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Overdamped Arterial Line — FRCA Primary MCQ

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ModeratePhysics & Clinical MeasurementOverdamped Arterial LineFRCA Primary

A radial arterial catheter is connected to a correctly levelled and zeroed fluid-filled transducer system. A fast-flush test demonstrates excessive damping. Which displayed waveform and pressure pattern is most likely?

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

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Correct answer: C — A slurred upstroke and absent dicrotic notch, with systolic pressure underestimated and diastolic pressure overestimated

Excessive damping attenuates the higher-frequency harmonics of the arterial pressure signal. The displayed waveform is therefore smoothed, with a slow or slurred systolic upstroke and loss of the dicrotic notch. Pulse pressure is narrowed: systolic pressure is underestimated and diastolic pressure is overestimated, while mean arterial pressure is usually relatively preserved. Thus, C is correct. Option A gives the wrong direction for the diastolic error. Option B combines an overdamped waveform shape with the pressure errors of underdamping. Option E describes an underdamped or resonant system, which produces an exaggerated systolic peak, oscillations and a falsely widened pulse pressure. Correct levelling and zeroing exclude a hydrostatic offset affecting all pressure values.

Reference: Lam S, Liu H, Jian Z, Settels J, Bohringer C. Intraoperative Invasive Blood Pressure Monitoring and the Potential Pitfalls of Invasively Measured Systolic Blood Pressure, Figure 1. Cureus. 2021;13:e17610. https://pubmed.ncbi.nlm.nih.gov/34646661/