A 34-week preterm neonate with respiratory distress syndrome is placed on nasal CPAP at 6 cm H2O. The neonate's work of breathing improves and oxygen saturation stabilizes. What is the PRIMARY mechanism by which CPAP improves oxygenation in RDS?

• A Increases surfactant production by type II pneumocytes
• B Recruits collapsed alveoli and maintains functional residual capacity ✓
• C Reduces pulmonary vascular resistance through nitric oxide release
• D Decreases interstitial fluid by increasing lymphatic drainage

Explanation

CPAP works by applying continuous positive pressure throughout the respiratory cycle, preventing alveolar collapse at end-expiration. This recruits collapsed alveoli and maintains functional residual capacity, thereby improving ventilation-perfusion matching. CPAP does not directly increase surfactant production, reduce pulmonary vascular resistance, or enhance lymphatic drainage.

Reference: Avery's Diseases of the Newborn, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.