Chapter 4: Ventilation Test Bank MULTIPLE CHOICE

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Luke Melton
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1 Instant download and all chapters Test Bank Respiratory Care Anatomy and Physiology Foundations for Clinical Practice 3rd Edition Will Beachey Chapter 4: Ventilation Test Bank MULTIPLE CHOICE 1. What is the partial pressure of oxygen in atmospheric air? c. 47 mm Hg ANS: B Because oxygen constitutes 20.93% of dry atmospheric air, its partial pressure (PO 2 ) at sea level is as follows: PO 2 = mm Hg = 159 mm Hg 2. What is the partial pressure of carbon dioxide in atmospheric air? c. 47 mm Hg The partial pressure of carbon dioxide (PCO 2 ) is calculated as follows:pco 2 = mm Hg = mm Hg 3. What is the partial pressure of water vapor at 37 C and 100% relative humidity (RH)? c. 47 mm Hg Because the body maintains lung temperature and RH at 37 C and 100%, respectively, the P H2O of gas in the lung is constant; under these temperature and humidity conditions P H2O is always 47 mm Hg. 4. What is the partial pressure of oxygen in the lung s airways?

2 c. 47 mm Hg To calculate P gas in the lung or blood, 47 mm Hg must first be subtracted from P B. In the lung s airways, PO 2 is calculated as follows: PO 2 = (760 47) mm Hg = 149 mm Hg 5. V E is the product of which of the following parameters? a. V T and V C b. V D and f c. V T and f d. V D and V T Regardless of the measuring method, V E is the product of V T and breathing frequency (f) per minute (V E = V T f). For example, if V T is 500 ml and breathing frequency is 12 breaths per minute, V E is calculated as follows: V E = 500 ml 12/minV E = 6000 ml/min or 6.0 L/minV E is easy to measure but is not extremely useful in evaluating the amount of ventilation that participates in respiration at the alveolar level. DIF: Recall REF: Which of the following terms defines the conducting airways from the mouth and nose down to and including terminal bronchioles? a. Physiological dead space b. Anatomical dead space c. Anatomical tidal volume d. Gas exchange units ANS: B The conducting airways from the mouth and nose down to and including terminal bronchioles constitute the anatomical dead space (V Danat ). DIF: Recall REF: Which of the following are characteristics of the anatomical dead space? I. It changes when a part of a lung is surgically removed. II. It increases when an artificial airway bypasses the upper airway. III. It increases during deep inspiration. IV. It increases with emphysema. a. I, IV b. II, III, IV c. I, II, III, IV d. II, IV

3 The volume in the conducting airways (V Danat ) does not change unless surgery removes part of a lung or unless an artificial airway (endotracheal or tracheostomy tube) bypasses the upper airway dead space. Anatomical dead space increases somewhat during a deep inspiration and with drugs that relax smooth airway muscle because these factors increase the airway diameter. Diseases characterized by hyperinflation of the lungs (e.g., emphysema) increase V Danat for the same reason. For clinical monitoring purposes, V Danat volume is considered to be constant. DIF: Application REF: What is the approximate amount of anatomical dead space in normal adults? a. 1 ml/pound IBW b. 2 ml/pound IBW c. 3 ml/pound IBW d. 4 ml/pound IBW V Danat is related to lung size; in normal adults, anatomical dead space is approximately 1 ml per pound of ideal body weight. DIF: Recall REF: Which technique allows a more precise measurement of V Danat? a. Dubowitz b. Ballard s c. Boyle s d. Fowler The Fowler technique provides a more precise measurement of V Danat. DIF: Recall REF: Which of the following gases is utilized in the measurement of V Danat? a. Carbon dioxide b. Oxygen c. Nitrogen d. Carbogen V Danat is the volume exhaled that results from the sharp rise in N 2 %. DIF: Recall REF: Which of the following determine the PCO 2 of alveolar gas and thus the PCO 2 of the blood leaving the lung? I. Metabolic CO 2 production per minute II. V A III. CO 2 rate of elimination IV. ph a. I, II, III b. II, III

4 c. I, II, III, IV d. II, III, IV The balance between metabolic CO 2 production per minute (V CO2 ) and its rate of elimination (V A ) determines the PCO 2 of alveolar gas and thus the PCO 2 of the blood leaving the lung. DIF: Application REF: Which of the following terms describes the rise in P a CO 2 above normal? a. Normal ventilation b. Hypocapnia c. Hypercapnia d. Acidosis If PaCO 2 is above normal (hypercapnia), hypoventilation exists. DIF: Recall REF: If a V A of 5 L/min produces a P A CO 2 of 40 mm Hg, a V A of 10 L/min will produce what level of P A CO 2? a. 80 mm Hg b. 40 mm Hg c. 20 mm Hg d. 10 mm Hg P A CO 2 is inversely related to V A ; if V A is reduced by half, P A CO 2 doubles. If V A doubles, P A CO 2 (and P a CO 2 ) is reduced by half. For example, if a V A of 5 L/min produces a P A CO 2 of 40 mm Hg, a V A of 10 L/min produces a P A CO 2 of 20 mm Hg. DIF: Analysis REF: What is the amount of CO 2 produced under normal resting conditions? a. 50 ml b. 100 ml c. 150 ml d. 200 ml Under normal resting conditions, the body produces approximately 200 ml of CO 2 each minute and alveolar ventilation is approximately 4 L/min. DIF: Recall REF: Normally, approximately what percentage of the inspired V T remains in conducting airways, never reaching alveoli? a. 5% to 10% b. 15% to 20% c. 20% to 30% d. 30% to 40%

5 Normally, approximately 30% to 40 % of the inspired V T remains in conducting airways, never reaching alveoli. DIF: Recall REF: Normally, approximately what percentage of the V E is dead-space ventilation? a. 5% to 10% b. 15% to 20% c. 20% to 30% d. 30% to 40% Dead-space ventilation constitutes approximately 30% to 40% of the V E. DIF: Recall REF: If a patient has a tidal volume of 450 ml, what is the approximate alveolar volume? a. 100 ml b. 150 ml c. 200 ml d. 300 ml For example, if a normal 150 lb adult has a V T of 500 ml and V D /V T equals 0.33, then 33% of the V T is dead space; the remaining 67% of the V T must be alveolar volume. DIF: Analysis REF: What happens to anatomical dead space if a patient is mechanically ventilated through a tracheostomy tube? a. It is reduced. b. It is increased. c. It is unchanged if the cuff is inflated. d. It is unchanged if fenestration has been done. Placing a tracheostomy tube in the trachea below the larynx reduces the anatomical dead space because it bypasses all upper airways. Thus, for a given tidal volume, the alveoli would receive more ventilation than if the patient breathed normally through the upper airways. Endotracheal intubation also reduces anatomical dead space because the volume of the tube is much less than the volume of the upper airways. DIF: Application REF: A 55-year-old woman is admitted to the hospital in obvious respiratory distress. Her increased rate and depth of breathing have raised her minute ventilation from 10 to 15 L/min. Arterial blood gases show a normal P a CO 2 of 40 mm Hg. It seems odd that this woman, with a minute ventilation this great, has a normal P a CO 2. What is the explanation for this? a. There is an increase in alveolar ventilation. b. This change in minute ventilation has little impact on the P a CO 2 ; therefore, P a CO 2 is

6 normal. c. This patient s dead space has decreased. d. A normal P a CO 2 associated with high minute ventilation indicates that much of this patient s ventilation is not in contact with blood flow. A normal P a CO 2 associated with high minute ventilation indicates that much of this patient s ventilation is not in contact with blood flow. Dead space is the term used to describe alveoli that have normal ventilation but no blood flow (perfusion) through their capillaries. Any factor that decreases perfusion increases alveolar dead space. Increased alveolar dead space decreases alveolar ventilation if minute ventilation stays the same. Pulmonary embolism (obstruction of pulmonary vessels by blood clots) and shock (decreased cardiac output and low perfusion) are conditions that cause increased alveolar dead space. The V D /V T ratio increases as a larger percentage of the V T becomes dead space. In conditions producing dead space, the body tries to maintain a normal P a CO 2 by increasing the V E. This increased minute ventilation does not necessarily mean alveolar ventilation increases because much of the minute ventilation is directed to dead space units. Thus a physiological consequence of increased dead space is the increased work of breathing required to maintain a normal P a CO 2. DIF: Application REF: The end-tidal PCO 2 is a reflection of which of the following? a. Mixed-expired PCO 2 b. Mixed-inspired PCO 2 c. Alveolar gas composition d. Arterial gas composition It is important to understand that end-tidal PCO 2 reflects alveolar gas composition and therefore is not equal to mixed-expired PCO 2, which reflects the composition of a mixture of dead space and alveolar gases (i.e., P ET CO 2 PCO 2 ). DIF: Recall REF: Which of the following breathing patterns is a common signal of respiratory distress and possible ventilatory failure? a. Rapid, shallow breathing b. Tachypnea c. Bradypnea d. Dyspnea Rapid, shallow breathing is a common signal of respiratory distress and possible ventilatory failure. DIF: Application REF: Which of the following breathing patterns is the most efficient in improving alveolar ventilation? a. Rapid, shallow breathing b. Rapid, deep breathing

7 c. Slow, deep breathing d. Slow, shallow breathing Rapid, shallow breathing is a common sign of respiratory distress and possible ventilatory failure. DIF: Application REF: Gas exchange can be maintained with tidal volumes smaller than dead space and high frequencies. What type of ventilation can accomplish this? a. Rapid, shallow, spontaneous breathing b. High-frequency ventilation c. Hyperventilation d. Dead space ventilation ANS: B Whatever the physical principles involved, HFV can maintain adequate gas exchange with extremely small volumes and rapid breathing rates. DIF: Recall REF: 93

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