Doppler ultrasound — FRCA Primary MCQ

Correct answer: E — Doppler frequency shift

Doppler ultrasound estimates velocity from the frequency shift of reflected sound, which depends on flow velocity and insonation angle. Residual non-depolarising neuromuscular block is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. EMG activity can falsely raise the index is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Leakage current control and isolation is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Desflurane heated pressurised vaporiser 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