Differences between venous and arterial blood
The differences between arterial and venous blood are summarized in Figure 5 and Table 1. The high content of carbon dioxide in venous capillary blood reduces the affinity of haemoglobin for oxygen leading to release of oxygen to the tissues.3 The oxygen dissociation curve shifts to the right (Bohr effect). Deoxygenated haemoglobin takes up more carbon dioxide than oxygenated haemoglobin (Haldane effect). Removal of oxygen from haemoglobin in the tissue capillaries causes the haemoglobin molecule to behave more like a base (better proton acceptor). Therefore, haemoglobin increases the amount of carbon dioxide that is carried in venous blood (Equation 4)