Fick technique

(Adolph Eugen Fick, 1829 - 1901, German physiologist) method for measuring cardiac output. It is based on the principle that the total uptake of oxygen by an organ is the product of blood flow to the organ and the arteriovenous concentration difference of oxygen across the organ. Cardiac output is measured as the product of oxygen consumption of the lungs per minute and the arteriovenous oxygen difference across the lungs. If there is no intracardiac shunt, then pulmonary blood flow is nearly equivalent to systemic blood flow or cardiac output. Oxygen consumption is measured as the oxygen extracted by the lungs per minute by the polarographic method or the Douglas bag. The formula for calculation of cardiac output is:

cardiac output (litre/min) = oxygen consumption (ml/min) / arteriovenous oxygen difference (ml/litre).

Arteriovenous oxygen difference is the difference between systemic arterial and pulmonary arterial oxygen content.

CBH