A preterm neonate of 28 weeks gestation develops refractory hypoxemia on day 3. Chest X-ray shows bilateral diffuse ground-glass opacities with air bronchograms. Surfactant therapy is administered endotracheally. Which phospholipid component, maximally reduced in surfactant-deficient lungs, is the primary determinant of surface tension reduction at end-expiration?
- A Dipalmitoylphosphatidylcholine (DPPC) ✓
- B Phosphatidylinositol
- C Phosphatidylglycerol
- D Sphingomyelin
Explanation
Dipalmitoylphosphatidylcholine (DPPC) is the dominant surface-active phospholipid in pulmonary surfactant, comprising ~40% of its lipid content. Its highly saturated fatty acid chains pack densely at the air-liquid interface during expiration, reducing surface tension to near zero. Phosphatidylglycerol, while a marker of lung maturity in amniotic fluid, is a minor component. Sphingomyelin serves as the denominator in the lecithin-sphingomyelin ratio (>2 indicates lung maturity) but does not reduce surface tension. Phosphatidylinositol appears early in fetal development and declines as phosphatidylglycerol rises near term.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.