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Non-invasive blood pressure cuff size error — FRCA Primary MCQ

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HardPhysics and Clinical MeasurementNon-invasive blood pressure cuff size errorFRCA Primary

A patient has non-invasive blood pressure measured with a cuff that is too small for the arm circumference. The oscillometric reading is repeatedly higher than the arterial line pressure. What is the most likely explanation?

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

Reveal the answer and explanation

Correct answer: E — Excess cuff pressure is required to occlude the artery

A cuff that is too small requires higher pressure to occlude the artery and tends to overestimate blood pressure. Oscillometric devices estimate systolic and diastolic pressures from oscillation algorithms rather than measuring them directly. Sinus rhythm does not remove cuff-size error. The teaching point is that cuff bladder width and length must match limb size.

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