Note: Some controversy exists over the size of the particles that deposit in the airways and lungs. This table lists what seems to be a majority opinion. Aerosol particle diameter sizes are listed in units of micrometers, which are one-thousandth of a millimeter. As a point of clarification, most references list the symbol for a micrometer as μ; others use the international system unit of micrometer, which is symbolized as μm.

* MMAD is defined as the aerosol diameter around which the mass is equally divided, that is, 50% of the aerosol mass is found in particles smaller than the MMAD, and 50% of the aerosol mass is found in particles larger than the MMAD.

4. Increased clearance of secretions

Traditionally, many patients with a mild case of bronchitis were given breathing treatments with a bland aerosol to help them mobilize secretions. The aerosol was thought to add enough liquid to the secretions to enable the patient to cough them out. The patient, as it is now understood, can cough more effectively because the aerosol irritates the airway, and the patient’s own bronchial/submucosal glands pour out additional mucus. This reflex is mediated by the vagus nerve. This form of therapy probably is not indicated in most situations. It is clinically more effective to increase the patient’s oral or intravenous fluids so that the bronchial/submucosal glands can produce secretions that are not thick.

5. Induced sputum production for a sputum specimen

Patients who have few, if any, secretions but from whom a sputum specimen is needed (e.g., patients with suspected tuberculosis or lung cancer) can have sputum production induced (see the mechanism of action described previously). Typically, the patient inhales an aerosol of hypertonic saline solution for about 5 to 10 minutes. Ultrasonic nebulizers are used often because they produce a dense mist of small particles.

2. Interview the patient to determine sputum production (Code: IB5c) [Difficulty: ELE: R, Ap; WRE: An]

Find out from the patient approximately how much sputum is produced in a day. Also, find out if certain times of the day are more productive or less productive than others. Try to relate this to breathing treatments, medications, activities, meals, and allergies.

3. Observe the patient’s sputum production

a. Observe the patient for changes in sputum characteristics (ELE code: IIIE5) [Difficulty: ELE: R, Ap, An]

b. Use inspection to assess the patient’s cough, sputum amount, and character (Code: IB1c) [Difficulty: ELE: R, Ap; WRE: An]

The patient’s sputum characteristics (e.g., consistency, color, smell) and amount must be known if the effectiveness of humidity or aerosol therapy is to be assessed. Review the related discussion in Chapter 1, and see Table 1-12. Try to relate this information to breathing treatments, medications, activities, meals, and allergies.

4. Assess the patient’s overall cardiopulmonary status by auscultation to determine the presence of normal or abnormal breath sounds (Code: IB4a) [Difficulty: ELE: R, Ap; WRE: An] and (Code: IIIE11) [Difficulty: ELE: R, Ap; WRE: An]

Review the discussion in Chapter 1, if necessary. The presence of expiratory crackles (also called rhonchi) would indicate airway secretions. If the patient is able to cough out the secretions, abnormal breath sounds, such as crackles, should improve. If the patient’s secretions are thick (high viscosity), then aerosol therapy, as well as increased fluid intake, probably is indicated.

Exam Hint 8-1 (ELE)

Be prepared to recommend starting or changing humidity or aerosol therapy to help reduce humidity deficit or to help in the management of increased secretions.

MODULE B

Humidity and aerosol generators and administrative devices

1. Humidity delivered through small-bore tubing

a. Manipulate bubble-type humidifiers by order or protocol (ELE code: IIA3) [Difficulty: ELE: R, Ap, An]

1. Get the necessary equipment for the procedure

Bubble-type humidifiers are used on patients with a normal upper airway who need some supplemental humidity because of the dryness of medical O₂. These devices usually are not heated and, in fact, deliver gas cooled to below room temperature. They provide around 40% RH at the delivered gas temperature. The rest of the humidity has to be made up by the patient (Figures 8-1 and 8-2). If clinically indicated, a wraparound type of heater can be added to raise the temperature of the delivered gas and reduce the patient’s humidity deficit.

Figure 8-1 Comparison of humidity content by bubble-type humidifiers and various nebulizers.

Figure 8-2 Oxygen leaving outlet of the bubble-type humidifier is cooler than room temperature because of evaporation. Some warming toward room temperature occurs as the oxygen travels through the tubing to the patient.

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

Three different types of these humidifiers are designed to add some humidity to dry O₂ delivered through small-bore tubing: traditional bubble humidifiers, jet humidifiers, and underwater jet humidifiers.

a. Bubble humidifiers.

Bubble humidifiers use a perforated capillary tube or a porous diffusion head to break the O₂ into small bubbles (see Figure 8-2). This allows for greater surface area contact of the O₂ with the water and raises the RH by evaporation. The water level in the reservoir must be kept within the manufacturers’ specifications and, if possible, as full as possible. The lower the water level, the lower is the RH because less time exists for evaporation. The faster the O₂ flow, the lower is the RH.

b. Jet humidifiers.

Jet humidifiers create an aerosol baffled out of the delivered gas flow. The RH is increased through evaporation of some of the aerosol droplets. These units deliver a higher RH than is delivered by bubble humidifiers. They have the additional advantage of delivering the same RH at higher flow levels and as the water level drops.

c. Underwater jet humidifiers.

Underwater jet humidifiers create water vapor and an aerosol. The aerosol is not baffled out as it is in jet humidifiers; therefore, these units deliver the highest RH. They can deliver the same humidity level at high gas flows and as the water level drops. Aerosol particles can carry pathogens, so strict infection control standards must be met to protect the patient. Often the water and the humidifier must be changed at least every 24 hours. If the patient needs the highest-possible-delivered RH, a jet humidifier or an underwater jet humidifier would be a better choice than a bubble type.

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

3. Troubleshoot any problems with the equipment

Many simple bubble humidifiers come prepackaged with sterile water and can be used for many short-term patients (e.g., those in the recovery room) or for a single long-term patient. When the water runs low, they are discarded. Bubble and other types of humidifiers consist of a reservoir jar for the water and a Diameter Index Safety System (DISS) O₂ connector lid that screws on. Turn on the flowmeter and make sure that O₂ flows through the delivery tube and bubbles into the water. Failure to bubble usually indicates that the lid and the jar are not screwed together tightly, or that the delivery tube is plugged. If the tube cannot be cleared, it must be replaced.

Most of the newer bubble-type units have a pop-off type of high-pressure relief valve that is released if the pressure builds up to 40 mm Hg or 2 psi. Pinch closed the small-bore tubing to build up pressure and test the pop-off valve. Feel for the gas to escape from the valve. Many valves whistle to signal a gas leak. Do not use a unit with a pop-off valve that does not open under pressure.

b. Nasal cannula

As has been discussed earlier, current guidelines state that humidity does not need to be added to these devices if the flow is 4 L/min or less. However, some patients complain of nasal dryness and discomfort if the cannula’s O₂ is not humidified. The physician and the practitioner may believe that the patient’s discomfort warrants the addition of a bubble-type humidifier. Agreement has been reached on the addition of humidity to flows greater than 4 L/min. See Figure 8-3 for a humidified nasal cannula setup. See Chapter 6 for the discussion on a high-flow nasal cannula.

Figure 8-3 Adult wearing a nasal cannula that delivers oxygen humidified by a bubble-type humidifier.

(From Guidelines for disinfection of respiratory care equipment used in the home, Respir Care 33:801, 1988.)

c. Oxygen masks

As has been stated, the addition of humidity to any O₂ mask with an O₂ flow of 4 L/min or less is considered unnecessary. Humidity should be added to any mask with more than 4 L/min of O₂ added. This would include simple O₂ masks at higher flows, higher O₂ percentage air entrainment masks, partial-rebreathing masks, and nonrebreathing masks.

2. Humidity delivered through large-bore tubing

Most patients who need delivery of humidity through large-bore tubing have had the upper airway bypassed by an endotracheal or tracheostomy tube; therefore, they cannot humidify inspired gas in the normal manner. In other cases, humidity is added because the patient is receiving dry medical O₂. In both situations, a heated humidifier is recommended. It should be set to deliver gas between 31° C and 35° C to the patient and should be able to provide 80% to 100% RH in this temperature range. The following humidity- and aerosol-generating devices deliver conditioned gas to the patient through large-bore (22-mm inner diameter [ID]) tubing.

a. Manipulate large-volume humidifiers by order or protocol: cascade, wick, and passover types (ELE code: IIA3) [Difficulty: ELE: R, Ap, An]

1. Get the necessary equipment for the procedure

Cascade, wick, and passover-type humidifiers have an adjustable heater so the water in the reservoir is at or greater than body temperature. This enables them to provide up to 100% of the patient’s body humidity. With all of these units, the temperature of the inspired gas near the patient must be measured. Ideally, the gas temperature is kept the same as the patient’s to provide 100% relative humidity. One of these types of units is used to provide humidity when the patient’s upper airway is bypassed by an endotracheal or tracheostomy tube (Figure 8-4).

Figure 8-4 Gases leaving outlet of heated humidifier are hot and saturated with water vapor. As cooling occurs in the tubing, vapor condenses and absolute humidity (AH) decreases, while relative humidity (RH) remains at 100% (saturated). Note that almost half of the original vapor is “lost” to condensate in this example.

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

The Bennett Cascade is a classic example of these types of humidifiers (Figure 8-5). It was used most commonly with a mechanical ventilator but also was used with other types of systems for delivering humidity with or without oxygen. Its basic principle of operation is an efficient bubble-type humidifier. The inspiratory gas must flow through the water before evaporation can occur. A variety of similar devices are now on the market. Note: Even though these units are no longer available, the NBRC refers to this basic type of device as a Cascade-type humidifier.

Figure 8-5 Cascade-type humidifier.

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

The wick-type heated humidifier employs a wick, often made of sponge or paper, to soak up water for evaporation (Figure 8-6). The water, wick, or both are heated so that 100% RH can be delivered. These units also are used with mechanical ventilators or other systems, including air entrainment devices, because they have very little resistance to the gas flowing through them as evaporation occurs. Some units are designed for use with a heated wire ventilator circuit and feature an automatic water feed system and a servo-controlled thermostat to keep the water and the circuit at the same temperature. This minimizes condensation.

Figure 8-6 Functional diagram of a wick-type humidifier with an automatic water feed system. Water automatically enters a warmed reservoir, where it is drawn up the wick. Dry gas flows past the wick, where evaporation takes place before the gas is directed to the patient.

(Redrawn from Hudson Respiratory Care, Temecula, CA. In: Cairo J, Pilbeam S: Mosby’s respiratory therapy equipment, ed 8, St Louis, 2010, Mosby.)

With passover-type humidifiers, the patient’s gas simply passes over the surface of a reservoir of hot water. These sometimes are called “hot pots.” By themselves, these units are probably the least effective at humidifying gas. When they are used on ventilators, other features such as copper mesh in a heated inspiratory tube are used to increase the surface area for evaporation.

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

3. Troubleshoot any problems with the equipment

Humidifiers must be assembled properly, especially when they are used to humidify a mechanical ventilator. Any loose connections may result in an air leak and loss of tidal volume (V_T). Make sure the water level is maintained properly.

Some cooling occurs as heated gas passes through the large-bore tubing, which results in condensation (so-called “rain out”) that must be drained away. Placing a water trap into the lowest point of the tubing drains the water and helps keep the tubing clear. Remember to continue to look periodically for water puffing or sloshing back and forth in the tubing. Make sure that any condensate is drained out of the tubing and thrown away. Do not drain the condensate back into the water reservoir because any microorganisms in the tubing or condensate could reproduce in the reservoir.

b. Manipulate a heat-moisture exchanger by order or protocol (ELE code: IIA3) [Difficulty: ELE: R, Ap, An]

1. Get the necessary equipment for the procedure

A heat-moisture exchanger (HME) is a passive humidifier that recycles the patient’s own exhaled water vapor. The HME contains a highly absorbent material that is warmed and moistened when a patient’s exhaled breath passes through it. The patient’s next inspiration is warmed and humidified by the water absorbed within the HME (Figure 8-7). These units are not as efficient as the humidifiers described earlier and are not able to provide 100% of body humidity to a patient. If possible, select an HME that has these characteristics: (1) is at least 70% efficient (provides at least 30 mg/L water vapor), (2) has a low compliance if used with a ventilator circuit, (3) is lightweight, (4) has little dead space, and (5) has little flow resistance.

Figure 8-7 Heat-moisture exchanger (HME). Left, Cut-away functional drawing shows the (left) ventilator side and (right) patient side of an HME. During exhalation, the warmed and saturated air (33° C and 100% relative humidity [RH]) from the patient passes through the HME in the water-absorbing material. During inhalation, the cooler and dryer room air is warmed and becomes more saturated with water vapor as it passes through the HME to the patient. Right, Photograph of an HME. The opening on the left side is 15 mm inner diameter (ID) and connects to a patient’s endotracheal tube. The opening on the right side is 22 mm ID and can have a ventilator circuit or T-piece attached for supplemental oxygen and aerosol.

(Courtesy Telefax Medical, Research Triangle Park, NC. In: Cairo J, Pilbeam S: Mosby’s respiratory therapy equipment, ed 8, St Louis, 2010, Mosby.)

Many brands of HME are available for either of two clinical applications. The first clinical use involves adding an HME to the outer part of a tracheostomy tube. A 15-mm ID opening allows the HME to be attached to the tube; the other end of the HME is open to room air. This type is small and convenient to use for many patients with a permanent tracheostomy; in addition, it improves a patient’s mobility. The second clinical use involves patients who require mechanical ventilation. The patient end of the HME is a 15-mm ID opening that can attach to the endotracheal or tracheostomy tube; the other end of the HME has a 22-mm ID opening so the ventilator circuit or supplemental oxygen can be attached.

2. Put the equipment together and make sure that it works properly (NBRC code: IIA3) [Difficulty: R, Ap]

3. Troubleshoot any problems with the equipment (NBRC code: IIA3) [Difficulty: R, Ap]

HMEs typically come preassembled by the manufacturer. The 15-mm ID opening must be placed over the patient’s endotracheal or tracheostomy tube. The other opening of the HME can be connected to the ventilator circuit or oxygen source, if needed. Follow the manufacturer’s recommendation regarding how frequently the HME should be replaced—often every 24 hours. However, current guidelines indicate that they can be used safely for at least 48 hours, possibly up to a week.

Secretions coughed into the HME can obstruct the flow of gas and thus make it difficult or impossible for the patient to breathe. The HME must be removed and discarded if it becomes obstructed, and it must be replaced by a new one. An HME should not be used with a patient known to cough out large quantities of secretions or blood.

3. Manipulate nebulizers and related delivery systems by order or protocol (ELE code: IIA4) [Difficulty: ELE: R, Ap, An]

a. Ultrasonic nebulizers

1. Get the necessary equipment for the procedure

Large-volume ultrasonic units often are chosen for delivery of bland solutions to the lower airways because of the small particle size and high output. (So-called “bland aerosols” are composed of particles of water or saline rather than medicated aerosols.) Ultrasonic nebulizers (USNs) work by converting electrical energy into high-frequency sound energy, which creates aerosol particles. The frequency is vital because it results in a stable aerosol with a mean particle size of about 3 μm in diameter. This is an ideal size for penetrating deeply into the lungs to the smallest airways. The only control on these units is used for amplitude (power), and it controls the aerosol output. The range is usually up to 3 to 6 mL/min, depending on the model. This output is greater than that possible with most pneumatic nebulizers. The aerosol can be carried to the patient via a built-in fan or by an outside O₂ source (Figure 8-8). The warm aerosol that is created minimizes the patient’s humidity deficit.

Figure 8-8 Functional diagram of the ultrasonic nebulizer. A, Electrical current generator; B, cable; C, piezoelectric crystal; D, couplant chamber; E, solution cup; F, carrier gas inlet; and G, aerosol outlet.

(From Barnes TA, editor: Core textbook of respiratory care practice, ed 2, St Louis, 1994, Mosby.)

Historically, ultrasonic nebulizers have not been chosen for upper airway aerosol deposition or for administration of pharmacologically active medications such as bronchodilators, mucolytics, and antibiotics. These medications may not nebulize at the same rate as the saline diluent, which creates the risk that a very concentrated dose may be delivered at the end of treatment. Some medications may be mechanically broken down by the high-frequency vibration and rendered useless.

Recently, small-volume USN units have been designed to specifically nebulize medications into the circuit of a mechanical ventilator. Depending on the manufacturer, the USN can be powered electrically by the ventilator, by any electrical outlet, or by batteries. These units are designed to rapidly nebulize the small volume of medication (with or without diluent). The tidal volume breath carries the medication into the patient’s airways. Be aware that even though drugs have been given this way, pharmaceutical companies have not included in their dosing information the delivery of undiluted medications.

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

3. Troubleshoot any problems with the equipment

Always follow the manufacturer’s instructions when you are setting up the delivery system. Figure 8-8 shows the common features, and Table 8-3 describes how to troubleshoot many common problems. Many clinical difficulties seem to involve keeping the proper fluid levels in the couplant chamber and the solution cup. If the sterile water in the couplant chamber is too low, the vibration cannot reach the solution cup and no aerosol will be produced. If the saline level in the solution cup is too low or too high, the vibrational energy will not focus properly on the surface of the saline solution, and no aerosol will be produced. Water should not be allowed to condense and fill low points in the large-bore tubing; if it does, ultrasonic particles will liquefy as the carrier gas is forced to pass through the condensate. The exiting gas would be humidified through evaporation but would carry no aerosol particles. If the carrier gas is O₂ blended with air through an air entrainment system, any backpressure could result in an increase in the O₂ percentage and a decrease in the total flow. Remember to always measure the O₂ percentage near the patient.

TABLE 8-3 Ultrasonic Nebulizer Troubleshooting

Symptom	Possible Problem	Suggested Check
Unit installed and connected as specified, but pilot light does not turn on when switch is turned to the “on” position	Electrical outlet defective Circuit breaker tripped

Check outlet with lamp or other appliance Fuse blown Reset the circuit breaker, or change fuse on the power switch; if the circuit breaker continues to trip or the fuse blows again, service is needed Unit installed and connected as specified; power pilot light turns on, normal ultrasonic activity visible in nebulizer chamber, but no aerosol output occurs Nebulizer chamber contaminated Wash nebulizer chamber; decontaminate Unit installed and connected as specified; power pilot light turns on, but little ultrasonic activity is visible in the nebulizer chamber, and aerosol output is low (even when on the no. 10 power setting)

Couplant water excessively aerated

Nebulizer module and couplant water too cold

Diaphragm distorted, permitting air bubbles to interfere with proper transmission of vibrational energy into the nebulizer chamber

Wait for deaeration

Use warmer couplant water

Check to see that diaphragm is properly shaped and installed; be sure that the concave (recessed) side faces the interior of the chamber

Clean couplant compartment and replace couplant water

Same as symptom described previously but at a lower power setting Power setting too low to start and establish nebulization Turn output control knob to maximum power setting, then reduce to desired setting Unit installed and connected as specified, and power pilot light turns on “Add couplant” light is on, and no ultrasonic activity is visible in the nebulizer chamber Insufficient couplant water Add water to the couplant compartment Unit installed and connected as specified, and power pilot light turns on “Add couplant” light is off, but no ultrasonic activity is visible in the nebulizer chamber Power supply overheated and its thermostatic control opened The cooling air has been restricted, or cooling fins need cleaning. The switch will reset when the equipment returns to room temperature Liquid reservoir filled and properly connected to nebulizer chamber, but chamber does not fill (for continuous-feed system only)

Foreign material or air bubbles in feed tubes

Liquid level control in nebulizer chamber plugged with foreign material

Air leaks at tube connection or reservoir cap

Flush the system

Clean or flush the system

Tighten all connections by pushing tubes into fittings

From Op’t Hole T: Aerosol generators and humidifiers. In: Barnes TA, editor: Respiratory care practice, Chicago, 1988_; Mosby.

b. Manipulate large-volume pneumatic nebulizers by order or protocol (ELE code: IIA4) [Difficulty: ELE: R, Ap, An]

1. Get the necessary equipment for the procedure

All large-volume, pneumatically powered nebulizers share the common feature of having a liquid reservoir of at least 250 mL and produce a bland aerosol. (So-called “bland aerosols” are composed of particles of water or saline rather than medicated aerosols.) These nebulizers also typically entrain room air to increase the total gas flow. They share the following common features:

• All are powered by air or O₂ that is delivered through a flowmeter. As the gas flow drops, the aerosol output decreases.

• All make use of Bernoulli’s principle with a jet that is used to entrain liquid, room air, or both into the main gas flow.

• All have a capillary tube that allows the liquid to flow up to the jet for nebulization. (Remember that with bubble-type humidifiers, O₂ flows down the capillary tube.)

• All have a baffle against which the aerosol is sprayed to create a more uniform particle size.

Many, but not all, pneumatic nebulizers allow for a changeable inspired O₂ percentage. Provided that the jet is powered by O₂, the air entrainment ports can be opened up to increase air entrainment and increase total flow (lowering the inspired O₂ percentage) or closed down to decrease air entrainment and decrease total flow (raising the inspired O₂ percentage). The O₂ percentage usually can vary from 35% to 100%. Remember to always analyze the inspired O₂ percentage near the patient because both water in the aerosol tubing and backpressure decrease the entrained air and raise the O₂ percentage.

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

3. Troubleshoot any problems with the equipment

Most pneumatic nebulizers have an appearance that is similar to that of bubble-type humidifiers. Key components include a large reservoir jar and a top with a DISS O₂ connector and a capillary tube to the jet. Make sure the nebulizer is screwed firmly onto the oxygen flowmeter and that the component parts are attached and work properly. Keep the capillary tube and jet clear of debris to keep the aerosol output from dropping. These units allow for variable O₂ percentages. Keep the air entrainment ports open so that proper gas mixing occurs and the desired O₂ percentage is provided (Figure 8-9). If water is present in the large-bore tubing or if the tubing is pinched, less room air will be entrained, and the delivered oxygen percentage will be higher than ordered. Keep the reservoir’s water level at the proper level. If the water level drops to below the refill line, no water will be drawn up the capillary tube to the jet. If the water is filled to above the maximum line, the jet may not operate properly. Heating of the water, aerosol, or both is accomplished in one of the following ways:

• A heated metal rod is immersed into the reservoir water through a port in the top of the nebulizer. A dial is used to control how hot the rod gets. Water temperature varies depending on how deep it is, so as the water level drops, the remaining water gets hotter. It is very important that the gas temperature near the patient be measured, and that the water level be kept stable to prevent burning of the airway. The heated rod presents the risk of burns to a practitioner who accidentally touches it. It must be disinfected between patients and changed as often as the nebulizer is changed. Because of these issues, these units are unlikely to be seen in clinical practice.

• Two other systems use variations on this idea of directly heating the water in the reservoir jar. The first heats the water as it passes through the capillary tube. The second type directly heats only a small amount of the reservoir water just before it is aerosolized. Each has the advantage of a short warm-up time compared with the heated metal rod systems. Some units have an external temperature probe for placement in the aerosol tubing. The probe acts as a servo-controller of the heating unit for better temperature regulation.

• A flexible heater is wrapped around the outside of the reservoir. A dial is used to control how hot the heater gets. The water temperature increases as the water level drops. Monitor the gas temperature near the patient for safety purposes.

• A clip-on heating base plate can be added to special reservoir jars with a metal plate. These are preferable to the previously mentioned types because they ensure a constant temperature to the aerosol as the water level drops.

Figure 8-9 Large-volume air entrainment nebulizer.

(From Shapiro BA, Kacmarek RM, Cane RD, et al, editors: Clinical application of respiratory care, ed 4, St Louis, 1991, Mosby.)

Heating the water or aerosol reduces the patient’s humidity deficit and usually is done if the secretions are thick. See Figure 8-1 for the location of the aerosol particles and their relationship with the dew point and with the patient’s body humidity.

4. Aerosol delivery systems

Large-bore tubing (also known as aerosol tubing or corrugated tubing) is needed to connect the aerosol generator with the patient. This tubing has a 22-mm ID so it can be connected to a face mask, T-piece, etc.

c. Aerosol masks

The aerosol mask looks similar to the simple O₂ mask, except that it has larger side ports for exhalation and a 22-mm outer diameter (OD) adapter for attachment of the large-bore tubing (Figure 8-10). This often is considered to be a low-flow O₂ mask because the ports are open to room air; therefore, it is difficult to ensure that the patient receives the set O₂ percentage. If the flow is high enough that aerosol mist can be seen flowing out of the side ports during an inspiration, little or no room air is being inspired and the aerosol mask is now a high-flow device. Some clinicians have increased the total flow through an aerosol mask by using a Y adapter to combine the large-bore tubing coming from two large-volume nebulizers In any case, it is best to analyze the O₂ percentage inside the mask to be sure of what the patient is inhaling. Any of the previously mentioned humidity or aerosol devices can be used and powered by compressed air or O₂.

Figure 8-10 Adult wearing an aerosol mask who is receiving supplemental oxygen and aerosol from a heated large-volume nebulizer. As the warmed, humidified gas cools on its way to the patient, condensation will result in water draining to the lowest part of the large-bore tubing.

(From Guidelines for disinfection of respiratory care equipment used in the home, Respir Care 33:801, 1988.)

d. Face tents, tracheostomy masks, tracheostomy collars, and Brigg’s adapter/T-piece

A face tent, a tracheostomy mask and collar, and Brigg’s adapter (T-piece) are discussed in Chapter 6. All have a 22-mm ID adapter so that large-bore tubing can be added to them. Any of the previously mentioned humidity or aerosol devices can be used with these and are powered by compressed air or O₂.

MODULE C

Environmental control devices

1. Manipulate incubators by order or protocol (WRE code: IIA12a) [Difficulty: WRE: R, Ap]

a. Get the necessary equipment for the procedure

An incubator is indicated in the care of a sick newborn who needs an enclosed space for an isolated, controlled environment. (See Figure 8-11.) (Some practitioners may refer to an incubator as an Isolette, which is a common brand of incubator.) Most incubators are used only in neonatal or pediatric care units and are powered electrically through standard electrical outlets. However, some incubators are designed to transport an infant between hospitals or within the hospital. They can make use of a standard electrical outlet but also feature self-contained batteries and oxygen tanks.

Figure 8-11 An incubator used to control an infant’s environment. Typically, the incubator is made of clear Plexiglass so the infant can be seen, and it has two closeable ports on each side. These can be opened so the caregiver can work with the infant. Controls below the infant are used to adjust the temperature, humidity, and possibly oxygen percentage within the incubator. A radiant warmer may be positioned over an incubator to keep the infant in a neutral thermal environment.

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

Traditionally, an incubator has been used to do four things for the infant: (1) manage the infant’s temperature, (2) manage surrounding humidity, (3) isolate the infant from the outside environment, and (4) control the infant’s inspired oxygen percentage. An incubator does the first three tasks very well. However, precise oxygen delivery cannot be done easily for two reasons. First, these units have never been designed to deliver an exact oxygen percentage. Some older units have only two basic oxygen flow settings. The low-flow setting is intended to limit the infant to no more than 40% oxygen. On some older units, a red plastic “flag” must be raised to deliver a higher flow of oxygen that may provide up to 80% or more oxygen. Second, whenever the side ports on the incubator are opened for patient care, internal gases flow out, resulting in a lower oxygen percentage.

Because of these limits, it is not recommended that an incubator’s built-in oxygen delivery system be used. Instead, it is recommended that the following components be assembled for precise oxygen delivery and humidity control: (1) an oxygen blender with flowmeter and small-bore oxygen tubing adapter (nipple); (2) small-bore oxygen tubing and an adapter to connect the flowmeter to a cascade-type or wick-type heated humidifier; (3) sterile, distilled water to fill the humidifier reservoir; (4) large-bore (aerosol) tubing to direct the heated, humidified, high-percentage oxygen; (5) an oxygen hood (also called an oxyhood) to receive the humidified oxygen (see Chapter 6 for discussion and an illustration); (6) an oxygen analyzer to check the percentage inside the oxygen hood; and (7) a temperature probe to check the temperature of the heated humidified oxygen; place this into the large-bore tubing before it enters the incubator.

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

An incubator comes preassembled as a unit. Sterile, distilled water must be added if the built-in humidification system is used. This is not necessary if heated, humidified oxygen is given by an oxygen hood. Make sure that the temperature control, the thermometer, and other systems on the incubator are working as directed by the manufacturer. The internal temperature of the incubator usually is kept at between 36° C and 36.5° C to keep the infant in a neutral thermal environment (NTE). The desired NTE is set by the physician and is maintained by the use of a temperature sensor placed on the infant’s skin. This sensor usually is placed on the abdomen and is connected to a servo-control that automatically raises or lowers the temperature inside the incubator as needed.

If an oxygen hood is being used to deliver supplemental oxygen to the infant, the components previously listed must be assembled properly. Check the temperature of the humidified oxygen and check the oxygen percentage inside the oxygen hood near the infant’s nose and mouth.

c. Troubleshoot any problems with the equipment

If the incubator is not maintaining the desired internal temperature, or if the internal humidification system is not working properly, follow the manufacturer’s recommendations to repair or replace the entire unit. Make sure that the oxygen hood system is assembled properly, maintaining the desired gas temperature to keep the infant’s neutral thermal environment and delivering the desired oxygen percentage. Adjust the cascade-type humidifier temperature or oxygen blender settings as needed.

2. Radiant warmers

a. Get the necessary equipment for the procedure

Note: Radiant warmers are not specifically listed by the NRBC as testable. However, because many incubators include a radiant warmer, this discussion is included. A radiant warmer is used to warm an infant to maintain a neutral thermal environment (NTE). A free-standing radiant warmer can be moved, as needed, to warm an infant who must be kept out in the open for frequent medical procedures. A radiant warmer also can be attached as part of an incubator. In any clinical situation, it is important to remember that it can be dangerous to allow a newborn to become chilled.

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

A radiant warmer comes preassembled by the manufacturer. It uses infrared light to heat the infant and the area on which the infant is laid and cared for. A temperature sensor is placed onto the infant’s skin, typically on the abdomen. The sensor uses a servo-mechanism so the infant’s skin temperature is used to turn the radiant warmer on or off to maintain the infant’s desired NTE. This usually is between 36° C and 36.5° C.

c. Troubleshoot any problems with the equipment

If the sensor and the servo system are not calibrated properly or working, the infant may be underheated or overheated. Either situation can be dangerous because newborns are very sensitive to temperature changes. Replace a sensor or servo that is not working properly.

2. Manipulate aerosol (mist) tents by order or protocol (ELE code: IIA12b) [Difficulty: ELE: R, Ap]

a. Get the necessary equipment for the procedure

Aerosol or mist tents are essentially like the O₂ tents discussed in Chapter 6. The main difference is that no supplemental O₂ is used because the patient does not need it. The top of the canopy then can be left open for better flow-through ventilation. Aerosol tents sometimes are used to treat an active child with an upper respiratory tract problem such as laryngotracheobronchitis (LTB, or pediatric croup). The tent is used because a small, active child will not keep an aerosol mask in place. A tent is not indicated for an older child or an adult who will keep an aerosol mask in place.

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

c. Troubleshoot any problems with the equipment

At least 10 L/min of compressed air still should be run through the nebulizer to ensure that no CO₂ builds up. The nebulizer or ultrasonic system should be cared for as described earlier to ensure that enough aerosol is available to treat the condition.

If the child has laryngotracheobronchitis, a cool aerosol is preferred over a warm aerosol to reduce airway edema. Never use so much aerosol that the child cannot be seen inside the tent. Also, be wary of fluid overloading in the young patient who is in the tent for a prolonged period.

Exam Hint 8-2 (ELE)

Typically, some examination questions cover troubleshooting of problems with aerosol delivery equipment. Examples include but are not limited to (1) water in the large-bore tubing that prevents aerosol from traveling through it, (2) a plugged capillary line in a nebulizer so that no aerosol is produced, (3) a missing baffle in a nebulizer so that no aerosol is produced, (4) an incorrect water level in an ultrasonic nebulizer so that no aerosol is produced, and (5) replacement of a heat-moisture exchanger fouled with secretions or blood. Also, it is important to remember that with an oxygen-powered jet nebulizer system, the inspired oxygen percentage increases if condensate water fills the low point of the aerosol tubing. This is because the backpressure on the jet and air entrainment ports prevents room air from being drawn into the system. (See Figure 8-10.)

MODULE D

Medication delivery systems

1. Manipulate small-volume pneumatic nebulizers by order or protocol (ELE code: IIA4) [Difficulty: ELE: R, Ap, An]

a. Get the necessary equipment for the procedure

A pneumatically powered small-volume nebulizer (SVN) is designed to hold a relatively small volume of fluid (typically 3 to 5 mL) and to nebulize liquid medications such as bronchodilators, mucolytics, or antibiotics for inhalation. Compressed air or O₂ can be used to generate the aerosol. These units operate under the same physical principles as the large-volume nebulizers described earlier.

Two different types of SVNs exist: mainstream and sidestream. Mainstream nebulizers are designed so the main flow of gas to the patient comes through the aerosol as it is produced. A second high-pressure gas flow is used to power the jet to create the aerosol (Figure 8-12). Sidestream nebulizers are designed so the aerosol is produced from the main flow of gas and is supplemented by the jet’s gas flow (Figure 8-13). Many manufacturers produce disposable medication SVNs, typically sidestream, for intermittent positive-pressure breathing circuits or hand-held circuits. Select the nebulizer that produces a particle size that matches the therapeutic target.

Figure 8-12 Mainstream-type small-volume nebulizer for medications.

(From Shapiro BA, Kacmarek RM, Cane RD, et al, editors: Clinical application of respiratory care, ed 4, St Louis, 1991, Mosby.)

Figure 8-13 Sidestream-type small-volume nebulizer for medications.

(From Shapiro BA, Kacmarek RM, Cane RD, et al, editors: Clinical application of respiratory care, ed 4, St Louis, 1991, Mosby.)

Figure 8-14 shows a typical small-volume nebulizer circuit. The nebulizer can be powered by compressed air or O₂. Flows of 4 to 6 L/min typically are used to nebulize 3 to 5 mL of medication in about 10 minutes. The nebulizer finger control allows the patient to power the nebulizer by covering the open hole in the “T.” Uncovering the hole permits the gas to exit; thus, the medication is not nebulized and wasted. The reservoir tube serves to hold O₂ and medication for the next inspiration.

Figure 8-14 Hand-held small-volume nebulizer with mouthpiece, reservoir tube for medication, and finger control to limit wasted medication.

(Adapted from Guidelines for disinfection of respiratory care equipment used in the home, Respir Care 33:801, 1988.)

Practitioners face two possible risks when they use SVNs. First, any aerosolized medications that escape into the room air may be inhaled. It is possible that the practitioner, or anyone else nearby, may have an allergic or other adverse reaction. Second, nebulized secretions from the patient’s airway and lungs may be inhaled; this may place the practitioner or others at risk for acquiring a pulmonary infection from the patient. Although actual problems like these rarely occur, they are possible. If either of these situations is a concern, an SVN with one-way valves and a downstream particle filter should be used. This filter will trap any exhaled aerosol droplets (Figure 8-15). A filtered SVN is recommended when pentamidine isethionate (NebuPent) is nebulized. A filtered SVN should be used for any other antibiotic or medication that should not contaminate the room air.

Figure 8-15 Diagram of the Respirgard II small-volume nebulizer system showing one-way valves and an expiratory filter to scavenge exhaust aerosol.

(From Rau JL Jr: Respiratory care pharmacology, ed 5, St Louis, 1998, Mosby.)

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

SVNs consist of a medication reservoir and a manifold (top piece) that contains a capillary tube and a baffle. The two pieces must be unscrewed so the liquid medication can be added, and then must be reassembled. A mouthpiece and an (optional) aerosol reservoir tube are added to the manifold. The attachment openings are of different sizes so the mouthpiece and the reservoir tube cannot be misplaced. Small-bore O₂ tubing must be connected between the SVN and the flowmeter. When the flowmeter is turned to about 4 to 6 L/min, an aerosol should be produced.

c. Troubleshoot any problems with the equipment

If an SVN fails to generate aerosol, make sure that the pieces are properly assembled, the liquid medication is at the proper depth (typically 3 to 5 mL), and the capillary tube is not plugged with debris. If the capillary tube is plugged, liquid will not be drawn up to the jet. Sometimes, the capillary tube can be cleared by running it under water or pushing a needle through the channel. Do not use a nebulizer that does not generate an aerosol. The therapist must be sure that the patient can properly assemble, disassemble, and operate the SVN. If the patient cannot, another medication delivery system, such as a dry powder inhaler (DPI) or a metered-dose inhaler (MDI), should be recommended.

2. Manipulate metered-dose inhalers by order or protocol (ELE code: IIA23) [Difficulty: ELE: R, Ap, An]

a. Get the necessary equipment for the procedure

Metered-dose inhalers (MDIs) are designed to dispense a premeasured amount of medication into the airway. Each activation of the MDI delivers a dose of medication to the patient. Available medications include sympathomimetic and anticholinergic bronchodilators, corticosteroid drugs, and an antibiotic (see Chapter 9 for details on the medications). All MDIs operate in the same way. They contained several milliliters of medication and compressed hydrofluoroalkane (HFA) gas inside of a metal container with a built-in jet nozzle. (The older MDI units that contained the environmentally hazardous propellant chlorofluorocarbon [CFC] have been replaced by HFA gas units.)

Tipping the metering chamber over and back upright results in its filling with medication. A plastic actuator opens the jet when it is pressed into the container (Figure 8-16). The patient then can inhale the medication through the built-in mouthpiece or a spacer/holding chamber.

Figure 8-16 The effect of a spacer on aerosol particle size and velocity coming from a metered-dose inhaler.

(From Gardenhire D: Rau’s Respiratory care pharmacology, ed 7, St. Louis, 2008, Mosby.)

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

c. Troubleshoot any problems with the equipment

When assembling the MDI, make sure that the medication canister nozzle fits into the jet of the actuator. If they are misaligned, no medication can be released. If needed, a spacer or a holding chamber can be added to the actuator. See the following discussion. To keep the jet channel open, patients should be instructed to use warm, soapy water daily to wash out the actuator. It can air dry overnight.

Some patients (e.g., those with arthritis of the fingers) may have difficulty squeezing the canister into the actuator to dispense the medication. In these cases, it may be possible to substitute a breath-activated MDI or add an MDI holder that can be squeezed easily to push the canister into the actuator. If a patient cannot properly manipulate an MDI with or without a spacer/holding chamber, the therapist should recommend a DPI or SVN medication delivery system.

3. Manipulate spacers and holding chambers for a metered-dose inhaler by order or protocol (ELE code: IIA23) [Difficulty: ELE: R, Ap, An]

a. Get the necessary equipment for the procedure

The addition of a spacer or a holding chamber between the actuator and the patient’s mouth has been shown to increase the amount of inhaled medication. These devices slow down the aerosol so that less of it impacts on the back of the throat. This should result in fewer systemic adverse effects such as the risk of oral thrush (candidiasis fungal infection) with an MDI-powered corticosteroid. Also, the patient with poor hand and breathing coordination wastes less medication.

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

c. Troubleshoot any problems with the equipment

A spacer is a simple, open extension tube that is placed between the actuator and the patient. Its main advantage over direct inhalation from the MDI mouthpiece is that the aerosol plume expands and slows down so that more medication is inhaled (see Figure 8-16). The patient should be told to refrain from exhaling through the spacer because any remaining medication will be blown out and wasted. Some spacers are designed for use with a ventilator circuit when an MDI-based medication is to be given. The spacer should be placed into the inspiratory limb of the ventilator circuit, about 18 inches from the patient. Typically, the MDI is activated during the expiratory phase so the medication can fill the spacer and inspiratory tubing before the next inspiration.

A holding chamber holds the medication as does a spacer, but it also has valves. These holding chamber valves prevent the medicine from being exhaled out through the unit. The valves also allow the patient to inhale several times from the unit and get more medication than through a simple spacer. This is especially helpful with children or small adults with small tidal volume breaths. Some holding chambers have a built-in whistle that sounds if the patient is inhaling too quickly. Several types of spacers or holding chambers are available (Figure 8-17). Some spacers are designed to fit with only one actuator, whereas others adapt to fit with any actuator. A face mask comes attached to some holding chambers so pediatric patients or uncooperative adults can be given the medication.