored so closely There can be large differences in the way the drug reacts even in the most ideal patients This is why there is such a major necessity for a device of this nature The most common and worst side effect of an overdose of the muscle relaxant drugs is a post operative respiratory
89. hat each function will do what is being passed in into it These functions are subject to change as the prototype and testing phase of the project is underway Function Name Function Description Function will pull sensor data and return it Function will format the sensor data Double formatSensorData some double that it received from the above function to prepare for send of Functions sends the sensor data to the wireless display to be graphed Table 4 5 2 Outline of Function for the Wireless Display Double getSensorData sensor_output Void sendData sensor_data 101 Group 14 Senior Design 1 4 7 Coding The two coding subsection below will be mostly dealing with sensor control and pulse control to get accurate readings with the least amount of noise The main point of these functions is to synchronize the electric pulses with sensor polling This kind of synchronization will reduce the amount of noise and will eliminate unnecessary polling from the sensor when there is no pulse sent to the person s thumb So here is the basic idea of how it functions when the pulse is active and current is applied to stimulate the muscle the sensor data is pulled at the same time Going with this approach you make the device more robust and less error prone to inaccurate twitches 4 7 A Pulse Control Now that the synchronization of the sensor polling and pulse activation is in place let s look at some functions
90. he following with its associated pros and cons The first and simplest option would be to build a simple RC network to divide off what we don t need The first challenge with this design would be rectifying the AC power so that it can then be smoothed to a reasonable DC approximation and as this will need to be applied to the second circuit it will be discussed here The simplest manner in which AC rectification can be achieved would by applying the signal to a Diode Bridge shown below on opposite sides so that no matter the polarity of the power the current will always travel in the same direction This orientation is shown in the diagram with a resistor wired as a general load Figure 3 6 1 Stolen from HyperPhysics 83 Group 14 Senior Design 1 As you can see from the diagram above the diode bridge rectifies the signal but in no way makes it DC At this point we need to add a fairly large capacitor to smooth the ripple down to less than ten percent As an example given a twelve volt AC source a twenty percent ripple means that the lowest expected voltage after rectification will be 10 8V at any given moment Inductors can also be used for this purpose but it has been determined for this project that to get an effective inductor the size would once again become cumbersome Once a rough rectification has been managed calculations will need to be done to determine the appropriate resistor values Because this method creates entirely
91. he group in senior design Il when questions arise as to how to integrate the circuits into the design He also gave the group some ideas as to how to approach the devices design which helped give the group a shove in the right direction when it came to brainstorming and researching ideas for the sensor Group 14 Senior Design 1 Chapter 2 Research 2 1 Required Medical Knowledge When a patient is going into surgery there has to be an anesthetic administered in order for the surgery to be performed This medicine blocks the receptors for pain and memory in the human body It also stops the movement of involuntary muscles With this the doctor would have to place a breathing tube in the patient in order for the patient to be able to breathe while the operation is being performed This breathing tube is also needed in the recovery room because the neuro muscular blockade does not wear off quickly so as it is wearing off so it is necessary to have a device that can help measure how much of the medicine has worn off in order to figure out if it is okay to take the breathing tube out at the present time If the breathing tube is taken out too soon because the device that was measuring the response was wrong or not used then there could be complications where the patient is unable to breathe on their own so the tube has to be reinserted These complications could be avoided with the help of a device that measures the muscle response to see how awake the mu
92. he previous ones and cause less fear in the ability of them to harm the patients 2 3 A The Anesthesiologist as the Sensor In the operating rooms today Dr Looke and many other anesthesiologists like him use a simple device that provides current in one of three ways a twitch one pulse of current per second a steady current flow based off of how long the button is pressed and the train of four four pulses over a period of two seconds While the patient is awake the anesthesiologist applies two electrodes to the nerves that control the body part the eye thumb or the toe that they have access to and are able to monitor While the current is pulsing through the nerve the anesthesiologist has two choices they can either watch to see if there 28 Group 14 Senior Design 1 is a twitch or they can place their pointer and middle finger underneath the corresponding body part and see if they can feel the twitches that are being produced by the lack of anesthesia in the patient s body and they can decide from there whether or not to administer more 2 3 B Force Transducer In certain designs such as in US Patent No 4 848 359 New Developments in Clinical Monitoring of Neuromuscular Transmission Measuring the Mechanical response by J Viby Mogensen the muscle response is measured using a force transducer This response is created by the stimulation of the muscle by an electrical current that is applied through the nerve in a similar way
93. hese devices measure either the compound muscle action potential MAP or the evoked contractile response Today there are several ways that stimulation during neuromuscular monitoring can be measured However because the project is based around certain parameters given by Dr Looke the focus will be finding a sensor that can accurately and reliably read the measurement results from the TOF stimulation According to present day research it has been found that acceleromyography is most commonly used to measure TOF stimulation because of its numerous benefits Therefore in the following section several examples of other types of sensors will be shown but the focus will be sensors used in acceleromyography 3 1 A Piezoelectric Sensors Modern AMG based nerve stimulators use a piezoelectric wafer made of ceramic as the acceleration transducer Acceleration of the transducer produces an electrical charge Piezoelectric accelerometers rely on the piezoelectric effect of quartz or ceramic crystals to generate an electrical output that is proportional to applied acceleration The piezoelectric effect produces an opposed accumulation of charged particles on the crystal This charge is proportional to applied force or stress The technique of the piezoelectric monitor is based on the principle that stretching or bending a flexible piezoelectric film e g one attached to the thumb in response to nerve stimulation generates a voltage that is proportiona
94. iced that the output current levels dropped dramatically as the output voltage increased This should have come as no surprise integrated circuits are good for a lot of things but when it comes to power an analog circuit can usually handle much higher wattages with significantly cheaper parts After a second thorough search which returned no better results it was decided that if a boost converter was intended to be used the circuit would need to be hand built Returning to the internet it was found that by using transformers or inductors a relatively simple circuit could be built that would create very high voltages in a relatively quick manner By referencing multiple designs a modified and slightly simpler 555 based boost converter was created by the team Figure 3 2 2 shown below This circuit takes the positive rail and runs it through a large inductor a MOSFET and a small high wattage resistor for a period of time Once a reasonable magnetic field has built up the MOSFET is turned off and the current in the inductor is shunted through the diode and in to the capacitor This happens because of the basic principle of inductors their inability to instantaneously change current Using that principle and using a capacitor to store the shunted current a voltage ten times the rail can be created within seconds depending on the switching speed The frequency of this switching will need to be determined through extensive trials but as of now a good
95. igital sensor systems data loggers and other general purpose applications that require very low power usage 35 Group 14 Senior Design 1 PROS CONS Relatively small in size Higher power consumption than other chips Samples available Not enough internal ADC channels Fast wake up in 3 5us Not many open source libraries 128KB of flash memory 63 I O pins 10240 Bytes of SRAM Three channel DMA controller Temperature sensor Table 2 4 3 Pros and Cons for Tl MSP430F5329 Microcontroller Q QO E EE EEEE Baansse COOOSLE aqeoeaa PPTI ER aaaa aa Ooo ag BSRRE pe aicaaaa 1 O P6 5 CB5 A5 P7 2 CB10 A14 O 7 P7 3 CB11 A15 O 8 P5 0 A8 VREF VeREF C 9 P5 1 A9 VREF VeREF AvVCC1 O n P5 4 XIN O 12 PS5 5 XOUT O 13 AVSS1 C 14 oyga e MSP430F53291PN MSP430F5327IPN MSP430F5325IPN ANARAN DITO e RFRERRER P7 7 TBOCLK MCLK P7 6 TB0 4 P7 5 TB0 3 P7 4 TB0 2 P5 7 TB0 1 P5 6 TB0 0 P4 7 PM_NONE P4 6 PM_NONE P4 5 PM_UCA1RXD PM_UCA1SOMI P4 4 PM_UCA1TXD PM_UCA1SIMO P4 3 PM_UCB1CLK PM_UCA1STE J P4 2 PM_UCB1SOMI PM_UCB1SCL P4 1 PM_UCB1SIMO PM_UCB1SDA P4 0 PM_UCB1STE PM_UCA1CLK P3 7 TBOOUTH SVMOUT 0 5 P3 4 UCAORXD UCADSOMI P2 6 RTCCLK DMAEO C 35 Figure 2 4 3 MSP430F5329 Pin Configuration Courtesy of Texas Instruments 2 4 B Microcontroller w Transceiver AlTmega128RFA1 This Atmega chip offers a unique
96. ign Senior design Il is going to require trial and error on the part of the team This is why the group is trying to lead ample time for the testing stages in order to make sure the finish product is something that the group is proud of 120 Group 14 Senior Design 1 Group 14 would like to thank Dr Samuel Richie Dr Thomas Looke and Dr Zhihua Qu for their support and the opportunity to expand our engineering learning experience with this invigorating project The group looks forward to the continued meetings with these men who have great knowledge in their particular fields each one able to assist our growth in learning with this project in different ways 121 Group 14 Senior Design 1 Appendices Appendix B Reference Works Cited Added Required Medical Knowledge http Awww encyclopedia com topic Anesthetics aspx 1 http www surgeryencyclopedia com A Ce Anesthesia General html b http emedicine medscape com article 1271543 overview showall faculty smu edu jouynak GeneralAnesthetics powerpoint ppt Validation of muscle relaxation measurements PDF located in Dropbox gt Articles gt Printed out Neuromuscular monitoring during Anesthesia http faculty washington edu ramaiahr Chapter 39 Neuromuscular Monitoring p df Book Ch 47 Neuromuscular Monitoring PDF located in Dropbox Articles Printed out Monitoring of Neuromuscular Junction PDF located in Dropbox gt Articles gt Printed out http medind nic in ia
97. ily be able to work though as this setup has a tendency to draw a lot of current for a significant amount of time This is why paying attention to the battery is necessary if the battery begins to get hot the indicates that a significant current is being drawn and that there exists the possibility that the switching time on the 555 might need to be adjusted 104 Group 14 Senior Design 1 If the multimeter does not find any components that have shorted out or failed in some manner and the battery doesn t meltdown in five seconds then it would be safe to move to a slightly higher voltage source 24V is suggested When connected to this new source rerun the same voltage tests again to ensure that everything still works Once again check the 555 s output first and then the voltage across the bleeder resistor If these both roughly represent what is expected then we can now add the capacitor back into the circuit and restart testing with the nine volt battery This time an oscilloscope or a second multimeter with clipping leads might be useful The 555 output along with the voltage build up in the capacitor will need to be watched It is important to check the rise time on the capacitor to make sure it is fast enough to be useful with the tetanic pulse since that is the fastest Assuming that nothing has gone critically wrong it is time to move to the constant current circuit If there are errors unfortunately they must be fixed with more trial a
98. interfacing would be done This interfacing schematic is very similar to what the design requires and will be used in this project Although some of these connections are not necessary the important part of this diagram is the antenna interfacing which is a blue circle all the way to the left of the diagram 100 Group 14 Senior Design 1 R4 NM AREF STK m AREF Place close to Ul pin59 i VTG INT x t AAN E Na 1 BLM21AG102SN10 Es ct tu EE ARE et S Zz PFVADC1 gt Z 3 2 S os PF2IADC2DIG2 3 PE2 XCKOJAINO 8 pE2 F W i S PE Pravapcamica E pesrxpo 4L PEI PFS PEORXDO PCINTS 48 a ED PFE Biy 7 VTG_INT z PB7 OCOA OC1C PCINT 4 a GND 4 ATmega128RFA1 PB6 OC1BIPCINT6 PEF H GND O ay 9 Tat VSS PESIMISO PDOIPCINTS 32 PE mea ca PeanioaorPen2 Fe ese OUT PBO SSN PCINTO 36 Peo Ri Par NSS Ts BND vi INT 100k PGZ ii or ae CLK 35a8 Zz s sacs 83 3 3 3 s efeit 3 cro 5 3 S38 Ss R2 GND 9O00 gt oa 100k aaan aa GI BS a ante e i 22 et 24 26 POS POG 31 PD 32 ho RS NM c12 os Pag m 22p 22p t PG4 ui I a Figure 4 5 1 Atmega128RFA1 to Antenna Interfacing Courtesy of Atmel 4 5 A Programming To complete the design and to have a working build the wireless section of this document just needs functions that will control what kind of data is sent though the wireless RF module The table below briefly described w
99. ired as a floating ground to an inverter These inverters are wired from the output of the previous to the input of the next By doing this you get double the voltage of the capacitor before it And this is where the downfall of the handmade charge pump comes in a relatively large capacitor must be used at each junction to handle the necessary charge needed for the delivery current and several stages of doubling are needed to get to a reasonable voltage level On their own either of these 66 Group 14 Senior Design 1 issues can be overcome but together they create an issue with the size of the capacitors and the space needed to hold all of them Because this device requires zero unique parts it can be built and tested but the team s judgment on its feasibility is a unanimous no So far a bought or built charge pump has been ruled out as well as the direct line driving of the current source This leaves the last choice of a boost convert to be investigated The decision was initially to simply buy a high voltage boost converter instead of designing one This decision was made because of the assumed complexity of the device and the hope that a highly efficient model could be found at a relatively inexpensive price At this point the team once again turned to TI among other companies to find the converter and was shortly presented with a major problem Though many boost converters of all input and output combinations could be found it was not
100. is it is fully certified This device also supports EDR and has a high performance PCB trace antenna type As far the data connection interfaces this chip supports UART and USB data connections Some of the important features of this device will be listed below in a pros and cons table to highlight them PROS CONS Embedded Bluetooth Stack Relatively Large 20 x 13 mm Bluetooth 2 1 EDR No Built in Antenna Error Correction Weak Wall Penetration 128 bit AES Encryption Relatively Expensive 15 USD Auto discovery pairing No Host Processor Required Backwards compatible with 2 0 and 1 1 Simple Setup Table 2 6 3 Pros and Cons for RN42 Bluetooth Module from Microchip SPBT2632C2A This STMicroelectronics Bluetooth module is from a class of micro sized modules This device support Bluetooth v3 0 2 1 and EDR and is also backwards compatible with previous versions of Bluetooth This is a class 2 module with a maximum data rate of 1 5Mbps which more than enough for the 49 Group 14 Senior Design 1 scope of this project This device is FCC and Bluetooth qualified This chip runs on ST micro Cortex M3 microprocessor with a frequency of up to 72MHz Below is a high level block diagram showing the major modules of this chip and highlighting some important features that make up this Bluetooth module Battery or Supply Figure 2 6 3 Block Diagram of STBT2632C2A Courtesy of STMicroelectronics
101. ise knowledge SPI Wi Fi PWR_EN Figure 2 6 1 Block Diagram for TiWi SL Module Courtesy of LS Research PROS CONS Embedded Software for Drivers Chip is Large 21 x 14 mm FCC Certified Complex Design Sample Application Available Cluttered 2 4GHz Band SPI Host Interface Fast Transfer Rate Not Needed 89dBM Rx Sensitivity User API Guide Table 2 6 1 Pros and Cons for TiWi SL 802 11 Module RN171 This WiFi is built by Microchip a very popular chip maker amongst hobbyists and even professional electronics manufacturers This chip is a full featured 802 11 b g WiFi module for ultra low powered embedded applications This device like many other similar device supports TCP IP protocol stack The 47 Group 14 Senior Design 1 device is interfaced with UART and SPI slave and includes a real time clock auto sleep auto wakeup modes and WEP WPA WPA2 authentication Below is the block diagram for the device that highlights the important features of this module Trace for PCB Antenna 128 KB 32 Bit RAM CPU 2 4 GHz be TXIRX 802 11 bg MACIPHY WAN gH Z Crypto Pwr accelerator ADC Mgmt Figure 2 6 2 RN171 Block Diagram Courtesy of Microchip PROS CONS Preloaded Firmware Chip is Large 27 x 18 x 3 mm FCC Certified No Built in Antenna 38 mA RX Power Usage Cluttered 2 4GHz Band 8Mbit Flash and 128KB
102. ith increasing degrees of blockade the twitches in the train of four slowly fade starting with the fourth twitch T4 and one by one eventually disappear As muscle contractions reappear they do so in the reverse order of their disappearance i e the first response in the series of four is able to be detected first then the second third and fourth There are several advantages with TOF stimulation which makes it a frequent choice in daily clinical use It can be applied to a patient at any time during the neuromuscular block and can still provide quantification of depth of block without the need for control measurement or a reference value before relaxant administration Due to the correlation between the depth of block with the number of responses frees the clinician from having to use a recording device to calculate the TOF ratio The relatively low frequency offers the capability to evaluate the response manually or visibly It may be delivered at submaximal current Also TOF stimulation unlike tetanic stimulation does not generally affect the degree of neuromuscular blockade 17 05s Group 14 Senior Design 1 Twitch tT 14 Tt m T t Injection of NMBA Onset of action monitoring T O 4 Intraoperative Recovery Figure 2 2 7 Pattern of electrical stimulation and evoked muscle response to TOF nerve stimulation before and after injection of non depolarizing neuromuscular blocking drugs arrow picture f
103. ive than the TOF in the manual or visual assessment of residual blockade DBS consists of two short bursts of 50 Hz tetanic stimulation pulses separated by a 750 msec interval The duration of each individual square wave impulse in the burst is 0 2 msec In the DBS3 3 mode which is considered to be the most popular there are three impulses in each of the two bursts However another choice is the DBS3 2 mode which has three impulses in the first burst but only two individual impulses in the second burst The response in the DBS3 3 mode in a non paralyzed muscle is two short muscle contractions of equal strength When the muscle has been partly paralyzed the response of the second muscle contraction will be weaker than the first and will show fade There 20 Group 14 Senior Design 1 is a close correlation between the TOF ratio and the DBS3 3 ratio when measured mechanically ee ay f H w a A 20 msec 750 msec WA A OLA A TOF DBS ratios 1 0 Control Recovery Stimulation Figure 2 2 10 comparing the stimulation and response of TOF and DBS3 3 2 2 C Measuring Methods There are different methods that can be used to objectively measure the depth of neuromuscular blockade in a patient The major ones include mechanomyography MMG electromyography EMG acceleromyography AMG kinemyography and phonomyography PMG These methods measure either the compound muscle action potential or
104. l to the amount of stretching or bending According to Newton s second law of motion force equals mass times acceleration F mxa At constant mass the acceleration measured and the voltage thereby generated can be used to derive the force of the stimulated muscle Thus acceleromyography can be performed on all muscles whose movement or acceleration is easily measured after electrical stimulation of its innervating nerve There are two types of piezoelectric sensors high impedance and low impedance Low impedance uses the same type of piezoelectric sensing element as the high impedance units but they also have a miniaturized built in charge to 53 Group 14 Senior Design 1 voltage converter Additionally they require an external power supply coupler to energize the electronics and decouple the succeeding DC bias voltage from the output signal Therefore with these features low impedance piezoelectric sensors will be the choice of use for the project Pros Used in acceleromyography AMG and kinemyography For acceleromyography measures the rate of angular acceleration of a skeletal muscle enervated by electrical stimulation of a peripheral nerve and gives an output current For kinemyography measures the deformation of a mechanosensor integrated in the piezoelectric element to generate the electrical current Nonisometric measurement less stringent requirements i e does not require patient cooperation rigid restraint o
105. lectrodes The stimulus electrodes conduct the current selected on the nerve stimulator against the skin resistance to the underlying tissue structures They are crucially important in the quality of neuromuscular monitoring because they help ensure that the target motor nerve is actually stimulated The electrode type can play an important factor in proper stimulation of the respective motor nerve 24 Group 14 Senior Design 1 Electrodes come in a few different varieties but the basis is the same An ECG electrode is usually composed of a small metal plate surrounded by an adhesive pad which is coated with conducting gel to help transmit the electrical signal The wire that connects the ECG electrode to the current source is clipped to the back of the electrode Some electrodes are reusable and other types are intended to be disposable after a single use For our project we will use ECG type electrodes of the silver silver chloride variety or Ag AgCl Reusable Ag AgCl Electrodes Pros Cons Permanently connected to leads which offer quick ease of access Reusable electrodes offer no waste and less expense to the consumers who are using them They do not have adhesive disks included which are required before use Therefore anesthetists have to take the time to add these on each time before use They do not come with recording gel which is needed before each use It takes time to clean them each time Possible chance of elec
106. levels Because the ground of the DC side of the circuit is relative to the common there exists a dinstinct possibility that this is not earth gt ground Any component that expects earth ground can be wired directly to the earth ground of the AC socket The 3V3 design of the circuit will attempt to gt eliminate the need for a true earth ground instead leaving it for emergency grounding purposes 3V3Reg Putting these pieces together in a single circuit diagram may help alleviate any confusion that may have developed 1N1200C 2 D3 ADI iE MA L1 DC gt I lt gt gt ollie pe Mae ict 820HH pa oie 3 5 Suom atter Ti J2 HN A v1 EE p g gt 120 Vrms 2 60 Hz 25 AMP HDR2X 0 4 3 Design for the Sensors 4 3 A Pressure Sensors Group 14 Senior Design 1 MPL115A by Freescale With the SPI interface MPL115A operates as a half duplex 4 wire SPI slave capable of bus speeds up to 8 Mb sec Freescale offers a sample eval board in SPI called the KITMPL115A1SPI Below is a simple PCB board with sensor parts associated pullup resistors and decoupling capacitors already soldered onboard This provides a quick sample tool to run evaluations of the small device given its land grid array LGA As able to be seen the pins for shutdown serial clock input serial data input serial data output and chip select line will be connected to the microco
107. lization guidelines that are set for the operating rooms All surfaces or devices that have come into immediate contact with the patient have to either be disposed of or cleaned with an approved hospital grade disinfectant These measures are in place to keep the cross contamination from patient to patient to a minimum so that the spread of diseases is not going from one patient to another This is why the electrodes and the sensor have to be given careful consideration when the group looked at them The electrodes need to be cheap enough that they are able to be thrown away when they are done Now they cannot be so cheap that they do not allow the current to pass from the current supply to the nerve that is being stimulated for the reaction The reason that these need to be discarded is because there is not a viable way to put a protective layer between the skin and the electrode that will also allow the current to pass This additional layer would either add additional 86 Group 14 Senior Design 1 noise to the system that would be impossible to get rid of when the group is trying to program the output display The sensor also has to come in contact with the skin This is why looking for a cheaper sensor is one of the group s first priorities If not then the sensor would have to be cleaned and sterilized after each time it was used If that is unable to work than the group will have to create some kind of a protective covering for the part o
108. look at this device in more detail in case the scope of the project changes and the built in microcontroller comes in useful The next step in the design step is to look at the chip s pin configurations and their descriptions Texas Instruments provides a very detailed diagram Figure 3 4 1 and table Table 3 4 1 in their specification sheet that explains everything very clearly P2_4XOSC32K_Q1 DCOUPL DVDD1 f s x N 8 oO x 5 N a AVDDE at DGND_USB 7 RBIAS usB P USB_N DVDD_USB 77 AVDD4 TI AVDD1 27 _ AVDD2 P1_5 RF_N P14 Z RF_P ZI AVDD3S XOSC_Q2 xOSC_Q1 ZI AVDDS P1_3 P12 P11 9 ON OHe UNa PETE a SR LOY ee a ele le GE Uh la le a ax O y m os DVDD2 P1_0 i rr on w ce Figure 3 4 1 CC2531 Pin Configuration Courtesy of Texas Instruments Now that the pin configuration for this device is known it is proper to look at the pin descriptions and their uses See Table 3 4 1 Below 75 Group 14 Senior Design 1 PIN NAME PIN DESCRIPTION USED AVDD1 6 2 V 3 6 V analog power supply connection Yes DCOUPL 1 8 V digital power supply decoupling Yes DGND_USB USB Ground Yes DVDD1 amp 2 2 V 3 6 V digital power supply connection Yes DVDD_USB 3 3V USB power supply connection Yes GND Ground pad must be connected to a solid Yes ground plane PO_0 7 Digital I O Ports 0 1 through 0 7 Yes
109. m is occupied by the patient as long as the procedure takes as well as the time it takes for the patient to wake up when the anesthetic wears off Therefore it is in the anesthesiologist s best interest to keep the patient as close to the edge of alertness as possible so they will be able to wake the patient up as soon as 10 Group 14 Senior Design 1 possible If the patient is too far past that edge then there is no other option for the anesthesiologist but to wait for a twitch to become apparent again 2 2 Biomedical Engineering Background Neuromuscular blocking agents NMBAs are widely used in anesthesia practice As a result researchers created neuromuscular junction NMJ monitors to observe their effects in clinical anesthesiology practice Traditionally the degree of neuromuscular blockade during and after anesthesia is evaluated with clinical criteria alone Recommendation has been made in recent years however for patients receiving NMBAs to have the application of neuromuscular monitoring throughout their medical procedure One reason is because of the variable individual response and sensitivity to muscle relaxants In awake patients muscle power and feeling can be evaluated by voluntary tests but during anesthesia and recovery from anesthesia this is not possible To precisely test the degree of neuromuscular blockade during anesthesia the response of muscle to nerve stimulation should be assessed The other big reason for u
110. nd describe the use according to the request for permission explained below g Newhaven International Group 14 Senior Design 1 From Atif Khan lt nhtech newhavendisplay com gt Subject RE Message from Newhaven Display International Inc To Me lt ce seriy knights ucf edu gt Cc customerservice newhavendisplay com Hi Sergey You may use our NHD 4 3 480272MF 22 controller board s image and part number in your documentation for reference Sincerely Atif Khan Engineering Newhaven Display International Inc www newhavendisplay com 2511 Technology Drive Suite 101 Elgin IL 60124 Phone 847 844 8795 Fax 847 844 8796 Original Message From Sergey Cheban mailto customerservice newhavendisplay com Sent Tuesday December 64 2012 8 44 PM To nhtech newhavendisplay com Subject Message from Newhaven Display International Inc From Sergey Cheban Email ce seriy knights ucf edu Hi I am a student at University of Central Florida We are working on our senior design project and will most likely use your graphics controller board for one of your 4 3 inch TFT displays NHD amp 8208 4 3 amp 8208 480272MF amp 8208 22 We are asking for your permission to use the image of the controller board on the main product page in our design document Please get back to me as soon as you can Thanks Sergey Cheban h Microchip Educational and Non Profit Use of Copyrighted Material If you use
111. nd more errors 5 3 Constant Current Circuitry For this circuit due to its simplicity the test is fairly straightforward hook it up to power with a potentiometer in place of the skin contact and vary the resistance reasonably The input voltage here can be whatever is high enough to be read with a multimeter so as long as the resistance are not excessively large it should work with a nine volt The idea with this test is to make sure it functions properly not to test it to its limits The components should be chosen with a factor of safety of at least two so that they can handle whatever the full circuit can throw at them 5 4 Sensors Once all of the sensors are acquired at the beginning of the semester the group will test each individual sensor to decide which sensor would be the best for the task at hand In order to test the sensor a volunteer from the group will apply the sensor to their hand and have them without connecting the current source create the motion of the twitch for the thumb The baseline for the force sensor will be created by placing a small weight on top of it and using the force calculations that are so well known This way the group will be able to see if it will read out the correct value before moving on to see if it will measure the force that is applied by the thumb twitching Looking at the datasheet the group can see the required voltage that correlates to the force 105 Group 14 Senior Design 1 This w
112. ns for TFT Display without Controller 2 5 D Display w built in Controller ITDB02 4 3 This ltead Studio display module is 4 3 inches measured diagonally with 65K colors and is 272 x 480 pixels in resolution This LCD is controlled by Solomon SSD1963 graphics controller This display also includes a touch screen and an SD card socket for extended memory if needed The connection is a parallel 16 bit data interface with 4 wire control interface This particular display is supported by the open source UTFT library that has many code examples and resources to interface and setup your display Below is the layout for the pin connection hardware interface 45 Group 14 Senior Design 1 ep O o Aaa egga Sa E EE E v 7 2 9 ES Be ee 8288 8888 R g wv e amp b gt 6o amp amp L J y a i A 4 b 3 E fw y eeabectiviititerss S8 ee ecccccccccccococees eeseeeeoeooeo eee eoeeeese Figure 2 5 4 ITDB02 4 3 TFT Pin Configuration Courtesy of Itead Studio PROS CONS SD Card Socket Only 65K Colors Built in Controller Limited Documentation Supported by UTFT Library 4 Wire Control Interface Table 2 5 4 Pros and Cons for TFT Display w Controller 2 6 Wireless Having a wireless display for this project would be an ideal solution This lets the person view the data from wherever they from different positions and much more frequently The government of course has many regulations wh
113. nt e Supports 4 Wire 5 Wire and 8 Wire Analog Resistive Displays e UART 9600 Baud Rate Communication AR1000 Series QFN Figure 2 5 3 Microchip AR1011 Pin Configuration Courtesy of Microchip Although this touch screen controller can simplify the control of touch input from the display unit this will raise the price of the project and potentially increase the 44 Group 14 Senior Design 1 overall size of the PCB board and the device as a whole Considering these drawbacks this controller will be used as the budget allows 2 5 C TFT Displays NHD 4 3 480272EF ATXL T This Newhaven TFT color LCD with Touchscreen is a 4 3 inches in size measured diagonally The touch panel of this display is a 4 wire resistive panel The resolution of this display is 480 x 272 pixels with a parallel 24 bit RGB interface and supports up to 16 7 million colors This display comes with no built in graphic controller but it does come with a built in driver As far safety is concerned this display is lead free and RoHS compliant The supply voltage Vdd for this display ranges from 3 0V to 3 6V and typically runs at 3 3V The backlight requires a maximum of 22V and a current of 20mA maximum with typical current of 32mA PROS CONS SD Card Socket 24 bit Interface Built in Controller Available Controller Board Up to 16 5 Million Colors Requires 5V of Supply Voltage 4 Wire Control Interface Table 2 5 3 Pros and Co
114. nt voltages Because a DC source is being used it may be necessary to mentally compensate for that The point here is to make sure everything is working at lower voltages before plugging in to 110VAC Which as it happens is the next step if everything checks out from the previous two parts For this step a cautious person will find insulated gloves to wear on the first plug in as a safety precaution If something were to fail this would be the 103 Group 14 Senior Design 1 time to fail catastrophically If nothing appears to have failed upon energizing the circuit then it is time to retest the voltages with the multimeter This time all voltages should read near their expected values Near is critical here because all components will have tolerances that cannot be controlled by the end user but on the flip side of that coin all values should be well within the planned tolerances of the project If the case arises that a certain part is not acting as it should then the first step is to de energize the circuit and pull out the spec sheet of the device Referring to this sheet double check that all pins are connected properly and that nothing is left to unintentionally float or some other common problem Once the datasheets are re referenced any problem can usually be fixed If there appears to be no wiring issue it is possible that the component was DOA and needs to be replaced Upon replacing the part or fixing the issue the previous te
115. ntroller of the design The Vpop pin is for the power supply connection which can range from 2 375V to 5 5 V Connected to this node is a 1 uF capacitor that is connected to ground The maximum ratings of voltage for SHDN SCLK CS Din and Dour is from 0 3V to Vppt 0 3V Following the diagram is a table of the pin functions for the pressure sensor Lastly is the MPL115A1 SPI interface board or KITMPL115A1SPI u Microcontroller Figure MPL115A block diagram with pin outputs 94 Group 14 Senior Design 1 VDD Power Supply Connection VDD range is 2 375V to 5 5V External Capacitor Output decoupling capacitor for main intemal regulator Connect a 1 uF ceramic capacitor to ground Shutdown Connect to GND to disable the device When in shut down the part draws no more than 1 pA supply current and all communications pins CS SCLK DOUT DIN are high impedance Connect to VDD for normal operation o ee a s Figure table of pin descriptions for the MPL115A CAP cs KITMPL115A1SPI MPL115A1 SPI Interface Board MPL3115A2 by Freescale Freescale s Xtrinsic MPL3115A2 offers several features in its design This sensor offers an on board intelligence design with a flexible sampling rate up to 128 Hz The device power is supplied through the Vpp line shown at Pin 4 Power supply decoupling capacitors 100 nF ceramic plus 10 uF bulk or 10 uF ceramic should be placed as near as possible to pin 1 of the device whic
116. o electrodes the pack is able to be used on 50 patients Therefore the price for two electrodes or for one person is 0 76 Because disposable electrodes do not come with leads one must include the added expense for those as well With the EL500 series the BIOPAC Systems Inc website recommends the LEAD110 series electrode leads For best results use shielded leads with recording electrodes for minimal noise interference On the other hand the unshielded leads work best with ground or reference electrodes As listed one of each lead in the series is needed for each Biopotential amplifier module These lead types are LEAD110S W LEAD110S R and LEAD110 Budget Item Shielded Unshielded Color Price LEAD110S W Shielded White 39 LEAD110S R Shielded Red 39 LEAD110 Unshielded Black 15 Total Price of Leads 93 Another example that could be used is the EL500 series by BIOPAC Systems Inc They have been specially developed for peripheral nerve stimulation and recording for nerve conduction measurements The EL500 is an electrode pair that has a 4 1 cm spacing from center to center They are advantageous because not having the correct distance might alter the penetration depth of the stimulation current thus potentially preventing optimal stimulation of the target nerve The EL500 electrodes have foam backing of size 42mm x 82mm x 1 5mm 27 Group 14 Senior Design 1 n F v e v a A e amp
117. om Ch 47 Neuromuscular Monitoring PDF Train of Four TOF This is the most popular mode of stimulation for clinical monitoring of neuromuscular blockades The aim of this stimulation pattern was to deliver sound results even with a simple nerve stimulator and without the need for complicated objective monitoring Its introduction made it possible for the first time to obtain essential information about the relevant phases of neuromuscular blockade i e at the onset of action during surgical blockade and neuromuscular recovery in particular after administration of non depolarizing relaxants This mode involves four successive stimuli that stimulate the target motor nerve every 0 5 seconds The stimulation frequency here is thus 2 s or the equivalent of 2 Hz Just like any other stimulation if it is applied too frequently progressive fade of the motor response may indeed be observed To prevent this from appearing and falsifying the interpretation of the neuromuscular blockade a sufficiently large interval must be given between two TOF series to let the neuromuscular endplate regenerate If a minimum interval of 10 seconds is maintained between two successive TOF series this fading can be ruled out with certainty The ratio of the amplitude of the fourth response by the amplitude of the first response provides the TOF ratio Before the administration of muscle relaxants all four responses are ideally the same thus the TOF ratio should be 1 0 W
118. omplete design When comparing it to microcontrollers and FPGA can be treated as part of a microcontroller FPGAs allow you to perform many logic functions but if you need to perform any arithmetic or mathematical calculation communicate with other devices then you will need an MCU for that For this project in particular an FPGA board would be insufficient and would require more knowledge to run a microcontroller in an FPGA board Because FPGA boards are generally much slower and consume large amounts of power you would not use one for this kind of project Below are some of the reasons why research of FPGA boards was not pursued in detail for this project The Cons outweigh the Pros in this case PROS CONS Simple to use Slower than other MCUs Easy prototyping High power consumption Uses simple logic Limited in its functionality Can be used in many applications Large in size Table 2 4 6 Pros and Cons for an FPGA board 2 5 Wireless Display 2 5 A Capacitive vs Resistive For this project there is going to be a wireless display unit to graph the sensor data received from the thumb sensor In order to use a wireless display it is required to know what kind of display you are going to use the size of the display that will be optimal for this application At this time there two main types of displays right now capacitive and resistive Capacitive touchscreen display is made up of a glass panel that is coated wit
119. onABeginnersGuidetotheAtmelAV RAtmega32 aspx LCDs http yvampblog blogspot com 2009 08 resistive vs capacitive touch screens html http www geeetech com 2012 04 interface 3 2tft lcd module to arduino http www digikey com us en techzone microcontroller resources articles desiqni ng with tft displays html Group 14 Senior Design 1 Appendix C Permissions a Atmel permission pending F Send W Spelling 7 y Attach Security ind fg Save s From Sergey Cheban lt ce seriy ucf gmail com gt CE SERIY UCF X To a southeast atmel com L Subject Permission to used product schematics and diagrams _ AAA Il Mi Ilil a _ 1 2 Preformat Y Fixed Width Ban Hi I am a student at University of Central Florida Our group is working on a senior design project and would like to get your permission to used your schematics diagrams and material of that sort for the parts we will be using in our design document Please get back to me as soon as you can b Itead Studio permission pending Group 14 Senior Design 1 CONTACT US Contact Information Name Email Sergey Cheban ce seriy knights uchedu Telephone Comment Hi I am a student at University of Central Florida Our group is working on a senior design project and would like to get your permission to used your schematics diagrams and material of that sort for the parts we will be using in our
120. oo sensitive that they are picking up every tiny vibration that may be caused by someone bumping into the device and can cause false readouts This will help when the whole Paralytic Twitch Sensor is built so the group knows there will not be any false positives from bumps that may be a result from the actual atmosphere of the operating room 5 5 LCD The LCD unit will have to be tested early in the prototyping phase because any faults or errors could delay this project Testing the LCD will require an ad hock setup of the components before everything is in its final build state The main reason for testing the LCD is to see if graphing the sensor data on an XY plane is possible and if not what is preventing it from graphing First a single point check should be done to see it gets graphed properly on the screen then more points can be added gradually If a single point is not getting graphed then there is a potential that data is not transmitted to the display and in this case back tracing each part one by one to find the broken link In addition to all this a proper power measurement test should be done for the LCD to make sure it is getting the right amount of power and that power levels stay within the specified operating range If the above test fail and the LCD module is not displaying any data then the next step is to double check every pin connection and make sure that each pin is connected to the right data bus and it is getting the data from a
121. or an extra comma somewhere and the list goes on Here is a list of test scenarios in order of importance that can reveal problem or holes in programming 1 Check the syntax with 2 or more people 2 Look for simple logical mistakes in the for loops or in the if statements 3 Check the base case scenario using the value 4 Trace through the code using a blank piece of paper to catch errors Software testing for this project will be a very involved process and will include many scenarios that will not get covered in this design paper that s just the nature of coding During the prototyping phase many issues will arise on the spot and will have to be dealt right then and there If the code is correct and there is 108 Group 14 Senior Design 1 no errors found then there is a possibility that some of the hardware is failing or is just not mounted properly In addition to all of the above testing case one can t forget about using wrong values to see if the code catches that and throws any errors or even crashes Going through these kinds of tests will add more stability to the program and make it less error prone in the future Because software testing is so complex and involved there is thousands of testing cases that are possible and covering all of them is not possible The cases that were discussed above are the most critical testing cases for all coding programs and will cover most of the errors 5 9 Full Assembly 5 9 A Initial Power
122. p 116 Group 14 Senior Design 1 Initial Budget Part Quantity Price Comments PCB Board 150 Batteries 50 Microcontroller 125 Wiring 20 Display 140 Accelerometer 15 Not all of these sensors will Flexion Sensor 15 be used in the final product they are just being 7 2 Project Milestones Piezoelectric Sensor 15 purchased for testing The Force Meter 45 final price will only be based on using the Force Meter Display Housing 100 Electrodes 100 38 The final price per patient would be 0 76 knowing that each patient needs two Experimenter Board Tl 1 149 Bluetooth Evaluation Kit 99 Tl USB Debugging Interface 99 Tl Total 1 060 Figure 7 1 1 Depicted below are the projected project milestones for the Paralytic Twitch Sensor Device While the dates for the fall semester are accurate the spring semester milestones may change to fit the needs of the group s members The majority of senior design one was left to research There was a large portion of the engineering part of the design that needed to really be researched because the group is implementing different parts to the design that none of the members had a class on like the wireless Not only that but a major part of this project falls on the medical information that is necessary to know and understand in order for the device to be fully functional in the way that the group need
123. processed by an amplifier a rectifier and an electronic integrator and results display as the TOF ratio Data captured by electromyography show very good agreement with those obtained by mechanomyographic methods for assessing the neuromuscular blockade EMG proves beneficial for practical application because it does not require complete immobilization or a constant preload of the selected test muscle instead measurements can be taken with the hand in any position This feature makes it extremely useful for everyday clinical use where operating rooms are small and crowded with medical staff and equipment In addition an evoked electromyogram can also be recorded on muscles like the diaphragm that are not monitorable by mechanomography Overall electromyography is far less complicated to perform as well However evoked EMG does entail some difficulties The results of recordings are not always reliable One reason is because inadequate pick of the compound EMG signal may result if there is 22 Group 14 Senior Design 1 improper placement of the electrodes In addition recording electrodes may pick up an electrical signal even though neuromuscular transmission is completely blocked as a result of direct muscle stimulation Technical problems which can arise overtime with EMG include drift over time the EMG potential does not return to control levels failure to descent completely in fully relaxed muscles and interference with other el
124. pto 16 MIPS Throughput at 16MHz and ultra low 1 8V e 128KB of In System Self Programmable Flash e On chip Debug Support with the JTAG Interface e 38 Programmable I O Lines e Fully Integrated RF Transceiver as an SoC Solution e 16KB of Internal SRAM Memory 70 Group 14 Senior Design 1 PIN NAME PIN DESCRIPTION USED EVDD External analog supply voltage Yes DEVDD External digital supply voltage Yes AVDD Regulated analog supply voltage internally generated DVDD Regulated digital supply voltage internally Yes generated DVSS Digital ground Yes AVSS Analog ground PB7 __PBO 8 bit bidirectional I O port with internal pull up Voc resistors PD7 PDO 8 bit bidirectional I O port with internal pull up Vas resistors PE7 _PEO 8 bit bidirectional I O port with internal pull up resistors PF7 _PFO 8 bit bidirectional I O port with internal pull up resistors PG5 PG0 6 bit bidirectional I O port with internal pull up Yes resistors Dedicated ground pin for the bi directional gee ee differential RF I O port LeS Dedicated ground pin for the bi directional o differential RF I O port Positive terminal for the bi directional differential RF RFP Yes I O port RFN Negative terminal for the bi directional differential RF We I O port RSTN Reset input Yes RSTON Reset output Yes XTAL4 Input to the inverting 16MHz crystal oscillator Yes amplifier X
125. r Looke approached the senior design class with his proposal for integrating a sensor to measure the force of the patient s finger toe or eyelid instead of having him either hold his hand up to the twitching body part or just merely watching to see if a twitch resulted from the electrical current pulsing through the nerves His idea got our group thinking and thus came the initial brain waves that started the building of the Paralytic Twitch Sensor Naturally using a sensor to monitor this paralytic twitch makes sense because it frees up space around the operating table for the surgeon and his staff to work but this will also make checking while the patient is waking from his her paralytic state somewhat easier and would allow for more anesthesiologists to check before removing the breathing tubes or other devices that were needed to support the life of the patient while they underwent surgery The Paralytic Twitch Sensor is designed with the intention of being able to set up within the operating room and be the helping hands of the anesthesiologist The device will apply a current source through electrodes placed above the nerves that correspond to the muscle that we are trying to stimulate If the muscle responds then the part of the body that it controls will twitch The sensor will measure the force exerted by the resulting twitch to see how much the paralytic drug has an effect on the body The sensor will be integrated with a circuit that is
126. r devices The power cord used on the device will not be a special or custom piece it will be a standard computer power cord This means that in the even the original cable is lost another can be used in its place so long as the plugs match on the device The current rating on the cable will need to be at least 15 amps to be able to safely handle the draw from the device The electrodes used are likewise also currently generic If the provided electrodes are too big or have run out a number of other options exist to replace them The initial suggestion would be to use ECG pads as a replacement because they operate closely to how the stimulators work The difference is pads will require the baseline to be modified for the patient but this should impose no extra problems One precaution that is suggested when using nonissue electrodes is the need to clean the area that the electrodes will be applied to This is necessary in the event that the electrodes have unknown built in resistances If the leads for the stimulator are lost and new ones are needed a simple replacement will be temporarily using alligator clips These are available everywhere today and there may even be a stock available in the hospital All other replacements or fixed should be left to those who know what they re doing not hospital staff as the possibility of causing grievous harm to the staff or patient increases exponentially 115 Group 14 Senior Design 1 C
127. r than other chips that were researched it has many open source libraries and examples of code that it will simplify the design in future phases of product development Below will be a highlight list of important features for this design For a detailed specifications and features for this MCU refer to section 2 4 A of this document Below is a table provided by Microchip that lists many important features of this device that will help decide on the final choice for the project and give a quick overview of how the chip is structured 72 Group 14 Senior Design 1 PIGZaFIEAGAROG PICZAFJ120GA306 Operating Frequency DC 32 MHz Sa Oooo o a o o E Program Memory instructions g D Interrupt Sources soft vectors 65 61 4 NMI traps O Ports Total VO Pins Remappable Pins Timers Total Number 16 bit 32 Bit from paired 16 bit timers nput Capture Channels Output Compare PWM Channels nput Change Notification Interrupt Serial Communications UART SPI 3 wire 4 wire ro Digital Signal Modulator Parallel Communications EPMP PSP JTAG Boundary Scan 12 10 Bit Analog to Digital Converter Ports B C D E F G 30 29 I O 1 Input only lt amp lt Analog Comparators CTMU Interface CD Controller available pixels JERE z amp c 5 T S g gt gt e 2 lt 240 30 SEG x 8 COM Core POR VoD POR VeatT POR BOR RESET Instruction MCLR WDT Illegal Opco
128. range 2 Hz to 10 000 Hz Pros e surface electrodes are convenient and are noninvasive Cons e good electrical contact is difficult to maintain at the skin electrode interface e Due to the small magnitude and short duration of the signals the system is difficult to isolate from electrical interference 3 5 Accelerometers e Measures acceleration of the stimulated peripheral nerve e Most commonly used are either single axis or triaxial accelerometers Pros e Convenient e They offer good results if mounted correctly e Triaxial accelerometers have proved to be an accurate monitoring tool for facial measurement Cons e device is both expensive and fragile e the single axis accelerometers measure movement in only one direction thus accelerometer mounting orientation is critical 62 Group 14 Senior Design 1 e Triaxial accelerometers however are too expensive with the added hardware and software e Triaxial acceleromets are more accurate but are not usually used on the ulnar nerve because other simpler ways are available e Patent 4 817 628 3 2 Constant Current Circuitry Now to move on to the heart of the project its shocking circuit this is the part that triggers the muscle to move so that its response can be measured Because of the importance of this circuit all avenues for its build will initially be considered passive active purchased and any other possibility for the optimally functioning device Before desc
129. re from http ionphysiology com ssep 20settings htm Similar results have been found for the posterior tibial nerve as for the ulnar nerve It is always a good choice for neuromuscular monitoring whenever the arms have to be immobilized or tucked in the body or access to them proves to be too much of an inconvenience One big disadvantage however is that the stimulation site and response for that site are both localized on the median side of the foot resulting in a higher risk of direct muscle stimulation compared to stimulation of the ulnar nerve Moreover monitoring the posterior tibial nerve is often challenging because in many cases anesthesiologists remain near the head of the patient during surgery and have drapes separating them from the lower parts of the patient s body Facial Nerve Lastly for facial nerve stimulation electrodes should be placed on the orbicularis oculi muscle to measure the twitch of the eyelid Correct electrode placement for stimulation of the facial nerve will show as it the facial nerve leaves behind the stylomastoid foramen near the tragus 2 3 cm posterior to the lateral border of the orbit Monitoring of Neuromuscular Junction PDF negative electrode positive electrode Figure 2 2 5 electrode placement for facial nerve stimulation Picture from Train of Four Monitoring PDF Like previously mentioned the anesthesiologist is mostly if not always at the head of the pa
130. ribing the different build options for this circuit it is necessary to describe its intended characteristics and a good way to do that is by starting with the existing version which has been touched upon lightly before The currently used design gets its power from a 9V battery which it uses to deliver one of the three different pules types the Train Of Four a 1Hz twitch and 100HZz tetanic contraction All three types can deliver a variable current between one and fifty milliamps This range is provided by varying a potentiometer on the side of the device labeled with the numbers 0 10 with zero being off As the title implies this must be as close to a constant current source as possibly because of the dynamic nature of human skin Over the course of any procedure and possibly any set of pulses skin resistance can change due to all of the factors discussed previously in this paper of these variations it is necessary to regulate the current so that the patient incurs no damage due to use of the device In order to deliver the necessary currents the device must overcome the possible 250 kOhm resistance of human skin part of this resistance can be overcome with a thorough cleaning of the skin as mentioned before but it should never be assumed that this cleaning will happen And with these basics down it is possible to move on to a discussion of the possible current circuitry 3 2 A Passive Circuit Designs The first instinct with this circuit i
131. ricting to the patient but something that allows for more stabilization and accuracy to the positioning of the stimulated nerve Therefore it is a possibility that testing it with a support similar to the TOF Watch hand adapter is very possible Kinemyography Kinemyography like acceleromyography is also based on the piezoelectric effect However the electrical current is generated by deformation of a mechanosensor integrated in the piezoelectric element unlike acceleromyography where the current is induced by acceleration of the piezoelectric element It has been proven useful for research studies but has not yet had accurate or reliable results for everyday clinical use Phonomyography PMG Phonomyography records the sounds emitted by a muscle contraction through a condenser microphone applied to the skin s surface This method is a relative new method of monitoring neuromuscular function The contracted muscles generate intrinsic low frequency sounds which can then be recorded by the microphone These signals are measured peak to peak between 4 and 6 Hz and are proportional to the force developed Although good feedback has been seen from this method it is unsure whether it will ever be used in daily use One of the biggest advantages with PMG is that in theory it has the ability to monitor the different muscle groups that have been unable to be previously measured such as the diaphragm larynx and eye muscles Stimulation E
132. ries as listed on the website Pending approval by Measurement Specialties Inc 56 Group 14 Senior Design 1 A way to offer the most reliable results without having to restrict the patients arm is using a hand adapter for the thumb The makers of the TOF Watch first implemented this idea to provide the most accurate and reliable data possible This has been done because the thumb always returns to its original position after being stimulated In past uses it was common for monitoring results to be unusable because shifting of the original position for the thumb would change after each stimulation As a result the makers of the TOF Watch came up with their own hand adapter It proves to be beneficial for patients in the operating room especially when patients must be repositioned thus throwing off all the results If the project is to use a hand adapter the website of Mainline Medical offers a Bluestar Enterprises Hand Adapter Figure 3 1 6 Bluestar Enterprises Hand Adapter Pending approval by Mainline Medical Price quantity 1 43 95 Bluestar Enterprises hand adapter Pros Cons Positions hand and holds acceleration May require too much time to prepare transducer in place over thumb thus on everyday clinical usage providing more reliable and accurate measurements May not be applicable with designed stimulator 3 2 B Force Sensors A force sensor is defined as a transducer that converts
133. rightness output Very cheap at this point No multi touch support Very durable and reliable Table 2 5 2 Pros and Cons for Capacitive LCD Displays 41 Group 14 Senior Design 1 Looking at the pros and cons above for each display technology it can be concluded that under the circumstances and the project specifications given the resistive touch screen would be a suitable choice Being that this project has a very limited budget and the budget affects the selection of parts the resistive screen makes most sense and will most likely be used in the project design The TFT resistive screen is much easier to setup and drive using the graphics controller so this is a major reason in choosing to go with resistive touch screen 2 5 B Graphics Display Controllers Each display needs a controller to drive the display and for each display type and size there is a variety of controllers Let s look at some of the ones that are considered for this project NHD 4 3 480272MF 22 This Newhaven TFT display controller evaluation board was specifically made for the 4 3 Inch Newhaven TFT touch screen display that is described in the next section of this design paper This board can control a display of 480x272 RGB pixels and uses 22 POS FCC interface with 8 bit data input The controller chip that is included with this evaluation board is Solomon s SSD1963 which is a very popular controller for this type and size of screen This
134. rom book TOF Approximate Clinical Significance Response Percentage of Receptors Blocked by Agent Four 0 to 75 Patient may be able to move but may twitches experience weakness Responsive to antagonist or a reversal drug for the blockade Three 75 Administration of additional drug may be twitches needed to prolong relaxation Short or intermediate acting agents may be reversible Two 80 Suitable for both short term relaxation as twitches well as long term mechanical ventilation One twitch 90 Conditions suitable for short term procedures including intubation and long term mechanical ventilation No twitches 100 Best conditions for intubation Long term saturation may lead to prolonged effects Table 2 2 1 Table displaying the approximate percentage of receptors blocked Tetanic and the clinical significance based on number of twitches 18 Group 14 Senior Design 1 Tetanic stimulation is the concept of using a very rapid delivery of electrical stimuli It was brought about to reveal more affectively the incomplete neuromuscular recovery of a patient Tetanic stimulation is done with a high frequency impulse between 50 to 200 Hz for a duration of usually 5 seconds sometimes less when given a higher frequency Due to the individual stimulatory responses blending together the anesthesiologist can only detect one strong continuous muscle contraction If the recovery of the NMBAs i
135. room a blue drape is put up to separate the sterile surgical field from the rest of the people in the room So even if the hand is readily available they may have to go under the drape to check the patients thumb in order to see if there is a resulting twitch once they turn on the current device This becomes rather inconvenient and this is under the best circumstances One of the surgeries that Ryan watched they were unable to even get to the hand because it was tucked to the side of the patient and was covered by blankets so only the eye was available to monitor When the arms are tucked to the sides of the patient this causes any of the sensors that require a restrained arm not to be allowed to be used So the force transducer would not be a viable option for surgeries of this nature Also when the arm is restrained there is a chance of damaging the nerve or tissue if the arm is not position properly with respect to the transducer In hospitals cost is an issue because they try to keep everything that they use on the patients to be disposable in order to keep cross contamination to a minimum With this in mind the devices that use the force transducer and the accelerometers that measure in more than just one direction are too costly in order to make them disposable so the hospital would need to put a protective barrier between the patient and the device or resort to washing it after each use This becomes a bit of a pain and in most cases probably
136. rve To ensure that the selected stimulation current is conducted at full strength against the skin s resistance it is important to make sure the electrodes have contact with the smallest possible area Typically the contact area of the stimulation electrodes should not exceed a diameter of 7 11 mm Furthermore the electrodes should be positioned somewhere between 3 6 cm apart on either side of the course of the nerve Any significantly larger or small distance between the two electrodes should be avoided so it does not alter the penetration depth of the stimulation current The three main sites of stimulation to monitor neuromuscular blockade are the ulnar nerve the posterior tibial nerve and the facial nerve Ulnar Nerve The ulnar nerve is the most popular site for neuromuscular monitoring For stimulation at this site electrodes should be placed on the adductor pollicis muscle to measure thumb adduction For correct stimulation the positive electrode should be place approximately 2 to 4 centimeters proximal to the wrist crease and the distal negative electrode should be placed at the ulnar head 13 Group 14 Senior Design 1 directly over the groove for ulnar nerve which should be about 2 to 3 centimeters from the positive electrode Figure 2 2 3 electrode placement for ulnar nerve stimulation Picture from http ionphysiology com ssep 20settings htm One reason the ulnar nerve is used so frequently is that neuromusc
137. ry wakes up from standby mode in less than 5us and three 16 bit timers When it comes to serial communication interfaces this device is similar to the PIC24F chip it has up to four interfaces with each supporting UART IrDA encoder and decoder I2C and synchronous SPI This device has a large flash memory size of 256KB 16KB of SRAM along with 87 pins of I O PROS CONS Fairly fast 25MHz system clock Not many open source libraries 16 bit registers No LCD Driver for TFT Displays Free IDE for MSP430 chips Too large in size for this project 256KB of flash memory Smaller SRAM than other MCUs 87 I O pins Relatively large in size 14 x 14 mm Compile code in C and Assembly Four USCI_A Low price and available samples Table 2 4 2 Pros and Cons for TI MSP430F5438A Microcontroller 34 Group 14 Senior Design 1 PN PACKAGE TOP VIEW Q o x Fi 2 2 382 cotn gyee ss zaaae ey exc e eee a x lt lt az Cc xx PPH FEFEFE PeeekereekPPaokee eee 68 66 64 P6 4 A4 P6 5 A5 P6 6 A6 P6 7 A7 P7 4 A12 P7 5 A13 P7 6 A14 P7 7 A15 P5 0 A8 VREF VeREF 60 P8 0 TA0 0 59 P7 3 TA1 2 58 P7 2 TBOOUTH SVMOUT 57 P5 7 UCA1RXD UCA1SOMI se P5 6 UCA1TXD UCA1SIMO 55 P5 5 UCB1CLK UCA1STE 54 P5 4 UCB1SOMVUCB1SCL 53 P4 7 TBOCLK SMCLK 52 P4 6 TB0 6 z MSP430F5437AIPN P5 1 A9 VREF VeREF MSP430F5435AIPN 511 DvCC2 avec t
138. s incomplete it will be seen by an increase in muscle force when initially stimulated followed by a viewable fade Thus the higher the frequency of tetanic stimulation to the patient the more pronounced the fade Tetanic stimulation is not suitable for monitoring intraoperatively but has proven useful for evaluating neuromuscular recovery Additionally tetanic stimulation is extremely painful because of its high frequency For that reason it is mostly only employed on anesthetized patients and even further only reserved for research studies when stimulating at the higher frequencies Currently it is mainly only used as a component in the post tetanic count Tetanus 100Hz r Stimulation tetanic impulse Response moderate non depolarizing blockade Figure 2 2 8 tetanic stimulation from book Post Tetanic Count PTC With making this stimulation pattern the aim was to find a more powerful alternative to TOF when monitoring deep neuromuscular blockades When initially being injected with neuromuscular blocking drugs there is such a large dose to ensure smooth tracheal intubation During this time no response is shown to either TOF or single twitch stimulation under these conditions Therefore these stimulations are not able to be used to determine the degree of the blockade of a patient at the onset of the drug being given It has been made possible however to quantify intense neuromuscular blockade of the peripheral
139. s it to be 117 Group 14 Senior Design 1 The research topics were distributed equally among the group members each topic was researched by two members that way there was always somebody to confer with on what was being researched so it was never just a solo member working on something that they couldn t ask for help with The team met every Thursday before class for approximately three hours in order to catch up and fill the rest of the group in on ideas of things that were believed to be able to help the project and things that we did not need to worry about anymore These meetings served as brainstorm opportunities and greatly helped with motivating the group to keep on task Figure 7 2 1 shows the progress of the group throughout senior design 1 Duration Project Part Phase Start Date End Date Days Fall Semester Initial Document 4 Sept 12 11 Sept 12 7 Research Important Medical Topics 12 Sep 12 12 Oct 12 31 Research Previous Designs 12 Sep 12 12 Oct 12 31 Research Sensors 10 Oct 12 10 Nov 12 31 Research Constant Current 10 Oct 12 10 Nov 12 31 Research Controllers 10 Oct 12 10 Nov 12 31 Research LCDs 10 Oct 12 10 Nov 12 31 Research Wireless 10 Oct 12 10 Nov 12 31 Research Power Supply 10 Oct 12 10 Nov 12 31 Operating Room Visits 10 Nov 12 16 Nov 12 6 Writing Senior Design Paper 11 Oct 12 1 Dec 12 51 Figure 7 2 1 Depicted in Figure 7 2 2 is what the group is expecting to
140. s project a lot of resources and sample code is available online as open source Registers LFRAME LLINE ia a gt nterface LSHIFT LCD nn Controller a Frame Buffer d Reset M REBR SERSN ISS Rotation Mirror Clock LDATA 23 0 LDEN aveau GO GPIO 3 0 GAMAS 120 PWM Figure 2 5 2 SSD1963 Block Diagram Courtesy of Solomon Since this project will require a lot of parts to be surface mounted and the cost of mounting can grow very quickly this particular chip will we purchased as a built 43 Group 14 Senior Design 1 in chip on the Newhaven controller board discussed above in section 3 4 b This Solomon controlled comes mounted on this controller board and mounting is not required AR1011 The Microchip mTouch AR1011 resistive touch screen controller is a complete easy to integrate and cost effective universal chip solution for applications that require a use of resistive touch screen panels This chip uses a very sophisticated touch decoding algorithm to process touch data that was received from the surface layer of the display This chip is not to be confused with a display controller because this chips main function is to control the touch input of a display not the LCD itself Here are some of the features that are important to this project e Power Saving Sleep Mode e 128 Bytes of EEPROM e 2 5to 5 0V Operating Voltage e 17mA Typical Operating Curre
141. s to use the K I S S method and keep things simple toward that end it was decided to investigate a purely passive circuit that would be able to manipulate the applied voltage and output the required currents The first circuit suggested was a resistive network with a potentiometer in series with the patient that would allow for the sought after variability in current The design would simply be a very large resistor in series with the potentiometer this resistor represents the resistance of skin in a test circuit Because of the 63 Group 14 Senior Design 1 simplicity of this circuit there will be no diagram merely a short explanation why it would be foolish to try and make it work The first flaw of the resistive network circuit and any purely passive system is its inability to automatically compensate for varying load resistances something that more advance circuit can manage easily This leaves all precision in the hands of the anesthetist who will be focusing on several other things more vital to the patient s survival of the surgery Moving on another issue arises with the inability to even tell how much current is being delivered This becomes a problem because as mentioned before different patients not only have different resistances but they also have different tolerances susceptibilities to current levels A supramaximal stimulation current of 30mA in one patient may not achieve supramaximal in another that patient may require
142. scles are in the patient In order to build or create this device some medical knowledge is imperative to know in order to make sure that the device will work properly without causing the patient any harm 2 1 A Types of Anesthesia In the medical world there are four types of anesthetics Topical Local Regional and General Although they all temporarily cause an absence of pain to the patient they vary in degree of their resulting effect on the patient depending on what type of procedure the medical staff has to perform Topical anesthetics are the least abrasive and are administered on the skin by a spray cream gel etc They temporarily block nerve endings in skin and mucous membranes They do not produce unconsciousness to the patient Local anesthetics are given intravenously and temporarily block transmission of nerve impulses and motor functions in a specific area They also do not cause unconsciousness to a patient Regional anesthetics are administered and used for more severe surgeries They temporarily interrupt transmission of nerve impulses such as temperature touch or pain and motor functions in a large area to be treated However they do not produce unconsciousness to the Group 14 Senior Design 1 patient General anesthetics which are the most powerful of the four types produce total unconsciousness affecting the entire body They are administered intravenously or through inhalation Agents used for the latter of
143. sing neuromuscular junction monitors is because of the narrow therapeutic window Monitoring of Neuromuscular Junction There is no detectable block until 75 to 85 of receptors are occupied and paralysis is complete at 90 to 95 receptor occupancy Adequate muscle relaxation therefore corresponds to a narrow range of 85 to 90 receptor occupancy With neuromuscular monitoring optimal surgical relaxation is able to be achieved by knowing how much NMBAs should be permitted to a patient In addition it provides a quicker and more reliable turn around when patients are given the medication to reverse the general anesthesia after the medical procedure It has been shown that when monitoring of NMJ function is not performed and clinical criteria alone are used up to 42 of the patients are inadequately reversed upon arrival to the recovery room This residual neuromuscular block is a major risk factor for many critical postoperative events such as ventilator insufficiency hypoxemia and pulmonary infections However the widespread use of perioperative NMJ monitoring has helped reduce these complications drastically 11 Group 14 Senior Design 1 Setpoint entered by clinician PC based control system I A Computer Data A ree controlled 17 acquisition Validatio P Control drug infusion pump Neuromuscular Transmission K Patient lt Monitor j Figure 2 2 1 Architecture of a control s
144. slow respiration or blood flow to the brain It also has the fastest induction and recovery time However it can diffuse into air containing cavities and can result in a collapsed lung or lower the oxygen content of tissues Because it is a relatively weak anesthetic it is not suitable for being the primary agent in any type of major surgery Sevoflurane works quickly and offers rapid awakening Additionally because it does not irritate the airway it can be administered through a mask and as a result it is quickly becoming the first choice of use for pediatric patients Its downside it that it may cause increased heart rate and should not be used in patients with a narrowed aortic valve Also one of the breakdown products can cause renal damage Finally there is desfluorane a second generation version of isoflurane Its advantage is that is offers rapid awakening with few adverse effects However it seems to have several disadvantages It is irritating to the airway and therefore cannot be used for mask inductions especially not in Group 14 Senior Design 1 children It may increase the heart rate and should not be used in patients with heart problems It also may cause coughing and excitation during induction 2 1 D Intravenous Anesthetics Just like inhalation anesthetics there are several types of intravenous anesthetics that each offer their own individual advantages and disadvantages of use Ketamine produces a different set of reac
145. spend on each stage of the project for senior design II The group realizes that these dates are not set in stone and it will not be the end of the world if something ends up taking a little more time than expected The goal for senior design Il however is to keep as close to this timeline as possible but mainly be able to have at least one test where everything is connected so that the device can be tweaked before the final senior design presentation in April Over the break into the first week of classes the group hopes to acquire the majority of the parts that are needed The most important parts to get in as soon as possible are the sensors so that the decision 118 Group 14 Senior Design 1 of which sensor is being used in the final design can be finalized so the group can start working on how to integrate it into the other parts of the design The majority of the class then will be spent on building and testing with the last month or so dedicated to full design testing and finalizations being made so that the device works at the end of the semester i Duration Project Part Phase Start Date End Date Days Spring Semester Acquire all sensors 12 Dec 12 11 Jan 13 31 Test Sensors and make final 11 Jan 12 18 Jan 13 8 decision on which one to use Create and Test Circuit for Power 48 Jan 13 31 Jan 13 14 Supply Design and Test Constant Current 21 Jan 13 5 Feb 13 15 Circuits
146. ss sensitive by lowering the reference resistance 1kQ min and or the drive voltage 0 5 V 0 10 V etc thus it will increase its active force range This recommended drive circuit results in a linear 3 output from FlexiForce sensors 97 Group 14 Senior Design 1 Var Me TARAR f ae Maan lars Piexirorce sc ee a a v GND No 5 POWER Supply Voltages should be constant Reference Resistance R is 1kQ to 100kQ Sensor Resistance R at no load is gt 5MQ Max recommended current is 2 5mA Figure Recommended drive circuit for FlexiForce sensors 4 4LCD This part of the design document will go over some of the LCD requirements and features that were discussed in detail in the research and design sections of this document but will mostly focus on the methods that will be used to program the LCD module and display the data received from the thumb sensor The below table with pros and cons that are relevant to the build of this display IDTBO2 4 3 PROS CONS SD Card Socket Only 65K Colors Built in Controller Limited Documentation Supported by UTFT Library 16 bit Data interface instead of 24 bit 4 Wire Control Interface Table 4 4 1 Pros and Cons for ITDB02 4 3 Display w Controller Earlier in section 3 5 A the pin configuration and description was detailed and to 98 Group 14 Senior Design 1 make it more clear and relevant to the build of the LCD a s
147. st should be rerun to make sure the problem was actually fixed From here the next step is the current source 5 2 Voltage Boost Circuitry This particular part of the circuit is actually the trickiest this is because so few of its principles were taught to learned by the group that a significant amount of time was spent just figuring out its basics So to be thorough every possible failure scenario must be considered before moving to the next phase of testing For this circuit the first thing to test its ability to hold up to a low DC voltage to test this the charge capacitor should be removed leaving on the bleeder resistor between the inductor and ground Then hook up a nine volt battery to the two input leads and test the 555 Timer s output for a decent square wave of the appropriate frequency These steps are the simple part if something is wrong here it means that either a resistor or capacitor was soldered poorly or that the 555 Timer does not work Once this issue is isolated and fixed the circuit needs to be rerun with and the voltage across the bleeder resistor needs to be measured to make sure that the inductor is functioning as is expected At this point it is necessary to pay attention to the battery as well as the circuit to see if everything works properly If all the correct voltages are measured at the junctions prior to the inductor then everything is electrically correct there This does not mean that the circuit will necessar
148. take place in each section the members of the group can check as they go instead of having everything assembled and having to guess what is not working and causing major problems at the end of the semester 5 1 Power Source Because the power source is base for every other component it will be tested first Testing this piece on its own will allow the group to verify that everything was wired appropriately and that there are no cold solder joints creating partial open circuit conditions Referring to the AC DC diagram it is obvious that the first test will simply be two plug the source in WRONG Unless the intention is to electrocute yourself never assume everything functions properly and start playing with high voltages The first test will actually be to use the continuity setting on a multimeter to make sure that all wires are functional and all connections made won t spontaneously appear and disappear If any loose or bad connections are found now would be the time to fix them Once all repairs are made the next step is to connect the AC terminals to the positive and negative of a DC power source Because a transformer was used to create an isolation from the AC wall socket it may be necessary here to current limit the DC source Once current limited the source should then be turned up to 24 volts This voltage should transfer across the transformer and through the diode bridge With the source hooked up go through and check all releva
149. that will control that The following table shows the outline of each function Function Name Function Description This function will pull the system time off the chip This function will create a pulse timer based on the given double pulseTimer current_time specifications for either a TOF pulse or a constant pulse for a given period of time Functions will active the pulse and void sendPulse time send the muscle stimulating current to the electrodes Table 4 5 2 Outline of Function for the Wireless Display double getTimeStamp System_time 4 7 B Sensor Polling Function Name Function Description This function will get sensor data double getSensorData sensor_output from the sensor output pins and return it as a double This function will synchronize void synchronizePolling time polling with the pulse timer to reduce sensor noise Functions will prepare the sensor double sendSensorData data_array data and format it to send it to the wireless screen 102 Group 14 Senior Design 1 Chapter 5 Test Plan A major part of this project is to make sure that it works at the end of the spring semester With that it only makes sense to set out a plan that will help guide the group as a whole through the process of testing each part of the design as well as testing the project as a whole at the end This way the group will know how the testing is expected to go and when changes need to
150. the two may either be gases or volatile liquids that are vaporized and inhaled with oxygen 2 1 B General Anesthesia The definition of General anesthesia is the induction of a balanced state of unconsciousness accompanied by the absence of pain sensation and the paralysis of skeletal muscle over the entire body It is used during major surgery and other invasive surgical procedures http www surgeryencyclopedia com A Ce Anesthesia General html b The five distinct reasons for electing to use general anesthesia are to produce unconsciousness to relax the muscles of the body to block memory of the procedure amnesia to inhibit normal body reflexes to make surgery safe and easier to perform and to give pain relief analgesia to the patient General anesthesia occurs in four stages which can occur very rapidly During the first stage the patient is conscious although mental and physical capabilities become progressively sluggish as the deeper part of the stage is approached The sense of pain is dulled until it becomes abolished often just before consciousness is lost The second stage or the excitement stage includes uninhibited and sometimes dangerous responses to stimuli resulting in the patient possibly becoming violent Blood pressure rises and becomes irregular and breathing rate increases However this stage is usually shortened or even bypassed by administering a barbiturate a drug with hypnotic and sedative effects During
151. thesiologist can make sure that the dose of anesthesia that is given is appropriate and safe for the particular person Like many other drugs that are used today there are risks involved when the patient is taking other medicine smoking and drinking alcohol can increase the chances of having problems Medicines like ones that Kelly takes for seizures can actually make the anesthetics that are used wear off quicker But some patients can have a metabolism that for some unknown reason is able to reverse the effects of the anesthesia faster than others These are just some of the cases when being able to test the force of the twitch is essential so that the anesthesiologist can periodically check the patient in an easier fashion If there were an easier way to test the fears that patients have about waking up and being able to feel what is going on will help them out It will also keep the surgeons from having to tell the anesthesiologists that the patient is waking up 89 Group 14 Senior Design 1 Chapter 4 Build Chapter 4 1 AC DC Power Supply Now that all of the individual components have been considered and chosen it is time to assemble them It seems wisest to begin with the most essential component of the entire project its power supply Recapping the design section it was decided that building a custom power supply for the project was the best idea This was for multiple reasons not the least of which being a way to prove that all
152. this ToF a continuous repeating pulse a one shot function or to run it a certain number of times If the one shot option is selected then this will be the last setting available for this pulse type If the option is selected to run a specified number of times then the next screen presented to the user will be to enter the number of times that the pulse train is intended to run This setting is suggested to be used when patient is waking up because it allows for a short repeat test of whether the patient has a return of muscle control If it is selected that this pulse should repeat itself then a time must be chosen where the pulse will run at the start of every counting sequence i e if a time of 20s is selected then every twenty seconds the ToF will run This must be kept in mind because the time frame selected must not be so short that the ToF sequence never gets a chance to end pulse 4 If a time period this short is attempted to be entered there will be no warning This setting is suggested when attempting to monitor the patient while keeping then paralyzed A single twitch of the four should be seen at every issue of the pulse train 6 1 B Twitch Moving on to the Twitch setting if it is selected this setting is intended to be used over long periods of time It creates a single supramaximal current pulse to test whether there is any return of muscle movement This setting is most commonly used in multi hour surgeries where a neuromuscular
153. tient Therefore the main reason the facial nerve is favored as the stimulation site is that it usually gives the anesthesiologist a good and unimpaired access to the regions of the head throughout the entire surgery Unfortunately this stimulation site also offers the greatest risk of direct muscle stimulation compared to the ulnar and posterior tibial nerve As a result extra care must be taken so that the stimulation response is correct and not to falsely interpret the 15 Group 14 Senior Design 1 effect of neuromuscular blockade by another twitching muscle Also research has shown that lower currents as little as 25 30 mA are sufficient to elicit a response Additionally using higher currents for stimulation creates a greater risk of direct muscle stimulation due to the nerve s close proximity to the mimic muscles To measure neuromuscular blockade at this site an acceleration transducer should be used However stimulation at the orbicularis oculi muscle has proven to be difficult and frequently unsatisfactory in clinical practice Patterns of Nerve Stimulation For evaluation of neuromuscular function the most commonly used patterns of peripheral nerve stimulation are single twitch train of four TOF tetanic post tetanic count PTC and double burst stimulation DBS Single Twitch Single twitch monitoring is the simplest form of nerve stimulation and for many years also offered the only mechanical means of monitoring
154. tion increases during the first 15 minutes Thus recording of the control response before injection of the muscle relaxant should not be made until an appropriately long stabilization phase has passed as to avoid falsification of the measurement At this point the reference value is determined by the device then the NMBA can be injected and the actual measurement started This measuring method is very time consuming and prone to malfunction and the MMG devices are awkward and bulky to prepare making it an unsuitable choice for this project Electromyography EMG The electrical activity of a muscle is proportional to its force development As an alternative to the direct measurement of muscle force electromyography can be used to record the electrical activity of the muscle and thus to indirectly quantify neuromuscular blockades Evoked EMG records the compound action potentials produced by stimulation of a peripheral nerve In addition to the two stimulation electrodes this method requires another three surface electrodes applied over the belly of the test muscle to record the action potentials Most often the evoked EMG is done to the ulnar nerve and the EMG response is obtained from the thenar or hypothenar eminence of the hand preferably with the active electrode over the motor point of the muscle Typically electromyographical stimulation is applied in the TOF mode After stimulation the signal is picked up by the analyzer and is
155. tions from other intravenous anesthetics It affects the senses and produces a dissociative anesthesia This is where patients cannot respond to sensory stimuli even though they may appear awake and reactive This anesthetic is not usually given to adult patients because it often makes them have sensory illusions and vivid dreams during post operative recovery This anesthetic is useful for use in developing countries and trauma casualties in war zones where anesthesia equipment may be difficult to obtain It is also frequently used in pediatric patients because it causes unconsciousness and a loss of sensation with an intramuscular injection Ketamine is also popular for patients in shock because it also provides cardiac stimulation Thiopental is a barbiturate that induces a rapid hypnotic state for a short duration of time It should not be continuously infused though because toxic accumulation can occur since it is slowly metabolized by the liver Additionally patients may experience side effects that include nausea and vomiting when awakening Opioids are frequently used prior to anesthesia and surgery as a sedative and analgesic Opioids are extremely useful for cardiac surgery and other high risk cases because they rarely affect the cardiovascular system Opioids are the most common agent used in epidurals for spinal anesthesia because they act directly on the spinal cord receptors Side effects for a patient may include nausea vomiting itching
156. trodes not being cleaned thoroughly which can affect results of next use They have several warnings for handling that can be easily forgotten These include not cleaning them in hot water making sure they are completely dry before returning to storage and not allowing the electrodes to come into contact with each other during storage because it may cause an adverse reaction to take place Disposable Ag AgCl Electrodes Pros Always sanitary which is extremely important for hospital use Convenient and easy to use because they are pre gelled and have peel and stick backing that already have the adhesive disk Saves time Don t have to handle them with caution like one would with reusable electrodes Some have been specially developed for neuromuscular monitoring 25 Group 14 Senior Design 1 Cons e Although individually cheaper they cost more overall because they are disposable and therefore must constantly be purchased e Not eco friendly e Does not come with an electrode lead Because of all the major benefits of using disposable electrodes unlike the reusable electrodes with their numerous disadvantages this project will be using the disposable type of electrodes Dr Looke also says disposable items are the way of the future for hospitals which allow them to keep things as sanitary and efficient as possible LEAD WIRE SILVER FOIL CONDUCT IVE HYDROGEL SILVER CHLORIDE Figure 2 2 1 cross section of
157. uire them again Since his diagnosis Ryan has been considering a career in the medical field and this project presents the perfect opportunity to test those inclinations The other member of the group is Kelly who grew up with both of her parents in the medical field In addition to its current function and although this part of the project does not focus on it she hopes this project will continue and lead to research that will one day find a monitor for conscious activity even under sedation Currently anesthesiologists use bi spectral indexing BIS to see the brain activity of a patient who has been given general anesthesia however with a patient such as Kelly who has epilepsy she has become interested in what they can possibly do to measure brain activity while there are constant abnormal electrical discharges in the brain Her interest stems from the infrequent but possible occurrence of an anesthesiologist forgetting to administer or administering too few pain blocking agents If this project were to continue she would like to find a way for the patient to communicate pain without being able to move or speak 1 2 Project Specifications The main goal and only real specification for this project is to find a way to quantify the twitches that occur as a result of the supplied current From that requirement the group was lead to a couple different goals First the Train of Four device that sends the pulses must be recreated This device
158. ular monitoring of this nerve muscle unit will not normally affect the surgical conditions Additionally it is easily accessible intraoperatively as long as the arm is placed in an outstretched position A big advantage is that the adductor pollicis muscle is located on the lateral side of the arm while the ulnar nerve runs along the middle side thus there is little risk of any direct muscle stimulation which can alter the results Posterior Tibial Nerve If ulnar placement is not possible for the electrodes neuromuscular monitoring can also be measured with the posterior tibial nerve For stimulation electrodes should be placed on the flexor hallucis brevis muscle to measure the flexion of the big toe For correct stimulation the positive electrode should be placed between the medial malleolus of the ankle and the Achilles tendon just proximal to the malleolus http ionphysiology com ssep 20settings htm The negative electrode should then be placed approximately 2 to 3 centimeters from the positive electrode This placement overlies the nerve as it follows a path around the malleolus The ideal stimulation site is posterior to or slightly above the level of the malleolus so as to stimulate both the medial and lateral plantar terminal nerve branches http ionphysiology com ssep 20settings htm Pe S Figure 2 2 4 electrode placement for posterior tibial nerve stimulation 14 Group 14 Senior Design 1 Pictu
159. ving the breathing tube There will be a mechanical time limit applied to this device that limits the length of time that it can be used doing this prevents permanent damage from being induced on the patient because of a careless operator 6 1 D Custom Some devices will come with a fourth pulse option labeled Custom this is exactly what it sounds like it should be This pulse type comes with a variety of options the first two and most important are the current strength and whether or not to repeat the signal These two options will reflect the limitation imposed in the ToF setting once again care must be taken not to set adjacent pulse to overlap doing so can harm the patient The next possible setting is if repeated pulses are desired a choice between timing the individual pulses and counting them Given a 16 bit system there should be no reasonable restriction on the number of pulses required or the time between them The next option is what the pulse train will look like Options available are a square wave a triangular wave or a rectified sine wave The square wave will generally appear much like the ToF does the difference between the two here is the ability to control the frequency and duration of this wave Both options will be presented following the selection of Square wave If the settings to be chosen are the same as the ToF then no difference in performance will be seen 113 Group 14 Senior Design 1 If the triangular
160. wave is chosen then the next two options available to the user are frequency and step size For the triangular pulse the available currents will be stepped through one by one with each pulse that is issued until they reach a maximum in which case they reverse until they reach the minimum The frequency option allows for a quick or slow delivery depending on how fast the user decides to deliver the waveform The last option is the step size This option is available because it is not necessary to switch through all of the current strength multiple can be left out and still deliver the desired triangular waveform This setting is added to allow a doctor to see what current strengths are required to receive any kind of response The last waveform available is the rectified sine wave This option operates much like the triangular wave except it steps through all available current levels to allow for a slower contraction and release of the muscle This option is still in beta testing 6 2 Trouble Shooting In the event that the stimulator does not work this section will cover all of the generic testing procedures that an operator can perform mid operation To being with if the startup sequence is not flashed to the screen and the device does not appear to have suffered substantial damage the most likely cause is a lack of power Check both the power cord and the On switch If both of these are as they should be then check the cable connecting the scr
161. will not happen In the designs that use electromyography the problems lie with the difficulty of the actual application and the sophisticated equipment that is used There is also the problem of excessive noise that creates a problem when the anesthesiologist is trying to decipher if there is activity that needs to be addressed or if it is just a false negative 2 4 Controllers This section of the document will look at different types of controllers that will be used in this project The types of controllers that will be looked at are microcontrollers graphics display controllers wireless transceivers and SoC chips for wireless transmission In addition to various controllers section 2 5 will look into wireless display modules for this project and compare two different display types capacitive and resistive Each part will be looked at in more depth and the pros and cons of each will be highlighted to help make a decision on the 31 Group 14 Senior Design 1 best suitable parts for the project design and how one device better fits the intended design and scope of this project 2 4 A Microcontrollers A microcontroller is a dedicated chip in computer electronics that is used to perform very specific tasks functions For the purpose of this project a microcontroller will be used because of its small size low cost and low power consumption A microcontroller takes input from the devices it controls and sends signals to different proje
162. working beforehand and it appears that all the components still work after disassembly then there was likely to be a simple wiring issue that was overlooked Instead of attempting to find one wire in dozens it is simpler to disassemble and reassemble the section that isn t working This should fix the problem If in fact it turns out that the section in question does not work post assembly then most likely there was an unexpected power overload If this is the case then every piece needs to be re checked individually to ensure that it was not also ruined Now assuming that all pieces are still functional and reassembly fixed the startup sequence with the LCD two important facts are known first that the LCD is connected properly this time second the microcontroller is operating up to this point as it is intended 5 9 C Component checking 110 Group 14 Senior Design 1 Chapter 6 User s Manual Because this device will be particularly user friendly unless someone manages to shock themselves this user manual will mostly be intuitive things that should be evident to a user who is used to the old designs 6 1 Normal Condition Operation For normal conditions the device should resemble an automatic blood pressure monitor The main power switch will be location on the side of the actual device when it is thrown an initial power sequence will be run This sequence will display a few useful pieces of information on the LCD before sending
163. y an 8 bit MCU 2 4GHz transceiver Small memory size 6 Timers Built in A D converter Wake on Radio communication Small in size 9 x 9 mm Code examples in Assembly and C Table 2 4 4 Pros and Cons for Atmel ATmega128RFA1 MCU with Built In RF 37 Group 14 Senior Design 1 PE7 ICP3 INT7 CLKQ PE6 T3 INT6 PES5 0C3C INT5 PE4 0C3B INT4 PE3 0C3A AIN1 ZR 88 S S r amp u ul aa PF2 ADC2 DIG2 PF3 ADC3 DIG4 PF4 ADC4 TCK PF5 ADC5 TMS PF6 ADC6 TDO PF7 ADC7 TDI AVSS_RFP RFP RFN AVSS_RFN 48 PE2 XCKO AINO 47 PE1 TXD0 46 PE0 RXDO PCINT8 45 DVSS 44 DEVDD 43 PB7 0C0A 0C1C PCINT7 PB6 0C1B PCINTE 41 PB5 0C1A PCINT5 40 PB4 0C2A PCINT4 39 PB3 MISO PDO PCINT3 36 PB2 MOSI PDI PCINT2 37 PB1 SCK PCINT1 36 PBO SSN PCINTO PGO DIG3 35 DVSS PG1 DIG1 34 DEVDD PG2 AMR 33 CLKI V o gt 8 o a gt a PDO SCL NTO PD3 TX D1 INT3 Figure 2 4 4 ATmegai28RFA1 Pin Configuration Courtesy of Atmel CC430F5137 This Texas Instruments device is a true System on Chip SoC that has a built in wireless sub 1GHz RF transceiver built in This part is a combination of two devices the MSP430 microcontroller and the CC1101 RF transceiver The MCU part of this chip is very similar to other TI microcontrollers described above so the features of this specific M
164. y of their use In an attempt to minimize the differences between the currently used device and the new design reducing the hassle of completely relearning the device it was proposed to attempt to use a 9V battery as the main source At most the design should require less than three of these batteries at a time to minimize its size and weight A standard nine volt alkaline battery will nominally supply 9V at 565 mAh while Lithium supplies 9 6V at 1200mAh Given a precision design the device might manage to make a single battery a sufficient source though this project is likely to require at least two and in doing so already begins to diverge from the current standard In an effort to be as thorough as possible other battery sources were considered as well those options will be briefly listed in the table below next to the 9V for comparison 81 Group 14 Senior Design 1 Tvpe Alkaline NiCd Lithium Nominal yP mAh mAh various mAh Voltage C cell 8000 4500 6000 N A 1 5V D cell 12000 2200 12000 N A 1 5V Lantern Spring 26000 N A N A 6V CR V3 Camera N A N A 1300 3000 3V 9V 565 120 500 9V 9 6V Table 3 6 2 Taken from Wikipedia need to find better source As can be seem from the table above even with the spectacular power that a D cell can deliver over time its voltage makes it unusable as a source for this project A feasible implementation would be to chain several of these batteries in s
165. y or design a DC DC charge pump or find a higher power source to use instead of the main chosen one The last option while valid was immediately ruled out for reasons of safety Given that the power source most likely to be used is an 110VAC wall outlet it seems like a poor choice to wire that directly to a patient Even after converting the AC source to a relatively stable DC source the current levels present are more than sufficient to burn tissue if not accidentally kill the patient if the intended implementation critically failed Ruling that out the next component to consider is a charge pump which intuitively sounds like exactly what the design needs Unfortunately upon further inspection it became apparent that the integrated circuit versions of these devices were intended for low voltage low amperage applications While there may be some use to them in the circuit later on they cannot be considered here for this application After which it was decided to possibly look in to a handmade version using bigger higher capacity devices Designs for such circuits were found to be readily available on the internet and thoroughly documented which is always a nice thing It appeared after looking at multiple designs that the way these devices work is through voltage doubling This is achieved by running multiple capacitors in parallel with their positive or negative terminals connect across diodes The terminal that isn t connected to diodes is w
166. ystem for muscle relaxation by Validation of muscle relaxation measurements PDF 2 2 A Nerve Stimulation Peripheral nerve stimulation is caused by a battery powered device that delivers depolarizing current via the electrodes When a single muscle fiber reacts to this stimulation it follows an all or none pattern In contrast the response of the whole muscle depends on the number of muscle fibers activated The muscle s strength progressively increases with increasing electrical current until it reaches its maximum response or when the stimulation current is great enough to stimulate all of the muscle fibers This response is called the threshold current this baseline threshold should be found prior to initiating neuromuscular blockade Once the muscle strength is at its peak the stimulus must be truly maximal throughout the period of monitoring Many factors can affect the intensity of the electrical stimulation and therefore the muscle response of a patient during surgery For example changes in skin temperature as well as anesthetic drug induced changes in vessel tone can alter the skin s resistance Resistance is the force opposing the flow of energy between the electrodes of the peripheral nerve stimulator Therefore an increase in tissue resistance must be compensated with a proportional increase in voltage in order to maintain a constant stimulating current CURRENT VOLTAGE RESISTANCE As a result the muscle is stimulated wit

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