A patient who underwent abdominal aortic aneurysm (AAA) repair has an indwelling arterial line for continuous blood pressure monitoring. The nurse performs a fast-flush dynamic response test (square wave test). The pressure tracing demonstrates a slow, rounded rise with no oscillation after the flush (an overdamped waveform). How does an overdamped arterial line waveform affect recorded blood pressure readings?

Answer and explanation

Correct answer: B. It falsely underestimates systolic pressure and falsely overestimates diastolic pressure

  1. Step 1: An overdamped arterial line waveform occurs due to air bubbles in the transducer tubing, blood clots, kinking, or loose connections.
  2. Step 2: Overdamping blunts high-frequency pressure waves, resulting in a falsely low recorded systolic blood pressure and a falsely elevated diastolic blood pressure, although the Mean Arterial Pressure (MAP) generally remains accurate.
Answer
It falsely underestimates systolic pressure and falsely overestimates diastolic pressure.
Why not the others: 'Falsely overestimates systolic and underestimates diastolic' describes an underdamped ('ringing') waveform, typically caused by excessive tubing length; 'Zero impact' is incorrect as damping causes significant measurement error; 'Flattens MAP to zero' occurs only if the stopcock is closed or the line is disconnected.

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