Cardiac output and mixed venous O2 content measurements by a tracer bolus method: animal validation study.

A bolus method for noninvasive measurement of cardiac output (CO) and mixed venous oxygen content (O2) has been tested against absolute CO and O2 standards in dogs. No statistical differences in CO were found between bolus method and electromagnetic flowmeter measurement comparisons in an 18-dog study in which CO varied from 0. 5 to 3.0 l/min. The SD for all paired differences was 0.14 l/min; however, data averaging over 10-min intervals were found to reduce the CO measurement uncertainty to <0.08 l/min. The ability of the bolus method to follow rapid CO changes, experimentally produced by control of a pump (surgically placed between the superior and inferior vena cava and the right atrium), was documented and found to satisfy CO monitoring requirements of unstable subjects. O2 bolus values were found to be statistically equivalent to reference measurements.