Question 11.2

The image (Figure 11.2) below represents a tracing of the arterial wave form.

a)    What procedure has been performed and what is its purpose?    (10% marks)

b)    What is your impression of the fidelity of the arterial system? Give two reasons.
(10% marks)

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College answer

Not available.


This is indeed a square wave test, demonstrating an underdamped arterial waveform.  We know this, even though "(Image removed from exam report.)", because this question is identical to Question 11.2 from the first paper of 2010.  The underdamping is revealed by the multiple oscillations and the systolic overshoot.

The dynamic response testing of arterial lines is discussed in greater detail elsewhere.

In brief: the under-damped trace will overestimate the systolic, and there will be many post-flush oscillations.

Underdamped arterial line waveform


McGhee and Bridges Monitoring Arterial Blood Pressure: What You May Not Know (Crit Care Nurse April 1, 2002 vol. 22 no. 2 60-79 )

Thomas, Gary, and Victoria Duffin-Jones. "Monitoring arterial blood pressure." Anaesthesia & Intensive Care Medicine 16.3 (2015): 124-127.