The percentage of hemoglobin that is bound with C2 is called percent saturation of hemoglobin. It depends upon the partial pressure of oxygen (Po2) in blood. The relationship between (Po2) and percentage saturation of hemoglobin with O2 is graphically illustrated by a curve called oxygen hemoglobin dissociation curve. Changes in body temperature and blood pH as well as, in the concentrations of CO2 in blood and of 2,3 diphosphnglvcerate in red blood corpuscles affect the oxygen affinity of hemoglobin resulting into a shifting of the O2 hemoglobin dissociation curve. When partial pressure of CO2 rises (blood pH decreases dissociation curve of oxyhaemoglobin at 37∘C shift to right.