Po2 In Area With Bronchial Obstruction

Directions: Each of the numbered items or incomplete statements in this section is followed by answers or by completions of the statement. Select the ONE lettered answer or completion that is BEST in each case.

1. Which of the following lung volumes or capacities can be measured by spirometry?

(A) Functional residual capacity (FRC)

(B) Physiologic dead space

(C) Residual volume (RV)

(D) Total lung capacity (TLC)

2. An infant born prematurely in gestational week 25 has neonatal respiratory distress syndrome. Which of the following would be expected in this infant?

(A) Arterial Po2 of 100 mm Hg

(B) Collapse of the small alveoli

(C) Increased lung compliance

(D) Normal breathing rate

(E) Lecithinrsphingomyelin ratio of less than 2:1 in amniotic fluid

3. In which vascular bed does hypoxia cause vasoconstriction?

(A) Coronary

(B) Pulmonary

(C) Cerebral

(D) Muscle

Questions 4 and 5

A 12-year-old boy has a severe asthmatic attack with wheezing. He experiences rapid breathing and becomes cyanotic. His arterial Po2 is 60 mm Hg and his Pco2 is 30 mm Hg.

4. Which of the following statements about this patient is most likely to be true?

(A) Forced expiratory volume/forced vital capacity (FEVi/FVC) is increased

(B) Ventilation/perfusion (V/Q) ratio is increased in the affected areas of his lungs

(C) His arterial Pco2 is higher than normal because of inadequate gas exchange

(D) His arterial Pco2 is lower than normal because hypoxemia is causing him to hyperventilate

(E) His residual volume (RV) is decreased

5. To treat this patient, the physician should administer

(A) an a-adrenergic antagonist

(B) a fSradrenergic antagonist

(C) a p2-adrenergic agonist

(D) a muscarinic agonist

(E) a nicotinic agonist

6. Which of the following is true during inspiration?

(A) Intrapleural pressure is positive

(B) The volume in the lungs is less than the functional residual capacity (FRC)

(C) Alveolar pressure equals atmospheric pressure

(D) Alveolar pressure is higher than atmospheric pressure

(E) Intrapleural pressure is more negative than it is during expiration

7. Which of the following will occur as a result of residing at high altitude?

(A) Hypoventilation

(B) Arterial Po2 greater than 100 mm Hg

(C) Decreased 2,3-diphosphoglycerate (DPG) concentration

(D) Shift to the right of the hemoglobin-02 dissociation curve

(E) Pulmonary vasodilation

(F) Hypertrophy of the left ventricle

(G) Respiratory acidosis

8. A person has a vital capacity (VC) of 5 L, a tidal volume (TV) of 0.5 L, an inspiratory capacity of 3.5 L, a functional residual capacity (FRC) of 2.5 L, and a residual volume (RV) of 1.1 L. What is his expiratory reserve volume (ERV)?

9. When a person is standing, blood flow in the lungs is

(A) equal at the apex and the base

(B) highest at the apex owing to the effects of gravity on arterial pressure

(C) highest at the base because that is where the difference between arterial and venous pressure is greatest

(D) lowest at the base because that is where alveolar pressure is greater than arterial pressure

10. Which of the following is illustrated in the graph showing volume versus pressure in the lung-chest wall system?

Airway Pressure Overcome Trachea
Airway pressure

(A) The slope of each of the curves is resistance

(B) The compliance of the lungs alone is less than the compliance of the lungs plus chest wall

(C) The compliance of the chest wall alone is less than the compliance of the lungs plus chest wall

(D) When airway pressure is zero (atmospheric), the volume in the lungs plus chest wall is the functional residual capacity (FRC)

(E) When airway pressure is zero (atmospheric), intrapleural pressure is zero

11. Which of the following is the site of highest airway resistance?

(A) Trachea

(B) Largest bronchi

(C) Medium-sized bronchi

(D) Smallest bronchi

(E) Alveoli

12. If blood flow to the left lung is completely blocked by an embolism in the pulmonary artery, which of the following will occur?

(A) Ventilation/perfusion (V/Q) ratio in the left lung will be zero

(B) Systemic arterial Po2 will be elevated

(C) V/Q ratio in the left lung will be lower than in the right lung

(D) Alveolar Po2 in the left lung will be approximately equal to the Po2 in inspired air

(E) Alveolar Po2 in the right lung will be approximately equal to the Po2 in venous blood

Questions 13 and 14

Po2 (mm Hg)

13. In the hemoglobin-02 dissociation curves shown above, the shift from curve A to curve B could be caused by

(A) increased pH

(B) decreased 2,3-diphosphoglycerate (DPG) concentration

(C) strenuous exercise

(D) fetal hemoglobin (HbF)

(E) carbon monoxide (CO)

14. The shift from curve A to curve B is associated with

(A) increased P50

(B) increased affinity of hemoglobin for 02

(C) impaired ability to unload 02 in the tissues

(D) increased 02-carrying capacity of hemoglobin

(E) decreased 02-carrying capacity of hemoglobin

15. The pH of venous blood is only slightly more acid than the pH of arterial blood because

(B) there is no carbonic anhydrase in venous blood

(C) the H+ generated from C02 and H20 is buffered by HCO:; in venous blood

(D) the H+ generated from C02 and H20 is buffered by deoxyhemoglobin in venous blood

(E) oxyhemoglobin is a better buffer for H+ than is deoxyhemoglobin

16. Compared with the systemic circulation, the pulmonary circulation has a

(A) higher blood flow

(B) lower resistance

(C) higher arterial pressure

(D) higher capillary pressure

(E) higher cardiac output

17. A person with a tidal volume (TV) of 0.45 L has a breathing frequency of 16 breaths/min. His arterial Pco2 is 41 mm Hg, and the Pco2 of his expired air is 35 mm Hg. What is his alveolar ventilation?

18. Compared with the apex of the lung, the base of the lung has

(A) a higher pulmonary capillary Po2

(B) a higher pulmonary capillary Pco2

(C) a higher ventilation/perfusion (V/Q) ratio

19. Hypoxemia produces hyperventilation by a direct effect on the

(A) phrenic nerve

(B) J receptors

(C) lung stretch receptors

(D) medullary chemoreceptors

(E) carotid and aortic body chemoreceptors

20. Which of the following changes occurs during strenuous exercise?

(A) Ventilation rate and 02 consumption increase to the same extent

(B) Systemic arterial Po2 decreases to about 70 mm Hg

(C) Systemic arterial Pco2 increases to about 60 mm Hg

(D) Systemic venous Pco2 decreases to about 20 mm Hg

(E) Pulmonary blood flow decreases

21. If an area of the lung is not ventilated because of bronchial obstruction, the pulmonary capillary blood serving that area will have a Po2 that is

(A) equal to atmospheric Po2

(B) equal to mixed venous Po2

(C) equal to normal systemic arterial Po2

(D) higher than inspired Po2

(E) lower than mixed venous Po2

22. In the transport of C02 from the tissues to the lungs, which of the following occurs in venous blood?

(A) Conversion of C02 and H20 to H+ and HCO;i-in the red blood cells (RBCs)

(B) Buffering of H+ by oxyhemoglobin

(C) Shifting of HCOf into the RBCs from plasma in exchange for Cl~

(D) Binding of HC03~ to hemoglobin

(E) Alkalinization of the RBCs

Directions: Each set of matching questions in this section consists of a list of four to twenty-six lettered options (some of which may be in figures) followed by several numbered items. For each numbered item, select the ONE lettered option that is most closely associated with it. To avoid spending too much time on matching sets with large numbers of options, it is generally advisable to begin each set by reading the list of options. Then, for each item in the set, try to generate the correct answer and locate it in the option list, rather than evaluating each option individually. Each lettered option may be selected once, more than once, or not at all.

Questions 23 and 24

(C) Expiratory reserve volume (ERV)

(D) Residual volume (RV)

(E) Functional residual capacity (FRC)

Match each numbered description to the correct lung volume or capacity.

23. Volume remaining in the lungs after a TV is expired

24. Volume remaining in the lungs after a maximal expiration

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