Noninvasive cardiac output estimates during quiet respiration through partial CO2 rebreathing

A noninvasive technique to measure cardiac output in spontaneously breathing subjects is evaluated. It is based on a differential form of the Fick equation and a partial rebreathing maneuver. Corrections for experimental error and a new ventilatory maneuver are introduced to reduce variability. Results suggest that the technique may attain error performance compatible with the invasive thermodilution method.