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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).〔Malpeli, ''Physical Education'', Chapter 4: Acute Responses to Exercise, p. 106.〕 ==Measurement== 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: :''a-vO2 diff = Ca – Cv'' ::where: :: *''Ca'' = the oxygen concentration of arterial blood (oxygenated blood) :: *''Cv'' = the oxygen concentration of venous blood (deoxygenated blood) 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. Arterial blood will generally contain an oxygen concentration of around 20 mL/100 mL.〔 Venous blood with an oxygen concentration of 15 mL/100 mL would therefore lead to typical values of the a-vO2 diff at rest of around 5 mL/100 mL. During intense exercise, however, the a-vO2 diff can increase to as much as 16 mL/100 mL due to the working muscles extracting far more oxygen from the blood than they do at rest.〔 Alternatively, in order to find the efficiency of the lungs in replenishing blood oxygen levels, the a-vO2 diff may instead be taken by comparing blood from the pulmonary artery and the pulmonary vein; in this case a negative value for a-vO2 diff would be obtained as the oxygen content of the blood would have increased. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Arteriovenous oxygen difference」の詳細全文を読む スポンサード リンク
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