Bacteriology USMLE Step 1 Practice Question
A 1-day-old male infant born at 26 weeks' gestation via spontaneous vaginal delivery presents with progressive respiratory distress. Vital signs show respiratory rate 52/min, heart rate 165/min, temperature 36.8°C, and blood pressure 50/28 mmHg. Physical examination reveals intercostal and subcostal retractions, nasal flaring, and cyanosis that improves minimally with supplemental oxygen. Breath sounds are diminished bilaterally. Chest radiograph demonstrates bilateral reticular-granular opacification with an air bronchogram. Laboratory studies show pH 7.22, PaCO2 58 mmHg, and PaO2 52 mmHg on FiO2 0.6. Which of the following substances is most deficient in this patient's lungs?
Answer choices
- AType I collagen in the alveolar basement membrane
- BThyroid hormone-responsive transcription factors
- CPulmonary macrophage opsonins (immunoglobulins)
- DPrenatal corticosteroid-induced proteins in the fetal airway
- EDipalmitoylphosphatidylcholine and associated apolipoproteinsCorrect answer
- FElastic fibers in the visceral pleura
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