Noninvasive cardiac output assessment during heart surgery

To evaluate the reliability of a new noninvasive method for the assessment of cardiac output with the partial carbon dioxide rebreathing technique.

This technique was applied to patients undergoing heart surgery. Values of cardiac index obtained with this equipment were compared with the artero-venous CO2 gradient, a reliable index of cardiovascular status. Positive and negative predictive values of the test were assessed.

A total of 21 simultaneous measurement of the cardiac index and of the artero-venous CO2 gradient were obtained. The positive predictive value of the test was 67% while the negative predictive value was 100%, indicating that a normal value of cardiac index recorded with the rebreathing technique predicts with a good reliability a normal cardiovascular state.

Working through a series of mathematical algorithms, accuracy in the computation of cardiac output can be decreased with this equipment; however, this limitation seems to be outweighed by the simplicity and noninvasive nature of the methods.