Continuous measurement of oxygen consumption using the reversed fick method.

We developed a continuous oxygen consumption (Vo2) measurement system employed the reversed Fick method, in which Vo2 in computed from continuously measured sured arterial and mixed venous oxygen saturation assed by pulse oximetry and mixed venous oximetry, respectively, and cardiac output by the heat deprivation technique. This system was compared with the conventional intermittent reversed fick method in 7 patients during surgery and with indirect calorimetry in 4 intensive care unit (ICU) patients. The Vo2 measured by the continuous reversed Fick method showed a high correlation with those simultaneously measured by the intermittent Fick method (r=0.97,P<0.01) and by indirect calorimetry (r=0.74,P<0.01). The 95% confidence limits (bias±2 SD) of the continuous reversed Fick method were -0.6±45 ml·min-1 with the intermittent Fick method and -31±56 ml·min-1 with indirect calorimetry. The continuous Fick method is in satisfactory agreement with the conventional methods for the measured of Vo2 and potentially allows for convenient assessment of Vo2 in critically ill patients.