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Surfactant deficiency physiology — MRCPCH TAS MCQ

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ModeratePhysiologySurfactant deficiency physiologyMRCPCH TAS

A 28-week preterm infant has grunting, low lung volumes and diffuse reticulogranular shadowing. What is the most likely physiological abnormality?

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Correct answer: A — Increased alveolar surface tension

Respiratory distress syndrome results from surfactant deficiency, increasing alveolar surface tension and causing atelectasis. Reduced pulmonary vascular resistance is a normal transition and does not cause low-volume lungs. The pearl is that surfactant reduces the pressure needed to keep small alveoli open.

Reference: Rennie and Robertson Textbook of Neonatology; Ganong's Review of Medical Physiology; RCPCH Theory examination syllabi