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Chapter 7. Pulmonary Circulation and Capillary Fluid Dynamics

A 61-year-old man presents with shortness of breath. His temperature and other vital signs are normal. The patient has a long history of aortic valvular insufficiency. His spouse reports that the patient takes all prescribed medications regularly. He has never smoked and denies any history of lung disease, but pulmonary function testing now shows an obstructive pattern. A new chest radiograph shows an enlarged heart and evidence of bilateral pulmonary edema. What mechanism most likely accounts for the airway obstruction in this patient?

a. Increased cardiac dimensions

b. Previously undiagnosed pneumonia

c. Excessive mucus production

d. Loss of elastin from upper airways

e. Bronchial and bronchiolar edema

The most correct answer is e.

The man’s aortic insufficiency has worsened to now distend the left atrium and pulmonary veins, and initiate cardiogenic edema that increases airway resistance. Because he does not smoke, is not febrile, and his sputum production is not remarkable, he likely does not have pneumonia (answers b and c) or emphysema (answer d). Increased cardiac dimensions (answer a) are more common in patients with congestive heart failure secondary to systemic hypertension; in any case such cardiomegaly would rarely reduce the diameters of conducting airways directly.

A group of sixth-graders who all play on the same soccer team gather on the playground to judge by acclamation who is likely to be the best swimmer when they attend summer camp in a week. All agree to pinch their nostrils closed, take a deep breath at the same instant, and then hold it as long as possible. One child collapses to the ground within 15 seconds, immediately attracting the attention of a nearby teacher and scattering the rest of the children. What primary physiological effect best explains what occurred in the child who has apparently fainted?

a. Undiagnosed PDA

b. Grand mal epileptic seizure

c. Acute asthma attack

d. Cerebral anoxia or ischemia

e. Unilateral pneumothorax

The most correct answer is d.

The single most consistent effect of a forced breath hold begun at or near total lung capacity is an acute increase in PAW that will create global Zone 1 conditions throughout the respiratory parenchyma. The resulting rapid fall in pulmonary perfusion, and thus in venous return to the left ventricle, invariably reduces aortic blood flow. The appropriate autonomic response to ...

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