Arteriovenous oxygen difference

The arteriovenous oxygen difference, or a-vO₂ diff, is the difference in the oxygen content of the blood between the arterial blood and the venous blood. It is an indication of how much oxygen is removed from the blood in capillaries as the blood circulates in the body. The a-vO₂ diff and cardiac output are the main factors that allow variation in the body's total oxygen consumption, and are important in measuring VO₂. The a-vO₂ diff is usually measured in millilitres of oxygen per 100 millilitres of blood (mL/100 mL).

The arteriovenous oxygen difference is usually taken by comparing the difference in the oxygen concentration of oxygenated blood in the femoral, brachial, or radial artery and the oxygen concentration in the deoxygenated blood from the mixed supply found in the pulmonary artery (as an indicator of the typical mixed venous supply).

Put in simple terms:

The usual unit for a-vO₂ diff is millilitres of oxygen per 100 millilitres of blood (mL/100 mL), however, particularly in medical uses, other units may be used, such as micromoles per millilitre (μmol/mL).

In practice, a-vO₂ diff may be determined using the Fick Principle rather than by taking direct blood samples. In order to do so oxygen consumption (VO₂) may be measured using a spirometer to detect gaseous concentrations in exhaled air compared to inhaled air, while cardiac output can be determined using a Doppler ultrasound.

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