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Closing capacity and age — FRCA Primary MCQ

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HardPhysiologyClosing capacity and ageFRCA Primary

A 74-year-old desaturates soon after induction despite uneventful intubation. Pre-oxygenation was adequate, and auscultation is symmetrical. Which age-related change best explains this susceptibility?

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Correct answer: B — Closing capacity exceeding FRC when supine

Closing capacity rises with age and may exceed FRC in the supine anaesthetised patient, causing small airway closure during tidal breathing. Lung elastic recoil tends to decrease with age rather than increase. Closing volume does not fall with age, and alveolar surface area is reduced. This is why older patients desaturate quickly even after apparently satisfactory pre-oxygenation.

Reference: West Respiratory Physiology; Nunn's Applied Respiratory Physiology