Direct Fick application for measurement of cardiac output in rat

Abstract

The direct Fick procedure for cardiac output determination in the rat was validated by simultaneous comparison with electromagnetic flowmeter techniques. Significant coefficients of correlation were obtained between absolute cardiac output values (r = 0.798, P < 0.001), increases (r = 0.768, P < 0.001) and decreases (r = 0.672, P < 0.01) in cardiac output detected by the 2 methods. Cardiac output values of the Fick procedure in the rat were between 40-58% greater than respective electromagnetic flow probe values; however, percent changes in cardiac output obtained by the 2 methods were similar. The larger values of cardiac output obtained by the direct Fick method may be related, to a great extent, to the distribution of blood flow to the coronary and bronchial circulations. Fick cardiac output measurements were reproducible within rats, and the degree of variation in values among rats was similar to that obtained with the flowmeter procedure. The Fick method provides a valid estimation of cardiac output in the rats, with the ability to detect moderate changes (22-36%) in cardiac output.