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Vaporiser Altitude Output — FRCA Primary MCQ

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HardPhysics & Clinical MeasurementVaporiser Altitude OutputFRCA Primary

At altitude a variable bypass vaporiser delivers:

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

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Correct answer: A — Higher volumes percent but the same partial pressure of anaesthetic

At altitude atmospheric pressure is reduced. The vaporiser delivers approximately the same partial pressure (clinically relevant) but higher volumes percent because the same partial pressure is a larger fraction of the lower total pressure. MAC defined by partial pressure is unchanged.

Reference: Al-Shaikh Stacey 2019 Essentials of Anaesthetic Equipment