CH 6 Oxygen and Medical Gas Therapy

B. About 22 hours See the sample H-tank duration calculation given earlier in the chapter. Common calculation errors include using the E-tank factor and failing to convert from minutes to hours by dividing by 60.

A home care patient has a problem with his O2 concentrator and needs to change to the H tank of O2. If the patient's nasal cannula is receiving a flow of 3 L/min and the tank pressure is 1300 psig, how long can the patient receive O2? A. About 2 hours B. About 22 hours C. About 120 hours D. About 1300 hours

A. Nonrebreathing mask A properly fitting nonrebreathing mask with enough flow to keep the reservoir bag inflated will deliver the highest O2 percentage of all available devices.

The physician asks the respiratory therapist which O2 delivery device would be best for a patient who needs about 75% O2. What should be recommended? A. Nonrebreathing mask B. 6 L/min nasal cannula C. Air entrainment mask D. Simple O2 mask

B. 1.6 hours Review the sample E-tank duration calculation in this chapter. Common calculation errors include using the H-tank factor and failure to convert from minutes to hours by dividing by 60.

What is the duration of flow of an E cylinder with 1700 psig that is running at 5 L/min? A. 0.9 hour B. 1.6 hours C. 7.7 hours D. 13.7 hours

B. Begin nitric oxide therapy. INOmax is indicated to dilate the pulmonary vascular bed of a newborn with PPHN. When the pulmonary vascular bed dilates, more blood flows through the lungs, and oxygenation should improve. Instillation of intratracheal surfactant is indicated only in a newborn with infant respiratory distress syndrome (RDS). Surfactant therapy is not indicated in PPHN. Although PEEP increases the functional residual capacity of an infant with RDS and improves oxygenation, PEEP must be used with great care, if at all, in a newborn with PPHN. PEEP at 10 cm water may overexpand the alveoli of a newborn with PPHN and prevent blood from flowing through the capillary bed. Oxygenation will worsen rather than improve. Carbogen (carbon dioxide and oxygen mix) may be harmful to a newborn with PPHN, because an increased carbon dioxide level further constricts the newborn's pulmonary vascular bed. Carbogen is indicated in a newborn with HLHS.

A 36-week gestational age neonate is hypoxemic despite mechanical ventilation and has clinical evidence of persistent pulmonary hypertension of the newborn. What can be done to correct the hypoxemia? A. Instill intratracheal surfactant. B. Begin nitric oxide therapy. C. Begin 10 cm water PEEP. D. Begin carbogen therapy.

D. Increase the oxygen flow to the current system to 3 L/min. The patient's current blood gases show unacceptable hypoxemia with a PaO2 of 47 torr and an SaO2 of 80%. Increasing the patient from 2 to 3 L/min through the transtracheal oxygen catheter should help to correct the situation. The patient should be monitored for a possible increasing carbon dioxide level as well as an improving oxygen level. Changing the patient to 24% oxygen by an air entrainment mask probably will not change his actual inspired oxygen percentage. In addition, there is no indication that the transtracheal oxygen catheter has failed. The patient's ventilation is stable, with no indication that bilevel mask ventilation is needed. Changing the patient to a nonrebreathing mask with 10 L/min of oxygen is potentially dangerous. This much oxygen may blunt his hypoxic drive to breathe.

A 58-year-old patient with advanced emphysema is admitted with an acute exacerbation of the condition. While breathing 2 L/min of oxygen through a transtracheal oxygen catheter, the patient has the following ABG results: pH, 7.38 PaCO2, 57 torr HCO3−, 31 mEq/L PaO2, 47 torr SaO2, 80% Based on these findings, what should be done? A. Change the patient to 24% oxygen by an air entrainment mask. B. Initiate bilevel mask ventilation. C. Change the patient to a nonrebreathing mask with 10 L/min of oxygen. D. Increase the oxygen flow to the current system to 3 L/min.

D. 3, 4, and 5 only The three listed items are all important for minimizing hypoxemia during a treatment or procedure. Increasing the O2 by 20% will help to minimize hypoxemia, but it is appropriate to raise the percentage much higher.

To minimize the risk of hypoxemia during a treatment or procedure, which of the following should be done? 1. Increase the O2 percentage by 20% above the normal setting before suctioning or changing equipment. 2. Keep the O2 percentage the same as if the patient were not hypoxemic at this time. 3. Minimize the time that the patient would be breathing room air. 4. Increase the O2 percentage to 100% before suctioning. 5. Make sure the replacement equipment is working properly before you place it on the patient. A. 1 and 3 only B. 2 and 5 only C. 3 and 4 only D. 3, 4, and 5 only

B. Air entrainment mask An air entrainment mask (high-flow delivery system) is designed to provide enough flow of the prescribed O2 percentage (fixed concentration) at any patient rate, VT, and so forth. The other three devices do not provide enough flow to deliver a consistent, known O2 percentage

What O2 delivery device should be recommended for a patient who has a variable respiratory rate, I:E ratio, and VT? A. Nasal cannula B. Air entrainment mask C. Simple O2 mask D. Transtracheal catheter

B. Carbogen therapy Carbogen will help to keep an open patent ductus arteriosus to maintain system circulation. Nitric oxide is indicated for pulmonary hypertension, not for HLHS. It would be dangerous to close the patent ductus arteriosus in this patient. Heliox is indicated for airway obstruction, not for HLHS.

A newborn infant with HLHS has just been transferred to the hospital. Mechanical ventilation is being instituted. What else can be done to help improve the neonate's heart function? A. Nitric oxide therapy B. Carbogen therapy C. Close the PDA D. Heliox therapy

B. Hypoventilation A patient with COPD who is hypercarbic and is breathing on hypoxic drive should be given supplemental O2 with great care. Too much O2 will result in too high an arterial O2 level and will blunt the hypoxic drive. Hypoventilation will result in a rising CO2 level. Pulmonary edema from O2 toxicity would necessitate a high percentage of O2 for an extended period. ROP is seen only in premature infants. Hyperventilation is not caused by breathing of supplemental O2.

What is the most likely problem to watch for in a patient with severe COPD who is receiving supplemental O2? A. Pulmonary edema from O2 toxicity B. Hypoventilation C. Retinopathy of prematurity D. Hyperventilation

B. Replace the cannula The reservoir membrane is defective, so the cannula should be replaced. The O2 flow should not be increased because this would give the patient more O2 than is intended. Decreasing (or increasing) the O2 flow will not unstick a defective reservoir membrane. Changing to an air entrainment mask would be a possible remedy if a replacement cannula did not exist.

When checking a home care patient's reservoir-type nasal cannula, the therapist notices that the reservoir does not fill and empty in synchrony with the patient's breathing pattern. Based on this, what should be done? A. Increase the O2 flow. B. Replace the cannula. C. Decrease the O2 flow. D. Switch the patient to an air entrainment mask.

C. 12.8 (13) L/min The heliox factor for a 70% helium/30% oxygen mix is 1.6. To calculate the total flow of this heliox mix through an oxygen flowmeter, the following calculation is made: 8 L/min of gas observed on the oxygen flowmeter × 1.6 = 12.8 (13) L/min actual heliox gas flow. See Exam Hint 6-6 for the heliox factors and an example of how to make this calculation.

A 16-year-old patient with status asthmaticus is started on a 70% helium/30% oxygen (heliox) mix through a nonrebreather mask. It is noticed that the oxygen flowmeter shows the delivery of 8 L/min of gas. What is the actual heliox gas flow? A. 5 L/min B. 8 L/min C. 12.8 (13) L/min D. 14.4 (14) L/min

D. Begin an HFNC at ≥10 L/min oxygen A high-flow nasal cannula should be able to provide enough oxygen to the patient to correct her hypoxemia. In addition, she should keep it on because it will not make her feel claustrophobic. A traditional nasal cannula is not run at over 6 L/min of oxygen. It could be dangerous to sedate a hypoxic patient. It is likely that the CPAP mask also will make her feel claustrophobic.

A 65-year-old female patient with pulmonary edema is very short of breath and hypoxemic. She is ordered to have a nonrebreathing mask with 10 L/min of oxygen going to it. However, she keeps taking off her mask because of anxiety and claustrophobia. When she removes the mask, her pulse oximeter reading drops from 90% to 82%. What should be recommended to help manage the patient? A. Give her a nasal cannula at 10 L/min oxygen. B. Sedate the patient so that she will keep her nonrebreathing mask on. C. Initiate CPAP by mask at 8 cm water and 40% oxygen. D. Begin an HFNC at ≥10 L/min oxygen

A. Add aerosol tubing to the end of the T-piece. Adding 100 mL of aerosol tubing as a reservoir will help to maintain the patient's inspired O2 percentage. No clear reason exists for changing the patient's O2 percentage by protocol, and no physician order exists to do so. Changing the flow probably will not stabilize the patient's O2 percentage without the added reservoir tubing. A comatose patient will not follow instructions to "not breathe so deeply."

A comatose patient is intubated and is receiving 35% O2 with aerosol through a T-piece. While watching the patient breathe, the therapist notices that during each inspiration, the mist disappears from the downstream end of the T-piece. What should be recommended? A. Add aerosol tubing to the end of the T-piece. B. Change the O2 to 30% and increase the flow. C. Change the O2 to 40% and decrease the flow. D. Tell the patient not to breathe so deeply.

B. Decrease the nitric oxide to 10 ppm. Because the patient's PVR is now in the normal range, the concentration of nitric oxide can be slowly reduced. The patient's PVR then should be reassessed. It is more prudent to wean off the NO level rather than to discontinue the gas in one step. There is no need to increase the NO to 30 ppm because the patient's PVR is in the normal range. It also is possible that this level of NO could be toxic. Carbogen is not indicated for pulmonary hypertension.

A neonatal patient has primary pulmonary hypertension and is receiving mechanical ventilation. After the neonate receives 20 ppm of nitric oxide therapy, PVR returns to the normal range. What should be recommended at this time? A. Discontinue the nitric oxide therapy. B. Decrease the nitric oxide to 10 ppm. C. Add 1% carbogen to the nitric oxide mix. D. Increase the nitric oxide therapy to 30 ppm.

C. Bourdon A Bourdon flowmeter is the only unit that will accurately indicate the flow when it is laid horizontally. The others read accurately only in a vertical position.

A patient has a nasal cannula and needs to be transported on a stretcher. The E-sized O2 cylinder will have to be laid flat under the stretcher. Which flowmeter should be recommended? A. Backpressure-compensated Thorpe B. Non-backpressure-compensated Thorpe C. Bourdon D. Backpressure-compensated kinetic

D. Nonrebreathing mask A properly applied and used nonrebreathing mask should deliver at least 60% O2. CPAP is not indicated in a patient with CO poisoning and more than 40% O2 should be delivered. A simple mask or 50% oxygen air entrainment nebulizer does not deliver as much O2 as is provided by a nonrebreathing mask.

A patient has just been admitted through the Emergency Department with suspected CO poisoning. The physician wants the patient to receive the highest possible O2 percentage. What should be recommended? A. CPAP mask at 5 cm H2O and 40% O2 B. Simple mask at 6 L/min flow C. 50% air entrainment nebulizer to aerosol mask D. Nonrebreathing mask

D. Decreased inspired O2 Because the face tent is open on top and O2 is heavier than room air, the O2 in the face tent tends to "pour" out if the patient lies supine. When all is set up properly, CO2 should not build up in a face tent, no matter the patient's position. A face tent should not influence a patient's VT. Lying supine may result in decreased VT.

A patient is wearing a face tent because of recent facial surgery. It is set at 35% O2. The nurse moves the patient from an upright to a supine position in bed. What effect will this have on the patient's respiratory status? A. Increased VT B. Increased inspired O2 C. Increased inspired CO2 D. Decreased inspired O2

D. Increase the O2 flow When properly operating, a partial-rebreathing mask's reservoir bag should not collapse during inspiration. Raise the O2 flow so that the bag stays at least two-thirds full during inspiration. Hypoxic patients usually breathe in at whatever pattern and rate is most efficient for them. It may be counterproductive to try to have the patient breathe differently. A standard, low-flow nasal cannula cannot deliver as high an O2 percentage as can be delivered by the partial-rebreathing mask.

A patient is wearing a partial-rebreathing mask. The reservoir bag almost totally collapses during inspiration. Which of the following should be done? A. Tell the patient to breathe more slowly. B. Put a standard nasal cannula on the patient. C. Tell the patient to breathe more rapidly. D. Increase the O2 flow.

A. Molecular sieve oxygen concentrator At a flow of 1 L/min, a molecular sieve oxygen concentrator delivers at least 90% oxygen to the patient. A portable LOX system is not needed if the patient is not actively and frequently mobile. A semipermeable-membrane oxygen concentrator delivers only about 40% oxygen to the patient. A piston compressor is useful for delivering pressurized air to power a small-volume nebulizer. However, it does not deliver more than 21% oxygen (room air) to the patient.

A patient with COPD is going home. After a hospital exercise test is conducted, it has been determined that the patient will require 1 L/min of supplemental oxygen only when exercising on a stationary bicycle or when the patient feels short of breath. Which of the following oxygen delivery systems should the respiratory therapist recommend? A. Molecular sieve oxygen concentrator B. Portable LOX system C. Semipermeable membrane oxygen concentrator D. Piston compressor

D. Switch oxygen from the transtracheal catheter to a nasal cannula Because a major obstruction exists in the transtracheal oxygen catheter, it must be replaced. But first, 577the patient must switch her oxygen delivery system to a nasal cannula. Attempts to force out the obstruction by doubling the oxygen flow or forcing the saline or cleaning rod through the catheter can result in injury to the trachea

A phone call is received from a home care patient. The patient reports that the high-pressure pop-off valve on the bubble humidifier to the transtracheal oxygen catheter is venting. In addition, the patient cannot flush out the catheter with saline or push the cleaning rod through it. What should the patient be told to do? A. Remove the humidifier and double the oxygen flow rate to the catheter. B. Force the saline through the catheter until the obstruction is cleared. C. Force the cleaning rod through the catheter until the obstruction is cleared. D. Switch oxygen from the transtracheal catheter to a nasal cannula.

A. Begin heliox therapy. Heliox therapy should be helpful in reducing the patient's work of breathing. This should allow more time for the corticosteroid and aminophylline medications to begin working. Nitric oxide is a pulmonary vasodilator and is not indicated for status asthmaticus. Review Box 6-1 if needed. It is not necessary at this time to go against a patient's wishes and begin mechanical ventilation without first trying heliox therapy. Absolutely no reason justifies allowing this patient to die of status asthmaticus! It should not be fatal if managed appropriately and aggressively.

A respiratory therapist is assigned to the Emergency Department of a major medical center when a 24-year-old patient with status asthmaticus is transferred by ambulance from a small, rural hospital. The patient has been given continuous bronchodilator therapy and intravenous corticosteroids and aminophylline. The patient is becoming exhausted but refuses to allow intubation and mechanical ventilation. What should be recommended? A. Begin heliox therapy. B. Begin nitric oxide therapy. C. Intubate and ventilate the patient despite protests. D. Follow the patient's wishes.

D. Decreased inspired O2 The reservoir tubing holds O2 from which the patient can inspire. Losing the reservoir results in inhalation of room air and a decrease in the overall O2 percentage. When set up properly, any exhaled CO2 is blown clear from the reservoir tubing before the next inspiration.

A respiratory therapist is making general rounds in the hospital and finds a patient whose reservoir tubing has fallen off his 40% T-piece. This would result in which of the following? A. Increased inspired O2 B. Increased inspired CO2 C. Decreased inspired CO2 D. Decreased inspired O2

A. Use a portable LOX system at 2 L/min. A portable liquid oxygen system should have a long enough duration to provide her with oxygen for the trip. An E tank of oxygen could be awkward to take on the trip. It would be challenging to prestage oxygen tanks at various stores. The patient should not decrease her oxygen flow just to increase the duration of the E tank.

A socially active female patient with COPD requires 2 L/min of continuous oxygen. She wishes to go with her Better Breathers Club on a bus trip to shop in Chicago. What should be recommended for her in this situation? A. Use a portable LOX system at 2 L/min. B. Take a portable E tank of oxygen with her and run it at 2 L/min. C. Pre-position E tanks of oxygen for her use in the various stores. D. Take a portable E tank of oxygen with her and run it at 1 L/min.

B. 4.4 L/min Setting 4.4 L/min on the oxygen flowmeter will deliver 7 L/min of a 70/30 heliox mix. See Exam Hint 6-6 for the heliox factors and an example of how to make this calculation.

An 8-year-old patient with asthma is going to be given a 30% oxygen and 70% helium mix of heliox through a nonrebreathing mask and reservoir bag. The physician has ordered the child to receive 7 L/min of the gas mix. Because it will be delivered through an oxygen flowmeter, what flow should be set? A. 3.9 L/min B. 4.4 L/min C. 9.8 L/min D. 11.2 L/min

D. 2 and 5 Review the information on pinholes in Table 6-3.

An E cylinder of O2 needs to be prepared for transport of a patient. A regulator with which pinhole locations should be used? A. 1 and 5 B. 2 and 6 C. 3 and 5 D. 2 and 5

B. Change the patient to a nonrebreathing mask. The significant discrepancy between the pulse oximeter reading and the CO oximeter can be explained only by the patient's having CO poisoning. In this situation, only the CO oximeter reading will be accurate. A CO oximeter reading of 73% indicates severe hypoxemia. Therefore the patient should be changed to a nonrebreathing mask with enough flow to keep the reservoir bag inflated. This maximizes the inspired oxygen percentage to the patient. Maintaining the simple oxygen mask at the present flow or decreasing the oxygen flow to the simple oxygen mask to 4 L/min will worsen rather than improve the patient's condition. Nothing indicates that the CO oximeter is malfunctioning and should be recalibrated.

An adult patient who was rescued from a house fire is being received in the Emergency Department. The patient is wearing a simple oxygen mask at 5 L/min. The SpO2 value by pulse oximeter is 100%, and his SaO2 value from an ABG sample analyzed on a CO oximeter is 73%. What should be recommended at this time? A. Maintain the simple oxygen mask at the present flow. B. Change the patient to a nonrebreathing mask. C. Decrease the oxygen flow to the simple oxygen mask to 4 L/min. D. Maintain present therapy and recalibrate the CO oximeter.

A. HFNC Many patients who do not tolerate a face mask find an HFNC acceptable. The HFNC is able to deliver the same high oxygen percentage as a nonrebreathing mask. It is unlikely that the anxious patient will tolerate any type of face mask. None of the other masks provide as high an oxygen percentage as the nonrebreathing mask or HFNC.

An anxious 68-year-old patient with congestive heart failure will not keep the nonrebreathing mask on. What should be recommended to treat the patient's hypoxemia? A. HFNC B. Partial rebreathing mask C. 50% air entrainment mask D. 40/60 heliox mix by nonrebreathing mask

C. 1, 2, 4, and 5 only In addition to the special high-flow nasal cannula, a blender with high-pressure air and oxygen sources and humidifier will be needed. Sterile water is needed rather than sterile saline.

An order is received to set up a HFNC on a patient. What will be needed? 1. Humidifier 2. High-pressure oxygen source 3. Sterile saline 4. Blender 5. High-pressure air source A. 2, 4, and 5 only B. 2, 3, and 4 only C. 1, 2, 4, and 5 only D. 1, 2, 3, 4, 5

C. Nonrebreathing mask with reservoir bag A nonrebreathing mask with reservoir bag is the best way to deliver heliox because it will provide all of the patient's inspiratory flow needs. A partial-rebreathing mask with reservoir bag is not a sealed system. Room air will be entrained, which will reduce the patient's helium and oxygen percentages. A heliox mix can be given by a high-flow nasal cannula. However, the patient would have to cooperate to use a hand-held small-volume nebulizer. There is no indication at this time that mechanical ventilation is needed. In addition, several technical challenges are associated with providing heliox through most mechanical ventilators.

An uncooperative 13-year-old patient with status asthmaticus is being treated in the Emergency Department. The physician has ordered the patient to receive a 70% helium/30% oxygen mix and continuous nebulized albuterol. What should be recommended as the best way to deliver this? A. Partial-rebreathing mask with reservoir bag B. HFNC C. Nonrebreathing mask with reservoir bag D. Through a mechanical ventilator

A. Give the patient an 80/20 heliox mix to breathe. It is likely that the biopsy site has developed some edema, which is causing the shortness of breath and "tight" throat feeling. Giving the patient 80% helium and 20% oxygen should help to ease the patient's shortness of breath because helium is less dense than nitrogen. Commonly, a patient's head is put down 30 degrees when the patient's blood pressure is low; this is unlikely to ease a feeling of shortness of breath. Carbogen (carbon dioxide and oxygen mix) stimulates the breathing center of the brain but will not relieve the patient's shortness of breath caused by laryngeal edema. The 7-minute helium dilution test is performed in the pulmonary function laboratory to measure the patient's residual volume. It is not intended to relieve the patient's feeling of shortness of breath from laryngeal edema.

The respiratory therapist is assisting with a bronchoscopy to obtain a biopsy of a suspicious laryngeal node on a patient. Afterward, the patient complains of shortness of breath and a "tight" throat. Which of the following recommendations should be given to the physician? A. Give the patient an 80/20 heliox mix to breathe. B. Put the head of the bed down 30 degrees. C. Give the patient a carbogen mix to breathe. D. Do a 7-minute helium dilution test.

A. 1 and 3 only A polarographic oxygen analyzer does not have a gas sampling capillary tube; the paramagnetic type does. The other four listed problems can cause a polarographic analyzer to fail. The probe has a membrane through which oxygen diffuses. It must not be torn and must not have water, blood, or mucus covering it. An adequate amount of electrolyte solution must be present within the probe for the oxygen-related chemical reaction to take place. A functional battery is needed to drive the chemical reaction within the electrolyte solution.

The respiratory therapist is attempting to calibrate a polarographic oxygen analyzer but finds that it cannot be done. Possible reasons for this include: 1. The membrane is torn on the probe. 2. The gas-sampling capillary tube is plugged with debris. 3. The electrode solution has evaporated. 4. The battery needs to be replaced. 5. Water has condensed on the membrane. A. 1 and 3 only B. 2 and 3 only C. 3, 4, and 5 only D. 1, 3, 4, and 5 only

C. The O2 percentage will be increased. Covering the air entrainment ports on an air entrainment mask will result in the patient receiving a higher O2 percentage than desired. In addition, the total flow will be decreased.

The respiratory therapist is called to draw an arterial blood sample from a patient who is wearing a 35% air entrainment mask. Upon entering the room, the therapist notices that the patient's covers are drawn up over the air entrainment ports of the mask. How would this affect the function of the mask? A. The total flow will be increased. B. There will be no effect. C. The O2 percentage will be increased. D. The O2 percentage will be decreased.

C. 2 and 5 only The patient's ABG results show her PaO2 to be 84 torr. This is too high for many patients with COPD. It is likely that her hypoxic drive to breathe has become blunted. This has resulted in her hypoventilating, with an increasing carbon dioxide level and secondary drowsiness. Although it is not possible to know the patient's inspired oxygen percentage with a 6 L/min nasal cannula, this flow has resulted in a PaO2 that is too high. It is best to switch her to an air entrainment mask so that a known low oxygen percentage (24%) can be administered. Then, she should be monitored closely for returning alertness, and another ABG sample should be obtained. This should be evaluated for a lower, but safe, PaO2 and a lower PaCO2. The patient should not be left on her present oxygen flow through the nasal cannula because of her unnecessarily high oxygen level, hypoventilation, increasing carbon dioxide level, and secondary drowsiness. Changing her from a cannula to a simple face mask at the same oxygen flow will not correct these problems. She needs to be awakened because her drowsiness is not the result of simple fatigue.

The respiratory therapist is called to evaluate a female patient known to have advanced emphysema. She is wearing a nasal cannula at 6 L/min. The nurse says that she has become drowsy and less responsive since the oxygen was given to her an hour ago. Her ABG results on the oxygen show the following: PaO2, 84 torr PaCO2, 65 torr pH, 7.32 Which of the following should be recommended? 1. Leave her on the cannula. 2. Change her to 24% O2 on an air entrainment mask and repeat the ABG in 20 minutes. 3. Change her to a simple oxygen mask and repeat the ABG in 20 minutes. 4. Let her rest undisturbed. 5. Monitor her closely for becoming more alert. A. 1 and 4 only B. 3 and 4 only C. 2 and 5 only D. 3 and 5 only

D. The float will move downward and then to the bottom of the flowmeter. A Thorpe-type flowmeter will read accurately if backpressure is placed upon the exit of gas. Thus, the flowmeter will read less flow than zero, as the outlet is partially and then completely blocked.

The respiratory therapist is doing quality assurance on the department's flowmeters. After a backpressure-compensated Thorpe flowmeter is plugged in, the flow is set at 10 L/min. The flowmeter outlet is partially and then completely obstructed. Which of the following should be expected? A. The float will stay at the 10-L/min mark. B. The float will move upward in the flowmeter. C. The float will move upward and then downward in the flowmeter. D. The float will move downward and then to the bottom of the flowmeter.

C. Increase the flow of gas. Because the reservoir bag has collapsed, the flow of heliox must be increased. Ideally, the reservoir bag should not collapse by more than one-third on inspiration. Decreasing the flow of gas to the patient will worsen the problem of shortness of breath, not improve it. When the gas flow to the mask is inadequate, it does not matter what oxygen percentage the patient gets. There is no need to increase the patient to 40% oxygen. By doing so the helium percentage will drop and could decrease it beneficial effects.

The respiratory therapist is working with a patient who has a tracheal tumor. The patient is wearing a nonrebreathing mask with 70% helium and 30% oxygen mix. Pulse oximeter saturation is 96%. The patient says that it is getting harder to breathe and it is noticed that the reservoir bag has collapsed. The most appropriate action is to A. Decrease the flow of gas. B. Switch to a 28% air entrainment mask. C. Increase the flow of gas. D. Switch to a 60% helium and 40% oxygen mix.

C. O2-induced hyperventilation There is no condition called O2-induced hyperventilation. Do not confuse this with O2-induced hypoventilation, which needs to be monitored in some patients with COPD. See the rationale for question 2.

The risks of O2 therapy include all of the following EXCEPT: A. Pulmonary O2 toxicity B. Denitrogen absorption atelectasis C. O2-induced hyperventilation D. Retinopathy of prematurity