Hall: Guyton and Hall Textbook of Medical Physiology, 12th Edition
Chapter 39: Physical Principles of Gas Exchange; Diffusion of Oxygen and Carbon
Dioxide Through the Respiratory Membrane
Test Bank
1. A child has been eating M&Ms (plain) and inhaled one down his airway, blocking his left
bronchiole. Which of the following will describe the changes that occur?
Left Lung Alveolar pCO2 Left Lung Alveolar pO2 Systemic Arterial pO2
A.
B.
C.
D.
E.
2. If alveolar pO2 is 300 mmHg and alveolar pCO2 is 40 mmHg, what is the piO2
(humidified inspired pO2)?
A. 250 mmHg
B. 300 mmHg
C. 350 mmHg
D. 400 mmHg
E. 760 mmHg
3. Match the following with the letter indicating the most appropriate ANS: pO2 = 116
mmHg, pCO2 = 27 mmHg.
A. Atmospheric air
B. Alveolar air
C. Blood in the left heart
D. Blood in the right heart
E. Expired air
4. Twin patients, X and Y, both have respirations of 12/min, tidal volumes of 500 mL, and
dead space of 100 mL. Patient X decreases the respiratory rate by half, and doubles the
tidal volume. Patient Y doubles the respiratory rate and cuts the tidal volume in half.
After two minutes, what conditions would best describe their alveolar gases, as compared
to normal.
Patient X Alveolar ventilation
Patient Y Alveolar ventilation
Alveolar pO2 Alveolar pCO2 Alveolar pO2 Alveolar pCO2
Test Bank
39-2
A.
B.
C.
D.
E.
5. In an individual, the pO2 and pCO2 in different alveoli varies as follows:
pO2
pCO2
Alveolus A
100
40
Alveolus B
40
45
Alveolus C
150
0
Which of the following statements is true?
A. Alveolus B is indicative of a dead space ventilation
B. Alveolus C is indicative of pulmonary shunt
C. Breathing 100% O2 would increase PO2 in alveolus C
D. Hyperventilation would increase PO2 in alveolus B
6. A person with normal lungs at sea level (760 mmHg) is breathing 50% oxygen. What is
the approximate alveolar pO2?
A. 100
B. 159
C. 310
D. 330
E. 380
7. If a lung having a normal ventilation-perfusion ratio (=1) SUDDENLY develops
ventilation-perfusion ratio <1, which of the following will occur?
A. A decrease in arterial pO2
B. An increase in alveolar pO2
C. A decrease in cardiac output
D. A decrease in arterial pCO2
8. A 16-year-old girl is found unconscious in the street. She has no visible injuries and is
taking shallow breaths of 6-8/min. An arterial blood gas shows a pO2 of 55 mmHg and
her pCO2 is 75 mmHg. The cause of the hypoxemia is:
A. Low V/Q ratio
B. Intrapulmonary shunt
C. Increased dead space ventilation
Test Bank
39-3
D. Alveolar hypoventilation
E. Elevated V/Q ratio
ANS: D
Questions 9-11: Consider a patient with an anatomical dead space of 100 mL, a normal
respiratory rate of 12 breaths per minute and a normal tidal volume of 600 mL under resting
conditions. Match each of the conditions in questions 9-11 with the correct set of respiratory
rate, tidal volume, and metabolic changes. Answers may be used more than once.
Respiratory Rate Tidal Volume Metabolic Rate
A. 6 1,100 normal
B. 24 500 normal
C. 16 400 4 times normal
9. Systemic arterial pO2 >120 mmHg.
10. Systemic arterial PO2 of approximately 100 mmHg.
11. Systemic arterial pCO2 > normal.
12. Perfusion of capillaries without ventilation of an alveolus:
A. Results in an decrease in alveolar pO2
B. Results in an increase in systemic arterial pO2
C. Results in an increase in alveolar pCO2
D. Results in a increase in systemic arterial pCO2
13. For a patient at sea level (barometric pressure = 760 mmHg) and breathing 40%, oxygen
calculate alveolar pO2 is:
A. 149
B. 159
C. 235
D. 285
E. 304
14. While lying supine in bed eating, a child aspirates a peanut into the left lung. What would
be the V/Q ratio in the left Lung?
A. 0
B. 0.8
C. ∞