Mass spectrometer measurement of oxygen uptake and carbon dioxide exchange during cardiopulmonary bypass

Oxygen uptake (VO2) and carbon dioxide output (VCO2) were measured continuously in four children during cardiopulmonary bypass, using the variation in concentration of a tracer gas, argon, as a measure of flow, and a mass spectrometer to monitor gas concentrations. Normal values for the ratio of VCO2:VO2 (= 0.8) indicated that gas exchange equilibrium had been established following sudden changes in body temperature. During rapid cooling, 10% carbon dioxide is necessary to ensure carbon dioxide homeostasis within the body.