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1. Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User of water pressure or Kilopascals KPa le Systeme International d Unit s si or metric units Table 1 1 lists standard units of pres sure measurement A Bourdon gauge Figure 1 4 consists of a hollow coiled metal tube with an elliptical cross section that is exposed to an area where gas pressure measurement is desired Attached to the coiled tube are a gear mecha nism and a pointer As pressure increases the tube begins to straighten causing the gears to turn and the position of the pointer to change The tube straightens because the pressure causes the cross section of the tube to become rounder As the cross section changes the out side of the tube is stretched while the inside becomes compressed These gauges are com monly found on medical gas cylinders indi cating the pressure inside of the cylinder and are calibrated in pounds per square inch psi GAS FLOW Cause Gas flows from one point to another due to a difference in pressure between the two points Gas will flow from an area of greater pressure GEAR MECHANISM MEDICAL GAS SUPPLY EQUIPMENT e 5 TABLE 1 1 Units of Pressure Measurement Unit Equivalent 1 Atm B 760 mm Hg 29 921 in Hg 1034 cm H O 101 325 KPa 14 7 Ib in 35 mm Hg 0142 Ib in 1 36 cm H O 019 Ib in 133 mm Hg 0
2. Licensed to iC hona User THOMSO DELMAR LEARNING LT Edition j ba ae eS a pun prm Gary White Licensed to iChapters User THOMSON TM DELMAR LEARNING Equipment Theory for Respiratory Care Fourth Edition Vice President Health Care Business Unit William Brottmiller Editorial Director Cathy L Esperti Acquisitions Editor Hhonda Dearborn Developmental Editors Mary Ellen Cox and Sarah Duncan COPYRIGHT 2005 by Thomson Delmar Learning a part of the Thomson Corporation Thomson the Star logo and Delmar Learn ing are trademarks used herein under license Printed in the United States of America 1234 5 XXX 08 07 06 05 04 For more information contact Thomson Delmar Learning 5 Maxwell Drive Clifton Park NY 12065 Or find us on the World Wide Web at http www delmarlearning com by Gary C White M Ed RRT RPFT Marketing Director Jennifer McAvey Channel Manager Tamara Caruso Marketing Coordinator Kimberly Duffy Editorial Assistant Debra Gorgos ALL RIGHTS RESERVED Por tions of this book copyrighted 1999 1996 and 1993 No part of this work covered by the copy right hereon may be reproduced or used in any form or by any means graphic electronic or mechanical including photo copying recording taping Web distribution or information storage and retrieval systems without written permission of the publisher For permission to use material
3. sure within the tube may be used to introduce gases usually air or liquids into a low pressure region of gas flow VISCOUS SHEARING VORTICITY AND EJECTORS Viscous shearing is another means by which oxygen is mixed with ambient or sta tionary air Viscous shearing occurs when a high velocity jet is injected into a quiescent gas The high velocity gas from the jet forms a thin boundary layer where frictional forces develop between the high velocity gas and the stationary surrounding air cleaving it Figure 1 7 The rapidly flowing gas acceler ates the stationary gas while the stationary gas decreases the velocity of the jet Shear forces develop along the boundary layer between the two gases The decelerating high velocity jet forms vortices which envelop the ambient air along the boundary layer The vis cous shearing effect entrains the room air into the vortices mixing the oxygen with it By varying the size of the oxygen jet and the entrainment ports differing oxygen concentra tions can be obtained Manufacturers have developed specific combinations of entrain ment ports and jet sizes to deliver precise FjO levels This principle is applied in High Air Flow with Oxygen Enrichment HAFOE masks commonly called venturi masks MEDICAL GAS SUPPLY EQUIPMENT 7 Venturi s Principle Venturi expanded Bernoulli s principle by adding a specially shaped tube downstream from the jet This tube has an increasing radiu
4. Gas exiting from the regulator section then passes through a proportioning valve The oxygen percentage control adjusts the propor tions of air and oxygen If 80 oxygen is desired turning the control opens the oxygen side more while proportionally closing the air side Most manufacturers incorporate a built in alarm system into the blender If gas pressure from the supply lines air or oxygen drops within the regulation section an audible alarm will sound 90 PSI OXYGEN ESESSESSESSESESESESEESESESESESSESSESSSSS MIXTURE CONTROL PROPORTIONING VALVE Figure 1 37 A functional diagram of an oxygen blender m E m f BALANCE STAGE ee 50 PSI MIXTURE Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 42 e CHAPTER ONE ASSEMBLY AND TROUBLESHOOTING Assembly Oxygen Blenders To prepare a blender for use follow the instructions listed below 1 Ensure a supply of compressed oxygen and air at 50 psi The supply devices may include an oxygen piping system or cylinders with appropriate regulators Connect a 50 psi hose to the air supply and to the air inlet fitting on the blender Connect a 50 psi hose to the oxygen supply and to the oxygen inlet on the blender Read the pressure gauges on the blender to verify line pressure if provided Check the pressur
5. If you suspect a leak but can t detect it 1 Use a solution of mild detergent and water and brush the solu tion around the fittings Leaks will cause bubbles to form indi cating the presence of a leak d If a leak is detected turn off the cylinder valve bleeding all pressure from the regulator and retighten all connections If gas fails to flow from the cylinder check the pressure gauge to ensure that the cylinder has pressure a If the cylinder contains pressure check the regulator outlet for obstructions b If the above is satisfied replace the regulator with another and try again Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User MEDICAL GAS SUPPLY EQUIPMENT 35 OA 6A Jopul Ao y uo UN G Ssuonoeuuoo we uays v eunsseJd peelg JepuiAo eui yo uin Z uonnjos deos Buisn yea AjueA 4 S9A j uewdinbs ueB xo au pue Jepui Ao y u m q yes e 1 y S ON SAIPUYAD SUS vo1pauu 1001 52 q04 04 moy Buiquosap myguosp uy p p OW uo Nea JapUI AD uin G Ssuonoeuuoo iie uays v nss d p jg OAJCA JOPUI AD eui yo uin Z uonnjos deos Buisn yee AjueA 4 Sor JapuljAo y eoejdey JoyejnBai pue Jepui Ao u m q yes e 9Jau1 S ON ounsseaid SOA ejyenbope a9u S ON juened y Jojyuo
6. KS that can participate in gas exchange oxygen is conserved when these devices are compared to continuous flow oxygen delivery devices Since these devices deliver a minimal flow of dry gas humidification requirements are elim inated These devices are most commonly used in the home setting where oxygen con servation can result in substantial cost savings When initially setting up an oxygen system on ambulatory patients it is helpful to per form an exercise oximetry study with both continuous flow and demand pulse flow oxy gen systems to insure adequate oxygen satura tion Not all patients will be able to maintain adequate oxygen saturations during demand pulse flow delivery Therefore it is important to adjust the demand pulse oxygen delivery flow rate to meet the patient s needs during exercise as documented by oximetry Some patients with severe pulmonary disease may not tolerate demand pulse flow oxygen deliv ery systems at all In these patients continuous flow oxygen systems are required to maintain adequate oxygen saturations INHALATION EXHALATION INHALATION El Usable oxygen Figure 1 44 A graph illustrating usable and nonusable oxygen during pulsed demand flow delivery Courtesy Puritan Bennett Corporation Lenexa KS Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 50 CHAPTER ONE Transtrach
7. MEDICAL GAS SUPPLY EQUIPMENT 37 Figure 1 32 Differing threads and pitches for cylinder valve connections Note the threads on the left are external acetylene and the threads on the right are internal oxygen left and right hand threads and external threading to prevent the attachment of equip ment not designed for the gas contained in the cylinder Figure 1 32 shows acetylene and oxygen American Standard fittings Note how one is internally threaded and the other is externally threaded The smaller cylinder valves sizes AA E use a yoke type connection between the cylinder valve and the reducing valve The Pin Index Safety System incorpo rates pins in the reducing valve yoke and holes on the cylinder valve at specified posi tions to prevent the attachment of equipment not designed for the gas contained in the cylinder Figure 1 33 illustrates how this safety system works using the different pin positions In addition to the indexing safety systems pressure release devices are built into the cylinder valves These pressure relief devices will open if pressure or temperature rises beyond safe limits The two types of pressure relief devices are the frangible disk and the fusible plug These devices may be used singly or in combination with one another The frangible disk pressure relief consists of a thin metal disk that contains the pressure within the valve If the pressure within the cylinder rises abnormally
8. Z 2 22 4 lessrssasst10 17002 64 a p DIXIT 9 SSS 3 NOZZLE DIAPHRAGM POPPET VALVE Figure 1 36 Functional diagram of a two stage reducing valve Note how two single stage regulators are connected in series to form a two stage regulator REGULATORS When a flowmeter and a reducing valve are joined together into a common unit it is termed a regulator Regulators are more con venient than separate reducing valves and flowmeters Only one high pressure connec tion is required between the cylinder and the regulator and they are more compact in size A regulator consists of a reducing valve with a Bourdon type flowmeter or a reducing valve with a Thorpe tube flowmeter Both of these flowmeters are discussed later in this chapter ASSEMBLY AND TROUBLESHOOTING Assembly Oxygen Reducing Valves Troubleshooting Troubleshooting a cylinder and reduc Follow the suggested guidelines when assembling a reducing valve for use 1 Select a reducing valve appropriate for the intended use If high flow rates are desired 80 120 liters min use a two stage or modified single stage reducing valve Remove the protective valve cap H cylinder or protective tape E cylin der and crack the tank by opening and closing the valve quickly to expel any foreign material Perform this task with the valve pointing away from yourself and other people Attach the reducing valve to an appro priate c
9. Gas A percentage 15 mmHg 240 mmHg 6 3 Gas B percentage 25 mmHg 240 mmHg 10 4 Gas C percentage 200 mmH g 240 mmHg 83 3 Another example of this law s use is the calcu lation of the partial pressures of the various gases in the atmosphere Air is composed of nitrogen oxygen argon and other gases sometimes referred to as trace gases Nitrogen 78 08 Oxygen 20 95 Argon 93 Carbon Dioxide 03 Trace Gases 01 At an atmospheric pressure of 640 mmHg Denver Colorado what is the partial pres sure of oxygen and how does that compare to the partial pressure of oxygen in Seattle Washington atmospheric pressure of 760 mmHg Denver Colorado 640 mmHg x 2095 134 08 mmHg Seattle Washington 760 mmHg x 2095 159 22 mmHg There is a partial pressure difference of 25 14 mmHg for oxygen between the two cities due to a difference in atmospheric pressure Gay Lussac s Law Gay Lussac described the relationship between pressure and temperature of a gas He found that as temperature increases pres sure will increase as long as volume is con stant This is known as Gay Lussac s law This relationship is described in the following formula li NE h h Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User For example A gas at 30 C and 700 mmHg is com pressed to 900 mmHg What is the new te
10. be copied scanned or duplicated in whole or in part Licensed to iChapters User 4 CHAPTER ONE EVACUATED METAL CONTAINER A Ss _ Figure 1 2 A functional diagram of an aneroid barometer As air pressure causes the evacuated container to expand or contract the pointer moves adjacent to the scale Measurement of Gas Pressure where pressure measurement is desired As Other Devices gas exerts a force against the diaphragm or In addition to barometers mechanical container it causes the pointer s position to manometers and Bourdon gauges can be used change indicating the pressure Note that to measure gas pressure A mechanical these instruments are calibrated so that atmos manometer Figure 1 3 is similar in construc pheric pressure measures zero on the instru tion to an aneroid barometer A diaphragm or ment s scale The majority of manometers in evacuated container is exposed to the area respiratory care are calibrated in centimeters VESEEPSSE SE ES a 60 ath al ah af y A 4 4 A A A A A 4 4 4 j A 4 A A A A A A 4 j 4 j i y 0 BOEHRINGER 15 fpos V y dii 2 wu coo o L EE CM 15086 E 30 auno 7 POINTER U TH vibus Sa DIAPHRAGM Figure 1 3 A photograph and functional diagram of an inspiratory force manometer As pressure causes the evacuated container to expand or contract the pointer A moves adjacent to its scale
11. both A manifold consists of two or more cylinders connected together using high pressure steel or copper tubing When two or more cylinders are interconnected the total volume of gas available is greater than a single cylinder alone Part C of Figure 1 22 depicts a schematic of an oxygen supply system using two cylinder manifolds Figure 1 22 illustrates the three primary types of supply systems The supply system is designed to meet the Figure 1 22 Bulk oxygen supply systems that are typical for most medical care facilities A Liquid primary and liquid reserve B Liquid primary and cylinder reserve and C Cylinder primary and cylinder reserve institution s needs and requires periodic fill ing from an oxygen vendor Liquid gas can be delivered whenever the reservoir requires filling or on a regularly scheduled basis It is transported to the institution by truck or by rail A reserve supply is required to provide up to 24 hours of oxygen in the event that the main supply becomes depleted The reserve supply can consist of a smaller liquid reservoir or a manifold of cylinders When pressure in the main supply drops a valve automatically opens activating the reserve supply The pressure is reduced by means of a reg ulator or reducing valve before the gas enters the piping system Piping System Construction A piping system conducts the gas through copper pipes to points of use This piping sys tem is similar in d
12. concentration is at a maximum A patient with reactive airway disease is experiencing bronchospasm The patient s work of breathing has dramatically increased in the last few minutes This is an example of I Poiseuille s law II the Bernoulli theorem III increased airway resistance IV decreased lateral pressure a Land III b Iand IV c IL and III d IL and IV Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 58 CHAPTER ONE 13 14 15 16 17 18 19 You measure the volume of gas exiting a delivery device at 22 degrees Celsius to be 1 50 liters The gas passes through a heater warming it to 37 degrees Celsius What is the actual volume delivered to the patient a 1 56 liters b 2 00 liters c 2 50 liters d 3 12 liters The rate of gas diffusion into or out of a liquid is directly proportional to the partial pressure of the gas best describes a Charles law b Fick s law c Henry s law d Gay Lussac s law Given the following gas mixture Gas A 20 Gas B 50 Gas C 30 Total pressure equals 600 mmHg Find the partial pressure of Gas A a 10 mmHg b 20 mmHg c 80 mmHg d 60 mmHg Which of the following is constructed in a similar way to a thermos bottle a oxygen cylinder b oxygen concentrator c liquid oxygen reservoir d oxygen piping sy
13. exchanger converts the liquid to a gas by warming it Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User MEDICAL GAS SUPPLY EQUIPMENT 23 Figure 1 20 A contemporary portable liquid home oxygen system The larger reservoir is for use in the home The smaller portable reservoir may be filled from the larger one for trips away from home lasting up to eight hours at flow rates less than 2 liters per minute Courtesy CAIRE Inc Bloomington MN of these units when full vary from 5 3 to 9 0 Ibs Oxygen conservation devices such as pulse demand flow regulators described later in this chapter when used in conjunction with the liquid reservoirs can dramatically extend the duration of oxygen supply These devices when coupled with liquid supply systems and cylinders can result in oxygen savings of 3 7 times when compared to con ventional continuous oxygen flow delivery Mallinckrodt Puritan Bennett HELIOS Portable Liquid Oxygen System The HELiOS portable oxygen system is a small lightweight liquid oxygen reservoir that incorporates a pneumatic oxygen conserving device Figure 1 21 Patients requiring contin uous oxygen may be independent and ambu latory with this unit for up to 8 to 10 hours at a setting of 2 on the conserving device The weight of the unit when full is 3 6 pounds and only 2 7 pounds when empty The u
14. ir M a m LLL Figure 1 11 gas flow The Reynolds number formula is as follows _ Velocity Density Diameter Viscosity R e R Reynolds number Note that if you include the correct units in the calculation of Reynolds number the units cancel one another resulting in a number that is dimensionless As a general rule if the Reynolds number is greater than 2000 flow will be turbulent If the Reynolds number is less than 2000 flow will be laminar Poiseuille s Law Poiseuille described the resistance to the flow of gas or liquid through a tube when the flow is laminar He determined that it is directly related to volumetric flow length of the tube and viscosity of the gas and inversely related to the radius of the tube to the fourth power This law is generally expressed in the following formula y APQnyr 8 D u volumetric flow rate velocity X area V AP pressure gradient 3 1415 radius of the tube TT r u viscosity of the gas length of the tube A Laminar and B turbulent gas flow Resistance is equal to the change in pressure divided by the volumetric flow rate Solving Poiseuille s law for resistance R AP 8D m r This formula is often simplified for clinical applications to the following AP V R y AP R AP pressure gradient V volumetric flow rate R resistance Simply stated as the radius of a tube decreases by one half res
15. the disk will burst or fracture releasing pressure before the cylin der walls rupture The fusible plug pressure relief is made from an alloy that will melt when the ambient temperature exceeds 208 220 Fahrenheit When the plug melts or distorts pressure will be released preventing rupture of the cylinder OXYGEN 2 5 AIR 1 5 He O gt 80 and under CO gt 2 O gt 7 or under NITROUS OXIDE Figure 1 33 Pin index positions for medical gases Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 38 CHAPTER ONE REDUCING VALVES Single Stage Reducing Valve A single stage reducing valve reduces the pressure from the cylinder to a working pres sure in one step or stage All reducing valves operate by using two opposing forces spring tension and gas pressure separated by a flexi ble diaphragm Figure 1 34 illustrates the com ponent parts of a single stage reducing valve and its operation Gas pressure in the cylinder displaces the diaphragm upward When gas pressure and spring tension are equal the diaphragm is flat closing the poppet valve As the pressure within the chamber drops spring tension forces the diaphragm down opening the poppet valve This cycle repeats itself with the diaphragm oscillating back and forth opening and closing the poppet valve Spring tension determines the outlet pressure from the red
16. the gram molecular weight Compar ing oxygen and carbon dioxide oxygen s solubility is 023 while carbon dioxide s solu bility is 510 0 510 0 023 22 1 Solubility of CO This relationship shows that carbon dioxide is over 20 times more soluble in the blood than oxygen Once the gases are dissolved they must diffuse through the blood In determin ing the rate of diffusion you must now account for the gram molecular weight Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 14 CHAPTER ONE Solubility Sol Coef COJ igmw O Sol Coef O gmw CO _ 0 510 32 0 023 44 m 1 This relationship shows that carbon diox ide is 19 times more diffusible in the blood than oxygen This relationship is true assum ing that the partial pressures for the two gases are equal Normally in the alveolus the partial pressure of oxygen is greater than that for car bon dioxide resulting in a slightly greater rate of diffusion for oxygen MEDICAL GAS SUPPLY EQUIPMENT COMPRESSORS Medical compressors provide oil free com pressed air to power equipment and also to mix with pure oxygen to provide lower oxy gen concentrations The compressed air must ELECTRIC MOTOR VLLLLLALLLLLLLLLLLLALLLALALAL ALAA AAA A LLAMA La 2777777777777777 CONNECTING ROD Figure 1 12 A functional diagram of a piston
17. the liquid to a gas Figure 1 19 Once the liq uid has vaporized to a gas pressure will have increased The pressure is reduced to 50 psi by passing through a reducing valve After the pressure has been reduced to 50 psi the gas is then fed into the piping system Portable Reservoirs Smaller liquid reservoirs have been designed for home and ambulatory use Figure 1 20 The principles of construction are similar to the large bulk systems described earlier only smaller in scale The larger reservoirs designed for station ary use in the home vary in capacity from 20 to 43 liquid liters Although the capacity may seem small remember that one liquid liter of oxygen is equal to 861 gaseous liters This makes the capacity in gaseous liters range from 16 400 to 35 200 liters Physical size ranges of these reservoirs are diameters of 12 15 inches and heights of 27 38 inches and weights that vary when full between 84 and 160 Ibs The smaller portable reservoirs are designed to be easily carried on the shoulder or placed into a small cart for ambulation The liquid capacities of these portable units range from 6 liters to 1 23 liters giving them a gaseous capacity of 500 to 1058 liters Weights LLLA SSIS GASEOUS OXYGEN LIQUID OXYGEN HEAT EXCHANGER 2 7 A REGULATOR OUAU Figure 1 19 A bulk liquid oxygen storage and supply system Note the insulated container control valve and heat exchanger The heat
18. to Degrees Fahrenheit Celsius Temperature 32 Degrees Fahrenheit O1 Degrees Celsius to Degrees Kelvin Celsius Temperature 273 Degrees Kelvin 30 C 273 303 K Degrees Fahrenheit to Degrees Rankine Fahrenheit Temperature 460 Degrees Rankine 70 F 460 530 R with the pressure Boyle s law is described in the following formula Pi V a P gt V2 P original pressure Vi original volume P V new volume new pressure This formula is commonly rearranged as fol lows to solve for the original pressure P or the new pressure P P P V gt V P P V V For example Given the following V 500 ml P 700 mmHg and P 300 mmHg find the new volume P4 Vi EIC e V 700 mmHg 500 mL 1 167 mL 300 mmHg This law is often applied in the mechanics of ventilation of the lungs and calculating resid ual volume using a body plethysmograph Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 12 e CHAPTER ONE Charles Law Charles law states that if pressure remains constant the volume of a gas varies directly with the temperature in degrees Kelvin As the temperature increases the volume of the gas also will increase As the temperature of the gas decreases volume will decrease Charles law is summarized in the following formula Vi V h h Be
19. velocity The momentum transferred from these multiple collisions is what creates pressure or the force on the walls of a con tainer The temperature of a gas influences the level of kinetic activity and therefore the velocity of the molecules Pascal s Law Blaise Pascal a seventeenth century inves tigator described how force is transmitted in a fluid Pascal discovered that a fluid confined in a container will transmit force or pressure uniformly in all directions and that the pres sure or force at the walls of the container acts perpendicular to that surface Since gases behave according to fluid prop erties Pascal s law also applies Pressure at any point in a closed container is equal to the pressure at any other point in the same con tainer If you take a long closed tube and pres surize it with a gas the pressure at one end will be equal to the pressure at the opposite end Also the pressure acts equally in all directions with the force applied perpendicu lar to all surfaces of the tube Measurement of Gas Pressure Barometers The atmospheric pressure is measured with an instrument called a barometer There MEDICAL GAS SUPPLY EQUIPMENT 3 are two types of barometers mercury and aneroid The mercury barometer uses the weight of a column of mercury opposing the force of the atmosphere to measure atmospheric pressure Figure 1 1 The barometer consists of a closed column of mercury inverted in a s
20. 05 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User MEDICAL GAS SUPPLY EQUIPMENT 45 or adjusting an outlet orifice size At a given inlet pressure only so much flow can pass through a restricted orifice choked flow prin ciple When a large orifice is selected flow will be high Conversely a small orifice will provide a lower flow rate for a given inlet pressure It is important to use these flow meters with the correct inlet pressure the flowmeter is designed for typically 50 psi Figure 1 39 is an example of a fixed orifice reg ulator for an E cylinder This unit incorporates a reducing valve and a fixed orifice flowmeter into a single compact unit 7A Sen ul Uncompensated Thorpe Tube Flowmeter The components of an uncompensated Thorpe tube flowmeter include a V shaped tapered tube Thorpe tube a float and a nee dle valve Figure 1 40 Note how the needle valve is positioned proximal to the Thorpe EE tube The Thorpe tube becomes a variable ori fice The Thorpe tube gradually increases in Figure 1 40 An uncompensated Thorpe tube diameter from its base to the top of the tube flowmeter The flowmeter is calibrated with the pressure inside of the tube equal to ambient pressure The float provides a means of indicating the flow rate As the needle valve is opened gas pressure pushes the ball up in
21. 98 cm H O 6 895 Ib in 51 7 mm Hg 70 34 cm H O 1 cm H O 1 mmHg 1 KPa 1 Ib in to an area of lower pressure The area of greater pressure contains gas molecules with greater kinetic activity As a result of the increased kinetic activity energy the molecules push COILED TUBE J A EEE EEE Figure 1 4 A functional diagram of a Bourdon gauge As the coiled tube expands the gear mechanism rotates causing the pointer to move Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 6 CHAPTER ONE one another moving from the area of higher energy to the area of lower energy The rate of gas flow or velocity is depend ent on two factors the difference in pressure energy and the size of the opening between the two areas If the pressure difference is large gas flow will be faster If the pressure difference is small gas flow will be slower If the opening between the two areas is large more gas can pass through and the flow will be greater than if the opening is small Figure 1 5 Bernoulli s Principle During the eighteenth century Daniel Bernoulli studied the flow of gas through tubes He discovered that as the velocity of a gas increases the lateral pressure within the tube decreases This is due to the fact that the total energy content of the gas is constant The total energy of the gas r
22. Cylinders Do not lift a cylinder by its cap A OON Do not drag or slide cylinders use a cart Gray and green Brown and green Gray and white Brown and white White and black SAFETY RULES FOR CYLINDER USE Common sense and the practice of certain safety precautions will ensure safety for both you and your patient Remember at all times that a medical gas cylinder contains gas pres surized up to 2200 psi If the cylinder or cylinder valve were to rupture disastrous consequences could result Rules and pre cautions recommended by the Compressed Gas Association and published in their pam phlet Characteristics and Safe Handling of Medical Gases 1971 are summarized in Table 1 4 Always leave protective valve caps in place when moving a cylinder Do not drop a cylinder strike two cylinders against one another or strike other surfaces 5 Use a cart whenever loading or unloading cylinders Storing Cylinders 1 Comply with local and state regulations for cylinder storage as well as with those established by the National Fire Protection Association 2 Post the names of gases stored 3 Keep full and empty cylinders separate Place the full cylinders in a convenient spot to minimize handling of cylinders 4 Keep storage areas dry cool and well ventilated Storage rooms should be fire resistant 5 Do not store cylinders close to flammable substances such as gasoline grease or petroleum product
23. TROUBLESHOOTING Assembly Oxygen Conserving Devices 1 Connect the conserving device to an oxygen source cylinder or liquid system a An oxygen cylinder requires the use of a regulator to reduce the cylinder pressure and to set the oxygen deliv ery to the prescribed flow The con serving device is attached to the outlet of the regulator A liquid system requires the use of a flowmeter which is used to set the desired flow rate The conserving device is attached to the outlet of the flowmeter A portable liquid reservoir may also be used by threading a barbed hose fitting adapter into the inlet port of the conserving device and attaching the other end to the outlet of the portable reservoir set at the appro priate flow rate Connect the delivery tubing of the nasal cannula or transtracheal catheter to the barbed outlet of the conserving device Delivery tubing should never exceed 35 feet in length 3 Depress the On Off button on the top of the unit to turn the unit on The unit will perform a self calibration about 1 second and then will operate normally Troubleshooting When troubleshooting oxygen conserv ing devices please follow the suggested troubleshooting algorithm ALG 1 6 1 If the unit fails to deliver oxygen flow a Check tubing and cannula or trans tracheal catheter for obstructions or kinks Make certain that the oxygen flowmeter is on and that there is a suf
24. anagement systems 20 50 liquid oxygen and high pressure oxygen service and repair manual Ft Pierce FL Author Puritan Bennett Corporation 2003 HELiOS portable liquid oxygen unit operating instructions Pleasanton CA Author Puritan Bennett Corporation 1989 Companion 5 oxygen saver operating instructions Lenexa KS Author Puritan Bennett Corporation 1989 Puritan Bennett Companion 5 oxygen saver service manual Lenexa KS Author Sacci R 1979 Air entrainment masks Jet mixing is how they work The Bernoulli and Venturi principles are how they don t Respiratory Care 24 10 928 931 Tiep B L et al 1990 Pulsed nasal and transtracheal oxygen delivery Chest 97 2 364 368 Ward J J 1988 Equipment for mixed gas and oxygen therapy In T A Barnes et al eds Respiratory care practice Year Book Medical Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part APPENDIX ANSWER KEYS TO SELF ASSESSMENT QUESTIONS Chapter 1 Medical Gas Supply Equipment 1 b 6 a 11 a 16 c 21 6 26 b 2 Zs d 12 a 17 e 22 27 9 6 8 c 13 a 18 d 23 b 28 b 4 d 9 a 14 c 19 c 24 c 29 a D uc 10 d 15 e 20 c 25 b 30 a This page contains answers for this chapter
25. as a result of the smaller molecules of the gas col liding with them This random movement can be observed today by watching the behavior of cigarette smoke under a microscope The random motion of the larger particles is termed Brownian motion The collisions between molecules are com pletely elastic This means that there is no energy transferred as a result of these colli sions Energy is not lost or gained by the mole Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User cules as a result of this process Therefore the total energy of the gas remains constant The Kinetic activity or speed of the mole cules is largely determined by the temperature As the temperature of a gas increases so does the kinetic activity Conversely as the temper ature of a gas decreases its kinetic activity decreases In ideal gas behavior the gas molecules do not attract or repel one another There is no physical attractive force between individual molecules The molecules move about freely without any significant attractive forces between them GAS PRESSURE Causes Gas pressure force per unit area is caused by the individual gas molecules colliding with one another and the walls of a container This exerts a force on the container walls Even gas molecules have mass and a velocity and thus possess a certain momentum momentum mass X
26. be copied scanned or duplicated in whole or in part Licensed to iChapters User 60 CHAPTER ONE 27 A potential disadvantage to the Mallinckrodt Puritan Bennett HELiOS system is a itis heavier than other portable liquid reservoirs b it has a smaller capacity than competing units c it must be used with the HELiOS7 dual lumen cannula d it can only provide flow rates of up to 2 L min 28 Back pressure will affect the accuracy of which of the following flowmeters I Compensated Thorpe tube II Uncompensated Thorpe tube III Bourdon flowmeter a I and IL only b IL and III only c Land III only d II only 29 A back pressure compensated flowmeter I reads correctly if back pressure is applied II reads lower than the actual flow when back pressure is applied III has the needle valve downstream from the Thorpe tube IV has the needle valve upstream from the Thorpe tube a I and III b Iand IV c IL and III d II and IV 30 When using a fixed orifice flowmeter it is important to calibrate it using a calibration flowmeter use the correct inlet pressure ensure that there isn t a restriction in the inlet tubing adjust the regulator to the pressure on the label aoe Selected Bibliography Chad Therapeutics 1993 Product information and instructions for use Model 301 Oxymatic electronic oxygen conserver Chatsworth CA Author Chad Therapeutics 1993 Product information and instructions for u
27. between molecules is much greater than the actual diameter of the individual molecules Therefore gases consist of large amounts of open space between the modified single stage reducing valve multiple stage reducing valve regulator oxygen proportioner demand pulse flow regulators e Differentiate between the following oxygen flowmeters describe their construction and principles of operation Bourdon gauge uncompensated Thorpe tube compensated Thorpe tube fixed orifice flowmeter Henry s law Pressure Kinetic theory Reducing valve Laminar gas flow Regulator Manifold Reynolds number Mechanical Thorpe tube manometer flowmeter Membrane enricher Torr Mercury barometer Molecular sieve concentrator Oxygen concentrator Oxygen conserving device OCD Poiseuille s law Turbulent gas flow Venturi mask Viscous shearing Zone valves gas molecules The volume of the molecules if they could be gathered together is very small when compared to the total volume of the molecules and space as a whole Gas molecules are in constant random motion The molecules travel in a straight line or path This motion continues until they col lide with something else These collisions can occur with other molecules the walls of the container holding the gas or other particles Evidence of these collisions was first described by Robert Brown in 1827 He described the motion of larger particles that moved
28. c Use of excessive length of connect ing tubing Use a maximum of 50 feet or 15 meters of tubing If the unit operates but you are unable to obtain the appropriate oxygen concentration a Ensure the patient has an adequate supply of compressed oxygen or liquid oxygen b Remove the unit from service and return it to an authorized service center Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User MEDICAL GAS SUPPLY EQUIPMENT 21 ON amp pe ooIq p p u se eoe doJ Buiqni uorsueixe pue syu 10 49949 eui S amp pe oo q eoIep eui eotep AJeAI Op gorda 10 ueo 3 eui S juened eui IN Jojuouu pue yun 9je1edo 0 enuinuo ON eui SI eui SI amp pexooIq eBueuosip sre amp pe ooiq eyelul Jie SOA Jie eByeuosip Jo yed 1e98 5 Joy exye1ur eui BOIAJAS AO 40M yun eui seoq C 1HVIS jJ 4010414232100 uas xo j0015231qn04 04 MOY SUIQUISIP 1111140810 uy c i 91V ON ON ON gpeddiy JexeoJq uno y SeH JeyeeJq N9119 y Josey 49mod eaey Jepno eou1oeje au seoq duJe 1S9 UM UND y YOSYD ep no e911 99 jepnno eougoo o ue 0 pajooeuuoo ue OjuI JO e1 USDUOD yun eui S y Bnid uo p u n u ym JOM 0 I8 3 Sog Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned
29. c manometer d reducing valve A Bourdon gauge I uses a coiled tube II uses a sealed diaphragm III measures pressure IV measures flow a Land II b Iand IV c IL and III d IL and IV The statement As temperature increases pressure also increases best describes a Gay Lussac s law b Dalton s law c Henry s law d Charles law Bernoulli s theorem best describes a the relationship between temperature and pressure of a gas b the relationship between volume and pressure of a gas c an energy balance or conservation between velocity and pressure d the relationship between pressure of a gas and its ability to dissolve into a liquid An air entrainment mask operates by mixing source gas oxygen and room air This device operates using a viscous shearing and vorticity b Bernoulli s theorem c Venturi s principle d Poiseuille s law You are analyzing the F O of a patient s HAFOE device which reads 0 85 The entrainment port is set at 40 Why would the analyzed oxygen concentration differ so much from the setting a The analyzer is malfunctioning b The patient s respiratory rate is affecting oxygen delivery c More room air is being entrained d There may be an obstruction distal to the entrainment port A gas s velocity is said to be choked when a velocity can no longer increase b a maximum temperature is reached C pressure is at a maximum d the
30. capillary tube at the boundary layer by shear forces and vorticity When these high velocity jets are used in ventilators the gas flow downstream from the nozzle at a distance of approximately three times the diameter of the nozzle exit ceases to be well behaved or laminar At this point a shear layer develops and ambient gas may be entrained by vorticity When used in this application these jets are sometimes referred to as injectors although the term ejector is technically more correct If designed properly the flow output from an ejector will exceed the flow provided by the nozzle alone Reynolds Number Reynolds number is used to determine if gas flow through a tube is laminar or turbu lent Laminar gas flow is a smooth uniform flow that requires less energy pressure to sustain Turbulent gas flow is more erratic and irregular requiring more energy to sustain Figure 1 11 compares turbulent and laminar OBSTRUCTION VENTURI TUBE Figure 1 10 An obstruction can result in decreased air entrainment through a venturi tube P1 is less than P2 atmospheric and the obstruction causes P3 to be greater than P2 Note that the obstruction increases pressure distal to the entrainment ports thus decreasing gas entrainment Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 10 CHAPTER ONE LLL A WLLL Mop PE
31. cated in whole or in part Licensed to iChapters User MEDICAL GAS SUPPLY EQUIPMENT 17 Suonoeuuoo Ie ueyui 9sou Jo Buiqni eoejdeu z JO uononusqo seajD 4 Jey 1o ut ooe doJ 10 uea 2 juened eui JOWUOW pue j1ueuudinbe y ejejedo 0 enunuo5 Ayyioey aeda Jeoipeui oiq 0 pues Suonoeuuoo Jo sBumiy 1e syed Aue 919 oy pejonijsqo sesou Jo Buiqny Bunoeuuoo Aue aly ZAUIP 4941 J9 U amp MO indino eui S yO Bunejedo JosseJ4duioo eui S C 1HVIS ON so 40ssa4dui02 v j001531qn04 04 MOY SUIQUISIP 1111140810 UY b i 919V ON p ddu Jo e9Jq N3119 e JO umojq BSN e S So MNO I9nno eougoe e eui S ON uo peuunj U9UM XJOM 1 Seoq SoA ON Jeyealg nouo 1eseu Z JO asnj eoejdeu 4 JoyeoIpul 1991 10 dur e YUM 19 no eui X99490 Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 18 CHAPTER ONE PURGE VALVE 4 WAY VALVE RESERVOIR COMPRESSOR BACTERIA FILTER ee horrere OLII e o e ed n f INLET FILTER SIEVE BEDS BACTERIA FILTER Figure 1 15 A functional diagram of an oxygen concentrator flow rate out of the concentrator If the flow rate is set for 2 liters L per minute or less the oxygen concentration will be 90 or some times higher If flow is increased to 10 liters per minute t
32. common alkaline C size batteries The battery life averages 3 to 4 weeks of use Inspiratory Detection During inspiration a sub ambient pressure is created in the lungs as the lungs expand During exhalation chest wall recoil creates a pressure in the lungs that is greater than ambi ent pressure These very small pressure changes are communicated to the Oxymatic units through the patient s nasal cannula The Oxymatic units have an internal flexi ble diaphragm that changes position in response to the pressure changes in the patient s lungs The neutral position position between exhalation and inspiration is elec tronically detected When diaphragm motion away from the neutral position is detected inspiration is detected An electronic signal is transmitted to the solenoid valve opening it and delivering a 35 mL pulse of oxygen within 0 2 seconds of the start of inspiration Oxygen Flow Control The Oxymatic units deliver a constant 35 mL pulse of oxygen when the solenoid valve opens The units control oxygen flow delivery by altering how frequently these con stant volume pulses are delivered Clinical trials have shown that when the Oxymatic units deliver 35 mL pulse of oxygen every breath this is equivalent to a continuous oxygen flow of 4 L min determined by oxy gen saturation When a pulse is delivered three out of every four breaths 7576 of the time this is equivalent to a continuous flow of 3 L min When a pul
33. compressor be oil free for two primary reasons 1 oil par ticles when inhaled are not healthy 2 oil droplets when mixed with oxygen may result in spontaneous combustion Spontaneous combustion is the ignition of a substance without the addition of heat There are three types of compressors piston diaphragm and centrifugal Piston Compressor A piston compressor utilizes a piston driven by an electric motor Figure 1 12 Carbon or Teflon piston rings seal the piston against the cylinder wall eliminating the need for oil The compressed air is fed into a storage reservoir providing a large supply of air to meet high flow demands A filter at the outlet removes any particles from the compressed air The pressure is then reduced to 50 psi by means of a reducing valve before the air is fed into a piping system Diaphragm Compressor Diaphragm compressors utilize a flexible diaphragm driven by an electric motor to compress the air Diaphragm compressors are typically employed to power small nebulizers They are not capable of providing the large amounts of compressed air needed for large ONE WAY VALVES PISTON Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User MEDICAL GAS SUPPLY EQUIPMENT 15 ASSEMBLY AND TROUBLESHOOTING Assembly Compressors To prepare a compressor for use com plete the following
34. ctor X gauge pressure 28 liters psi X 1000 psi 280 liters Step 3 Duration in minutes cylinder contents liter flow 280 L 15 L min 18 minutes Answer No the cylinder will not last MEDICAL GAS SUPPLY EQUIPMENT 33 Note It is common to arrive at an answer of hours expressed as a decimal form for example 6 3 hours Each tenth of an hour is 6 minutes so 6 3 hours equals 6 hours and 18 minutes It is common clinical practice to leave 500 psi remaining in the cylinder prior to changing it providing that a maximum dura tion is not desired airborne or ground trans port By leaving 500 psi in the cylinder water other gases and foreign material cannot enter the cylinder helping to extend its useful life To calculate the cylinder duration leaving 500 psi in a cylinder follow the example out lined below You are asked to set a patient up on an oxygen mask at 12 L min in the X ray depart ment The facility is in an older part of the institution and does not have piped oxygen You move an H cylinder to the area to sup ply oxygen for your patient The cylinder gauge reads 1250 psi How long will the cylin der last if you leave 500 psi remaining in the cylinder Step 1 H tank factor 244 cu ft 28 3 liter cu ft 2200 psi 3 14 L psi Step 2 Content of cylinder tank factor X gauge pressure 500 psi 28 L psi 1250 psi 500 psi 2355 L Step 3 Duration in minutes cyl
35. der Figures 1 27 and 1 28 Hydrostatic Testing Every five years a cylinder is subjected to a hydrostatic test to measure its elasticity The cylinder is filled to a pressure equal to 5 3 its working pressure and cylinder expansion is measured If the expansion is within tolerance the cylinder is returned to service If the cylin der fails the test it is removed from service and destroyed The inspector s mark and the date of the test followed by a sign steel cylinders only are then stamped into the shoulder of the cylinder If a star follows the inspection date the cylinder may go for ten years before another hydrostatic test is per formed steel cylinders only Some communities may be limited in their ability to provide hydrostatic testing for fiber wrapped cylinders since the designed service pressure is 3000 psi The testing site would need equipment capable of exceeding 5000 psi pressure to hydrostatically test a fiber wrapped cylinder FUP e S AR EAAS 2 012W WOCO Figure 1 28 Cylinder markings indicate that the cylinder is made from high tensile strength heat treated steel DOT 3AA and has a service pressure of 2015 psi 2015 The serial number is below the DOT numbers and the owner s stamp is below the serial number Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 30 CHAPTER ONE Cylinder Siz
36. e alarm by discon necting the air or oxygen source Adjust the blender to the desired FO fraction of inspired oxygen Attach the oxygen therapy device or other medical equipment to the outlet of the blender a If the outlet does not have a one way check valve attach the equipment to the blender before attaching the oxy gen and air supply lines 8 Verify oxygen concentration with an oxygen analyzer Troubleshooting Troubleshooting a blender consists of checking for leaks and verifying oxygen concentration The following is a sug gested algorithm ALG 1 6 1 Sources of leaks a Between the gas source piping sys tem or regulator and the high pres sure hoses Between the high pressure hoses and the blender Between the blender and the oxygen equipment 2 Verify the oxygen concentration using an oxygen analyzer If there is a tremen dous discrepancy greater than 2 calibrate the analyzer and repeat verifi cation If the discrepancy still exists replace the blender and have the defec tive unit repaired by your local vendor or authorized biomedical repair facility Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User MEDICAL GAS SUPPLY EQUIPMENT 43 START Continue to use the blender and monitor the patient Is the blender working OK NO NO Is there a
37. e then tested for purity Oxygen and air lines are checked with analyzers to ensure that they are delivering the correct gas Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User Once the purity test has been completed the system may be used for patient care Safety Features Safety features in a medical gas piping sys tem include alarms zone valves riser valves and pressure sensors Alarms are included in a piping system These alert personnel to pressure drops in the system caused by leaks or depletion of the gas supply The alarm must be placed in an area that is attended 24 hours a day For this reason the hospital telephone switchboard is a com mon location for medical gas alarm panels Zone valves are shutoff valves placed at strategic positions so that gas supply to differ ent areas may be cut off in the event of a fire Zone valves also are placed at the base of risers pipes conducting gas from one floor to another as shown in Figure 1 23 In some acute care facilities Respiratory Care Practi tioners RCPs are required to identify and turn off the appropriate zone valves in the 3rd FLOOR 2nd FLOOR MAIN SUPPLY SHUT OFF D lt VALVE J STATION OUTLETS MEDICAL GAS SUPPLY EQUIPMENT 27 event of a fire If a zone valve is turned off the RCP is also responsible to ensure that patients requiring oxy
38. eal Systems DOC 2000 Demand Oxygen Controller The Transtracheal Systems DOC 2000 demand oxygen controller is a pulse demand oxygen delivery device that conserves oxygen by delivering it only during inspiration Fig ure 1 45 The unit is electronically controlled and may be powered by a rechargeable Ni Cad battery or a 120 v 60Hz power adapter which also functions to recharge the Ni Cad battery When the Ni Cad battery is fully charged the DOC 2000 can operate between 8 and 10 hours before requiring a recharge Inspiratory Detection The DOC 2000 detects inspiration using a sensitive pressure transducer During inspira tion a sub ambient pressure is created in the patient s nares as the lungs expand When the pressure transducer senses the drop in pres Figure 1 45 A photograph of the DOC 2000 demand oxygen controller Courtesy Transtracheal Systems Englewood CO sure a valve opens delivering oxygen to the patient Oxygen Flow Control The operation of the DOC 2000 is based upon switching the patient between the oxy gen source valve 2 and the pressure sensor valve 1 When valve 2 is not energized oxy gen flows from the source directly to the patient Figure 1 46 Simultaneously when valve 2 is not energized valve 1 is energized which connects the transducer U11 to the normally closed atmospheric port Each time the pressure transducer is referenced to ambi ent pressure it recalibrates itself which ma
39. educing valves or regulators when attaching equipment designed for lower operating pressures than those contained in the cylinder Do not force any threaded connections Verify that the threads you are using are designed for the same gas or gas mixture in accordance with the American Standard Safety System Connect a cylinder to a manifold designed for high pressure cylinders only Use equipment only with cylinders containing the gases for which the equipment was designed Open cylinder valves slowly Never use a wrench or hammer to force a cylinder valve open Treat cylinders and cylinder valves with care Do not use compressed gases to dust off yourself or your clothing Keep all connections tight to prevent leakage Before removing a regulator turn off the valve and bleed the pressure Never use a flame to detect leaks with flammable gases Do not store flammable gases with oxygen Keep all flammable anesthetic gases stored in a separate area Reprinted with permission from Gary C White Basic Clinical Lab Competencies for Respiratory Care 4th Edition Thomson Delmar Learning 2003 DURATION OF GAS FLOW Once these facts have been committed to In order to calculate how long a cylinder will last at a given liter flow it is important to remember four key facts memory the duration of any H or E cylinder may be calculated Tank Factors 1 When full an H cylinder contains 244 cubic feet of oxygen 2 When
40. en connected to a gas source Back pressure applied distally to the nee dle valve has no effect on its performance Additional pressure or restriction causes the flowmeter to behave as if the needle valve is closed further restricting flow If enough pres sure is applied to stop the flow eventually the pressure proximal and distal to the needle valve will equal 50 psi the float will no longer be suspended and gas flow will cease When working with Thorpe tube flowme ters it is often necessary to know if it is com pensated or uncompensated There are three ways to identify a compensated flowmeter 1 The label will state Calibrated at 760 mmHg 70 F 50 psig inlet and outlet pressure Figure 1 41 A compensated Thorpe tube flowmeter 2 With the needle valve closed the float will rapidly jump up the Thorpe tube when the flowmeter is connected to an oxygen source 3 Check the position of the needle valve if it is downstream from the Thorpe tube it is compensated Ranges of Flowmeters Several manufacturers offer flowmeters with expanded calibration scales that extend beyond the range of the typical 0 to 15 L min flowmeter s calibrated range A high range flowmeter is calibrated from 0 to 75 L min in 5 L min units Figure 1 42A The high range flowmeter is useful in Continuous Positive Airway Pressure CPAP and high flow oxy gen delivery systems with high flow clinical applications Low range flowme
41. enomenon in which the gas molecules are system can be damaged by water that may be forced under pressure into the pores of the contained in the high pressure supply lines To Zeolite As the nitrogen oxygen mixture air avoid this potential problem the use of water flows through the pores of the Zeolite the traps is recommended by most manufacturers nitrogen molecules stick or adhere to the sur face and the oxygen molecules pass through CONCENTRATORS When the sieve is depressurized the nitrogen is released to the atmosphere and exhausted Oxygen concentrators are electrically pow separating it from the oxygen enriched gas ered devices that separate the oxygen from the Oxygen concentrators use some of the oxy atmosphere and deliver it under pressure for gen rich gas flowing from one sieve to purge medical use There are two types of oxygen the other sieve This is done prior to pressur concentrating devices molecular sieve and ization to improve oxygen percentage levels membrane types The purge cycle helps to rid the canister of The molecular sieve concentrator is more nitrogen before it is again pressurized with effective than the membrane type Inlet air toa room air compressor is passed through a particle filter Oxygen concentration will vary between to remove large particles from the air Then the 50 to greater than 90 depending on the Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or dupli
42. es Medical gas cylinders are manufactured in many sizes Figure 1 29 The most com mon sizes encountered in the hospital envi ronment are the H and the E cylinders The H cylinder contains 244 cubic feet of oxygen and weighs approximately 135 pounds The E cylinder contains 22 cubic feet of oxygen and weighs approximately 16 pounds Since the E cylinder is smaller and lighter it is usually used for ambulation of patients with a cart and for transporting COMMON METRIC EQUIVALENTS APPROX 1 Cubic Foot 7 48 gallons 28 3 liters 1 Gallen 3 785 liters 0 132 cubic feet Liter 0 264 gallons 0 035 cubic feet m HU 337 332 1 ib 8 oz 3 ids 13 oz o mM ie 23 3 2 Ibs 0 oz 3 jr 500 132 17 6 0 Ibs 29 oz 500 132 17 6 o y 1590 249 z 332 56 3 ibs 13 oz 6 ibs 7 oz i 660 174 aii 141 tib Joz 1 Ib 15 oz 375 vy 32 t ib 0 oz 3703 Figure 1 29 Cylinders are manufactured in different sizes Courtesy BOC Gases formerly Airco Murray Hill NJ patients from one place to another within the hospital Color Coding The Compressed Gas Association has developed a color code for the different med ical gases and gas mixtures This code was published by the Department of Commerce through the recommendation of the Bureau of Standards An international color code also exists for medical gases The only difference between the two color code
43. esign to the water system in your home or apartment however it must conform to stricter standards of construction These systems are made from seamless K or L type copper tubing The tubing must meet specific standards regarding its ability to with stand pressure without rupturing All joints are sweat soldered using silver solder Sweat soldering is accomplished by apply ing heat to the joint using a torch The solder is melted flows into the joint and seals it Flux may be used to clean the joint and allow the solder to adhere to the metal better After soldering joints are carefully checked for leaks The pipes are independ ently supported to the building structure at specified intervals This means that nothing else may be attached to the building s struc ture at the same point where the medical gas piping system is attached Following construc tion the system is cleaned of any flux or debris and pressure tested The system is pres surized to 1 5 times its working pressure with dry oil free air or with nitrogen Each joint is then checked for leaks The system is allowed to stand for 24 hours at this pressure and must remain leak free during this time in order to pass final inspection Following the pressure test both the oxy gen and air supply lines are charged with gas The oxygen piping system is supplied by a bulk oxygen system while a medical air com pressor supplies gas for the air piping system The outlets ar
44. essure remains constant Figure 1 7 The principle of viscous shearing Note how the quiescent gas reduces the high velocity of the gas stream through the formation of vortices Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 8 e CHAPTER ONE PRESSURE Xy M LT qe xz B VENTURI TUBE Figure 1 8 Venturi s principle A an illustration of the pressure gradient through a venturi tube B a functional diagram of a nozzle combined with a venturi tube to form an ejector Bb m m MA III c7 nmmEEEEEEE CONSTANT AREA DUCT EJECTOR Figure 1 9 A functional diagram of a constant area duct ejector because the diameter of the tube is constant tube These devices are employed in nebuliz unlike the venturi tube An advantage of this ers and oxygen air entrainment devices device is that an increased pressure down where there is moderate resistance down stream from the straight walled tube has less stream from the tube effect on gas entrainment than with a venturi Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User Effects of Increased Distal Pressure on Venturi and Constant Area Ducts An increase in pressure downstream from an ejector will decrease the amount of ambient air entrainment An increase i
45. esults from the kinetic energy created by the velocity and pressure energy As velocity increases the pressure must decrease for the total energy to remain constant conservation of energy As gas flow increases more of the gas s energy is con Figure 1 5 Factors influencing gas flow A two different pressures B two different orifice sizes tained in kinetic energy causing a further area along its length A cross sectional change reduction in lateral pressure Figure 1 6 In is required to change the velocity Bernoulli s this application Bernoulli s principle applies equation assumes that the fluid is incompress to the flow of gas within a tube that changes in ible that is that the specific weight weight gt mE gt ts Figure 1 6 Diverging and converging ducts A the diverging duct slows the velocity and increases the pressure B the converging duct increases the velocity and decreases the pressure Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User per unit volume is constant If the fluid were to be compressed volume would decrease while the weight would remain constant increasing the specific weight Keep in mind that gases will remain incompressible at low velocities generally less than 100 meters per second This principle is commonly applied in respiratory care equipment The reduced pres
46. eter is out of calibration replace it ALG 1 7 An algorithm describing how to troubleshoot medical gas flowmeters DEMAND PULSE FLOW OXYGEN DELIVERY DEVICES Demand pulse flow oxygen delivery devices are oxygen delivery devices which are designed to deliver oxygen only during the inspiratory phase A common name for these devices is an oxygen conserving device OCD During a normal ventilatory cycle when using continuous flow oxygen oxygen delivered during the last part of inspiration dead space volume and the oxygen delivered during exhalation are not usable Dead space volume is the portion of oxygen delivered which does not participate in gas exchange at the alveoli Figure 1 43 Demand pulse flow oxygen delivery devices are able to sense the start of the inspiratory phase and deliver oxygen only during inspiration Figure 1 44 By delivering oxygen only during that part of the ventilatory cycle that is usable oxygen Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User EXHALATION 77 XC e Ses C 260505092 S X X X X CR 405 5 MEDICAL GAS SUPPLY EQUIPMENT 49 INHALATION Pre inspiratory Pause OOOO TIME Bb Non usable oxygen Ed Usable oxygen Figure 1 43 A graph illustrating usable and nonusable oxygen during continuous flow delivery Courtesy Puritan Bennett Corporation Lenexa
47. ficient quantity of oxygen pres sure for cylinders or weight for liq uid systems The patient may not be generating a sufficient inspiratory effort to acti vate the inspiratory detection circuit Patients with advanced lung disease may not be candidates for pulsed oxygen delivery and may require continuous flow Verify that the batteries are in good condition and are in place if the unit is battery powered Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User MEDICAL GAS SUPPLY EQUIPMENT 55 a N J juened y Op uow pue 14 p eui esn 0 BNUIUOD amp pooD s n yeq y eJ Jamod Bunje6 HUN eui S SOA 22102p SULAAASUOI UASAXO uv jooisajqno4 0 MOY SUIGLIISAP myos UY 8 OW seuejeq y eoejdeu yO Bunejedo yun eui S C 1HVIS jJ ON SOA 4 MO I seb 99lAop JeB6u1 1uened jueJeJlp e y ue Buisn jepisuo UO AJLA OAJ 6A Jopui o Japul Ao au S y uo WNL e nuueo eoe dai 10 uononuisqo 18919 peionuisqo e nuueo eui S o Duwoll ueD xo s Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 56 CHAPTER ONE CLINICAL CORNER Medical Gas Supply Equipment 1 You are on call for a home care com pany that employs you as a respi
48. fore beginning this calculation the tempera ture must first be converted to Kelvin or absolute temperature To convert from Celsius to Kelvin add 273 degrees For example given an original volume of 400 mL an original tem perature of 20 degrees Celsius and a new tem perature of 40 degrees Celsius find the new volume DWV Y 2 T Converting Celsius to Kelvin 20 4275 2994 amp 40 273 313K 313 K 400 mL 293 K 427 3 mL V An easy way to demonstrate this law is to attach an inflated balloon to a small narrow necked chemistry flask then heat the flask with a Bunsen burner As the gas warms it expands causing the balloon to become larger Dalton s Law Dalton s law is sometimes referred to as the law of partial pressures Dalton described how the pressure of a gas composed of a mix ture of gases is equal to the sum of the partial pressures of all the discrete gases That is the total is equal to the sum of the parts Further more he stated that the partial pressure each gas exerts would be the same as if the gas occupied the total volume alone Lastly the partial pressure of each gas is proportional to its volumetric percentage For example Gas mixture D is composed of 15 mmHg gas A 25 mmHg gas B and 200 mmHg gas C What is the total pressure GasA 15 mmHg Gas B 25 mmHg Gas C 200 mmHg Total Pressure 240 mmHg What is the percentage of each gas in the mixture
49. from this text or product contact us by Tel 800 730 2214 Fax 800 730 2215 www thomsonrights com NOTICE TO THE READER Art amp Design Specialist Jay Purcell Project Editor Natalie Wager Production Editor John Mickelbank Technology Project Coordinator Carolyn Fox Library of Congress Cataloging in Publication Data White Gary C 1954 Equipment theory for respiratory care Gary C White 4th ed p cm Includes bibliographical refer ences and index ISBN 1 4018 5223 8 1 Respiratory therapy Equip ment and supplies 2 Respirators Medical equipment DNLM 1 Respiratory Therapy instrumentation WB 26 W584e 2005 Title RC735 15W48 2005 615 8 36 dc22 2004015051 Publisher does not warrant or guarantee any of the products described herein or perform any independent analysis in connection with any of the product information contained herein Publisher does not assume and expressly disclaims any obligation to obtain and include information other than that provided to it by the manufacturer The reader is expressly warned to consider and adopt all safety precautions that might be indicated by the activities described herein and to avoid all potential hazards By following the instructions contained herein the reader willingly assumes all risks in connection with such instructions The publisher makes no representations or warranties of any kind including but not limited to t
50. full an E cylinder contains 22 cubic feet of oxygen It is common practice to use tank factors in the calculation of cylinder duration By know ing the four key facts listed above these fac tors may be derived Table 1 5 illustrates how 3 Full cylinders contain 2200 psi pressure these factors are derived 4 One cubic foot of oxygen equals 28 3 liters Once these factors have been derived it is Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User TABLE 1 5 Tank Factor Calculation Size cu ft X 28 3 liters cu ft Pressure when full Tank Factor 244 cu ft 28 3 liters cu ft 2200 psi 3 14 liters psi H cylinder E cylinder 22 cu ft 28 3 liters cu ft 2200 psi 28 liters psi easy to convert from gauge pressure psi directly to liters To accomplish this multiply the gauge pressure by the tank factor for that cylinder For example You are asked to help move a patient from the Emergency Room to the Intensive Care Unit which usually takes about twenty min utes You are manually ventilating the patient using a resuscitation bag at a liter flow of 15 liters per minute Will the department s E cylinder containing 1000 psi have enough gas for the transport Step 1 E tank factor _ 22 cu ft 28 3 liters cu ft 2200 psi 0 28 liters psi Step 2 Content of cylinder tank fa
51. fy the markings stamped on the cylinder shoulder e list fifteen rules established by the Compressed Gas Association and the National Fire Protection Association for the safe storage and handling of compressed medical gas cylinders e Differentiate between the following oxygen regulation devices describe their construc tion and principles of operation direct acting cylinder valve indirect acting cylinder valve single stage reducing valve KEY TERMS Absolute Choked flow temperature Combined gas law Adsorption Compressors Aneroid barometer Dalton s law Bernoulli s principle Diaphragm Blender compressors Bourdon gauge Direct acting cylinder Bourdon gauge valve flowmeter Ducted ejector Boyle s law Fick s law Brownian motion Fixed orifice Centrifugal flowmeter compressor Gay Lussac s law Charles law Graham s law PHYSICS OF THE PRINCIPLES BEHAVIOR OF GASES Gases behave according to the kinetic theory The kinetic theory describes the behav ior of ideal gases and it incorporates five important points These points are 1 gases are composed of discrete molecules 2 the molecules are in random motion 3 all molec ular collisions are elastic causing no energy transfer between molecules 4 the molecular activity is directly dependent upon the tem perature and 5 there is no physical attraction between the molecules composing the gas Gases are composed of very small discrete molecules The distance
52. gen receive it from cylinders or another source during transport from the scene of a fire and also when returning the patients to their rooms Pressure sensors are placed throughout the piping system to monitor pressure Line pres sure in most hospital systems is 50 psi Station Outlets Medical gas outlets located at the points of desired use are termed station outlets Special fittings are incorporated into these outlets preventing the connection of equipment designed for a different gas Examples of these fittings include Diameter Indexed Safety Fittings and quick connect fittings The Diameter Indexed Safety System DISS was designed by the Compressed Gas Association This system utilizes differing thread pitch connection diameter and inter nal and external threading to prevent the ZONE VALVES Figure 1 23 Placement of safety shutoff valves in a piping system Note the placement of the main supply shutoff riser valves and zone valves Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 28 CHAPTER ONE Figure 1 24 A photograph of a DISS oxygen fitting attachment of equipment designed for dissim ilar gases or gas mixtures Figure 1 24 It is designed for pressures less than 200 psi which by definition is termed low pressure Check valves incorporated into station outlets to prevent gas loss when not in
53. hal low reservoir open to the atmosphere When the column is inverted in the reservoir a vac uum is created as gravity pulls the column of mercury down from the top of the closed tube Atmospheric pressure against the open reser voir balances the gravitational force pushing the mercury upward in the closed tube The level of the mercury column rises or falls depending upon the atmospheric pressure exerted against the open reservoir A cali brated scale adjacent to the mercury column provides a method to measure the height of the column of mercury For medical and scientific purposes atmospheric pressure is measured in millimeters of mercury This measurement is also referred to as torr named after Evangelista Torricelli the inventor of this barometer The aneroid barometer Figure 1 2 con sists of an evacuated metal container that has a pressure lower than atmospheric pressure A spring is attached between the container and a pointer mechanism This indicates the pressure As gas pressure increases the con tainer is compressed This causes the pointer to move indicating an increased pressure The pointer moves adjacent to a scale calibrated in millimeters of mercury MERCURY COLUMN AIR PRESSURE CALIBRATED SCALE Lt Figure 1 1 A full section of a mercury barometer Note how air pressure causes the mercury column to rise in the vertical tube Copyright 2005 Thomson Learning Inc All Rights Reserved May not
54. he Ni Cad battery can be recharged in approximately 13 hours The DOC 2000 also incorporates a system default signal indicator alarm detector A red LED illuminates if the unit does not sense an inspiratory effort within approximately 45 sec onds When this occurs the red LED illumi nates and a continuous audible alarm sounds If an inspiratory effort is detected within 8 to 10 seconds the unit will reset itself If no inspi ratory effort is detected within approximately 50 seconds valve 2 opens delivering the pre scribed oxygen flow continuously DeVilbiss OMS 20 and EX2000D DeVilbiss Health Care Inc markets two electronically controlled demand pulse flow oxygen delivery devices Figure 1 47A and B The OMS 20 is designed to be used with 20 psi liquid oxygen systems The OMS 20 may be operated from an internal battery for up to 23 hours or by an optional 115 V 60 Hz power Ug L OMS To A MEDICAL GAS SUPPLY EQUIPMENT 51 adapter The unit senses the patient s inspira tory efforts and delivers a pulse of oxygen during early inspiration Pulsed oxygen deliv ery may be provided at flows of between 0 25 and 6 liters per minute The EX2000D is designed for use on small oxygen cylinders having a yoke type cylinder valve The EX2000D is powered by a standard alkaline C cell battery Once the battery is installed the unit is slipped over the cylinder yoke and the T handle is hand tightened until it seals aga
55. he oxygen concentration drops to 50 Figure 1 15 shows a schematic of a typical oxygen concentrator and its compo nent parts The membrane enricher commonly called an enricher uses a semipermeable polymer membrane to remove the nitrogen from the air An air compressor forces the air through the one micron thick membrane allowing the smaller oxygen molecules to pass A mem brane enricher can provide a concentration of 40 oxygen at flow rates between 1 and 10 liters per minute Invacare Platinum 5 Oxygen Concentrator The Invacare Platinum 5 oxygen concen trator is a unit that uses molecular sieve tech nology to separate oxygen from room air Figure 1 16 The unit is capable of providing low flow oxygen at concentrations between 95 6 to 87 from flows between 0 5 to 5 L min These concentrators allow patients to receive contin uous oxygen without the use of liquid oxygen systems or compressed gas cylinders Power consumption averages 400 watts during con tinuous operation Figure 1 16 A photograph of the Invacare Platinum 5 oxygen concentrator Invacare Venture HomeFill Il Oxygen Filling System Invacare Venture HomeFill II oxygen filling system is a small multistage compressor that is designed to interface with the Invacare 5 liter oxygen concentrators Figure 1 17 The oxygen filling system allows patients to transfill small ambulatory cylinders from the oxygen concentrator s outp
56. he war ranties of fitness for particular purpose or merchantability nor are any such representations implied with respect to the material set forth herein and the publisher takes no responsibility with respect to such mate rial The publisher shall not be liable for any special consequential or exemplary damages resulting in whole or part from the reader s use of or reliance upon this material Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User CHAPTER 1 MEDICAL GAS SUPPLY INTRODUCTION EQUIPMENT Administration of medical gases is involved in most of the tasks performed by a respiratory care practitioner It is important to understand how the supply equipment for oxygen therapy and mixed gas therapy operates and how to troubleshoot these devices when problems arise In this chapter you will study the physics of equipment operation focusing especially on gas supply systems Only by thoroughly understanding the equipment and its components can you safely use it and troubleshoot it if it fails to function properly OBJECTIVES After completing this chapter the student will accomplish the following objectives PHYSICS OF THE PRINCIPLES Describe the kinetic theory of gases Define the term gas pressure explain what causes it and how it is measured Explain Pascal s law Explain what causes gases to flow from one p
57. ignal sent to the solenoid valve Whenever the solenoid valve is opened the green Pulse Dose LED is also illuminated for the duration of the valve s open time A detection delay system is also incorpo rated into the design of the DeVilbiss units If an inspiratory effort is not detected within a specified time interval the time interval is adjustable from 6 to 60 seconds a red LED will illuminate and a continuous audible alarm will sound This feature may be turned ON or OFF by using the two position Delay Detector switch Chad Therapeutics Oxymatic 301 and Oxymatic 2400 Chad Therapeutics Inc has designed and is marketing two electronic demand flow pulse delivery oxygen conserving devices Figure 1 48 The model 301 is designed for portable operation intermittent and the model 2400 is designed for continuous use although it may also be used with portable etttttt ON BATT Ga Figure 1 48 Photographs of A the Chad Therapeutics Oxymatic 301 and B Oxymatic 2400 pulse flow oxygen delivery systems Courtesy Chad Therapeutics Inc Chatsworth CA Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User oxygen systems Both units electronically sense the end of expiration and the beginning of inspiration and deliver a pulse of oxygen within 2 seconds following the start of inspi ration Both units are powered by
58. in tains a consistent sensitivity threshold During exhalation valve 2 is energized which closes it and stops the flow of oxygen Valve 1 is not energized which connects the pressure transducer to the patient through the normally open port of valve 1 Figure 1 46 Once a pressure drop is detected valve 2 opens and valve 1 closes beginning the inspi ratory cycle once again Monitoring System The DOC 2000 uses a green light emitting diode LED for two functions When the unit is first turned on the LED illuminates and stays on for approximately 1 second indicating that power is on and that the unit is self calibrating Once the patient is connected to the DOC 2000 the green LED will illuminate during inspiration This tells the operator user that Oxygen supply Sensor U11 Atmosphere Common Common Normally closed Normally open open Patient connect Normally Figure 1 46 A schematic diagram of the DOC 2000 demand oxygen controller Courtesy Transtracheal Systems Englewood CO Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User inspiration has been detected and that oxygen flow is initiated A yellow LED and audible alarm alerts the operator user of a low battery level In the event this alarm system is activated discon tinue battery operation and connect the unit to its AC power pack charging unit T
59. in6a4 ay pue Jepui Ao y ueeweq yea e 1 y S ON Jepui Ao eui vLjd y UO AeA Jepui Ao eui S SOA aunsseid ojenbope oAeu Jepur Ao eui seoq juened eui NO ses Joyuouu pue Joje n69J Joje nboJ BU S y esn oj enunuo ldvls Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User PROPORTIONERS AIR OXYGEN BLENDERS Blenders are devices that mix air and oxy gen to precise concentrations These devices provide a stable 50 psi source of mixed gas Common applications of blenders include but are not limited to powering ventilators Continuous Positive Airway Pressure CPAP systems and controlled oxygen therapy Blenders are very compact and convenient to use requiring a 50 psi source of oxygen and air Principle of Operation Air and oxygen entering the blender are first directed into two chambers on opposite sides of a diaphragm that balances the air and oxygen pressures regulator section If the 50 PSI AIR MEDICAL GAS SUPPLY EQUIPMENT 41 incoming pressures are unequal the regulator portion of the blender balances the pressures so that they are equal Figure 1 37 It is important that the pressures are equal because if one gas entered the proportioning valve at a greater pressure more of that gas would be delivered altering the percentage from what is desired
60. inder contents liter flow 2355 L 12 L min 196 minutes 3 hours 12 minutes This type of problem and others like it are very common in clinical practice Your patient s safety may depend on your ability to remember how to perform these simple calculations Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 34 CHAPTER ONE ASSEMBLY AND TROUBLESHOOTING Assembly Oxygen Cylinders To prepare a cylinder for use complete the following instructions 1 Transport the cylinder to the point of use by employing a cylinder cart Be sure that the protective valve cap is in place when transporting the cylinder Position the cylinder upright and attach it using chains provided at the point of use or use a cylinder stand to prevent it from tipping over Remove the protective cap H cylin der The smaller E cylinders have a piece of shrink wrap plastic tape pro tecting the cylinder valve and outlet Remove the protective tape prior to attaching a regulator or reducing valve Announce to personnel or patients in the area that a loud noise will occur Position the cylinder such that the cylinder valve opening is pointing away from any people in the room Crack the cylinder by quickly open ing and closing the valve to eliminate debris from the cylinder valve opening Attach an appropriate
61. ing Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User MEDICAL GAS SUPPLY EQUIPMENT 25 START din oe in Is the reservoir sys eman mom or working OK the patient NO Yes Is the reservoir delivering oxygen NO NO Is the reservoir full Verify weight and contact gas supplier Yes Yes Check all i Is ther leak connections s there a lea NO Yes Replace the Is the humidifier humidifier obstructed NO Yes Is the delivery device blocked Replace the delivery device NO ALG 1 3 An algorithm describing how to troubleshoot a portable liquid oxygen reservoir Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 26 CHAPTER ONE PIPING SYSTEMS Piping systems provide a safe convenient way to distribute medical gases throughout an institution The initial cost of these systems is quite high however over time they may be more cost effective than cylinders depending on the quantity of medical gases used CONSTRUCTION OF PIPING SYSTEMS The National Fire Protection Association has established standards for the construction and operation of medical gas piping systems Supply Oxygen may be supplied from a manifold of two or more cylinders a bulk liquid reser voir or
62. inst the cylinder valve much like a standard regulator is secured A selector switch on the right of the unit allows the oper ator to select between continuous flow and pulsed dose oxygen delivery Inspiratory Detection The DeVilbiss units use a very sensitive pressure transducer to detect the patient s inspiration As the patient inhales through his or her nasal cannula the sub ambient pressure created in the patient s lungs is transmitted to the DeVilbiss unit through the cannula A sub ambient pressure Trigger Level 0 02 cm H O causes an electrical signal to be sent from the pressure transducer sensor to the solenoid valve Once inspiration is detected by the transducer an electrical signal opens the solenoid valve delivering a pulse of oxygen B Figure 1 47 A A photograph of the DeVilbiss OMS 20 B A photograph of the DeVilbiss EX2000D pulse flow oxygen system Courtesy DeVilbiss Health Care Inc Somerset PA Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 52 CHAPTER ONE Oxygen Flow Control Oxygen flow OMS 20 is determined by the setting on the Pulse Dosage switch The Pulse Dosage switch is a rotary switch which determines how long the solenoid valve remains open As the flow rate setting is increased by turning the Pulse Dosage switch the time the solenoid valve remains open is also increa
63. istance increases sixteen times As gas velocity increases resistance to gas flow also increases Increasing the length of a tube also will increase resistance to flow These relationships will become very important when studying mechanical ventilation of the lungs For example if secretions within the airways increase the effective radius of the airway decreases and resistance to gas flow increases dramatically This will require higher pressures within the airway to maintain a constant flow For turbulent flow the relationship between flow rate pressure gradient and the Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User radius of the tube is more complex This is because the flow is affected by the shape of the tube viscous forces that dissipate energy and the Reynold s number Generally the volumet ric flow rate is proportional to the radius to the 2 7th power expressed as the following Var The effect of radius on volumetric flow rate is not as great for turbulent flow as it is for laminar flow but the effect is still quite pro nounced If the radius decreases by one half the volumetric flow rate is decreased by a fac tor of sixteen for laminar flow and by a factor of between six and seven for turbulent flow Generally the flow of gas through most respi ratory care equipment is turbulent rather than laminar La
64. lace to another and how gas flow is measured Explain Bernoulli s principle Describe the principle of viscous shearing and vorticity Explain how ejectors work in conjunction with venturi tubes with constant area ducts Describe choked flow and the conditions under which it occurs Explain the significance of Reynolds number Apply the following laws to solve for volume temperature or pressure Boyle s law Charles law Dalton s law Gay Lussac s law Combined or ideal gas law Fick s law Henry s law Graham s law MEDICAL GAS SUPPLY EQUIPMENT Differentiate between the following supply systems describe their construction and their principles of operation cylinders liquid reservoirs including calculation of oxygen duration based on weight piping systems compressors concentrators Identify the contents of a medical gas cylinder using the U S and international color code system for the following gases oxygen carbon dioxide nitrous oxide cyclopropane helium carbon dioxide and oxygen helium and oxygen air Given an oxygen E or H cylinder gauge pressure and liter flow calculate how long the cylinder will last Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 2 CHAPTER ONE e denti
65. leak Yes Is the F O5 NO n wrong by 2 1 Check for leaks between the gas supply and the high pressure hoses 1 Calibrate the analyzer 2 Check F O5 again 2 Check for a leak at the DISS fittings on the blender NO Is the F Ob b wrong by 2 3 Bleed pressure and tighten all fittings Replace the blender ALG 1 6 An algorithm describing how to troubleshoot an oxygen blender Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 44 e CHAPTER ONE OXYGEN FLOWMETERS Bourdon Gauge Fixed Orifice Flowmeter A Bourdon gauge flowmeter consists of a Bourdon gauge and an adjustable reducing valve Figure 1 38 Gas flows through the adjustable reducing valve past the Bourdon gauge and then passes through a fixed orifice distal to the Bourdon gauge The adjustable reducing valve can vary the pressure between the reducing valve outlet and the fixed orifice As pressure increases flow out of the device also increases The increase in pressure between the reducing valve outlet and the fixed orifice causes the coiled tube in the Bour don gauge to straighten The gauge however is recalibrated to indicate flow rather than pressure as the coiled tube straightens employing Poiseuille s law This flowmeter is accurate as long as the outlet is at ambient pressure Any increase in pressure distal to
66. ment without removing the filter from the concentrator The filter must still be washed weekly If humidification has been prescribed a Fill the humidifier reservoir with distilled water to the fill line and then thread the humidifier directly onto the fixed oxygen Diameter Index Safety System DISS outlet so that the humidifier is suspended b Attach the desired length of oxygen delivery tubing not to exceed 50 feet or 15 meters to the humidifier outlet If condensation occurs when using longer lengths of oxygen tub ing condensation may be reduced by using a removable humidifier stand If humidification has not been pre scribed a Thread a green Christmas Tree fitting onto the fixed oxygen DISS outlet fitting and attach the desired length of oxygen delivery tubing not to exceed 50 feet or 15 meters Connect the cannula transtracheal can nula or mask to the oxygen delivery tubing Check to be certain that the power switch is in the OFF position Select an electrical outlet 120 V 60 Hz that is not connected by a wall switch and is independent of other appliances Depress the power switch to the ON position Adjust the flowmeter to the prescribed oxygen setting by turning the flowme ter knob counterclockwise to increase the flow of oxygen Verify oxygen flow through the cannula delivery tubing and or the humidifier An oxygen analyzer can be used to confirm that the concent
67. minar flow occurs physiologically within the lungs after several branches in the bronchial system GAS LAWS An understanding of the gas laws is important in the practice of respiratory care During mechanical ventilation volumes pres sures flows and the temperature of the gas delivered to a patient are routinely manipu lated to better match changes in the patient s condition It is important to be able to predict how these changes will affect gas delivery to the patient When performing mathematical calcula tions it is important to use consistent units in all equations For example one can not mix cmH O and psi and expect correct results It will be necessary to convert temperatures and sometimes pressures depending on the cir cumstances under which the gas laws are applied When converting temperature scales you will need to apply the formulas listed in Table 1 2 The two new temperature scales intro duced are called the absolute temperature scales Both scales are referenced to absolute zero Therefore neither scale will have nega tive numbers since the lowest temperature is Zero Boyle s Law Boyle s law relates the volume of a gas to its pressure With temperature remaining con stant the volume of a gas varies inversely MEDICAL GAS SUPPLY EQUIPMENT 11 TABLE 1 2 Temperature Conversion Degrees Fahrenheit to Degrees Celsius Fahrenheit Temperature 32 Degrees Celsius 0 Degrees Celsius
68. mperature P T T5 P 30 C 273 303K 900 mmHg 303 K 00 mmHg 389 6 K 389 6 K 273 117 6 C This law can be illustrated when a bicycle tire is inflated using a manual tire pump As the air is compressed in the pump its temperature increases After the tire is inflated the tire pump is noticeably warmer In respiratory care equipment air compressors have external fins that conduct and dissipate the heat gener ated when the ambient air is compressed Combined Gas Law The combined gas law or general gas law is a combination of Boyle s Charles and Gay Lussac s laws It is useful in determining pres sure volume or temperature changes The law is summarized in the following formula PV PA T it For example A gas at a pressure of 200 mmHg 300 K and occupying 6 liters has its temperature increased to 400 K while occupying the same volume Find the new pressure PW _ P Ti V5 200 mmHg 6 liters 400 K 300 K 6 liters 389 6 K GAS DIFFUSION Besides pressure volume and temperature relationships it is important to understand gas diffusion Gas diffusion is important phys iologically in that gases constantly move from the atmosphere into our bodies and then from our cells into our blood by means of diffusion There are three important laws of gas diffu sion Fick s Henry s and Graham s laws MEDICAL GAS SUPPLY EQUIPMENT 13 Fick s Law Fick s law describes h
69. n pressure may be caused by a kink in the delivery tubing or an obstruction distal to the point of air entrainment This increase in pressure distal to the jet results in less ambient air entrainment because the total flow through the tube decreases as the back pressure increases The flow through the jet s nozzle is constant thus the entrainment must decrease Figure 1 10 CHOKED FLOW OR COMPRESSIBLE FLOW When a gas is flowing through an orifice or nozzle the velocity of the gas increases as the pressure upstream head pressure of the nozzle increases When the head reaches pres sure 1 893 times the atmospheric pressure for air the velocity of the gas no longer increases and the flow is choked This corresponds to sonic flow at the orifice of the jet which for air at room temperature is approximately 347 meters per second This velocity corresponds to the speed of sound in air at room tempera ture Once the gas reaches sonic velocity the gas s velocity can no longer increase Increasing the head pressure will not result in an increased MEDICAL GAS SUPPLY EQUIPMENT 9 flow when the flow is choked The behavior of choked flow may be predicted using the choked flow equation but this is beyond the scope of this text Choked flow is used in nebulizers when the head pressure driving the jet exceeds 26 psi making the gas velocity out of the nozzle s exit sonic Liquids are drawn into the gas flow from the reservoir via the
70. ng this type of The patient requests that she be regulator Self Assessment Quiz 1 Gases being composed of discrete molecules in random motion best describes a the ideal gas law b the kinetic theory of gases c Dalton s law d Charles law 2 The kinetic activity of gases is largely dependent upon a their concentration b the pressure c the temperature d the type of gas 3 Chambers A and B are connected by high pressure tubing and separated by a valve If cham ber A contains 500 psi of gas and chamber B contains 50 psi of gas what will occur when the valve is opened a The pressures in the chambers will remain equal b Chamber A will be pressurized by chamber B c Gas will flow from chamber A to chamber B until pressures equalize d The pressure in chamber B will increase to a level greater than in chamber A 4 Pascal s law best describes a the relationship between volume and pressure of a gas b the relationship between pressure and temperature of a gas c the relationship between temperature and volume of a gas d the equal distribution of pressure transmitted by a fluid Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User m 10 11 12 MEDICAL GAS SUPPLY EQUIPMENT 57 A device used clinically to measure small pressures is termed a a mercury barometer b aneroid barometer
71. nit must be used with the dual lumen nasal cannula Figure 1 21 A photograph of the HELiOS portable oxygen system that allows the pneumatic system to sense the patient s inspiration delivering oxygen during the inspiratory phase of ventilation The rate of oxygen evaporative loss from the unit is between 1 to 1 5 pounds per day The portable unit can be filled from a larger liquid reservoir in less than one minute 40 seconds Portable Oxygen Duration It may be necessary to calculate the dura tion of oxygen flow from these portable liquid reservoirs These calculations are all based upon the weight of the units All portable sys tems incorporate some form of spring scale to estimate the contents remaining Many are cal ibrated in fourths and some use LED displays to further subdivide the contents into smaller increments However these scales are only estimates and do not accurately reflect the contents remaining in the reservoirs Sometimes it may be necessary to accu rately calculate the number of liters or dura tion in time remaining in a portable liquid system These calculations are also based upon weight However since the accuracy of spring scales varies all calculations shown incorpo rate a scale factor 80 to allow for variation in scales It is also required that you know the Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed t
72. o iChapters User 24 CHAPTER ONE empty weight of the reservoir you are working with This can be found in the owner s manual or service manual Derivation of the formula 1 Density of O at its boiling point 1141 kg m 2 1141 0 kg m 2 2 Ib kg 251021b n 3 2510 2 Ibs m 001 m L 2 5102 Ibs L 4 1 liter liquid 860 6 liters gaseous 860 6 liters gas _ 324 8 L gas 2 5102 Ibs L liquid Ibs liquid RESULT There are 342 8 L gaseous oxygen per Ib of liquid oxygen For example You are working with a patient in her home who is using a large portable reservoir at 2 L min She wants to know how long her reservoir will last before it needs to be refilled The indicator says it is 2 full but she is still concerned What is the duration of the reservoir Empty Weight 60 lbs from service manual Current Weight 145 lbs Scale Factor 80 145 Ibs 60 lbs liquid 342 8 L gas lb liquid x 80 23 310 L gas eo eS 2 tes mines 2 Lmin EOL L M 194 hours or 8 days 60 minutes hour Notice in the calculation that the capacity in liters was multiplied by 80 This scale factor gives you a reserve or cushion of 20 to allow for accuracy variation in the spring scale used to weigh the liquid reservoir ASSEMBLY AND TROUBLESHOOTING Assembly Portable Liquid Oxygen Systems Little is required for proper assembly of portable liquid reservoirs The follow ing guide will help y
73. only Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part
74. ons can be monitored on the top of the unit The battery test can be performed by moving the black rocker switch to the ON BATT position while the unit is on The BATT TEST display will indicate the battery s condition If the dis play is dark green the battery is in good con dition With use the color of the green indicator becomes progressively lighter When the display is amber in color approximately 48 hours of battery life remains If the indicator is red 24 hours of life remains and the battery should be changed The low battery warning is a blinking LED display in the Indicator Setting window that resembles a battery When the battery life falls to around 24 hours of continuous use the low battery warning will flash intermittently When this condition is observed the battery should be changed as soon as possible Apnea detection is built into the Oxymatic 2400 If the unit fails to sense inspiration over a period of 40 seconds the alarm system is activated An audible and visual alarm will alert the user to this condition A flashing red light labeled ALARM on the top of the unit will flash intermittently along with the audible alarm Besides apnea kinks in the patient s tubing or patient disconnects can also cause this alarm Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 54 e CHAPTER ONE ASSEMBLY AND
75. or duplicated in whole or in part Licensed to iChapters User 22 CHAPTER ONE LIQUID RESERVOIR SYSTEMS Bulk Supply Systems Bulk supply systems are used to supply large amounts of medical gas to a hospital or other institution It is more economical to operate a bulk system than to use many small cylinders The construction of a bulk liquid storage reservoir is very similar to an enlarged steel thermos An outer steel shell encloses several layers of insulation in a near vacuum The inner wall contains the liquid gas Figure 1 19 Standards of bulk reservoir construction have been established by the American Society of Mechanical Engineers Liquid oxygen is stored in the reservoir at a temperature of 183 Celsius Liquid oxygen continuously vaporizes creating pressure Pressure relief valves are incorporated into the reservoir to release pressure The release of pressure as the gas expands cools the reser voir Gay Lussac s law It is important to size the reservoir prop erly so that the use of gas exceeds the rate of vaporization If too much gas is lost to the atmosphere by vaporization it may not be economical to operate the bulk system An advantage of storing oxygen in liquid form is that one cubic foot of liquid oxygen expands to 861 heat exchanger cubic feet of gaseous oxygen 1 861 ratio The liquid oxygen is fed RELIEF VALVE CONTROL VALVE INSULATION into a heat exchanger like a radiator it warms
76. ortation and 3AA indicates heat treated high strength steel The designation 3AL denotes aluminum construction Typically cylinders are filled to a pressure 10 greater than the working pressure indicated on its shoulder providing the cylinder has passed the required hydrostatic testing Light weight aluminum cylinders rein forced with carbon fiber wrap have been developed for ambulatory patient use Figure 1 26 These cylinders incorporate an ultra thin aluminum wall reinforced with heli cal and hoop wraps of carbon fiber impreg nated with epoxy resin for reinforcement The weight savings over steel cylinders of similar size is approximately 70 and about a 30 weight savings is realized compared with con Figure 1 27 Cylinder markings indicate the cylinder has passed inspection The inspection was performed in March 1982 The inspector s mark is between the month and year The sign indicates the cylinder complies with the hydrostatic test The star marking indicates the cylinder may go ten years before being tested again MEDICAL GAS SUPPLY EQUIPMENT 29 ventional aluminum cylinder construction The cylinders are designed to be filled to a service pressure of 3000 psi When used with oxygen conserving devices these cylinders can provide a long duration with a very light weight package for ambulatory use Cylinder Markings The DOT requires that cylinder data be stamped on the shoulder of the cylin
77. ou in the assembly and preparation of the reservoir for use 1 Ensure that the reservoir is filled by checking the weight gauge provided a Should the reservoir require filling contact your local vendor Attach a flowmeter and humidifier to the threaded outlet of the reservoir Attach the oxygen therapy equipment to the outlet of the humidifier Turn on the flowmeter to the ordered setting and observe for proper flow When transfilling the ambulatory reser voirs follow the manufacturer s instructions carefully Since connections and attachment vary specific instruc tions are not included here When transfilling the portable reservoir exercise caution The extreme cold temperatures of the fittings may result in cryogenic burns Troubleshooting When troubleshooting this equipment please follow the suggested troubleshoot ing algorithm ALG 1 3 1 If gas fails to flow from the oxygen therapy device a Check to ensure the reservoir is full using the weight gauge or other gauge provided by the manufac turer Check all connections for tightness Check for leaks by feeling and by listening for escaping gas Make certain that the humidifier is assembled correctly and that it is not obstructed Check to ensure that all threaded connections are tight Check oxygen tubing for kinks or obstruction If a through d are satisfactory contact your local vendor Copyright 2005 Thomson Learn
78. ow a gas diffuses into another gas Fick s law states that the rate of diffusion of a gas into another gas is pro portional to its concentration That is as the concentration gradient between the gases increases the rate of diffusion will increase Given two gases where Gas A has a higher concentration than Gas B Gas A will diffuse more rapidly than Gas B due to its greater concentration Henry s Law Henry s law describes how gases diffuse into and out of liquids Henry s law states that the rate of a gas s diffusion into a liquid is pro portional to the partial pressure of that gas at a given temperature Applying Henry s law observe what happens when you open a bottle of soda pop Once the cap is removed bubbles can be seen moving toward the surface of the liquid and bursting once they reach the sur face The partial pressure of carbon dioxide is greater in the liquid than in the atmosphere Therefore carbon dioxide gas diffuses from the dissolved state liquid to a gaseous state and escapes into the atmosphere Graham s Law Gas diffusion in the blood is more complex than what occurs as described in Henry s law Other factors such as the gram molecular weight and solubility of the gases must be accounted for when understanding diffusion across the alveolar capillary membrane Graham s law states that the rate of gas diffusion through a liquid is proportional to the solubility of a gas and inversely propor tional to
79. ped circuit breaker II obstructed delivery tubing III obstructed humidifier IV a dirty filter a I b Land II c IL and III d I and IV Advantages of transfilling portable cylinders from a home oxygen concentrator include I convenience II cost savings III speed of filling the cylinder a Lonly b Land II c Land III d I IL and III When making a call on a home care patient you weigh her liquid reservoir which registers 80 Ibs You know the manufacturer s weight to be 60 lbs and that your patient uses 3 L min oxygen How much gas does her reservoir contain and can she wait for 5 hours before your company s delivery truck arrives I 12 340 L oxygen remaining II 5 484 L oxygen remaining III 30 hours duration remaining IV 84 hours duration remaining a Land III b Land IV c IL and III d IL and IV An advantage of using a demand pulse flow oxygen delivery system in the home care envi ronment is that I less oxygen is used II it is less expensive for the patient III a humidifier is not required a I b II c Iand II d I IL and III When selecting an oxygen conserving device for ambulatory use it is important to a select the unit based upon overall cost b perform an ambulatory oxygen saturation trial using the unit c draw arterial blood gases before and after ambulation d none of the above Copyright 2005 Thomson Learning Inc All Rights Reserved May not
80. ration being delivered is correct Troubleshooting Follow the suggested troubleshooting algorithm ALG 1 2 to assist you in troubleshooting this concentrator If the unit fails to operate when turned On a Check to be certain that the power cord is plugged into a 120 V 60 Hz electrical outlet b The electrical outlet may not have power Test the outlet with a house hold lamp or radio If the power is not on at the outlet use another outlet c The circuit breaker has tripped Press the black reset button on the rear cover If the breaker trips again contact your dealer for service If the air intake or exhaust is blocked a Check and service the gross particle filter if required b Check for objects blocking discharge air from the bottom right side of the unit If the unit is operating but you are unable to obtain the desired flow of enriched gas check the following a Blocked oxygen delivery device or connecting tubing 1 Remove the delivery device can nula catheter or transtracheal catheter from the extension tub ing If flow is restored clean or replace the delivery device 2 Disconnect the extension tubing from the humidifier If flow is restored check the tubing for kinks or obstructions or replace the tubing as required b Blocked or defective humidifier 1 Remove the humidifier from the outlet of the MC84 If flow is restored clean or replace the humidifier
81. ratory care practitioner A patient who was just set up at home on a liquid oxygen system calls with a complaint Over the phone Mr Smith says My new oxygen bottle is hissing I am worried it might explode What should you tell your new client and what would you recommend that he do You are preparing to transport a patient from the intensive care unit allowed enough freedom of movement to reach the bathroom the kitchen and her bedroom the location of the con centrator Describe how you would evaluate the concentrator s placement and any limitations you might impose regarding maximum lengths of exten sion tubing Describe a clinical situation in which you might select a single stage reduc ing valve and another in which you might select a two stage reducing valve You are evaluating a patient for a pulsed demand regulator for his portable oxygen system Describe how ICU to the floor In order to do so you set up an E cylinder to provide oxygen to his cannula When you turn on the cylinder valve you hear a leak Describe the steps you would take to correct the problem you would appropriately evaluate him state which of the devices dis cussed in the text is best for a given patient and explain why You are using a Bourdon gauge flowmeter for a helicopter transport You are setting up a new patient at What safety precautions should you home with an oxygen concentrator be aware of when usi
82. regulator to the cylinder and attach the oxygen therapy equipment to the regulator Slowly turn on the cylinder valve Read the pressure gauge and determine if the contents of the cylinder are ade quate for the duration of therapy Troubleshooting Troubleshooting a cylinder is quite simple since this oxygen supply system has so few moving parts The following is a suggested troubleshooting algorithm ALG 1 4 1 Check for leaks at the connection between the cylinder and regulator If leaks are present tighten the connection a A leak can be detected by a hissing sound The amplitude or volume of the sound indicates the severity of the leak b Subtle leaks may be detected by feel ing for gas flow with your hands around the connections c If you suspect a leak but can t detect it 1 Use a solution of mild detergent and water and brush the solu tion around the fittings Leaks will cause bubbles to form indi cating the presence of a leak d If a leak is detected turn off the cylinder valve bleeding all pressure from the regulator and retighten all connections Check for leaks between the regulator and the oxygen therapy equipment and tighten as appropriate a A leak can be detected by a hissing sound The amplitude or volume of the sound indicates the severity of the leak b Subtle leaks may be detected by feel ing for gas flow with your hands around the connections c
83. s continues Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 32 CHAPTER ONE TABLE 1 4 continued 6 8 Protect the cylinders from being damaged by cuts or abrasions Do not store them in areas where they may be damaged by moving or falling objects Keep cylinder valve caps on at all times Cylinders may be stored in the open however keep them on a platform so they are above the ground In some parts of the country shading may be required due to high temperatures If ice and snow accumulate thaw at room temperature or use water cooler than 125 F Protect cylinders from potential tampering by untrained unauthorized individuals Withdrawing Cylinder Contents 1 2 10 11 12 13 14 15 Allow cylinders to be handled by experienced trained individuals only The user of the cylinder is responsible for verifying the cylinder contents before use If the contents are in doubt do not use the cylinder Return it to the supplier Leave the protective valve cap in place until you are ready to attach a regulator or other equipment Follow safety precautions Make sure the cylinder is well supported and protected from falling over Always crack the cylinder valve prior to attaching a regulator or reducing valve Refer to previous Assembly and Troubleshooting section Use appropriate r
84. s such that the angle of the walls does not exceed 15 degrees Figure 1 8A Note the pressure curve as gas passes through the tube Pressure is reduced in the center and due to the Bernoulli effect progressively increases as the diameter of the tube increases near the outlet Figure 1 8B The high velocity of the gas from the nozzle causes ambient air to be mixed with the gas from the nozzle by vis cous shearing and vorticity described earlier in this chapter adding to the total quantity of gas flowing through the tube As the tube expands gas velocity slows and pressure increases Venturi tubes are often employed where gas flow can be increased through entrainment of ambient air Due to the Bernoulli effect gas velocities through venturi tubes are generally low Constant Area Duct This type of ducted ejector is similar to a venturi tube except that instead of restoring lateral pressure the tube s purpose is to maintain a high velocity following the jet or restriction The ejector consists of a straight walled tube that does not change in diameter down stream from the jet Gas is entrained at the entrance to the tube due to viscous shearing and vorticity between the source gas and ambient air increasing total flow through the device The tube downstream from the jet shields the flow of gas from entrainment with out significantly slowing the velocity of the gas through the device Figure 1 9 Velocity remains high and pr
85. s is the color for 188 15 Ibs 14 oz 106 8 ibs 15 oz 2260 4000 597 798 0 Ibs 13 2 oz 2260 597 79 8 7570 2000 267 30 Ibs 10 oz 3450 912 122 10 ibs 1 oz 3275 665 116 6 ibs 11 oz 1057 141 115 7502 4000 1057 141 13800 3657 489 56 Ibs 0 oz 16 ibs 6 oz Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User TABLE 1 3 Cylinder Color Coding MEDICAL GAS SUPPLY EQUIPMENT 31 Gas Color Code United States International Oxygen Green White Carbon dioxide Gray Gray Nitrous oxide Light blue Light blue Cyclopropane Orange Orange Helium Brown Brown Carbon dioxide and oxygen Helium and oxygen Air Yellow cylinders containing oxygen see Table 1 3 The international color is white while the United States still uses green In addition to the color code each cylinder is required to have a label indicating the cylinder s contents Labeling of cylinder contents is required by the United States Pharmacopeia USP a divi sion of the Food and Drug Administration FDA The USP controls the purity standards of compressed gases for medical use If the label and the color code do not match the cylinder should not be used and should be returned to the vendor The most reliable indicator of what is contained in the cylinder is the label TABLE 1 4 Safety Rules for Cylinder Use Moving
86. se Model 2400 Oxymatic electronic oxygen conserver system Chatsworth CA Author Chigier N 1981 Energy combustion and environment McGraw Hill Compressed Gas Association 1981 Handbook of compressed gases Van Nostrand Reinhold Company Contemporary Products Inc 2003 Composite fiber wrapped cylinder owners manual Portland ME Author DeVilbiss Health Care 1988 DeVO MC29 and DeVO MC44 patient guide Somerset PA Author DeVilbiss Health Care 1987 DeVilbiss DeVO MC44 90 oxygen concentrator service manual Somerset PA Author Grenard S 1973 The hazards of respiratory therapy equipment Lenn Educational Medical Services Gonzales S C 1986 Efficacy of the oxymizer pendant in reducing oxygen requirements of hypoxemic patients Respiratory Care 31 8 681 688 Kerby G R et al 1990 Clinical efficacy and cost benefit of pulse flow oxygen in hospitalized patients Chest 97 2 369 372 Invacare Corporation 2003 IRCSLX 5 liter concentrator owners manual Elyria OH Author Invacare Corporation 2003 Venture HomeFill oxygen filling system owners manual Elyria OH Author Pierson D J et al 1992 Foundations of respiratory care Churchill Livingstone Inc Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User MEDICAL GAS SUPPLY EQUIPMENT 61 Pulsair 1990 Oxygen m
87. se is delivered every other breath 5076 of the time this is equiva lent to 2 L min continuous flow When oxy gen is delivered one out of every four breaths 25 of the time this is equivalent to 1 L min continuous flow Because of the unique pulse delivery alter nate breath delivery below 4 L min some patients may be uncomfortable initially when using these units It is important to explain how these units work and that even though the patient may not feel oxygen flow on each breath it is equivalent to what they have been MEDICAL GAS SUPPLY EQUIPMENT 53 receiving As noted earlier in this section it is important to conduct an oximetry trial to determine the oxygen needs of a patient who is using a conserving device Monitoring Systems Oxymatic 301 The monitor on the Oxymatic 301 is a bat tery test indicator To use the battery tester move the thumbwheel selector on the top of the unit to the Battery Test position Observe the indicator to assess the battery s condition If the indicator is red replace the battery before use If the indicator is amber you should have a replacement battery available to use If the indicator is green the battery has sufficient electrical energy to operate the unit The Oxymatic 301 uses a common alkaline C size battery Monitoring Systems Oxymatic 2400 The Oxymatic 2400 has a battery test fea ture a low battery warning indicator and an apnea alarm All of these conditi
88. sed This is a time based variable circuit with a constant flow rate The volume of oxygen delivered to the patient is solely determined by the amount of time the sole noid valve remains open Therefore when the respiratory rate increases the patient actually receives more oxygen This would be referred to as a rate response type of oxygen delivery Liter flow on the EX2000D is adjusted by connecting the unit to a cylinder and by attaching a short length of tubing between the EX2000D and an external flowmeter used for calibration purposes An Allen wrench is inserted into the fitting on the bottom of the EX2000D and flow is adjusted until the desired flow is displayed on the external flowmeter Once the desired flow is set the wrench is removed along with the calibration flowmeter and connecting tubing Monitoring Systems The DeVilbiss OMS 20 and EX2000D have several monitoring features built into the units These features include low battery detection pulse delivery indication and a detection delay indicator The low battery indicator will light and an audible alarm will sound when the battery power becomes low When this condition is detected it is important to recharge the inter nal battery using the 120 V 60 Hz adapter sup plied with the unit During inspiration a green LED will illu minate when a pulse is delivered The sensor circuit sends an electrical signal to illuminate the LED simultaneously with the s
89. setting A Thorpe tube flowmeter can be identi fied when it is connected to a 50 psi gas source The float on a Thorpe tube flowmeter will quickly rise and fall when the tube is pressurized to the 50 psi line pressure Troubleshooting Troubleshooting a flowmeter primarily consists of checking for leaks Periodically a flowmeter should be checked against a calibration standard for accuracy calibra tion flowmeter or volume displacement spirometer When troubleshooting this equipment please follow the suggested troubleshooting algorithm ALG 1 7 1 Sources of leaks a Connection between flowmeter and 50 psi gas source b Connection between flowmeter and the therapy equipment 2 If the flowmeter fails to deliver expected flow or behaves erratically check it against a calibration standard and if necessary have it repaired Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 48 e CHAPTER ONE Continue to use the flowmeter and monitor the patient NO Is there a leak Yes 1 Check for a leak at the 50 psi gas source 2 Check for a leak at the oxygen equipment 3 Bleed the pressure 4 Tighten all connections START Is the flowmeter working OK NO NO Is the flow output not normal Yes 1 Check the flowmeter against calibration standard 2 If the flowm
90. stem Safety features incorporated into regulators or reducing valves include I DISS outlet II PISS inlet III American Standard inlet IV pressure relief valve s a Lonly b Land IL only c L IL and III only d I IL HI and IV Which of the following is are true for an H size oxygen cylinder I When full it contains 2 200 psi II It contains 22 cubic feet of gas III It will have 3AA stamped on the shoulder IV It contains 244 cubic feet of gas a land IL only b Land III only c I MI and IV only d L II and III only The marking 3AA indicates a the cylinder type b the contents of the cylinder c the cylinder serial number d the cylinder size Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 20 21 22 29 24 25 26 MEDICAL GAS SUPPLY EQUIPMENT 59 The lightest compressed gas cylinder for ambulatory use is a a 3AA steel cylinder b an aluminum 3AL cylinder c a fiber wrapped cylinder d a portable liquid reservoir A device that mixes air and oxygen is termed a an a concentrator b oxygen enricher c oxygen proportioner d reducing valve When troubleshooting an oxygen concentrator you find that the device is operating yet you are unable to obtain the desired flow of oxygen enriched gas Possible problems include I a trip
91. steps 1 Connect the power cord to the correct electrical outlet 115 volts alternating current VAC Attach equipment requiring com pressed air to the threaded outlet Check inlet filter for obstruction and if required clean or replace it Turn on the compressor with the on off switch equipment Figure 1 13 depicts a typical diaphragm compressor suitable for home use Centrifugal Compressor The centrifugal compressor utilizes an electrically powered impeller mounted eccen trically within the compressor housing As the impeller rotates it compresses the air Centrifugal force and the decreasing size of ELECTRIC MOTOR CL a T pA s o 5 Verify correct outlet pressure 50 psi with the gauge provided Troubleshooting Troubleshooting compressors is very easy Unfortunately if the unit fails to operate little can be done other than to take the compressor to an authorized repair center When troubleshooting this equipment please follow the suggested troubleshooting algorithm ALG 1 1 the chamber compress the gas as the impeller turns Figure 1 14 These compressors are incorporated in some adult mechanical venti lators such as the Bennett MA 1 A larger version of this type of compressor is used to provide a compressed air source for hospitals and other institutions These rotary compressors use similar principles of opera tion except that a working fluid usually water is used bet
92. ters have scales calibrated between 0 and 3 L min in quarter L min intervals Figure 1 42B and are useful in pediatrics and chronic obstructive lung disease patients T i 8 s3 NN F amp 760 MM HG 100 PSIG MAX A T Freee ee ug ELLE OPDIEN LJ 1 x a T e Ll 3 zd e ne i ce i N i J n T 4 2 Xl li BL ma ba TL i Hee Sa in im t P A inia oF Os TT FA Mok HG r utr T oT a r e iux s 7 s zal E Lens A B Figure 1 42 A A photograph of a high range flowmeter calibrated from zero to seventy five liters per minute B A photograph of a low range pediatric flowmeter calibrated from zero to three liters per minute Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User MEDICAL GAS SUPPLY EQUIPMENT e 47 ASSEMBLY AND TROUBLESHOOTING Assembly Oxygen Flowmeters Flowmeters are very easy to assemble for use Complete the following instruc tions to prepare a flowmeter 1 Attach the flowmeter to an appropriate 50 psi gas source using DISS or quick connect fittings Attach the appropriate therapy equip ment to the DISS fitting on the flow meter outlet When using a Bourdon flowmeter care fully check all supply tubing for kinks or obstructions Adjust the flow to the desired
93. the Thorpe tube overcoming gravity At equilibrium gas pressure equals gravitational attraction and the float is stable As the float moves up in the Thorpe tube the tube becomes larger and more and more gas flows around it The needle valve provides a means of adjusting gas flow into the Thorpe tube As the needle valve is progressively opened more gas flows into the tube The term uncompensated Thorpe tube flowmeter refers to the fact that it is uncompensated for back pressure If pressure is applied distally to the Thorpe tube for example from a kinked connecting tube or other obstruction the Thorpe tube becomes pressurized As the pres sure in the Thorpe tube increases the pressure gradient between the bottom and the top of the float decreases causing the float to fall The flow indication may actually be lower than the delivered flow Compensated Thorpe Tube Flowmeter Figure 1 39 A photograph of a fixed orifice A compensated Thorpe tube flowmeter is regulator for an E cylinder similar in design to an uncompensated one Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 46 CHAPTER ONE with one exception A compensated Thorpe tube s needle valve is distal to the Thorpe tube Figure 1 41 Since the needle valve is placed distal to the Thorpe tube pressure within the tube is equal to line pressure or 50 psi wh
94. the fixed orifice will cause this flowmeter to read inaccurately This can be caused by obstructions to flow or attach ment of equipment that causes back pressure GEAR MECHANISM PRESSURE REGULATOR hw to develop It is possible to obstruct the outlet and the Bourdon gauge will indicate a flow higher than is being delivered The Bourdon gauge flowmeter is light weight and very compact Another advantage of this device is that it will operate in any posi tion The flowmeter will operate in unusual positions because none of the moving parts is gravity dependent Therefore it is popular in emergency and transport settings ambulance intra hospital transport airborne transport Any oxygen connecting tubing or tubing to oxygen administration devices must be carefully checked for kinks or obstructions In a noisy bumpy environment ambulance or airborne transport physically touch and fol low the tubing with your hands to verify that the tubing has not been obstructed Stretchers equipment or other care providers feet placed on the tubing could obstruct oxygen flow You can t tell by monitoring the gauge if oxygen is flowing or not Fixed Orifice Flowmeters Fixed orifice flowmeters are designed to provide specific flow rate settings by selecting COILED TUBE ZZ A OUTLET J Yt a GAS INLET Figure 1 38 A functional diagram of a Bourdon flowmeter This is also known as a fixed orifice flowmeter Copyright 20
95. ucing valve The tension may be fixed or adjustable depending on the reducing valve s construction If the tension is adjust able there is usually a screw provided that will allow adjustment of the tension against the diaphragm Modified Single Stage Reducing Valve The modified single stage reducing valve is similar to the single stage reducing valve The difference between the two is that the modified single stage reducing valve has a poppet closing spring in addition to the spring above the diaphragm Figure 1 35 illustrates the component parts of this reducing valve The poppet closing spring allows the poppet valve to open and close faster providing greater flow rates PRESSURE INLET DIAPHRAGM POPPET VALVE NOZZLE Figure 1 34 Functional diagram of a single stage reducing valve Multistage Reducing Valves Multistage reducing valves are simply two or more single stage reducing valves in series with one another Figure 1 36 shows the com ponent parts of this reducing valve The first stage reduces the cylinder to an intermediate pressure of approximately 200 psi The second stage then reduces the pressure to the desired working pressure usually 50 psi Each stage operates independently from the other The addition of the additional stage allows more precise regulation of pressure and a greater flow rate than is possible with a single stage reducing valve Common applications of multistage reducing valves incl
96. ude powering of mechanical ventilators These applications require high flows and a stable pressure source Reducing Valve Safety Features Several safety features are incorporated into the design of reducing valves These include pressure relief valves or pop off valves and indexing of the inlet and outlet Each stage of a reducing valve is required to have a safety relief valve in the event that excess pressure develops within the stage The safety relief will exhaust excessive pressure before the reducing valve housing bursts The inlet of the reducing valve is indexed with either American Standard indexing or the Pin Index Safety System indexing Both of these systems were developed by the Com pressed Gas Association and discussed earlier in this chapter The outlet of the reducing valve uses Diameter Indexed Safety System threads This safety system was also discussed earlier in this chapter HIGH PRESSURE INLET DIAPHRAGM NOZZLE POPPET VALVE POPPET CLOSING SPRING Figure 1 35 Functional diagram of a modified single stage reducing valve Note the addition of a poppet closing spring Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User MEDICAL GAS SUPPLY EQUIPMENT 39 rd 3 77727277227 N ERE ej i FE HIGH KEEN ar PRESSURE Aue na INLET AT pg Lg 9 AAN N SAAS PSS NA 2 7 7 Z
97. ure 1 18 The unit is capable of providing 95 oxygen concentration 3 at flows between 1 and 3 L min If the oxygen flow is 4 L min oxygen concentrations are 92 3 During normal operation the Companion 492a will consume an average of 330 watts electrical power Ideally the concentrator should be the only item connected to the electrical outlet and on that electrical circuit ASSEMBLY AND TROUBLESHOOTING Oxygen Concentrators 1 Position the oxygen concentrator in the room where your patient will spend the majority of his or her time Be sure to choose a location away from heaters radiators and hot air registers Place the unit so that the back and sides are at least 6 inches away from any objects to ensure adequate air flow through the unit 2 Concentrators incorporate a particle fil ter Remove the filter from its housing or holder Inspect the particle filter for lint or other debris The patient should be instructed to wash this filter at least once a week The filter may be washed in a solution of warm water and dish washing detergent and then rinsed thoroughly with warm tap water and toweled dry The filter should be Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 20 CHAPTER ONE completely dry before it is reinstalled The particle filter may also be cleaned daily by using a vacuum cleaner attach
98. urned the threaded plunger moves up or down allowing the diaphragm to open or close the valve seat Gas pressure then dis places the diaphragm allowing gas to flow out of the cylinder These valves are usually employed with cylinders having a lower work ing pressure of 1500 psi or less Figure 1 31 Cylinder Valve Safety Features Several safety features are incorporated into cylinder valves Since cylinders contain many different gases the Compressed Gas Association CGA has designed a system to prevent the inter change of dissimilar gases In other words the safety system is designed to prevent the attachment of an oxygen regulator to a nitrous oxide medical gas cylinder The two types of valve outlet safety systems are the American Standard and the Pin Index Safety System PISS The American Standard Safety System ASSS is incorporated into the valves for the larger cylinders sizes M G H This system uses differing thread pitches internal HANDLE 4240122424414 72 Ve isis coed Ae 1 9 9 Fes bU AA DIAPHRAGM d d di din ud dici LT PTT VERI taeda Add oe AJ Se 7 s 2 PRESSURE RELIEF VALVE C LS a dS De AALLAR gt GAS INLET CHANNEL Figure 1 31 A functional diagram of an indirect acting cylinder valve Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User
99. use Quick connect fittings vary from one manufacturer to another These fittings are designed to be rapidly connected or discon nected without the use of threads Figure 1 25 shows an example of common quick connect outlets CYLINDERS Oxygen cylinders provide a convenient method of providing oxygen delivery to a patient The smaller cylinder sizes are portable facilitating their use in an emergency ambulatory or transport setting Oxygen cylinders are safe and effective when handled correctly Cylinder Construction The construction of oxygen cylinders is strictly regulated by the Department of Trans portation DOT Medical gas cylinders are seamless either made from high strength chrome molybdenum steel or a high strength aluminum alloy Steel cylinders are spun into shape while the steel is still hot Following shaping the steel is heat treated to retain its tensile strength Recently the aluminum alloy cylinders have gained popularity due to their lighter weight High strength steel cylinders are stamped with the marking DOT 3AA Figure 1 25 Three quick connect fittings Left to right are oxygen air and vacuum Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User Figure 1 26 A photograph of a carbon fiber wrapped cylinder developed for ambulatory patient use DOT refers to the Department of Trans p
100. ut The unit is Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User Figure 1 17 A photograph of the Invacare Venture HomeFill II oxygen filling system This unit is a multi stage pump designed to fill portable oxygen cylinders designed to interface with the Invacare ML6 164 liter and M9 248 liter capacity portable oxygen cylinders It takes approximately 11 2 to 2 hours to fill a cylinder ML6 and M9 respectively The filling system provides patient independence from their home care provider delivering filled portable oxygen cylinders for ambulatory use as well as long term cost savings Liter flow from the concentrator during transfilling is limited to 0 to 3 L min The input to the transfilling compressor during operation is 2 L min Power consumption averages 200 watts when transfilling the cylin ders An electrical outlet separate from the concentrator must be available for the Home Fill II oxygen filling system in that each unit has its own independent power supply Puritan Bennett Companion 492a The Puritan Bennett Companion 492a oxy gen concentrator operates using two molecu MEDICAL GAS SUPPLY EQUIPMENT 19 Figure 1 18 Companion 492a oxygen concentrator Courtesy Puritan Bennett Corporation Lenexa KS A photograph of the Puritan Bennett lar sieves to separate oxygen from room air Fig
101. uu pue Jepur o y BSN oj enunuo seb Buuenjep Jepui Ao eui S LYVLS Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 36 CHAPTER ONE OXYGEN REGULATION DEVICES Cylinders that contain highly pressurized gas would be dangerous to use without spe cialized equipment to regulate gas flow and allow safe attachment of other equipment It is important to understand the operation of cylinder valves and reducing valves to safely use cylinders Direct Acting Cylinder Valve As its name implies the direct acting cylinder valve operates by opening and clos ing the valve seat directly As the valve stem or wheel is turned the valve plunger moves up or down acting directly on the valve seat As the valve seat is opened gas moves from the area of high pressure within the cylinder to the area of lower pressure out of the cylin der Figure 1 30 shows the component parts of the cylinder valve The valve plunger is threaded so as the stem is turned it opens or TEFLON WASHERS GASLOC SEAL AND CAP Figure 1 30 A full section of a direct acting cylinder valve Courtesy BOC Gases formerly Airco Murray Hill NJ closes The direct acting cylinder valve is a type of needle valve Diaphragm Cylinder Valve In this type of cylinder valve a diaphragm opens or closes the valve seat As the valve stem is t
102. ween the impeller and the ONE WAY VALVES I I I y III DLL CONNECTING ROD DIAPHRAGM Figure 1 13 A functional diagram of a diaphragm compressor Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 16 CHAPTER ONE CHECK VALVES PPP A f Y Y JERRY IMPELLER Y J Q f 4 ROTATION KOT Figure 1 14 A functional diagram of a centrifugal compressor compressor housing The working fluid allows gas is passed through a bacteria filter that tolerances to be greater between the impeller removes particles as small as 0 3 microns The and the compressor housing reducing wear filtered air is then compressed by a compres and eliminating the need for lubrication sor to approximately 20 psi and conducted to A water separator and particle filters purify molecular sieves containing Zeolite The com the air prior to delivery to the hospital piping pressed gas alternately charges one sieve and system then the other The Zeolite in the sieve adsorbs Water traps should be used with all venti some of the nitrogen and passes the oxygen lators powered by compressed gases Water contained in the ambient air thus increasing can become condensed as air or oxygen is the oxygen concentration pressurized A contemporary ventilator s The process of adsorption is a surface pneumatic electronic control and monitoring ph
103. ylinder valve American Stan dard fitting or Pin Index fitting Attach the oxygen equipment to the reducing valve Turn on the cylinder valve ing valve primarily involves checking for leaks The following is a suggested trou bleshooting algorithm ALG 1 5 1 Check for leaks at the connection to the cylinder If leaks are present tighten the connection Check for leaks between the reducing valve and the oxygen therapy equip ment and tighten as appropriate If gas fails to flow from the cylinder check the pressure gauge to ensure that the cylinder has pressure a If the cylinder contains pressure check the reducing valve outlet for obstructions If the above is satisfied replace the reducing valve with another and try again Copyright 2005 Thomson Learning Inc All Rights Reserved May not be copied scanned or duplicated in whole or in part Licensed to iChapters User 40 CHAPTER ONE saoquo SUIINPAL PUV SAOJVINSAA SVS VILPAUL j001 sa qno4 04 MOY 8uiquuosap uuj4oSjv uy S L OW OA BA JepuiAo uo uin y suonoeuuoo Ife uei ACA Jopul o y uo uan p nss d Suoioeuuoo pee q pue AJLA Ife uays JepuiAo yo uin Z uonnjos deos YUM yea AjueA 1 eunsseJd pee q pue eA eA 1epul Ao eu yo WN Z uonnjos deos ua wd nb UUM yea AJu8A L u A xo y pue Joye nBe y u m q yes e 1 y S OA EA y uo uin Jo1e

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