Determination of cardiac output with a modified Fick method using estimated instead of measured oxygen consumption

Cardiac output (CO) was determined with a modification of the Fick method using estimated, instead of measured, oxygen consumption values. This avoids several possible sources of error in connection with air sampling and oxygen content analysis, thus a relaxed, steady state is obtained more easily. Using the thermodilution technique a good correlation with CO values was found (r = 0.92, p less than 0.001). We conclude that the modified Fick method is simple, accurate and offers reproducible CO estimates in the majority of patients.