Respiratory System MCAT Practice Question
A 28-year-old woman is admitted to the ICU with severe pneumonia complicated by acute respiratory distress syndrome (ARDS). Chest X-ray shows bilateral infiltrates, and she requires mechanical ventilation with increasing FiO2 requirements. Bronchoalveolar lavage fluid analysis shows markedly decreased surfactant levels and impaired surfactant function. Which of the following best explains the primary pathophysiologic consequence of surfactant depletion in this patient's lungs?
Answer choices
- AIncreased surface tension at the air-liquid interface, requiring greater transpulmonary pressure gradients to open and maintain alveolar inflationCorrect answer
- BDecreased surface tension causing unopposed elastic recoil and spontaneous alveolar collapse during expiration
- CReduced alveolar elastance leading to air trapping and hyperinflation of distal lung units
- DIncreased pulmonary capillary hydrostatic pressure causing hydrostatic pulmonary edema and alveolar flooding
- EDecreased mucus clearance in the airways promoting bacterial colonization and progressive infection
- FImpaired type II pneumocyte regeneration preventing restoration of the epithelial barrier
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