Oxygen and Medical Gas Therapy

6 Oxygen and Medical Gas Therapy


Note 1: This book is written to cover every item listed as testable on the Entry Level Examination (ELE), Written Registry Examination (WRE), and Clinical Simulation Examination (CSE).


The listed code for each item is taken from the National Board for Respiratory Care (NBRC) Summary Content Outline for CRT (Certified Respiratory Therapist) and Written RRT (Registered Respiratory Therapist) Examinations (http://evolve.elsevier.com/Sills/resptherapist/). For example, if an item is testable on both the ELE and the WRE, it will simply be shown as: (Code: …). If an item is testable only on the ELE, it will be shown as: (ELE code: …). If an item is testable only on the WRE, it will be shown as: (WRE code: …).


Following each item’s code will be the difficulty level of the questions on that item on the ELE and the WRE. (See the Introduction for a full explanation of the three question difficulty levels.) Recall (R) level questions typically expect the exam taker to recall factual information. Application (Ap) level questions are harder because the exam taker may have to apply factual information to a clinical situation. Analysis (An) level questions are the most challenging because the exam taker may have to use critical thinking to evaluate patient data to make a clinical decision.


Note 2: A review of the most recent Entry Level Examinations (ELE) has revealed that an average of 12 questions (out of 140), or 9% of the exam, will cover oxygen and medical gas therapy. A review of the most recent Written Registry Examinations (WRE) has shown that an average of 7 questions (out of 100), or 7% of the exam, will cover oxygen and medical gas therapy. The Clinical Simulation Examination is comprehensive and may include everything that should be known by an advanced level respiratory therapist.



MODULE A





1. Oxygen administration





c. Administer oxygen to achieve adequate respiratory support (ELE code: IIID6) [Difficulty: ELE: R, Ap, An]


Oxygen (O2) must be administered in doses (up to 100%) that are adequate to treat hypoxemia, decrease the patient’s work of breathing, or decrease the work of the heart. Because the U.S. Food and Drug Administration has declared supplemental oxygen to be a drug, a physician’s order is required to give it to a patient or to make a change in the percentage. The only exceptions are when recognized protocols exist in your institution to give oxygen under certain limited conditions. For example, all patients with a diagnosed heart attack are given a nasal cannula at 2 L/min, or all patients undergoing cardiopulmonary resuscitation (CPR) receive 100% oxygen.


See Chapter 3 (Module A) for a listing of indications for drawing blood for an arterial blood gas (ABG) measurement. This list should be fairly complete for conditions that justify the need for supplemental oxygen. In general, the goal of giving supplemental oxygen is to keep the patient’s Pao2 level between 60 and 100 torr. Exceptions include carbon monoxide poisoning, severe anemia, and CPR, when the hope is to fully saturate the hemoglobin and increase the plasma oxygen content as much as possible. Oxygen should not be given without proof of hypoxemia or another clinical justification. When those conditions have been corrected, the oxygen percentage should be adjusted accordingly.


Giving supplemental oxygen is not done without risk. Following are oxygen-related problems that may be seen clinically.










2. Manipulate oxygen and specialty gas analyzers by order or protocol (Code: IIA26) [Difficulty: ELE: R, Ap; WRE: An]





c. Troubleshoot any problems with the equipment


Because so many different models are available, consult an equipment book or the manufacturer’s literature for details of the various analyzers. All portable, hand-held analyzers fall into one of the following categories: electric, physical/paramagnetic, and electrochemical.





3. Electrochemical analyzers: polarographic and galvanic fuel cell


Both polarographic and galvanic fuel cells make use of the fact that each oxygen molecule accepts up to two electrons and becomes chemically reduced. The more oxygen is in the gas sample, the more electrons are released from an oxidizing electrolyte solution. This is measured as an electrical current that is proportional to the oxygen percentage. These analyzers can monitor continuously and display the oxygen percentage. Both types are safe by themselves in the presence of flammable gases, but the added alarm systems are powered electrically and may make the units unsafe. Polarographic analyzers use a battery to polarize the gas sampling probe. Because of this, they have a faster response time than do the galvanic fuel cell types. Galvanic fuel cell analyzers do not need a battery for power. However, they usually include alarms that are battery powered.


Failure to calibrate either type can be caused by a weak battery, an exhausted supply of chemical reactant in the gas sampling probe, an electronic failure, or a damaged membrane over the probe. A damaged or torn probe will allow water, mucus, or blood onto the probe. The galvanic units must have their probes kept dry to be read accurately. Both types are pressure sensitive. High altitude causes them to display a lower-than-true oxygen percentage, and high pressure as seen in a ventilator circuit with positive end-expiratory pressure (PEEP) causes the units to display a higher-than-true oxygen percentage.





MODULE B





1. Manipulate oxygen and other gas cylinders, bulk storage systems, and manifolds, by order or protocol (ELE code: IIA9a) [Difficulty: ELE: R, Ap, An]





c. Troubleshoot any problems with the equipment



1. Oxygen and other gas cylinders


The different types of gases in cylinders are identified by the color code of the cylinder and the cylinder label. Note that only E cylinders have mandatory color coding. Color codings on the other cylinders are voluntary but usually are followed by the manufacturers. However, always read the label to be sure of the contents of the cylinder. The most important cylinder colors to remember are those of oxygen and air, but all are included in Table 6-1 for the sake of completeness.


TABLE 6-1 Color Codes for Gas Cylinders

































Gas Color
Oxygen Green (white for international)
Air Yellow
Helium Brown
Helium and oxygen Brown and green (check the label for the percentage of each gas)
Carbon dioxide Gray
Carbon dioxide Gray and green (check the label for oxygen and the percentage of each gas)
Nitrous oxide Light blue
Cyclopropane Orange
Ethylene Red






2. Manipulate adjunct hardware, such as reducing valves, flowmeters, regulators, and high-pressure hose connectors, by order or protocol (ELE code: IIA9a) [Difficulty: R, Ap, An]





c. Troubleshoot any problems with the equipment



1. Reducing valves


Reducing valves are used to reduce the high pressure seen in a bulk oxygen storage system, manifold, or gas cylinder. One or more stages (pressure-reducing steps) can be used to reach the working pressure of 50 psig. Single-stage reducing valves reach the pressure in a single step. Multiple-stage reducing valves give finer control over pressure and flow by decreasing pressure in the first stage to about 200 psig and to 50 psig in the second stage. Occasionally, three stages are seen. All reducing valves (and regulators [combined reducing valve and flowmeter]) have the following built-in safety features:







TABLE 6-3 Pin Index Safety System Gases and Pinhole Locations

































Gas Pinhole Locations
Oxygen 2-5
Air 1-5
Oxygen/carbon dioxide (≤7%) 2-6
Oxygen/carbon dioxide (>7%) 1-6
Oxygen/helium (not >80% helium) 2-4
Oxygen/helium (helium >80%) 4-6
Nitrous oxide 3-5
Ethylene 1-3
Cyclopropane 3-6

It is necessary to “crack” or blow some gas out of a cylinder before putting any reducing valve or regulator onto the cylinder. Do this by attaching the tank wrench to the valve stem and slowly turning the valve stem in a counterclockwise (so-called “lefty-loosy”) direction to release some gas. This cracking is done to prevent any dust or debris from being forced into the reducing valve or regulator, which might cause a fire. See Figure 6-2 for a schematic drawing of an “E” tank of oxygen and how its yoke is connected. If the O-ring is missing or the yoke is misaligned on the post, a high-pressure gas leak will occur when the tank is opened with the tank wrench. Close off the tank to stop the leak by turning the tank wrench on the valve stem in a clockwise direction (so-called “righty-tighty”). Investigate the yoke-to-post connection to identify causes of the leak.


image

Figure 6-2 Details of an “E” size tank of oxygen and its yoke connector. A, A cross section through the stem (also called the control valve) of the tank shows its key features. B, A three-dimensional view shows how the yoke with its two pins aligns with the corresponding pin holes (locations 2 and 5) on the yoke. The plastic washer ensures a seal between the gas outlet on the stem and the yoke. (Not shown is the regulator that attaches to the yoke. See Figure 6-9.) C, A tank wrench that is attached to the valve stem (also called a control valve). Turn the wrench in a counterclockwise direction to open the tank and allow gas flow; close the tank to stop gas flow by turning the wrench in a clockwise direction.


(Redrawn from Sills JR: Respiratory care for the health care provider, Albany, 1998, Delmar Publishers.)



2. Flowmeters


Flowmeters are designed to regulate and indicate flow. They come with the following safety features so that they cannot be attached to the wrong reducing valve, regulator, high-pressure hose, or appliance:




Flowmeters usually are categorized by how they react to backpressure. To complicate matters further, we must remember that the three different manufactured types of flowmeters may or may not be backpressure compensated:


1. Non–backpressure-compensated (pressure-uncompensated) flowmeters will inaccurately indicate the flow through them in the face of backpressure. Figures 6-3 and 6-4 show non–backpressure-compensated kinetic and Thorpe types of flowmeters, respectively. Note that the Thorpe and kinetic flowmeters have the flow-control valve upstream from the meter. They read accurately if they are kept upright and do not have to “push” against any backpressure. If laid on their sides, the plunger and ball bearing do not indicate the set flow. They both read a lower flow than that actually delivered when faced with a backpressure.

2. The Bourdon flowmeter is designed similarly to the Bourdon gauge in the reducing valve (Figure 6-5). The face piece is marked in liters of flow rather than pressure. It is the flowmeter of choice in a transport situation because it may be laid flat with no effect to its flow if no backpressure is present. These flowmeters will display a higher flow than that actually delivered when faced with a backpressure.

3. Backpressure-compensated (pressure-compensated) flowmeters accurately indicate the flow through them in the face of backpressure. For this reason, they should be used whenever possible. Figures 6-6 and 6-7 show backpressure-compensated kinetic and Thorpe types of flowmeters, respectively. Note that both of these flowmeters have the flow-control valve downstream from the meter. Because of this, they read accurately in the face of backpressure as long as they are kept upright. Besides reading the label, this simple test enables the practitioner to tell whether a flowmeter is backpressure compensated:









d. Perform quality control procedures for flowmeters (Code: IIC6) [Difficulty: ELE: R, Ap; WRE: An]


When a quality control procedure for a flowmeter is performed, it is critical that a known flow be sent through it so that the flowmeter can be checked for accuracy. This should be done without any backpressure against the flowmeter. Review the previous discussion on troubleshooting flowmeters for the effects of backpressure on non–backpressure-compensated flowmeters and Bourdon flowmeters. Do not use any flowmeter that does not give an accurate reading.







3. Manipulate pulse-dose oxygen-conserving devices by order or protocol (ELE code: IIA9b) [Difficulty: R, Ap, An]



a. Get the necessary equipment for the procedure


Three types of intermittent-flow oxygen-conserving devices are available: pulse-dose oxygen delivery devices (PDODs), demand oxygen delivery systems (DODSs), and hybrid units. All are used in the home care setting and save money by delivering oxygen to the patient only during inspiration. These units take the place of a regulator and flowmeter that deliver a steady flow of oxygen to the patient.


The characteristics of each unit will vary depending on the manufacturer. However, the following main operational features are found:






Depending on the manufacturer, the unit can be used with oxygen tanks, a low-pressure liquid oxygen (LOX) system, or an oxygen concentrator. Be careful not to place a low-pressure unit on a high-pressure gas source because it will be damaged.





4. Manipulate air compressors by order or protocol (Code: IIA9f) [Difficulty: ELE: R, Ap; WRE: An]





c. Troubleshoot any problems with the equipment


Air compressors are used whenever a high-pressure gas source other than oxygen is needed. All three systems are alike in that they use an electrically powered motor, filter the room air as it enters and exits the compressor, and have a condenser to remove water vapor as it leaves the compressor. See Figure 6-11.







5. Manipulate air/oxygen proportioners (blenders) by order or protocol (ELE code: IIA9a) [Difficulty: ELE: R, Ap, An]







6. Manipulate oxygen concentrators (Code: IIA9c) [Difficulty: ELE: R, Ap; WRE: An] and portable oxygen concentrators (WRE code: IIA9e) [Difficulty: WRE: R, Ap, An] by order or protocol



a. Get the necessary equipment for the procedure


Two different types of oxygen concentrators (also known as oxygen enrichers) are available for the delivery of continuous low-flow oxygen in the home: molecular sieve and semipermeable plastic membrane.







c. Troubleshoot any problems with the equipment


The molecular sieve–type units deliver dry gas; therefore a humidification system is frequently added to the flowmeter. With the permeable plastic membrane–type units, the condensed water vapor must be emptied from the collection jar. In both types of oxygen concentrators, it is important to check the air-inlet filter on a monthly basis to keep it clean of dust and debris. Follow the manufacturer’s requirements regarding when filters should be replaced. The delivered oxygen concentration also should be checked each month. Follow the manufacturer’s guidelines for its preventative maintenance needs. The molecular sieve–type units must have the zeolite pellet canisters replaced on a scheduled basis.


Some units have a visual or audio alarm that warns when a problem occurs, such as power failure, low or high pressure, or low oxygen percentage. If the unit does not have a low oxygen percentage alarm, some home care practitioners have added an external analyzer with an alarm system. This alerts the patient to call the home care company to repair the equipment. If a patient says that he or she cannot feel any gas coming out of the cannula, have the patient place the prongs into a glass of water. If no bubbling is seen, have the patient check the tubing for any disconnections. If the concentrator is malfunctioning, have the patient turn it off and switch to oxygen from the backup oxygen cylinder until repairs can be made.




Jun 18, 2016 | Posted by in RESPIRATORY | Comments Off on Oxygen and Medical Gas Therapy

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