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Electrical safety and isolation transformers — FRCA Primary MCQ

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HardPhysics and Clinical MeasurementElectrical safety and isolation transformersFRCA Primary

A patient undergoing hysteroscopy with monopolar diathermy is at risk of electrical injury. Which safety feature most reduces the risk of macroshock from mains-powered equipment?

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

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Correct answer: A — Using a high oxygen concentration

An isolated power supply reduces the risk of current flowing from live to earth through the patient, decreasing macroshock risk. Electrode placement does not provide mains isolation. A neutral electrode matters for diathermy burns but does not address mains macroshock in the same way. The clinical pearl is that electrical safety depends on both equipment design and correct use.

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