A 32-week preterm neonate on nasal CPAP with FiO2 0.35 shows persistent respiratory distress and CXR reveals bilateral ground-glass opacification with air bronchograms. Surfactant is administered intratracheally. Which specific phospholipid component of surfactant is MOST critical for reducing alveolar surface tension?

• A Phosphatidylglycerol
• B Phosphatidylinositol
• C Sphingomyelin
• D Dipalmitoylphosphatidylcholine (DPPC) ✓

Explanation

Dipalmitoylphosphatidylcholine (DPPC) is the primary surface-active component of pulmonary surfactant, constituting about 40% of its total lipid content. DPPC forms a tightly packed monolayer at the air-liquid interface that reduces surface tension to near zero during expiration, preventing alveolar collapse. The lecithin-to-sphingomyelin (L:S) ratio in amniotic fluid uses sphingomyelin as a stable reference, not as the active agent.

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.