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. 2008 Feb 18:8:3.
doi: 10.1186/1471-2253-8-3.

A Prospective Study to Evaluate the Accuracy of Pulse Power Analysis to Monitor Cardiac Output in Critically Ill Patients

Maurizio Cecconi  1 , Jayne Fawcett, R Michael Grounds, Andrew Rhodes
Affiliations

A Prospective Study to Evaluate the Accuracy of Pulse Power Analysis to Monitor Cardiac Output in Critically Ill Patients

Maurizio Cecconi et al. BMC Anesthesiol. .

Abstract

Background: Intermittent measurement of cardiac output may be performed using a lithium dilution technique (LiDCO). This can then be used to calibrate a pulse power algorithm of the arterial waveform which provides a continuous estimate of this variable. The purpose of this study was to examine the duration of accuracy of the pulse power algorithm in critically ill patients with respect to time when compared to measurements of cardiac output by an independent technique.

Methods: Pulse power analysis was performed on critically ill patients using a proprietary commercial monitor (PulseCO). All measurements were made using an in-dwelling radial artery line and according to manufacturers instructions. Intermittent measurements of cardiac output were made with LiDCO in order to validate the pulse power measurements. These were made at baseline and then following 1, 2, 4 and 8 hours. The LiDCO measurement was considered the reference for comparison in this study. The two methods of measuring cardiac output were then compared by linear regression and a Bland Altman analysis. An error rate for the limits of agreement (LOA) between the two techniques of less than 30% was defined as being acceptable for this study.

Results: 14 critically ill medical and surgical patients were enrolled over a three month period. At baseline patients showed a wide range of cardiac output (median 7.5 L/min, IQR 5.1 -9.0 L/min). The bias and limits of agreement between the two techniques was deemed acceptable for the first four hours of the study with percentage errors being 29%, 22%, and 285 respectively. The percentage error at eight hours following calibration increased to 36%. The ability of the PulseCo to detect changes in cardiac output was assessed with a similar analysis. The PulseCO tracked the changes in cardiac output with adequate accuracy for the first four hours with percentage errors being 20%, 24% and 25%. However at eight hours the error had increased to 43%.

Conclusion: The agreement between lithium dilution cardiac output and the pulse power algorithm in the PulseCO monitor remains acceptable for up to four hours in critically ill patients.

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Figures

Figure 1
Figure 1
Linear regression and Bland Altman plots for PulseCO versus LiDCO at 1 (a), 2 (b), 4 (c) and 8 (d) hours following calibration. The solid lines in the Bland Altman plot represent the bias and the dotted lines represent the limits of agreement (2 × standard deviation of the bias).
Figure 2
Figure 2
Linear regression and Bland Altman plots for percentage changes in PulseCO versus changes in LiDCO at 1 (a), 2 (b), 4 (c) and 8 (d) hours following calibration. The solid line in the regression plots represents the regression line, the dotted lines represent the 95% confidence intervals around this line. The solid lines in the Bland Altman plot represent the bias and the dotted lines represent the limits of agreement (2 × standard deviation of the bias).
Figure 3
Figure 3
Percentage errors between PulseCO and LiDCO for Individual patients over an eight hour period.
Figure 4
Figure 4
Graphs representing values of cardiac output for each individual patient as measured by both LiDCO and PulseCO.
See this image and copyright information in PMC

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