Body tissue obtains oxygen from oxyhaemoglobin because of its dissociation caused by low O2 and high CO2 concentration. Under a given concentration of oxygen in the blood, dissociation of oxyhaemoglobin will increase if the pH of the blood falls (increase in H+ concentration). When the partial pressure of CO2 rises (blood pH decreases), the dissociation curve of Oxyhaemoglobin at 37 °C shift to the right. Effect of high pCO2, high temperature and low pH are similar. p50 indicates the oxygen concentration at which 50% haemoglobin of blood is saturated with O2.