Beat-to-beat measurement of cardiac output by intravascular pulse contour analysis: a prospective criterion standard study in patients after cardiac surgery.

OBJECTIVE: To evaluate the accuracy of a new pulse contour method of measuring cardiac output in critically ill patients.

DESIGN: A prospective criterion standard study.

SETTING: Cardiac surgery intensive care unit in a university hospital.

PARTICIPANTS: Nineteen cardiac surgery patients requiring intensive care treatment with pulmonary artery catheters after surgery.

INTERVENTIONS: None.

MEASUREMENTS AND MAIN RESULTS: The pulse contour cardiac output monitor uses transpulmonary bolus thermodilution measurements to calibrate the system. In each patient, the pulse contour cardiac output values were compared with conventional thermodilution. The method described by Bland and Altman and linear regression analysis were used for comparison. The mean difference (bias) +/- standard deviation of differences (precision) was 0.31 +/- 1.25 L/min for pulmonary bolus thermodilution cardiac output versus pulse contour cardiac output and 0.21 +/- 0.73 L/min for pulmonary bolus thermodilution cardiac output versus transpulmonary bolus thermodilution cardiac output. Linear regression (correlation) analyses were pulse contour cardiac output = 0.97 thermodilution + 0.53 (r = 0.88), and transpulmonary cardiac output = 0.87 thermodilution + 1.09 (r = 0.96). There was a small increase 60 minutes after recalibration but not a statistically significant difference between pulse contour cardiac output and pulmonary bolus thermodilution cardiac output (p = 0.52).

CONCLUSIONS: Bias and precision are acceptable, and the system provides results that agree with conventional thermodilution. This study demonstrates the clinical applicability of the pulse contour cardiac output monitoring system.