Comparison of Fick and dye cardiac outputs during rest and exercise in 1,022 patients

The Fick and indicator-dilution techniques for measurement of cardiac output (CO) were compared at rest in 1,022 patients and in 786 during exercise. Duplicate measurements of dye CO at rest revealed that 92.7% fell within 10% of the line of identity and 99% within 20%. For the resting Fick and dye comparisons, 44.6% were within 10% of the identity line and 74.7% within 20%. When mean CO was less than 4.4 L/min, dye CO was higher than Fick. This relationship persisted for CO between 4.4 and 7.4 whereas for above 7.4 L/min, Fick was higher than dye. During exercise, 50.2% of the Fick and dye comparisons fell within 10% and 77.1% within 20% of the line of identity. There was a systematic difference between the two methods during exercise with dye CO higher than Fick CO. This study agrees with Fick and dye comparison studies with 74.7% and 77.1% of values within 20% of the identity line during rest and exercise, respectively. However, these results differ from others in that dye CO was higher than Fick CO for low and normal values whereas Fick was greater for the higher CO values. The overall agreement between the two methods in a large group of patients with diverse cardiac diseases over a broad spectrum of CO values supports use of either method for clinical studies.