in 1870 A. Fick proposed that cardiac output can be calculated as the quotient of total body oxygen consumption divided by the difference in oxygen content of arterial blood and mixed venous blood. In the direct Fick method, all variables are measured. The indirect Fick method employs a variety of means to avoid measuring mixed venous oxygen content. By extension, the Fick method may be used to measure cardiac output or organ blood flow with any indicator substance for which the rate of uptake or consumption, and the arterial and mixed venous concentrations, can be measured, provided the indicator does not enter or leave the system by any route not being measured.
Synonym(s): Fick principle
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