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Overdamped arterial pressure trace — FRCA Primary MCQ

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HardPhysics and Clinical MeasurementOverdamped arterial pressure traceFRCA Primary

After radial arterial cannulation, the flush test shows a sluggish upstroke and a blunted waveform with loss of the dicrotic notch. Which factor is most likely responsible?

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

Reveal the answer and explanation

Correct answer: B — Air bubble in the catheter-transducer system

Air bubbles, clot, loose connections or compliant tubing can overdamp an arterial line, producing a slow upstroke and underestimated systolic pressure. A very stiff short system tends to improve frequency response rather than cause overdamping. Correct levelling does not blunt the waveform. The pearl is to troubleshoot the measurement system before treating the displayed pressure.

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