Carbon Dioxide

Carbon dioxide is generated as a by-product of aerobic respiration and plays a major role in determining the pH level of the blood. It is transported in the circulation in three forms : 

1: Bound to proteins (haemoglobin and carbamino compounds)

2: As bicarbonate (under the influence of carbonic anhydrase) 

3: Dissolved in solution within the plasma 

Carbon dioxide is much more soluble in the plasma compared to oxygen (its solubility coefficient is > 20 times greater). Despite this, the majority of carbon dioxide is transported as bicarbonate. In the lungs, the high partial pressure of oxygen promotes the release of carbon dioxide, which dissolves from the plasma into the alveoli before being exhaled from the body. 

Failure to eliminate carbon dioxide can lead to hypercapnia – an accumulation of carbon dioxide in the blood. This will acutely cause respiratory acidosis which can be detected clinically and may indicate impending respiratory failure.