Sidestream delay — FRCA Primary MCQ

Correct answer: E — Sampling tube transit delay

Sidestream gas analysers have a delay because sampled gas must travel through tubing before measurement. Saturated vapour pressure is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Microshock through an intracardiac conductor is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Oxygen-enriched fire risk is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Doppler frequency shift is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. In Primary FRCA physics and measurement, the safest answer is the one that follows the underlying physical principle and the limitations of the device.

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