Carbon Dioxide Control

Carbon dioxide is highly soluble (twenty times more so than oxygen). The transport is by 3 means- i) Dissolved directly in the plasma – approx 10%, ii) as part of the bicarbonate buffer system – approx 70% and iii) bound to haemoglobin- approx 20%.[12]

Chemoreceptors in the medulla and the carotid and aortic bodies sense changes in pCO2 and H+. This is then used to regulate alveolar ventilation. When ventilation rises, pCO2 falls. This occurs because ventilation lowers the alveolar pCO2 below that of mixed venous blood. CO2 molecules then diffuse into the alveolar gas, thus lowering the CO2 concentration in pulmonary capillary blood.