The difference between the oxygen content of arterial blood and mixed venous blood. It may be expressed as millilitres of oxygen per 100 mL of blood. The value represents the extent to which oxygen is removed from the blood as it passes through the body. Usually, the arterial oxygen concentration is measured in blood from the femoral, brachial, or radial artery, and the oxygen content of mixed venous blood is measured from blood withdrawn from the pulmonary artery. At rest, the average arterial-venous oxygen difference is about 4–5 mL per 100 mL of blood, but it increases progressively during exercise reaching up to 16 mL per 100 mL of blood, indicating that more oxygen is extracted from the blood by active muscles. The maximum arteriovenous oxygen difference of a trained athlete usually exceeds that of an untrained person. The training effect may be due to adaptations in the mitochondria, increased myoglobin content of muscles, or improved muscle capillarization.
Subjects: Sports and Exercise Medicine.