EVALUATION USING DOGS OF A METHOD FOR ESTIMATING MIXED VENOUS AND ARTERIAL PCO2 FROM A SINGLE BREATH

Estimates of arterial and true mixed venous CO2 tension (PCO2) were made from the continuous records of the changes in CO2 and O2 tensions in the expired gas of dogs during a single prolonged expiration, as described by Kim, Rahn and Fari. The results were compared with the results of direct analyses of systemic arterial and pulmonary arterial blood. There was no systematic error of the arterial estimates over a range of 32-48 torr or of the venous estimates over a range of 33-59 torr. The random errors of the arterial and venous estimates were .+-. 1.5 and .+-. 1.2 torr (2 SD), respectively. These results are better than those obtained by other noninvasive methods.