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Chapter 5. Pulmonary Physiology

A 50-year-old man with a persistent cough and difficulty breathing is referred by his family physician for pulmonary function tests. The test results show that the forced vital capacity (FVC), forced expired volume in 1 s (FEV1), and functional residual capacity (FRC) are all significantly below normal. Which of the following diagnosis is consistent with these pulmonary function test results?

A Asthma

B Chronic bronchitis

C Emphysema

D Pulmonary fibrosis

D. FVC and FEV1 are expected to be reduced in all these conditions. The coexistence of low FRC indicates reduced resting lung volume and is consistent with the low static lung compliance found in patients with pulmonary fibrosis.

A 19-year-old man is taken to the emergency department after being stabbed in the right side of the chest. The entry of air through the wound resulted in a pneumo­thorax on the right side of his chest. What difference between the right and left sides of the chest would be apparent on a plain chest x-ray?

A The lung volume on the right would be larger

B The position of the diaphragm on the right would be higher

C The thoracic volume on the right would be larger

D There would be no differences in thoracic geometry

C. A pneumothorax interrupts the pleural fluid between the lung and chest wall, allowing each structure to assume its equilibrium position. Therefore, the lung collapses to a small volume and the chest wall expands; the diaphragm is part of the chest wall and also moves outward (i.e., flattens to a lower position compared to the unaffected side).

A 28-year-old man is involved in a high speed motor vehicle accident in which he suffers multiple rib fractures. On arrival at the emergency department, he is conscious but in severe pain. His respiratory rate is 34 breaths/min, and his breathing is labored. His blood pressure is 110/95 mm Hg, and his pulse is 140 beats/min. His arterial Po2 is 50 mm Hg, and he is unresponsive to supplemental O2. His arterial Pco2 is 28 mm Hg. What is the most likely cause of this patient's hypoxemia?

A Alveolar hypoventilation

B High ventilation/perfusion (image/image) ratio

C Increased dead space ventilation


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