Noninvasive cardiac output assessment during heart surgery

Objective. To evaluate the reliability of a new noninvasivemethod for the assessment of cardiac output with the partial carbondioxide rebreathing technique. Methods. This technique wasapplied to patients undergoing heart surgery. Values of cardiac indexobtained with this equipment were compared with the artero-venousCO₂ gradient, a reliable index of cardiovascular status.Positive and negative predictive values of the test were assessed.Results. A total of 21 simultaneous measurement of the cardiacindex and of the artero-venous CO₂ gradient were obtained.The positive predictive value of the test was 67% while thenegative predictive value was 100%, indicating that a normalvalue of cardiac index recorded with the rebreathing technique predictswith a good reliability a normal cardiovascular state.Conclusions. Working through a series of mathematical algorithms,accuracy in the computation of cardiac output can be decreased with thisequipment; however, this limitation seems to be outweighed by thesimplicity and non-invasive nature of the methods.