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 measur ing 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 tr eatment with pulmonary artery catheters after surgery. Interventions: None. Measurements and Main Results: The pulse contour cardiac output monitor use s transpulmonary bolus thermodilution measurements to calibrate the system. In each patient, the pulse contour cardiac output values were compared wit h 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. L inear 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 minut es after recalibration but not a statistically significant difference betwe en pulse contour cardiac output and pulmonary bolus thermodilution cardiac output (p = 0.52). Conclusions: Bias and precision are acceptable, and the system provides res ults that agree with conventional thermodilution. This study demonstrates t he clinical applicability of the pulse contour cardiac output monitoring sy stem. Copyright (C) 2000 by W.B. Saunders Company.