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Boyle's law gas expansion — FRCA Primary MCQ

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ModeratePhysics and Clinical MeasurementBoyle's law gas expansionFRCA Primary

A cuffed tracheal tube is inserted before aeromedical transfer. During ascent, cuff pressure rises despite no extra air being injected. Which gas law best explains this?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: C — Boyle's law

Boyle's law states that gas volume increases as pressure falls at constant temperature, so an air-filled cuff can expand during ascent. Charles' law concerns volume and temperature at constant pressure. Henry's law concerns dissolved gas, and Fick's law concerns diffusion. Cuff pressure should be monitored during altitude changes or nitrous oxide use.

Reference: Primary FRCA physics texts; Dorsch and Dorsch Understanding Anesthesia Equipment