With training the muscles also improve in their ability to extract oxygen from the blood and process the oxygen, possibly due to adaptations of the mitochondria and an increase in the muscle's myoglobin content. The increase in capillary beds in the muscle means that blood supply to that muscle can be greater and diffusion of oxygen, carbon dioxide, and other metabolites increases. This is a result of aerobic exercise leading to hypertrophy of the slow twitch muscle fibres mainly due to increased capillarisation. The maximum a-vO 2 diff is also usually greater in trained athletes than in untrained individuals. As exercise intensities increase, the muscles increase the amount of oxygen they extract from the blood, and this therefore results in further increases in a-vO 2 diff. Physical exercise leads to an increase in the arteriovenous oxygen difference in all individuals. Īlternatively, in order to find the efficiency of the lungs in replenishing blood oxygen levels, the a-vO 2 diff may instead be taken by comparing blood from the pulmonary artery and the pulmonary vein in this case a negative value for a-vO 2 diff would be obtained as the oxygen content of the blood would have increased. During intense exercise, however, the a-vO 2 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. Venous blood with an oxygen concentration of 15 mL/100 mL would therefore lead to typical values of the a-vO 2 diff at rest of around 5 mL/100 mL. Īrterial blood will generally contain an oxygen concentration of around 20 mL/100 mL. In order to do so oxygen consumption (VO 2) 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. In practice, a-vO 2 diff may be determined using the Fick Principle rather than by taking direct blood samples. The usual unit for a-vO 2 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 micro moles per millilitre (μmol/mL). C v = the oxygen concentration of venous blood (deoxygenated blood).
C a = the oxygen concentration of arterial blood (oxygenated blood).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).
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