Respiratory distress syndrome of prematurity — branching viva

Branch 1 — Mechanism and recognition

The examiner opens: "Explain why this infant is in distress." A strong candidate traces surfactant deficiency through raised surface tension, alveolar collapse at end-expiration, low functional residual capacity and compliance, ventilation-perfusion mismatch with hypoxaemia and hypercapnia, and acidosis that further inhibits surfactant and constricts the pulmonary vasculature. The candidate then names expiratory grunting as auto-positive end-expiratory pressure and explains the chest radiograph triad of low volumes, granular opacities and air bronchograms. ^[1]