ABSTRACT

Draw the oxygen-haemoglobin dissociation curve (OHDC). The OHDC is a graph relating the percentage of haemoglobin saturated with oxygen to the partial pressure of oxygen (PO2).

GRAPH 1.1 The oxygen-haemoglobin dissociation curve

Normal oxyhaemoglobin dissociation curve ➤ Arterial PO2 is 13.3 kPa with a Hb saturation of 97% (it is not 100% due to venous

admixture constituting physiological shunt). ➤ Venous PO2 is 5.3 kPa with a Hb saturation of 75%. ➤ P50 is 3.5 kPa (this is the PO2 at which Hb is 50% saturated and it is the conventional

point used to compare the oxygen affi nity of Hb).