A method originally used to measure cardiac output but of greater applicability. Three variables need to be measured: 1. the amount of substance taken up per unit time (oxygen by the whole body in the original application), 2. input concentration (concentration in arterial blood), 3. output concentration (concentration in venous blood). This approach can be used to estimate rate of uptake of a substance if the blood flow to the organ is known, or to estimate the blood flow to an organ, e.g. to the kidney, by measuring urinary excretion of a marker.
Subjects: Sports and Exercise Medicine.