[Assessment of cardiac output by a non-invasive method. Estimation of partial pressure of CO2 by rebreathing of expired gas. Comparison with thermodilution].

The cardiac output was measured in 65 patients by the FICK principle after estimation of the pp CO2 in mixed venous blood by rebreathing. This technique has been used mainly during exercise, and recently in intensive care units. We used it in resting patients hospitalised for diagnosis and treatment of a range of cardiac diseases, and in patients referred to our Physiological Laboratory. The reproductibility of our results using the rebreathing method was good: the variation of the individual results averaged 8.9%. The values of the cardiac output by rebreathing were compared to those obtained by thermodilution in 30 patients. A high coefficient of correlation was found: r = 0,897 (2p less than 0,001). This non-invasive technique is simple, rapid, and easily repeatible. Its use for serial estimations of the cardiac output should be retained.