a. Recommend changes in the patient’s position to minimize hypoxemia (Code: IIIG2a) [Difficulty: ELE: R, Ap; WRE: An]

b. Position the patient to minimize hypoxemia (Code: IIID8) [Difficulty: ELE: R, Ap; WRE: An]

Usually a patient who is short of breath when lying supine should be repositioned to sit more upright in a Fowler’s or semi-Fowler’s position. This seems to work best in patients with bilateral pulmonary problems such as congestive heart failure or pneumonia. If the patient cannot sit up and the lung problem is one-sided, roll the patient so that the more functional lung is down. The good lung should be positioned up in the following exceptions:

In either case, always ask the patient whether the new position helps to make breathing easier. If not, reposition the patient until breathing is more comfortable with less shortness of breath. In general, Trendelenburg is not well tolerated. A patient with a closed head injury and brain edema should not be put into the Trendelenburg position.

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.

d. Measure the patient’s oxygen percentage, oxygen liter flow, or both (ELE code: IIIE10) [Difficulty: ELE: R, Ap, An]

Always measure the patient’s inspired O₂ percentage (Fio₂) if possible. The gas sample should be taken as close as possible to the patient to minimize the chance of dilution from room air. Record the oxygen percentage on the ABG order slip, in the department records, and in the patient’s chart if needed. As discussed in Chapter 3, the oxygen percentage must be known before the patient’s Pao₂ level can be interpreted.

The oxygen liter flow is all that can be recorded with the following devices: nasal cannula, nasal catheter, simple mask, partial-rebreather mask, nonrebreather mask, and transtracheal oxygen catheter. A direct relation is found between the liter flow and the oxygen percentage, but it is not predictably accurate.

e. Prevent the patient from becoming hypoxemic by using proper technique (ELE code: IIID9) [Difficulty: ELE: R, Ap, An]

Use caution and plan ahead to minimize any time that the oxygen supply to the patient is cut off or reduced. When changing equipment of any kind, have the replacement set up and tested for proper function before replacing the current setup.

It is well known that suctioning the airway reduces the patient’s oxygen level. This can result in dangerous dysrhythmias. Remember to increase the patient’s inspired oxygen percentage about 1 minute before, during, and for at least 1 minute after suctioning. It is acceptable and safe to give 100% oxygen to an adult for short periods like this. Remember to reduce the oxygen percentage or liter flow to the previous level once the patient is stable after the procedure. Reanalyze the percentage if possible.

a. Get the necessary equipment for the procedure

b. Put the equipment together and make sure that it works properly

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.

a. Get the necessary equipment for the procedure

b. Put the equipment together and make sure that it works properly

c. Troubleshoot any problems with the equipment

a. Get the necessary equipment for the procedure

b. Put the equipment together and make sure that it works properly

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:

• A frangible disk that breaks to release gas pressure in the event of mechanical failure or breakage

• A fusible plug that melts to release gas pressure in the event of a fire

• American Standard Compressed Gas Cylinder Valve Outlet and Index Connections (usually called the American Standard Safety System [ASSS]), which prevent the accidental connection of the wrong reducing valve (or regulator) to a large gas cylinder

• The Pin Index Safety System (PISS) is a special section of the American Standard System that applies to gas cylinders that are E-sized and smaller. It is designed to prevent an accidental connection of the wrong gas to a reducing valve or regulator. These reducing valves and regulators are designed with a specifically pinned yoke to wrap around the valve stem of a gas cylinder. A soft plastic O-ring washer is included to help ensure a tight seal. Figure 6-1 shows the location of the pinholes in the cylinder valve face. Table 6-3 shows the gases and pinhole positions. It is important to know the positions for oxygen and air; the others are included for the sake of completeness.

Figure 6-1 Locations of the Pin Index Safety System holes in the cylinder valve face.

(Modified from Branson RD, Hess DR, Chatburn RL: Respiratory care equipment, ed 2, Philadelphia, 1999, Lippincott Williams & Wilkins.)

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.

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:

• Diameter Index Safety System (DISS) inlets and outlets that are specific to the various gases, so a mixup with the wrong appliance or connector cannot occur. The DISS system applies to flowmeters that attach to all American Standard and DISS reduction valves.

• Flowmeters with quick-connect inlet adapters instead of DISS inlets. These quick-connects are designed specifically for the hospital’s piped-in oxygen and air outlets. They are not interchangeable between gases or between manufacturers. Occasionally a piped oxygen outlet will jam open and will let gas rapidly escape. Insert the proper flowmeter into the outlet, and turn the flowmeter off. This stops the leak until the defective wall outlet can be repaired.

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:

1. Make sure the flowmeter is turned off.

2. Plug the flowmeter into a gas outlet.

3. If the float or ball bearing bounces, the flowmeter is backpressure compensated.

Figure 6-3 Kinetic-type non–backpressure-compensated (pressure-uncompensated) flowmeter.

(Modified from McPherson SP: Respiratory care equipment, ed 4, St Louis, 1990, Mosby.)

Figure 6-4 Thorpe-type non–backpressure-compensated (pressure-uncompensated) flowmeter.

(Modified from McPherson SP: Respiratory care equipment, ed 4, St Louis, 1990, Mosby.)

Figure 6-5 Bourdon-type non–backpressure-compensated (pressure-uncompensated) flowmeter.

(From McPherson SP: Respiratory care equipment, ed 4, St Louis, 1990, Mosby.)

Figure 6-6 Kinetic-type backpressure-compensated (pressure-compensated) flowmeter.

(Modified from McPherson SP: Respiratory care equipment, ed 4, St Louis, 1990, Mosby.)

Figure 6-7 Thorpe-type backpressure-compensated (pressure-compensated) flowmeter.

(Modified from McPherson SP: Respiratory care equipment, ed 4, St Louis, 1990, Mosby.)

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.

1. Regulators

Regulators combine a reducing valve and a flowmeter (Figure 6-8). Everything that has been discussed so far relates to regulators. Bourdon gauge reducing valves usually are seen and can have a second Bourdon gauge added as a flowmeter (Figure 6-9) or a Thorpe or kinetic flowmeter. As mentioned earlier, use a backpressure-compensated flowmeter in all situations except for patient transport.

Figure 6-8 Drawing of the key components and features of a single-stage regulator. A regulator is composed of a reducing valve for the high tank pressure and a flowmeter. Gas pressure is shown on the cylinder gauge. Also shown is a Thorpe-type backpressure-compensated flowmeter.

(From Cario J, Pilbeam S: Mosby’s Respiratory Therapy Equipment, ed 8, St Louis, 2010, Mosby.)

Figure 6-9 Drawing of an “E” tank of oxygen showing how the yoke and regulator are connected and their features. A Bourdon-type pressure gauge is shown. Turn the crank to let gas flow through the Bourdon-type non–backpressure-compensated (pressure-uncompensated) flowmeter. A nipple adapter is attached for the connection of small-bore oxygen tubing. If the nipple adapter is unscrewed, a bubble-type humidifier or other oxygen delivery system can be attached. Note: This type of regulator is recommended for patient transportation if the “E” tank must be placed horizontally.

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

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:

Figure 6-10 A pulse-dose oxygen delivery system with its key features shown. A specific type of nasal cannula is needed with this system. One channel transmits the negative pressure from the patient’s inspiration back to the demand valve. This negative pressure opens the demand valve to allow a bolus of oxygen to travel down the second channel to the patient to inhale.

(From Cario J, Pilbeam S: Mosby’s Respiratory Therapy Equipment, ed 8, St Louis, 2010, Mosby.)

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.

b. Put the equipment together and make sure that it works properly

With a pulse-dose system, the proximal end of a special nasal cannula is attached to a pressure sensor on the pulse-dose system. It senses a decrease in pressure as the patient inspires. The sensor then opens a demand valve that delivers a burst of oxygen to the cannula. See Figure 6-10. Because the nasal cannula is directly attached to the pressure sensor, a bubble-type humidifier cannot be added into the system.

Most of the units allow the respiratory therapist to work with the patient to adjust the sensor or timer to change how long the oxygen is delivered, how much is delivered, and whether the patient receives oxygen every breath or every second or third breath.

Make sure that the patient can feel a flow of gas from the cannula after he or she starts to inhale. The gas should stop during exhalation. Check the patient’s pulse oximetry value at rest and during exercise to ensure that desaturation does not occur. Adjust the pressure sensor or timer to meet the patient’s oxygen needs.

c. Troubleshoot any problems with the equipment

If the patient cannot feel any oxygen flowing, the following should be considered: (1) the source of oxygen might be empty, (2) the tubing might be disconnected or kinked, or (3) the sensor may not be detecting the patient’s effort. The patient or therapist can switch to a second oxygen source and look for disconnections or kinks in the tubing. The therapist must adjust the nasal cannula or sensor to correct for a sensitivity problem. Do not use a system that is malfunctioning and cannot be adjusted.

a. Get the necessary equipment for the procedure

b. Put the equipment together and make sure that it works properly

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.

Figure 6-11 A piston-type large-volume medical air compressor. These units are used in hospitals or medical facilities. On the downstroke, the piston draws in room air that is then compressed into the reservoir tank on the upstroke. A pressure switch automatically turns the motor on and off to keep the pressure constant. As the compressed air leaves the reservoir tank, any water vapor is removed before it goes to the pressure-reducing valve. The piping system carries the air at 50 psig to any respiratory care equipment that is in use.

(From Wilkins RL, Stoller JK, Kacmarek RM, editors: Egan’s fundamentals of respiratory care, ed 9, St Louis, 2009, Mosby.)

1. Rotary-type compressors

Rotary-type compressors generate pressure with a rotating fan. They are used commonly in volume ventilators and in the home to power hand-held medication nebulizers. (See Figure 6-12.)

Figure 6-12 Photograph of a portable air compressor for home use. It is powered electrically with an on/off switch. Note the small-bore tubing that takes the compressed air to the small-volume nebulizer to aerosolize a medication.

(From Wilkins RL, Stoller JK, Kacmarek RM, editors: Egan’s fundamentals of respiratory care, ed 9, St Louis, 2009, Mosby.)

a. Get the necessary equipment for the procedure

Oxygen blenders are designed to change the ratio of oxygen and air to blend the specific percentage of oxygen from 21% to 100% (Figure 6-13). They are used whenever high-pressure gas is needed and the oxygen percentage may need frequent adjustment.

Figure 6-13 Example of an oxygen blender. Note the high-pressure air and oxygen hoses entering the bottom of the unit, the dial used to set the oxygen percentage (75%), and the blended oxygen outlet to the right. In this case, a Wye connector has been attached with two oxygen flowmeters.

(From Cairo JM, Pilbeam SP: Mosby’s respiratory care equipment, ed 8, St Louis, 2009, Mosby.)

b. Put the equipment together and make sure that it works properly

The oxygen and air gas sources must be pressurized to 50 psig. This can be done by taking both gases from the hospital’s gas piping system or from gas cylinders. High-pressure hoses connect the gas sources with the blender. The desired oxygen percentage is set simply by adjusting the knob to the desired amount. Because the blended gases are under pressure, they must be sent directly to a mechanical ventilator or other device that uses 50 psig or through an added flowmeter.

With a blender, the oxygen percentage will remain close to the desired amount even if a small decrease in one or both line pressures occurs. Always analyze the oxygen percentage to confirm that it is correct.

c. Troubleshoot any problems with the equipment

Keep the gas inlets and outlets clear of any debris. All current units give an audible whistle if one or both of the line pressures decrease to an unsafe level (often about 30 psig). If the unit has a water trap at the compressed air inlet, keep it emptied of any condensate.

d. Independently set up or change an oxygen blender (ELE code: IIIF2d2) [Difficulty: ELE: R, Ap, An]

As mentioned previously, a blender is indicated whenever 50 psig gas is needed and frequent oxygen percentage changes are likely.

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.

1. Molecular sieve

Molecular sieve–type oxygen concentrators use an air compressor to push room air through two canisters of zeolite pellets (inorganic sodium-aluminum silicate) to remove nitrogen and water vapor. The remaining oxygen is delivered to the patient through a flowmeter (Figure 6-14). Be aware that with this unit, the oxygen percentage varies inversely with the flow that is delivered (Table 6-4).

Figure 6-14 Drawing of the components of a molecular sieve oxygen concentrator. The molecular sieve beds remove nitrogen and pass oxygen through to the patient.

(Courtesy Sunrise Medical, Inc., Somerset, PA.)

TABLE 6-4 Comparison of Flow Rates and Oxygen Percentages in Oxygen Concentrators

Flow, L/min	Approximate Oxygen Percentage
MOLECULAR SIEVE CONCENTRATOR
1-2	95%-92%
3-5	92%-85%
>6	<85%
SEMIPERMEABLE MEMBRANE CONCENTRATOR
1-10	40%

2. Semipermeable plastic membrane

Semipermeable plastic membrane oxygen concentrators make use of a very thin plastic membrane as a filter. Room air is pulled through it by a vacuum pump. Molecular oxygen and water vapor can pass through the membrane faster than nitrogen. Any excess water vapor is removed by a simple condenser system. No need exists to add an external humidification system to the flowmeter (Figure 6-15). The oxygen percentage is fixed at 40% in these units; however, the flow can be varied from 1 to 10 L/min, as shown in Table 6-4.

Figure 6-15 Functional schematic of a semipermeable membrane oxygen concentrator. The membrane permits more oxygen and water vapor than nitrogen to pass through.

(Courtesy of the Oxygen Enrichment Company, Schenectady, NY.)

When one is deciding which type of concentrator to use, it is important to know the patient’s required oxygen percentage and flow. As can be seen from Table 6-4, the molecular sieve units can deliver a higher oxygen percentage at any liter flow as compared with the semipermeable plastic membrane units.

b. Put the equipment together and make sure that it works properly

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.

a. Get the necessary equipment for the procedure

A LOX system is used in the home when it is found to be more cost-effective than an oxygen concentrator or a battery of oxygen cylinders. An additional advantage is that the patient can carry a smaller portable unit in a shoulder bag for added mobility. Carrying it is less conspicuous than wheeling an E cylinder about. An early, widely known liquid oxygen system was the Linde Walker System (Union Carbide, Houston, TX). Figure 6-16 shows the key features of a large liquid oxygen reservoir that is kept in the patient’s home. Figure 6-17 shows its smaller portable companion, which can be filled from the large reservoir.

Figure 6-16 Drawing of the components of a home liquid oxygen supply unit.

(From Lampton LM: Home and outpatient oxygen therapy. In: Brashear RE, Rhodes ML, editors: Chronic obstructive lung disease, St Louis, 1978, Mosby.)

Figure 6-17 Drawing of the components of a portable liquid oxygen unit.

(From Lampton LM: Home and outpatient oxygen therapy. In: Brashear RE, Rhodes ML, editors: Chronic obstructive lung disease, St Louis, 1978, Mosby.)

b. Put the equipment together and make sure that it works properly

Current portable liquid oxygen systems weigh only a few pounds and can be carried over the shoulder by a strap. They can be refilled from the larger reservoir tank kept in the home. The flow rate can be adjusted to meet most patients’ needs. Humidification is provided by the patient’s own airway. As with any pressurized system, all fittings must be kept tight to prevent leakage.

The National Fire Protection Agency (NFPA) has established several regulations to ensure that home LOX systems are installed safely. Key safety regulations include the following:

c. Troubleshoot any problems with the equipment

Check that all connections are airtight to avoid spills and minimize the loss of oxygen. Make sure that the unit is functioning at its designed working pressure. Check that the pressure relief valve operates properly and that proper oxygen flow is delivered.

d. Independently modify a liquid oxygen system (ELE code: IIIF2d3) [Difficulty: ELE: R, Ap]

A home care therapist may need to adjust the flow of oxygen, within guidelines established by the physician, to maintain patient oxygenation.

a. Get the necessary equipment for the procedure

Helium/oxygen (He/O₂ [heliox]) has been used historically in the management of patients with an upper airway obstruction. This may include tracheal tumor, postextubation laryngeal edema, and croup. More recently, heliox has been used with success in patients with status asthmaticus. The decreased density of a helium/oxygen mix compared with a nitrogen/oxygen mix reduces the patient’s work of breathing.

Various heliox gas mixtures come in high-pressure cylinders and require the use of an American Standard System reducing valve (or regulator) designed specifically for the gas or gas mix. As is shown in Table 6-3 and Figure 6-1, a reducing valve or regulator for an E cylinder must match the appropriate pinholes on the cylinder valve face. Corresponding high-pressure hoses also may be needed. Table 6-1 shows the color codes for the various gas cylinders. Pure helium comes in a brown cylinder, whereas helium and oxygen mixes come in brown and green cylinders. Always check the cylinder label for the exact percentage of the gases within it. Heliox comes in standard mixes of 80% He/20% O₂, 70% He/30% O₂, and 60% He/40% O₂.

b. Put the equipment together and make sure that it works properly

The additional equipment needed depends on how the ordered heliox mixture is to be delivered to the patient.

1. Nonrebreather mask

In most clinical situations, a nonrebreather mask with reservoir bag is used to deliver heliox to a spontaneously breathing patient. A snugly fitting mask with one-way valves and a full reservoir bag will minimize breathing of any room air. (The next Module includes additional discussion on nonrebreather masks.) A helium flowmeter can be used to set the flow of heliox to the face mask. However, if a helium flowmeter is not available, an oxygen flowmeter can be added to the reducing valve on a heliox mix cylinder. In either case, set the gas flow high enough that the reservoir bag does not collapse on inspiration. The gas is humidified by attaching to the flowmeter a bubble humidifier with sterile water. Connect small-bore tubing between the humidifier nipple and the nonrebreather mask nipple.

If the patient is being treated for asthma, the nonrebreather mask can be modified to accept a small-volume nebulizer for bronchodilator medication delivery. (See Figure 6-18.) Care must be taken if the nebulizer is powered by the heliox mix, as shown. Some nebulizers will not operate normally. It may be necessary to increase the heliox flow by 50% to 100% from the usual rate of oxygen flow to get the unit to operate properly. Others simply choose to power the nebulizer with oxygen, as intended, for the treatment.

Figure 6-18 A modified nonrebreathing mask and reservoir bag for delivering helium/oxygen. The Y-connector allows the heliox to be breathed from the reservoir bag while the nebulizer is aerosolizing a bronchodilator medication. A separate flowmeter is used for each component. Use enough heliox flow to keep the reservoir bag from collapsing. The nebulizer can be powered by heliox, as shown, or by oxygen.

(From Hess DR: Nonconventional respiratory therapeutics. In: Hess DR, MacIntyre NR, Mishoe SC, et al, editors: Respiratory care principles & practices, Philadelphia, 2002, WB Saunders.)

In the common situation where an oxygen flowmeter is being used, a calculation must be done to convert the flow seen on the oxygen flowmeter to the actual flow of heliox. This is necessary because helium is less dense than oxygen.

Exam Hint 6-6 (WRE)

Often one question requires the calculation of actual flow of a heliox mixture. The heliox factor must be known to do the calculation. One possible calculation involves figuring out the heliox flow from an observed flow through an oxygen flowmeter. The other possible calculation involves setting the observed flow through an oxygen flowmeter to achieve the desired heliox flow. See the following sample calculations.

The heliox factor must be used to determine the actual flow of heliox through an oxygen flowmeter, as follows:

	Helium/Oxygen Ratio	Heliox Factor
1.	80% helium/20% oxygen	1.8
2.	70% helium/30% oxygen	1.6
3.	60% helium/40% oxygen	1.4

The following examples show how the actual heliox flow can be calculated from the observed oxygen flow seen on the flowmeter:

1. When using an 80% helium and 20% oxygen mix, multiply the observed flow by the heliox factor of 1.8.

Example: Observed oxygen flow of 10 L/min × 1.8 = 18 L/min actual heliox flow.

2. When using a 70% helium and 30% oxygen mix, multiply the observed flow by the heliox factor of 1.6.

Example: Observed oxygen flow of 10 L/min × 1.6 = 16 L/min actual heliox flow.

3. When using a 60% helium and 40% oxygen mix, multiply the observed flow by the heliox factor of 1.4.

Example: Observed oxygen flow of 10 L/min × 1.4 = 14 L/min actual heliox flow.

The following examples show how to set an oxygen flowmeter to deliver a needed heliox flow by dividing the desired flow by the heliox factor:

1. When using an 80% helium and 20% oxygen mix, determine the observed flowmeter setting to deliver an actual heliox flow of 10 L/min.

Example: .

2. When using a 70% helium and 30% oxygen mix, determine the observed flowmeter setting to deliver an actual heliox flow of 10 L/min.

Example: .

3. When using a 60% helium and 40% oxygen mix, determine the observed flowmeter setting to deliver an actual heliox flow of 10 L/min.

Example: .

c. Troubleshoot any problems with the equipment

When using a nonrebreather mask, make sure that it is adjusted to give as tight a fit to the face as is practical and comfortable. All one-way valve flaps should open and close properly. Set the gas flow high enough that the reservoir bag does not collapse by more than one-third during inspiration. With a mechanical ventilator, make sure that the exhaled volume is measured accurately and that alarms are adjusted to actual patient values. With either system, it is extremely important that all connections be tight because helium easily leaks out of any openings. If the oxygen percentage is too low, be prepared to make the necessary adjustments. Clinical experience is recommended with the administration of helium/oxygen mixes.

a. Get the necessary equipment for the procedure

Oxygen hoods are used to provide a warmed aerosol, humidity, and a controlled oxygen percentage to pediatric patients who weigh no more than 18 lb (8.2 kg). (See Figure 6-19.) Often the oxygen hood and the infant are placed inside of an incubator for better control of the environment and maintenance of body temperature. (See Chapter 8 for discussion on incubators.)

Figure 6-19 Infant in an oxygen hood.

(Courtesy Utah Medical Products Midvale, Utah.)

b. Put the equipment together and make sure that it works properly

When an oxygen hood is used, the following procedures should be observed:

c. Troubleshoot any problems with the equipment

Make sure that the oxygen and aerosol delivery systems are working properly and that the oxygen percentage can be maintained. Be aware of the noise level inside the hood to minimize damage to the infant’s hearing. The sound level should be monitored and kept well below 65 dB.

a. Get the necessary equipment for the procedure

Oxygen tents formerly were used for adults but now are used only for children who are too large and active for an oxygen hood. The tent is a clear plastic canopy used to control the environment by providing a cooled aerosol, humidity, and a controlled oxygen percentage (Figure 6-20).

Figure 6-20 Timeter® CAM4™ Portable Child/Adult Mist Tent.

(Courtesy Allied Healthcare Products, Inc. St. Louis, Missouri).

b. Put the equipment together and make sure that it works properly

In addition to setup of the tent, the following must be done to make it operational:

c. Troubleshoot any problems with the equipment

It can be difficult to maintain the ordered oxygen percentage inside the tent. Remember to close any opened ports when patient care is finished and to keep the canopy sealed with the bottom edges tucked under the mattress. Be prepared to increase or decrease the oxygen flow until the desired percentage is reached. The child should not be allowed to have any electrically powered toys inside the tent to minimize the risk of a spark and fire. Make sure the humidification and cooling systems are working properly.

a. Get the necessary equipment for the procedure

Air entrainment masks are called high-flow devices because they are designed to provide the patient with a controlled oxygen percentage at a high enough flow rate to ensure that all of the patient’s inspiratory flow needs are met (Figure 6-21). To ensure that this happens, the total flow through the mask must be equal to or greater than the patient’s peak inspiratory flow. (The interested learner is encouraged to read about the Bernoulli principle, which regulates the mixing of fluids as the result of a decrease in pressure caused by a jet.) These masks are sometimes called Venturi masks, Venti masks, jet-mixing, and high airflow with oxygen enrichment (HAFOE) systems. See Table 6-5 for specific information on available air entrainment masks.

Figure 6-21 Adult wearing an air entrainment mask. A, High-velocity jet. B, An area of reduced lateral pressure (Bernoulli’s principle). C, Room air entrainment.

(From White GC: Basic clinical lab competencies for respiratory care, an integrated approach, Albany, NY, 1988, Delmar.)

These masks are recommended in any clinical situation in which a known, precise oxygen percentage must be given to the patient who has a variable respiratory rate, inspiratory/expiratory (I : E) ratio, tidal volume, or minute volume. Common situations include a patient with COPD and a patient in respiratory failure who needs increasing oxygen percentages.

b. Put the equipment together and make sure that it works properly

Depending on the manufacturer, the mask my come as a completed unit, may have air entrainment adapters to add to the mask, or may have an air entrainment adapter to adjust to set the desired oxygen percentage. See Table 6-5 for the recommended starting oxygen flow rate for the different oxygen percentage masks. Because it is difficult to ensure that the patient’s peak inspiratory flow is matched by the gas flow through the mask, the following guidelines are recommended:

Some patients may complain that the gas coming through the mask is dry. To resolve this problem, some manufacturers have designed an aerosol adapter to add at the jet. A separate bland aerosol then is added to the room air (21% oxygen that enters the jet stream). Make sure that the adapter fits properly and does not interfere with or block the jet or room air entrainment ports. Do not add a bubble-type humidifier to the jet on the mask because the high backpressure through the jet will cause the pressure relief (pop-off) valve to open, and the oxygen will leak out.

c. Troubleshoot any problems with the equipment

The two different types of air entrainment devices are based on the physical principles seen in the Bernoulli effect. It is important to know about the two different types to understand what can go wrong with them and how they can be fixed. Make sure that the correct liter flow of oxygen, jet size, and air entrainment port setting are selected to get the desired total flow and oxygen percentage.

a. Get the necessary equipment for the procedure

The traditional nasal cannula is a low-flow oxygen delivery tube that has been modified with two short prongs to deliver oxygen to the nostrils (Figure 6-22). Nasal cannulas come in neonatal, pediatric, and adult sizes based on the diameter of the prongs. Care must be taken to make sure that the patient’s nares are patent and are not plugged by a common cold, a deviated septum, or another unseen problem. This simple oxygen delivery device is used very widely because it is more comfortable for many patients than an air entrainment mask or other types of face masks. Current clinical practice guidelines indicate that, in an adult, an oxygen flow of 4 L/min or less does not require additional humidification if the patient has a normal upper airway.

Figure 6-22 Adult wearing a nasal cannula.

(From Wilkins RL, Stoller JK, Kacmarek RM, editors: Egan’s fundamentals of respiratory care, ed 9, St Louis, 2009, Mosby.)

b. Put the equipment together and make sure that it works properly

If an adult is getting from 1 to 4 L/min of oxygen and complains of nasal dryness, or if a higher flow is given, humidification will have to be provided. Often this is a bubble-type humidifier, as discussed in Chapter 8. Make sure that it is properly filled with sterile water and that the oxygen bubbles through it. Check the high-pressure pop-off valve for pressure release and a whistling sound. Before placing the cannula on the patient, check to see that the oxygen is flowing through the tubing. If available, use a cannula with curved prongs. They direct the gas flow toward the back of the nasal passages for better natural humidification and are better for patient comfort. Take care to avoid pulling the elastic restraining band too tightly around the head. Some brands loop the oxygen tubing over the ears to be drawn up snugly under the chin. Often this type is more comfortable than the types that have an elastic band.

The problem with a nasal cannula is that the delivered oxygen percentage is unreliable. Variations in the patient’s respiratory rate, I : E ratio, tidal volume, and minute volume result in different inhaled oxygen percentages. This is clearly unacceptable in an unstable patient in whom Pao₂ values are being used to help judge the changing cardiopulmonary status. Because of this clinical limitation, this device and the other low-flow oxygen delivery systems in the discussions that follow should be used only with stable patients. In the adult, the delivered oxygen percentage can be estimated at approximately 4% for each liter of oxygen per minute (Table 6-6). Flows usually are limited to 6 L/min to avoid excessive irritation to the nasal passages. Flows usually are limited to no more than 1 to 2 L/min in infants and 4 L/min in older children. The pulse oximetry value or Pao₂ level should be checked in patients of any age whenever a flow change is made or when the patient’s condition changes significantly.

TABLE 6-6 Estimated Delivered Oxygen Percentage in Adults Based on the Oxygen Liter Flow Through a Nasal Cannula

c. Troubleshoot any problems with the equipment

Replace a cannula that is obviously soiled or permanently obstructed. If a bubble-type humidifier is used, refill the water as needed and replace the humidifier according to protocol.

a. Get the necessary equipment for the procedure

Oxygen-conserving nasal cannulas are used for patients who need long-term, low-flow oxygen therapy and wish to reduce their costs.

b. Put the equipment together and make sure that it works properly

At least two different types of oxygen-conserving cannulas are found. Figure 6-23 shows a reservoir nasal cannula and how it operates. It has an 18-mL reservoir that fills when the patient exhales and gives up its oxygen bolus during the next inspiration. Figure 6-24 shows a pendant nasal cannula with its reservoir that hangs on the chest.

Figure 6-23 Drawing of the Oximizer reservoir nasal cannula and its functions.

(Courtesy of CHAD Therapeutics, Chatsworth, CA.)

Figure 6-24 Drawing of a patient wearing a pendant reservoir nasal cannula made by CHAD Therapeutics (Chatsworth, CA).

(From Wilkins RL, Stoller JK, Kacmarek RM, editors: Egan’s fundamentals of respiratory care, ed 9, St Louis, 2009, Mosby.)

c. Troubleshoot any problems with the equipment

Both types of cannulas can have problems with tubing disconnections or kinks that can happen with any type of cannula. The only problem that is unique to both of these units is failure of the diaphragm, which moves back and forth as the reservoir fills and empties. This membrane may wear out after about a week and prevent the reservoir from filling or emptying properly. Watch as the patient breathes to make sure that the diaphragm is moving properly. If not, replace the cannula.

a. Get the necessary equipment for the procedure

A high-flow nasal cannula (HFNC) is designed to provide warmed and humidified oxygen at a high enough flow rate to fully meet the patient’s peak inspiratory flow needs. This type of nasal cannula is better tolerated by many severely hypoxic patients than a nonrebreather mask because it provides 100% relative humidity at body temperature (BTPS [body temperature, pressure, saturated gas] conditions), and there is no drying of the nasal mucosa. For these reasons, the HFNC has found a growing clinical application in adult and neonatal populations. Adults with congestive heart failure and pulmonary edema may be kept off of continuous positive airway pressure (CPAP) or mechanical ventilation through the use of an HFNC.

Early evidence indicates that an HFNC may be used with some premature neonates as an alternative to CPAP or mechanical ventilation. Evidence suggests that neonatal patients receiving HFNC have a positive mouth pressure of about 3 to 4 cm water, which corresponds to a similar CPAP level. However, this pressure is maintained only when the mouth is closed. There is also the risk that an HFNC will create a higher CPAP level than desired. So, the smallest possible nasal cannula should be used to allow for a leak.

Although future research will indicate the best patient populations and application methods for HFNC, currently three systems are available: Vapotherm 2000i (Vapotherm, Stevensville, MD), the Salter Labs (Arvin, CA) high-flow cannula and humidifier, and the AquinOx High Flow Humidification System (Smiths Medical ASD Inc., Kent, UK). The Vapotherm 2000i will be used in the following discussion.

b. Put the equipment together and make sure that it works properly

Figure 6-25 shows a Vapotherm 2000i that is opened to show the vapor transfer cartridge. Water is continuously supplied into the unit and is warmed before entering the cartridge to be vaporized to humidify the patient’s oxygen. The temperature can be adjusted but usually is kept at body temperature. A pediatric cartridge will be used for a flow of 1 to 8 L/min. An adult cartridge will be used for flows of 5 to 40 L/min. An oxygen hose is attached at the bottom of the unit and then is attached to the patient’s nasal cannula. It is possible to attach the patient’s nasal catheter (rarely used clinically anymore) or transtracheal oxygen catheter. The flow of oxygen is adjusted to meet the patient’s clinical goal for oxygenation. The higher the oxygen flow, the higher the delivered oxygen percentage—possibly up to 100% oxygen.

Figure 6-25 The Vapotherm 2000i high-flow nasal cannula system. The vapor transfer cartridge is shown inside. It can be switched out as needed and is available in adult and pediatric sizes.

(Courtesy Vapotherm 2000i, Annapolis, MD.)

c. Troubleshoot any problems with the equipment

Make sure that the proper vapor transfer cartridge is selected for the oxygen flow needed. Set the appropriate temperature. Make sure that the water supply system does not run out.

a. Get the necessary equipment for the procedure

b. Put the equipment together and make sure that it works properly

c. Troubleshoot any problems with the equipment

1. Simple oxygen mask

This mask, like all others, is designed to fit over the patient’s nose and mouth and act as an oxygen reservoir for the next breath (Figures 6-26 and 6-27). Various adult and pediatric sizes are available, and the patient should wear one that best fits the facial contours and size of the face. This is recommended for comfort, as well as to try to increase the inspired oxygen percentage by decreasing the amount of room air that is inspired. However, because a simple oxygen mask does not provide all of the patient’s tidal volume gas, it is classified as a low-flow device. Exhaled breath escapes through the exhalation ports. The patient’s breathing pattern affects the amount of room air that is breathed in through the same exhalation ports. These ports also are important in case the oxygen flow to the mask is cut off.

Figure 6-26 Close-up view of a simple oxygen mask.

(From McPherson SP: Respiratory care equipment, ed 4, St Louis, 1990, Mosby.)

Figure 6-27 Child wearing a simple oxygen mask.

(From Gaebler G, Blodgett D: Gas administration. In Blodgett D, editor: Manual of pediatric respiratory care procedures, Philadelphia, 1982, Lippincott.)

Because the oxygen reservoir in the mask is not large enough to meet the patient’s tidal volume, the inspired oxygen percentage is unpredictable. Oxygen flows between 5 and 10 L/min should provide approximately 35% to 60% inspired oxygen. The pulse oximetry value or Pao₂ level should be checked whenever a flow change is made, or when the patient’s condition changes significantly.

A bubble humidifier is often added so that the gas is not dry. Make sure that it works properly and that oxygen is flowing through the tubing before putting it on the patient. This and all other masks use an adjustable elastic strap that goes behind the head to hold it in place. Make sure that the mask fits snugly but not so tight as to cut off circulation.

2. Partial-rebreathing mask

The partial-rebreathing mask has a 500- to 1000-mL plastic bag added to the mask to act as an oxygen reservoir for the next breath (Figures 6-28, 6-29, and 6-30). Child- and adult-size masks are commonly available. When properly applied, the first third of the patient’s exhaled gas from the anatomic dead space is exhaled back into this bag. This gas is close to pure oxygen and has no carbon dioxide. Exhaled breath escapes through the exhalation ports. The patient’s breathing pattern affects the amount of room air that is breathed in through the same exhalation ports. Because of this room air entrainment, a partial-rebreathing mask is classified as a low-flow device. These ports also are important in case the oxygen flow to the mask is cut off; the patient will breathe in room air. The added reservoir of oxygen results in a higher percentage being given to the patient than with a simple oxygen mask. In all cases, set an oxygen flow high enough that the reservoir bag does not collapse by more than one-third on inspiration. For example, an initial oxygen flow of between 6 and 10 L/min should provide approximately 35% to 80% inspired oxygen.

Figure 6-28 Outside view of a partial-rebreathing mask.

(From McPherson SP: Respiratory care equipment, ed 4, St Louis, 1990, Mosby.)

Figure 6-29 Cutaway view of a partial-rebreathing mask showing gas flow.

(From Thalken FR: Medical gas therapy. In: Scanlan CL, Spearman CB, Sheldon RL, editors: Egan’s fundamentals of respiratory care, ed 5, St Louis, 1990, Mosby.)

Figure 6-30 Child wearing a partial-rebreathing mask.

(From Gaebler G, Blodgett D: Gas administration. In Blodgett D, editor: Manual of pediatric respiratory care procedures, Philadelphia, 1982, Lippincott.)

A bubble humidifier often is added so that the gas is not dry. Make sure that it works properly, that the oxygen is flowing through the tubing, and that the reservoir bag has been filled before putting it on the patient. Adjust the flow as needed to ensure that the reservoir does not collapse by more than one-third on inspiration. This ensures that the mask and the reservoir are filled with as much oxygen as possible. A pulse oximetry value or Pao₂ level should be checked whenever a flow change is made, or when the patient’s condition changes significantly.

3. Nonrebreathing mask

The nonrebreathing mask initially looks like the partial-rebreathing mask with its plastic bag added as an oxygen reservoir for the next breath (Figures 6-31 and 6-32). However, it should be noted that a one-way valve has been added between the mask and the reservoir bag. This allows the bag to be filled with pure oxygen that is available for the next breath. No exhaled gas can enter the reservoir. Two (sometimes one) one-way valves are added to the exhalation ports on the mask. In theory, with a tight-fitting mask and a high enough oxygen flow, the patient breathes in only oxygen from the mask and reservoir and no room air. However, because of leaks between the mask and the patient’s face, the nonrebreathing mask is classified as a low-flow device. Exhaled breath escapes through the exhalation ports as with the partial-rebreathing mask. Not shown is an emergency pop-in valve that allows room air to be drawn into the mask if the oxygen supply is cut off. Adult and pediatric sizes are available. The mask should be conformed to fit the patient’s facial contours and size as much as possible. As mentioned earlier, this is for comfort and to try to increase the inspired oxygen percentage by decreasing the amount of room air that is inspired. In theory, it is possible to deliver 100% oxygen with this mask if the oxygen flow is high enough and the mask is airtight over the face. However, experience has shown that the disposable masks that are usually available in the hospital do not prevent room air from being drawn in. In all cases, set an oxygen flow high enough that the reservoir bag does not collapse by more than one-third on inspiration. For example, an initial oxygen flow between 8 and 10 L/min should provide approximately 60% to 80% (or more) inspired oxygen.

Figure 6-31 Outside view of a nonrebreathing mask.

(From McPherson SP: Respiratory care equipment, ed 4, St Louis, 1990, Mosby.)

Figure 6-32 Cutaway view of a nonrebreathing mask showing gas flow.

(From Thalken FR: Medical gas therapy. In: Scanlan CL, Spearman CB, Sheldon RL, editors: Egan’s fundamentals of respiratory care, ed 5, St Louis, 1990, Mosby.)

A bubble humidifier often is added so that the gas is not dry. Make sure that it works properly, that the oxygen is flowing through the tubing, and that the reservoir bag has been filled before putting it on the patient. Adjust the flow as needed to ensure that the reservoir does not collapse by more than one-third on inspiration. This ensures that the mask and the reservoir are filled with oxygen, and that the patient’s tidal volume comes completely from the reservoir bag. Try to make the mask fit as closely as possible to minimize room air entrainment. The patient’s pulse oximetry value or Pao₂ level should be checked whenever a flow change is made, or when the patient’s condition changes significantly.

Exam Hint 6-9 (ELE, WRE)

Expect to see one question dealing with the reservoir bag collapsing on inspiration. Solve the problem by increasing the flow of therapeutic gas to the mask and bag.

Exam Hint 6-10 (ELE, WRE)

Expect to see one question that deals with the need to switch from a low oxygen percentage mask to a nonrebreather mask to give the seriously hypoxemic patient as much oxygen as possible.

4. Face tent

These masks are designed to fit around the patient’s neck, under the jaw, and around the cheeks in front of the ears. The front edge should be higher than the level of the patient’s nostrils (Figure 6-33). Face tents sometimes are used to provide oxygen to a patient who cannot wear a mask or cannula because of oral and nasal trauma, burns, or surgery. The patient using a face tent should be sitting as upright as possible, because oxygen is heavier than air and tends to settle in the mask around the patient’s nose and mouth if the fit is tight. If the patient is lying flat or if the mask fits loosely, the oxygen will simply “pour” down out of it. This makes it difficult to know with any certainty what inspired oxygen percentage is available to the patient. Flows of 5 to 10 L of oxygen per minute are commonly used with adults.

Figure 6-33 Young adult wearing a face tent.

A face tent usually is ordered with the oxygen run through a humidifier or nebulizer so that the gas is not dry. Make sure that the humidifier or nebulizer is filled with sterile water, that the high-pressure pop-off works, and that gas is flowing through the tubing before the face tent is put on the patient. Try to analyze the oxygen percentage close to the patient’s nose and mouth with as much accuracy as possible. A pulse oximetry value or Pao₂ level should be checked whenever a change in the oxygen percentage is made, or when the patient’s condition changes significantly.

a. Get the necessary equipment for the procedure

The transtracheal oxygen (TTO₂) catheter is a 20-cm-long flexible, hollow plastic tube (Figure 6-34). This low-flow oxygen delivery device is inserted into the trachea via a puncture procedure at the suprasternal notch. To date, only adults with COPD have had the procedure performed. Oxygen is delivered directly into the trachea. The patient’s oxygenation can be maintained at lower oxygen flows than are needed by a regular face mask or nasal cannula.

Figure 6-34 Transtracheal oxygen catheter. A (top), Photograph of a flexible, plastic transtracheal oxygen catheter. The part to the left of the flange is inserted into the patient’s trachea. The part to the right of the flange is attached into standard oxygen tubing. A (bottom), The metal stylet may be used to help keep the catheter stiff during insertion and to clear the catheter of an obstruction. B, Drawing of a chain-link necklace keeping the external part of the catheter and flange secure. C, Cutaway drawing showing the catheter inserted into the trachea.

(From White GC: Equipment theory for respiratory care, Albany, NY, 1992, Delmar.)

b. Put the equipment together and make sure that it works properly

The following equipment is needed:

Under normal working conditions, regular oxygen tubing is used to connect the oxygen source to the catheter. Oxygen flow to the catheter is set high enough to keep a satisfactory Pao₂ or Spo₂ level. Usually, this is less than is previously needed by nasal cannula. When oxygen tubing is combined with a portable LOX system or a pulse-dose oxygen delivery system, the patient has a real opportunity for increased mobility and decreased cost.

c. Troubleshoot any problems with the equipment

The patient needs to be instructed to disconnect the oxygen tubing and flush the catheter with 3 mL of sterile saline twice a day. A cleaning rod also can be pushed through the catheter to make sure that no mucus accumulates. As with any tubing system, the components can become disconnected. Make sure that all connections are tight. If the saline or cleaning rod cannot be pushed through the catheter, an obstruction is likely. The patient should come into the hospital to have the catheter removed and replaced if necessary. It is possible that the proximal catheter tip has twisted into the tracheal mucosa. This can lead to subcutaneous emphysema. The patient should be instructed on how to identify the signs of this and to turn off the oxygen to the catheter. He or she should go back to using a nasal cannula for oxygen and should call the physician for guidance.

a. Get the necessary equipment for the procedure

b. Put the equipment together and make sure that it works properly

c. Troubleshoot any problems with the equipment

1. Tracheostomy mask/collar

The adult or pediatric tracheostomy mask or collar is shaped to fit over a tracheostomy tube or stoma to provide oxygen and aerosol (Figure 6-35). Because the patient’s upper airway is bypassed, a nebulizer is used for humidity. It is usually an air entrainment type of device, so the oxygen percentage can be adjusted. Make sure that the nebulizer is filled with sterile water; if there is a high-pressure pop-off valve, make sure that it is working and that adequate mist is flowing through to the mask before putting it on the patient.

Figure 6-35 Adult wearing a tracheostomy mask/collar.

Because the tracheostomy mask is an open system without reservoir, it is difficult to guarantee the patient’s inspired oxygen percentage. Set the gas flow high enough to make a “cloud” of aerosol around the tracheostomy. If an excess of aerosol can be seen around the tracheostomy during inspiration, it is likely that the desired oxygen percentage is being delivered. Analyze the oxygen percentage from inside the mask to try for as much accuracy as possible. A pulse oximetry value or Pao₂ level should be checked whenever a flow change or oxygen percentage change is made, or when the patient’s condition changes significantly.

2. Brigg’s adapter/T-piece

The Brigg’s adapter or T-piece is designed to provide air or supplemental oxygen and aerosol to an endotracheal or tracheostomy tube. It has one 15-mm inner diameter (ID) opening that fits over any endotracheal or tracheostomy tube adapter. The other two openings are 22 mm outer diameter (OD) so that aerosol tubing can be added (Figure 6-36). A nebulizer is commonly used for humidity because the patient’s upper airway is bypassed. Make sure that the nebulizer is filled with sterile water; if there is a high-pressure pop-off valve, make sure it is working and that adequate mist is flowing through to the adapter before putting it on the patient. The nebulizer is usually an air entrainment type of device, so the oxygen percentage can be adjusted.

Figure 6-36 Child with intubated airway with a Brigg’s T-piece adapter and aerosol tubing added to the endotracheal tube.

A length of aerosol tubing added downstream from the adapter acts as a reservoir so that the inspired oxygen percentage is ensured. A reservoir of 50 to 100 mL of aerosol tubing is commonly needed for the adult. Care must be taken to adjust the gas flow so that it is high enough to meet the patient’s peak inspiratory flow rate. This can be determined by watching the aerosol flow past the adapter and reservoir. Make sure that during inspiration the aerosol is still flowing past the tracheostomy or endotracheal tube and into the reservoir. Inadequate flow could cause the patient to rebreathe gas from the reservoir. This gas has just been exhaled and is high in carbon dioxide and low in oxygen.

Exam Hint 6-11 (ELE, WRE)

Know to increase the aerosol flow to a tracheostomy mask or Brigg’s adapter/T-piece if the aerosol cannot be seen during a patient’s inspiration. The National Board of Respiratory Care (NBRC) usually calls this a T-piece rather than a Brigg’s adapter in its questions.

a. He/O₂ (heliox) therapy

Patients who benefit from He/O₂ therapy can have an upper airway obstruction problem (tumor) or a lower airway obstruction problem (asthma). Because helium atoms are so much smaller than nitrogen molecules, patients find that their work of breathing is greatly reduced. Normoxic patients usually are given a mix of 80% helium and 20% oxygen, whereas hypoxic patients are given 70% helium and 30% oxygen or 60% helium and 40% oxygen. If more oxygen is needed, small-bore oxygen tubing can be used to add it into the mask or reservoir bag, or a special closed system will have to be assembled from components.

Ideally any helium/oxygen delivery system should have a reservoir bag. Usually the nonrebreathing mask and the reservoir are used. The reservoir should be filled with the He/O₂ mix before the mask is placed on the patient’s face. Again, the fit should be as tight as possible to minimize leaks. Adjust the flow so that the reservoir bag does not collapse by more than one-third during an inspiration. If it does, increase the flow. The flow should be increased if the patient complains of shortness of breath. Signs of increased work of breathing include agitation, increased use of accessory muscles of respiration, sweating, and increased respiratory rate, heart rate, and blood pressure.

b. Nitric oxide therapy

Because nitric oxide (NO) is a pulmonary vasodilator, it has been shown to be effective in the treatment of newborns with pulmonary hypertension (persistent pulmonary hypertension of the newborn [PPHN]). The FDA has approved the use of INOmax (0.8% nitric oxide and 99.2% nitrogen) to deliver inhaled nitric oxide to these patients. The currently recommended dosing range of inhaled NO to treat PPHN is 5 to 15 parts per million (ppm). The possible range for delivered NO is 2 to 80 ppm. Be prepared to increase the level of NO as needed, to reverse the pulmonary hypertension. When the patient improves, the NO level will need to be decreased. This usually is done by cutting the NO level in half, assessing the patient, and cutting the NO level in half again, etc., as tolerated.

To deliver the needed concentrations of nitric oxide and supplemental oxygen, the INOvent delivery system is needed. It is used to set the desired mix of INOmax to the newborn’s ventilator and to monitor the levels of NO, nitrogen dioxide (NO₂), and oxygen delivered. Because NO is chemically changed in the body to toxic NO₂ and nitric acid, it is important to closely monitor the level of nitrogen dioxide. Low levels of NO₂ can cause a pneumonitis, and higher levels can cause pulmonary edema. The patient’s methemoglobin level also should be monitored, as NO can cause an elevated level. Be prepared to decrease the level of NO to reduce the level of toxic NO₂.

Inhaled NO has not been approved for adult patients. However, some reports of nitric oxide administered to patients with pulmonary hypertension and acute respiratory distress syndrome (ARDS) show promising results.

c. O₂/CO₂ (carbogen) therapy

Carbon dioxide is available in tanks of pure CO₂ or a mix of 5%:95% or 10%:90% (carbon dioxide : oxygen ratio). Carbogen is used during cardiopulmonary bypass procedures to maintain the patient’s PaCO₂. Common clinical uses are listed in Box 6-1. Because inhaling carbon dioxide runs counter to a person’s normal exhalation of CO₂, the patient’s PaCO₂ can increase with resulting respiratory acidosis. So, the patient’s arterial blood gas values, vital signs, and mental status must be monitored closely. Be prepared to decrease the carbogen percentage or stop the breathing of carbogen if the patient shows any adverse signs or symptoms.

A child with hypoplastic left-heart syndrome (HLHS) usually is being mechanically ventilated. The infant with this congenital heart defect must maintain an open foramen ovale and patent ductus arteriosus (PDA) for adequate systemic circulation (a right-to-left intracardiac shunt). Carbogen is added by small-bore tubing connecting the gas cylinder with a T-piece connected into the ventilator circuit. Usually enough carbogen flow is added to result in measurement of 1% to 4% carbon dioxide on a capnometer. Because increased carbon dioxide is a pulmonary vasoconstrictor, the PDA can be maintained. The infant’s vital signs and ABG values must be closely monitored to guide the adjustment in carbogen.

The carbon dioxide response curve test is a measurement of the increase in minute volume caused by breathing different concentrations of carbon dioxide when the patient’s oxygen level is normal. This pulmonary function test is performed on patients with COPD to determine whether their breathing will increase when their carbon dioxide level is increased. Depending on the method of test performed, the patient inhales between 1% and 7% carbon dioxide. The flow and concentration must be adjusted to maintain the desired carbon dioxide level as measured on a capnometer. An oxygen analyzer also should be included in the system to make sure that the patient does not inhale less than 21% oxygen.

The treatment of hiccups usually requires only that the patient rebreathe from a paper bag. If necessary, a small amount of carbon dioxide can be added to stop the hiccups.

a. Terminate the treatment or procedure based on the patient’s response (Code: IIIF1) [Difficulty: ELE: R, Ap; WRE: An]

It may be necessary to stop the use of carbogen or nitric oxide if the patient has an adverse reaction to their use.

b. Recommend discontinuing the treatment or procedure based on the patient’s response (Code: IIIG1i) [Difficulty: ELE: R, Ap; WRE: An]

As was discussed at the beginning of the chapter, several possible hazards occur with the use of oxygen therapy. The NBRC is most likely to ask questions related to the use of or increase or decrease in oxygen in a patient with COPD. The specialty gases can be discontinued when the clinical problem (see Box 6-1) has been corrected.

a. Independently change the oxygen percentage (ELE code: IIIF2d1) [Difficulty: ELE: R, Ap, An]

b. Independently change the flow of oxygen (ELE code: IIIF2d1) [Difficulty: ELE: R, Ap, An]

c. Independently change the mode of administering the oxygen (ELE code: IIIF2d1) [Difficulty: R, Ap, An]

Every patient’s oxygen percentage or flow must be tailored to meet the patient’s clinical goals. Usually this means keeping patients who are acutely hypoxemic at a Pao₂ level between 60 and 100 torr and an Spo₂ value between 90% and 97%. Exceptions, when the blood oxygen level is kept as high as possible, include cardiopulmonary resuscitation and treatment for carbon monoxide poisoning. Another exception is the patient with COPD who is hypoxemic and hypercarbic. Usually these patients’ conditions are maintained with a moderate hypoxemia. The Pao₂ level should be between 50 and 60 torr and the Spo₂ value between 85% and 90%. It is imperative to keep the oxygen in this relatively narrow range. Further hypoxemia will result in pulmonary hypertension and cor pulmonale. Cardiac dysrhythmias or arrest and death can occur if the hypoxemia is severe (<40 torr). Oxygen levels in the normal range (>60 torr) may result in blunting of the hypoxic drive. This can result in bradypnea and even greater carbon dioxide retention with corresponding acidemia. When the carbon dioxide pressure (PaCO₂) level exceeds 80 to 90 torr, many patients become drowsy or somnolent. The goal of treatment is to decrease the Fio₂ to reduce the Pao₂ level to 50 to 60 torr. This, in turn, stimulates the hypoxic drive so that the patient increases his or her ventilation. See Chapter 3 for a complete discussion of the interpretation of arterial blood gas values.