Chapter 18: Administration of Gas Mixtures Test Bank

Multiple Choice

1. Vascular smooth muscle is largely dependent on which of the following intracellular ions?

a. Na+ b. K+ c. Ca2+ d. Mg2+

ANS: C

Current understanding suggests that vascular smooth muscle is largely dependent on intracellular calcium ion (Ca2+) concentration. Smooth muscle tissue comprises bundles of myofibrils, threadlike contractile fibers encased by the sarcoplasmic reticulum, a network of tubes or channels that store Ca2+ .

REF: p. 344 a. Intracellular cGMP b. EDRF c. cGMP-dependent kinase d. Calmodulin

2. Which of the following substances prevents the release of Ca2+ from the sarcoplasmic reticulum?

ANS: C

In the body, the process of smooth muscle relaxation uses cyclic guanosine monophosphate (cGMP) to reduce Ca2+ levels. In smooth muscle cells cGMP activates cGMP-dependent kinase, preventing the release of Ca2+ from the sarcoplasmic reticulum, resulting in smooth muscle relaxation. In the early 1980s researchers reported a potent smooth muscle–relaxing agent, endothelium-derived relaxing factor (EDRF), now understood to be endogenous nitric oxide.

REF: p. 344 a. Bronchodilation b. Pulmonary vasodilation c. Systemic vasodilation d. Cerebral vasodilation

3. What is the primary physiologic activity of inhaled nitric oxide?

ANS: B

The underlying principle of inhaled nitric oxide (iNO) is its selectivity as a pulmonary vasodilator. Inhaled NO will relax only pulmonary smooth muscle adjacent to functioning alveoli. Atelectatic or fluid-filled lung units will not participate in iNO uptake.

REF: p. 344 a. Dobutamine b. Dopamine c. Prostacyclin d. Prostaglandin A

4. Which of the following medications contributes to an increased right-to-left intrapulmonary shunting?

ANS: C

The intravenous vasodilators nitroprusside and prostacyclin will relax pulmonary vasculature globally, reducing pulmonary vascular resistance, but will also increase pulmonary blood flow past nonfunctioning alveoli and intrapulmonary right-to-left shunt.

REF: p. 344 a. Keep iNO at 20 ppm and wait at least 2 hours before considering any change. b. Increase iNO to 30 ppm and keep the same FiO2. c. Keep iNO at 20 ppm and wean the FiO2 by 10%. d. Increase iNO to 30 ppm with no changes in FiO2.

5. The respiratory therapist has initiated iNO at 20 ppm for an infant with pulmonary hypertension. After 2 hours a blood gas test reveals a 10% improvement in SaO2. What should the therapist do?

ANS: A

Several studies have used an increase in oxygen saturation of 20% over baseline as an indication that the infant is responsive.

REF: p. 345

6. The respiratory therapist has initiated nitric oxide for an infant with severe refractory hypoxemia. The initial dose was 20 ppm and titrated up to 30 ppm for the last 4 hours due to lack of response. However, there still is no response. What should the therapist do? a.

Increase iNO to 40 ppm b. Increase iNO to 60 ppm c. Increase iNO to 80 ppm d. Discontinue iNO and consider a different therapeutic intervention

ANS: D

Studies have suggested that optimal dosing is usually in the 20- to 30-ppm range. Some infants will not respond positively. The Neonatal Inhaled Nitric Oxide Study (NINOS) trial indicated that only 6% of nonresponders will demonstrate a positive response when given NO at 80 ppm. Typically, a response would be seen almost immediately; however, it is recommended that the time allotted for determining an infant's response last no longer than 4 hours to limit the exposure to NO.

REF: p. 345 a. HFOV improves ventilation and reduces the formation of NO2. b. Lung volumes are optimized with HFOV and further enhance the effects of iNO. c. The high frequency accelerates the diffusion of NO through the alveolar surface. d. HFOV reduces the need for higher doses of iNO.

7. Inhaled NO has been administered to an infant for nearly 4 hours. The respiratory therapist notices suboptimal response and suggests HFOV. What is the principle behind the potential benefit of adding this ventilatory modality to this infant?

ANS: B

If lung volume is optimized with HFOV, this could further enhance the effects of iNO. The use of HFOV improves oxygenation response to iNO.

REF: p. 345 a. Oxygen radicals b. N2O c. NO2 d. The two molecules do not react with each other.

8. What is the product of the reaction between oxygen and nitric oxide?

ANS: C

When combined with oxygen, NO produces NO2, a toxic gas. Although rare, the patient as well as health care providers can be adversely affected. Factors influencing NO2 production are oxygen concentration, NO concentration, and time of contact between NO and oxygen.

REF: p. 346

9. The therapist taking care of an infant on iNO observes that the NO2 levels have been increasing. In order to correct the situation he increases the inspiratory flow of the ventilator. What will be some of the limitations associated with this change?

I. It reduces time of contact between NO and O2

II. It affects the mean airway pressure because it changes the inspiratory time.

III. It may increase the delivered tidal volume.

IV. It reduces the mean airway pressure and increases the inspiratory time.a.I only b. II and IV only c. I, II, and III only d. II, III, and IV only

ANS: C

Decreasing the NO or oxygen concentration is usually not an option; therefore, to reduce NO2 delivery to the patient, reduce the duration of contact between NO and oxygen. Two methods accomplish this: (1) increase the inspiratory flow or (2) add the NO as close to the patient as possible. Each of these methods has practical limitations. Increasing the ventilator flow will reduce the time of contact between NO and oxygen before reaching the patient, but it may also affect inspiratory time, tidal volume, mean airway pressure, and so on.

REF: p. 346 a. A larger number of oxygen radicals are produced at this position. b. Adding NO too close to the patient reduces proper mixing, which is necessary to ensure accurate NO measurement. c. Adding NO in this position of the circuit is contraindicated. d. The contact time between NO and O2 is too long to be clinically useful.

10. After increasing the inspiratory flow of the ventilator to decrease the generation of NO2 the therapist notices many changes in the ventilator parameters. The therapist adds the NO into the inspiratory limb of the ventilator circuit close to the patient. What will be a limitation of the procedure?

ANS: B

Adding NO into the inspiratory limb of the ventilator circuit close to the patient will reduce contact time, but it also creates monitoring difficulties. The practitioner must allow an adequate distance for proper mixing to ensure accurate NO measurement.

REF: p. 346

11. Although very small amounts of NO2 are present at the bedside, which health care workers need to exert special precautions to minimize exposure to NO2? a. Nurses in the NICU b. Air transport team members c. Ground transport team members d. Respiratory therapists in the NICU

ANS: B

At first, scavenging was advocated to reduce the possible harmful inhalation of nitrogen dioxide by other personnel in the vicinity. Studies have shown this to be unnecessary because of the relatively small amounts of NO2 present at the bedside. Modern hospitals have adequate room air exchange rates, and the chance of NO or NO2 accumulation is remote. A possible caveat involves interfacility transport. Pressurized aircraft may not allow an adequate cabin air exchange rate to ensure safety. The aircraft crew must be made aware of this so that proper measures are taken to reduce this risk.

REF: p. 346

12. An infant has been receiving iNO for the last 3 days. Which important level should be monitored when ordering a co-oximetry? a. Methemoglobin b. Carboxyhemoglobin c. Reduced hemoglobin d. Oxyhemoglobin

ANS: A

The half-life of iNO is extremely short, about 5 seconds. Once NO crosses the vascular endothelium, it is rapidly bound by hemoglobin, forming nitrosyl hemoglobin (methemoglobin). Methemoglobin production results from the oxidation of the iron in the hemoglobin. The quantity of methemoglobin depends on iNO concentration and concurrent nitrate-based drug therapy (e.g., nitroprusside, nitroglycerin). If the methemoglobin level is excessive, a reduction in iNO or other nitro-based vasodilators is warranted.

REF: p. 346 a. To reduce the work of breathing b. To improve gas exchange c. To increase the functional residual capacity d. To improve pulmonary compliance

13. What is the purpose of administering helium–oxygen gas mixtures to patients?

ANS: A

It is important to note that helium is not used to treat the underlying cause of increased airway resistance but rather to decrease the work of breathing until more definitive therapies are effective. When helium is combined with oxygen, the resulting gas mixture density is one third that of air.

REF: p. 347 a. Less aerosol is deposited with heliox. b. More aerosol is deposited with heliox. c. The two gas mixtures are equally efficient. d. Definitive data are not available.

14. During the administration of aerosol therapy, how does a heliox mixture compare with an air–oxygen mixture as a carrier gas?

ANS: B

Patients who use the helium–oxygen mixtures show more improvement in expiratory peak flows than a group using air. Aerosol has deeper and prolonged deposition in the lung when it is delivered with heliox as the carrier gas.

REF: pp. 347-348 a. 5.5 L/minute b. 10 L/minute c. 12.5 L/minute d. 18 L/minute

15. The therapist is using an oxygen flowmeter to deliver an 80:20 heliox mixture to a patient. The reading on the flowmeter is 10 L/minute. What is the actual flow received by the patient?

ANS: D

An 80:20 heliox mixture is 1.8 times more diffusible than oxygen. To correct for the difference in gas density, the indicated flow on the flowmeter is multiplied by 1.8. A 70:30 heliox mixture is 1.6 times more diffusible than oxygen. To obtain the accurate flow rate for this mixture, the indicated flow is multiplied by 1.6.

REF: p. 348 a. Close-fitting nonrebreathing mask b. Close-fitting partial rebreathing mask c. Nasal cannula d. High flow nasal cannula

16. The therapist is treating a very irritable young child with upper airway obstruction. Which oxygen device will be the most appropriate to administer the greatest concentration of helium?

ANS: A

Spontaneously breathing patients with upper or lower airway obstruction can be given heliox via mask. Because the goal of heliox therapy is to reduce the density of the inspired gas, it is important to deliver the greatest concentration of helium. Therefore, the patient must be able to tolerate the lowest possible fractional concentration of inspired oxygen (FiO2), and room air entrainment must be minimized, resulting in a higher fractional concentration of inspired helium (FiHe). Nasal cannulas (with the exception of high flow nasal cannulas) and simple masks allow far too much room air entrainment, thereby diluting the helium concentration. Therefore, a close-fitting nonrebreathing mask should be used. This limitation makes the treatment of young patients difficult. Children in distress may not tolerate the tightly fitting mask required to minimize air entrainment.

REF: p. 348 a. The FiHe is too low in a 70:30 mixture to change work of breathing in this infant. b. The flow going through the infant hood is inadequate. c. A greater concentration of helium is present at the top of the hood and away from the infant's nose and mouth. d. The infant is breathing too fast; thus heliox is not reaching the airways.

17. The therapist is evaluating a small tachypneic infant receiving heliox mixture 70:30 through an infant hood. Although the SpO2 has improved, the child shows signs of worsening work of breathing. What is the most probable mechanism to explain this situation?

ANS: D

Stillwell and colleagues investigated the use of heliox mixtures delivered through an infant hood. Not surprisingly, they found a greater concentration of helium at the top of the hood (due to its lower gas density), away from the infant's nose and mouth. This resulted in a lower FiHe and therefore a denser gas being delivered to the infant.

REF: p. 348 b. It will decrease. c. It will increase. d. It will increase only if the infant’s respiratory rate increases.

18. An infant on high-flow nasal cannula also requires administration of albuterol every 6 hours. The flow of the cannula was adjusted from 4 to 5 liters per minute. How could this affect the aerosol delivery to this infant? a. It will be unchanged.

ANS: C

Heliox has been shown to reduce turbulence and improve aerosol delivery in a range of clinical settings. Ari and colleagues assessed the effects of heliox on medication delivery by comparing with 100% oxygen while testing the infant, pediatric cannulas running at flows of 3 and 6 Lpm, and adult cannulas running at 10 and 30 Lpm. At higher flows they found that heliox increased aerosol deposition compared to oxygen. At lower flows there was less benefit from the use of heliox compared to oxygen in the pediatric and adult cannulas and no benefit for the infant.

REF: p. 348 a. To improve pulmonary compliance b. To reverse bronchospasm c. To minimize air trapping d. To facilitate the removal of tracheobronchial secretions

19. What is the potential benefit of adding heliox to patients who have status asthmaticus while undergoing mechanical ventilation?

ANS: C

The use of heliox mixtures has been advocated to minimize air trapping and hemodynamic compromise and to reduce peak inspiratory pressures.

REF: p. 348 a. PEEP b. Plateau pressure c. Peak pressure d. Volume

20. Which of the following parameters of mechanical ventilation are affected negatively by the use of heliox?

ANS: D

The primary obstacle to heliox delivery via a mechanical ventilator is error in volume and flow measurement. Many mechanical ventilators rely on gas density to measure flows and volumes. Most errors result from underestimation of flow due to the low-density characteristics of helium. Volume is typically a mathematical integration of flow and time; therefore, volumes will be equally affected.

REF: p. 348 a. Administer heliox through the heliox-approved inlet of the mechanical ventilator b. Add a 16-inch piece of corrugated tubing between the wye adapter and the place on the inspiratory limb where heliox is administered c. Reduce the liter flow on the heliox d. Adjust ventilator settings to compensate for the lower viscosity of heliox

21. The therapist is performing a routine assessment and ventilator check on a patient who is receiving heliox near the wye adapter of the ventilator circuit. He notices a serious discrepancy between the set tidal and the exhaled volume. What should the therapist do to correct this situation?

ANS: A

The safest method to deliver helium–oxygen mixtures via mechanical ventilation is to connect an 80/20 heliox mixture to the heliox-approved inlet of the mechanical ventilator. The practitioner then uses the ventilator's oxygen concentration control to adjust helium and oxygen to the desired mixture. This allows the practitioner to deliver a helium concentration up to the 80% helium. It is important to note that ventilators may not function properly with helium as a source gas.

REF: p. 348

22. A patient who has been admitted with status asthmaticus is receiving beta adrenergics every 2 hours and heliox with very limited response. What should the therapist suggest at this time? a. Change heliox to 100% helium b. Administer nitrogen c. Administer inhaled anesthetics d. Add iNO

ANS: C

Patients in status asthmaticus (SA) can be placed on helium–oxygen therapy as a temporizing measure to reduce the work of breathing until another therapy ( -agonists, methylxanthines, and corticosteroids) is effective. However, these patients frequently have bronchospasm that is refractory to conventional therapy. Certain volatile inhaled anesthetics are known for their bronchodilatory properties. Although no clinical trials have investigated the use of inhaled anesthetics (IAs) in the routine treatment of SA, several case reports exist.

REF: p. 349

23. Which of the following inhaled anesthetic gases has/have demonstrated the possibility to treat status asthmaticus?

I. Halothane

II. Thromboxane

III. IsofluraneIV. Sevoflurane a. II only b. I, II, and III only c. I, III, and IV only d. II, III, and IV only

ANS: C

Of the several inhaled anesthetics used clinically for anesthesia, only halothane, isoflurane, enflurane, and sevoflurane have been widely reported as potential treatments for status asthmaticus.

REF: p. 349 a. Isoflurane b. Enflurane c. Sevoflurane d. Halothane

24. Which of the following inhaled anesthetics should the therapist recommend to administer via a face mask to a conscious, spontaneously breathing pediatric patient who has status asthmaticus?

ANS: D

Halothane is the gas of choice when delivering an inhaled anesthetic agent to a conscious, spontaneously breathing patient. The dose range for halothane is approximately 0.25% to 0.5%. The patient usually is sufficiently awake to communicate in short sentences. Bronchodilation is usually rapid (15 to 20 min). The patient benefits by the reduced resistance as well as the sedative effect.

REF: p. 350

Chapter 19: Extracorporeal Life Support Test Bank

Multiple Choice

1. Which of the following groups of patients has the best overall survival when treated with ECMO?

a. Neonates with respiratory support b. Pediatric patients with cardiac support c. Neonates with cardiac support d. Pediatric patients with respiratory support

ANS: A

Neonates treated with ECMO for respiratory support have the best survival rates of all groups, up to 75%. See table 19-1 in the textbook.

REF: p. 355 a. Newborns do not have as a high risk for bleeding as other age groups. b. Newborns require less ECMO flows. c. Newborns have fewer side effects when treated with heparin drips. d. Most clinical conditions treated with ECMO in newborns are reversible.

2. What is the key reason for making ECMO so successful in newborns?

ANS: D

Over 26,000 newborns with respiratory failure have been reported in the ELSO Registry, which represents the bulk of the neonatal ECMO experience. This includes patients with the diagnosis of persistent pulmonary hypertension of the newborn (PPHN), meconium aspiration syndrome (MAS), respiratory distress syndrome (RDS), sepsis, and air leak syndromes. All of these are reversible conditions, which is a key element for positive outcomes when providing ECMO.

REF: p. 355 a. The FiO2 is not 100% yet. b. The is not high enough to justify ECMO. c. The OI does not meet ECMO criteria. d. The PaO2 is within normal limits.

3. A neonate on mechanical ventilation with respiratory distress has a PaO2 of 50 mm Hg, a of 20 cm H2O and FiO2 of 0.8. Why should the therapist suggest therapies other than ECMO?

ANS: C

Ortega and colleagues proposed the oxygenation index (OI), a calculation based on mean airway pressure (P), FiO2, and arterial oxygenation (PaO2), as follows:

OI = P (FiO2/ PaO2) 100. The authors found that when the OI exceeded 40 during conventional mechanical ventilation, the risk of mortality exceeded 80%. Their results have been reproduced by other institutions, and OI remains a widely accepted predictor of mortality in neonates with respiratory failure and is used as part of the selection criteria for using ECMO.

REF: p. 355 a. High-flow oxygen therapy b. Airway pressure release ventilation c. Heliox d. HFOV

4. Which of the following strategies is greatly responsible for decreasing the need for ECMO in neonates?

ANS: D

The introduction of high-frequency oscillatory ventilation (HFOV) decreased the need for ECMO and is a standard of care in the management of hypoxemic respiratory failure. Since HFOV utilizes higher mean airway pressure than CMV, an OI of 60 has been considered a more realistic threshold for identifying mortality risk and the need for ECMO when this form of ventilation is used.

REF: p. 355 a. Meconium aspiration b. Less than 2 kg of weight c. Prolonged mechanical ventilation (7 to 10 days) d. Less than 36 weeks of gestation

5. Which of the following conditions are considered contraindications for neonatal ECMO?

ANS: B

Typically the need for ECMO is identified within the first couple of days. The need for ECMO following a prolonged period of mechanical ventilation, such as 7 to 10 days, suggests atypical lung pathology that may not be reversible. Another consideration for deciding not to use ECMO is the patient’s size and gestational age. There are ECMO catheter size limitations for newborns less than 2 kg, and newborns less than 32 weeks gestation may be at greater risk for developing intracranial hemorrhage when exposed to anticoagulants.

REF: p. 356

6. Which of the following parameters have been suggested as indications for pediatric ECMO?

7.

I. PaO2 < 50 mm Hg

II. PaO2/FiO2 < 75

III. OI > 35

IV. Pre-ECMO pH < 7.20a. II, III and IV only b. I, II, and III only c. I, II, and IV only d. II and IV only

ANS: A

There is no definitive consensus on when ECMO should be initiated in pediatric respiratory failure. Single-center reviews have attempted to identify pre-ECMO factors that may help predict outcome. Mehta and colleagues suggested that an OI > 35 or a pre-ECMO pH of < 7.20 may result in higher mortality. In a case series by Turner and colleagues, it was suggested that there are no true contraindications to using ECMO in pediatric patients with refractory respiratory failure. They further commented that ECMO is appropriate if patients are transferred to an ECMO center early, if lung-protective ventilation is used, and when severe neurologic injury is not present. A PaO2/FiO2 ratio of < 200 mm Hg is one criteria used to identify patients with ARDS. In severe cases the PaO2/FiO2 ratio may be < 75 and mortality risk exceeds 80% a point when ECMO is considered.

REF: p. 356

Which of the following conditions are cardiac applications of ECMO?

I. ECPR

II. CDH

III. Fulminant myocarditisIV. Cardiomyopathy b. III and IV only c. I, III, and IV only d. I, II, III, and IV

ANS: D a. I and II only

The availability of ECMO is an important facet in the medical-surgical management of congenital heart disease (CHD). In the preoperative period, ECMO is used to augment cardiac output and support organ function until palliative or corrective surgery is undertaken. ECMO is also used in the postoperative period, particularly in complex CHD, as more challenging surgical repairs are attempted. ECMO has also been used during interventional procedures. Patients with cardiac muscle disease, such as fulminant myocarditis or cardiomyopathy, may have such poor heart function that the need for mechanical support with ECMO is necessary. Although other mechanical circulatory support devices would provide equivalent support, ECMO systems are more readily available and can be implemented in the ICU. When cardiac function fails to recover, ECMO becomes a key support device while heart transplantation options or other support devices are considered. The use of ECMO for cardiac support continues to grow, particularly as an aid to resuscitation, or ECMO during cardiopulmonary resuscitation, referred to as ECPR.

REF: p. 357 a. A cannula is inserted into the subclavian vein for the removal of blood. b. Blood is removed from the venous circulation through the external jugular vein. c. Blood returns to the heart through the subclavian artery. d. A cannula is inserted into the right common carotid artery for arterial return.

8. Which of the following statements describes venoarterial ECMO?

ANS: D

ECMO support begins by accessing the vasculature in order to establish drainage and reinfusion sites. In newborns and infants, perfusion cannulas are surgically placed in a vein, commonly the right-internal jugular, and an artery, usually the right common carotid. This is the classic venoarterial (VA) configuration in which deoxygenated venous blood is drained from the patient and blood that is fully saturated with oxygen is artificially pumped and returned to the arterial system (refer to Figure 19-1A in the textbook).

REF: p. 357 b. Recirculation is excessive. c. Native cardiac output has increased. d. iNO is being administered concomitantly.

9. During administration of venovenous ECMO, the therapist notices that the SvO2 is greater than SaO2. What is the best explanation to this phenomenon? a. The blood flow through the pump is too slow.

ANS: C

If SO2 is greater than SaO2, the recirculation is excessive, which would require either an adjustment in cannula position or change in blood flow rate.

REF: p. 358 a. An increase in cardiac output will have a significant effect on the patient’s oxygenation. b. A decrease in cardiac output will have a major impact on the patient’s oxygenation. c. Changes in cardiac output either way will have little influence on the patient’s oxygenation. d. The influence of alterations in cardiac output on the patient’s oxygenation cannot be predicted.

10. During venovenous ECMO, what effect does the cardiac output have on oxygenation?

ANS: C

VV ECMO does not provide the same level of oxygenation as VA, and the maximal SaO2 achievable can be as low as 85% until lung function improves. Because VV ECMO is essentially operating in series with the native circulation, alterations in cardiac output will not have a significant effect on oxygenation. The volume of blood removed is equal to the volume reinfused, so there is also no effect on the patient's hemodynamics.

REF: p. 358 a. Pulsatile flow in maintained. b. Cardiovascular support is uninvolved. c. It is less expensive than VA ECMO. d. The internal jugular vein is not cannulated twice.

11. What are the major advantages of venovenous ECMO?

ANS: B

One advantage of VV support is that carotid artery ligation is not required, full pulsatile native blood flow is maintained, and the potential for air or particulate emboli from the circuit is less. A disadvantage is the lack of cardiovascular support. However, the presence of mild to moderate myocardial dysfunction should not discourage the use of the VV approach because the improved oxygenation and lower airway pressures achieved with implementation of VV ECMO often improve cardiac function.

REF: p. 358

12. Which of the following mechanisms affect the output of VV ECMO?

I. Size of the tubing

II. The rotations per minute

III. Tension of the rollers

IV. Blood pressure a. I. II, and III only b. I and IV only c. II, III, and IV only d. I, II, III, and IV

ANS: A

The output depends on the size of the tubing, the rotations per minute (RPMs), and the tension or occlusion of the rollers on the raceway.

REF: p. 359 a. Inadequate flow b. Increased bladder tension c. Hemolysis d. Recirculation

13. The therapist should evaluate raceway occlusion because too much roller tension could be associated with which of the following events?

ANS: C

Evaluating raceway occlusion is essential: too much roller tension (overoccluded) may cause tubing damage and hemolysis, and too little roller tension (underoccluded) may result in inadequate flow.

REF: p. 359 a. It avoids placing increased pressures on the heart. b. It eliminates lowering pulmonary vascular pressures. c. It maintains regulated flow through the system. d. It ensures that the blood flows smoothly through the membrane oxygenator.

14. What is the advantage of having the centrifugal pump automatically respond to resistances against which it is pumping?

ANS: C

Centrifugal pumps are nonocclusive devices because energy is transferred to the blood by a rapidly rotating cone-shaped pump head that creates a constrained vortex. Blood is actively pulled inward and propelled outward by the energy created by the vortex, thus drainage is considered active. Because this type of pump is nonocclusive is it dependent on the patient’s preload and afterload. As preload decreases, such as decreased venous drainage, or if afterload increases due to increased systemic vascular resistance, flow will decrease.

REF: p. 360

15. In the gas membrane exchanger, what is one of the limiting factors to the transfer rate of oxygen across the membrane? a. The flow of blood b. The concentration gradient of the gas across the membrane c. The thickness of the blood film between the membrane layers d. The flow of gas in relationship to the flow of blood

ANS: C

The transfer rate of O2 is limited by the thickness of the blood film between the membrane layers. As the blood film becomes thicker, the oxygenating efficiency decreases.

REF: p. 361

16. Because the minimum flow rate required to remove condensation in the gas compartment usually results in excessive elimination of carbon dioxide, what should the therapist do? a. Reduce pump flow b. Blend sweep gas with a carbogen mixture c. Reduce the amount of oxygen blended in the sweep gas d. Add more oxygen to the sweep gas

ANS: B

Because the minimum flow rate required to remove condensation usually results in excessive elimination of carbon dioxide, sweep gas is often blended with a carbogen mixture, which reduces the driving pressure across the membrane and maintains normocarbia.

REF: p. 364

17. What are the most common causes of a decrease in venous return in ECMO?

I. Hypovolemic state

II. Malpositioning of the venous cannula

III. Kinking of the cannulaIV. Shifting of the mediastinum a. I and III only b. II and III only c. I, II, and III only d. I, II, III, and IV

ANS: D

The most common causes of a decrease in venous return include malpositioning of the venous cannula, kinking of the cannula, shifting of the mediastinum, or a hypovolemic state.

REF: p. 362 a. Add either colloids or crystalloids to fluid challenge the patient. b. Perform hemofiltration. c. Add either vasodilators or vasoconstrictors d. Conduct plasmapheresis.

18. It is not uncommon for patients undergoing ECMO to experience renal failure. What can be done to enhance renal function?

ANS: B

It is not uncommon for patients requiring ECMO to develop renal insufficiency from preECMO fluid resuscitation, acute renal dysfunction, and blood product replacement. To augment renal function and remove larger quantities of fluid, a semipermeable membrane or hemofilter can be added to the ECMO circuit.

REF: p. 363

19. The ECMO specialist has noticed excessive clotting in the circuit despite increase doses of heparin. What is the most feasible explanation for this event? a. Too many platelet transfusions b. Defective heparin c. Blood flow too slow d. Deficiency of ATIII

ANS: D

If excessive clotting in the circuit is noted, a deficiency in ATIII is a possible cause. Heparin has no direct anticoagulant effect on the blood by itself but combines with a cofactor, antithrombin III (ATIII), to prevent thrombi from forming. This stops the conversion of fibrinogen to fibrin and ultimately prevents blood from clotting. A deficiency in ATIII can cause heparin to be ineffective, resulting in use of excessive amounts of heparin.

REF: p. 363 b. Increase the heparin dose. c. Add plasminogen. d. Increase blood flow to decrease contact time.

20. The therapist in charge of a patient on ECMO is monitoring ACT every 30 minutes. The last ACT was 100 seconds. What should the therapist suggest at this time? a. Decrease the amount of platelets transfused.

ANS: B

The classic method for monitoring anticoagulation is to measure the activated clotting time (ACT) with a point-of-care device. The heparin dose is titrated to achieve an ACT range of typically 160 to 180 seconds.

REF: p. 363

21. The therapist in charge of a patient on ECMO has noticed an increase in premembrane pressures. What is the most probable explanation? a. Very high pump flow b. Clotting in the circuit c. Damage of the raceway d. Excessive sweep flow

ANS: B

As circuit or membrane resistance changes, as is common with clot formation, the pressures will change. As an example, a membrane that has been in use for a fairly prolonged duration will tend to develop clot and increased resistance, which would be identified by an increase in premembrane pressure.

REF: p. 363 a. Narrowing of the premembrane and postmembrane PaCO2 b. Widening of the premembrane and postmembrane PaO2 c. Presence of large clots in the circuit d. Presence of air bubbles

22. How can membrane malfunction be suspected?

ANS: A

Membrane function is also evaluated by periodically measuring premembrane and postmembrane blood gases. Gas exchange across the membrane may become less efficient over prolonged ECMO duration, which may be diagnosed by changes in the pre-and postblood gas values. For instance a narrower premembrane and postmembrane PaCO2 gradient is suggestive of a decrease in CO2 elimination.

REF: p. 363

23. Which of the following ventilator settings are typically used in ECMO for respiratory support?

I. Vt 5-7 ml/kg

II. PIP 25-25 cm H2O

III. PEEP 2-3 cm H2O IV. Frequency 10-12 a. I and III only b. II and III only c. I, II, and IV only d. I, II, III, and IV

ANS: C

The patient requiring ECMO primarily for a cardiac reason is not likely to have significant pulmonary issues, in which case the ventilator strategy is to maintain lung function near normal. In this scenario the ECMO ventilator settings are minimized to achieve a tidal volume of around 5 to 7 mL/kg and PEEP to maintain sufficient end-expiratory lung volume typical settings would be PCV-SIMV, 10-12 breaths/min, PIP/PEEP 25-27 / 5-7 cm H2O.

REF: p. 365 a. 100 mL/Kg b. 80 ml/kg c. 50 mL/Kg d. 30 mL/Kg

24. What is the ECMO flow considered as minimal support?

ANS: D

Once ECMO flow rates are weaned to around 20 to 30 mL/kg ECMO, support is considered minimal. At this point if reasonable ventilator settings result in adequate gas exchange, the patient is isolated from the ECMO circuit.

REF: p. 366 a. Disseminated intravascular coagulopathy b. Pneumonia c. Intracranial hemorrhage d. Hemosiderosis

25. What is considered the most concerning complication of ECMO in the newborn?

ANS: C

The most concerning patient complication that can occur, particularly in the newborn, is an intracranial hemorrhage (ICH).

REF: p. 367