Fuel cell oxygen analysis — FRCA Primary MCQ

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ModeratePhysics and Clinical MeasurementFuel cell oxygen analysisFRCA Primary

An anaesthetic machine oxygen analyser shows a rapid response when oxygen is changed to air and generates a small voltage without an external power supply. Which analyser type is most likely being used?

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Correct answer: D — Paramagnetic analyser

A fuel cell oxygen analyser is an electrochemical cell that generates a voltage proportional to oxygen partial pressure. Paramagnetic analysers require a different physical principle based on oxygen's magnetic susceptibility and do not consume oxygen in the same way. Infrared absorption is used for gases such as CO2 and volatile agents rather than oxygen. Fuel cells have a finite life because the electrode is consumed.

Reference: RCoA Primary FRCA Syllabus 2026; Davis and Kenny Basic Physics and Measurement in Anaesthesia