Ts. Ahrens et L. Schallom, Comparison of pulmonary artery and central venous pressure waveform measurements via digital and graphic measurement methods, HEART LUNG, 30(1), 2001, pp. 26-38
BACKGROUND: Techniques to measure pulmonary artery (PA) pressure waveforms
include digital measurement, graphic measurement, and freeze-cursor measure
ment. Previous studies reported the inaccuracy of digital and freeze-cursor
measurements. However, many of the previous studies were small and did not
thoroughly examine the circumstances of when digital measurements might be
inaccurate.
OBJECTIVES: To compare digital measurements and graphic measurements of PA
and central venous pressure (CVP) waveforms in patients with a variety of r
espiratory patterns, and to compare digital measurements and graphic measur
ements of CVPs in patients with abnormal or right ventricular waveforms.
METHODS: A total of 928 patients were enrolled in this study. Waveforms fro
m the PA and CVP were collected from each patient. The monitor pressure val
ue (digital measurement) printed on the recorded waveform was compared with
the pressure value obtained by a graphic strip recording and measured by o
ne of the primary investigators (graphic measurement).
RESULTS: Digital measurements were found to be inaccurate in measuring wave
forms in all respiratory categories and in measuring right ventricular wave
forms. PA diastolic values and CVP values were the most inaccurately measur
ed waveforms. Digital errors of more than 4 mm Hg were common.
CONCLUSION: There were instances in which the monitor's digital measurement
was substantially different from the graphically measured value. This diff
erence has the potential to mislead interpretation of clinical situations.
The monitor's ability to occasionally give digital measurement values simil
ar to the graphic measurements may lead to a false sense of security in cli
nicians. Because the accuracy of the monitor is inconsistent, the bedside c
linician should interpret waveforms through use of a graphic recording rath
er than rely on the digital measurement on the monitor.