Comparison of pulmonary artery and central venous pressure waveform measurements via digital and graphic measurement methods

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.