What is Pulse oximetry? With Pulse oximetry the arterial oxygen saturation in blood and the pulse rate are measured in patients by non-invasive method. The oxygen saturation is ascertained with the aid of light absorption method during systole. Only the absorption is measured through pulsating blood flow. That is the reason why it is named as “Pulse oximetry”. The process is based on the property of haemoglobin, to change colour depending on the oxygen binding. Hereby, the oxygen-deficient (deoxygenated) haemoglobin absorbs more light than the oxygen-rich haemoglobin (oxygenated). As per the device, a clip, a blood-pressure cuff or a flexible sensor can be attached or clipped to the hand, finger, toe, ear lobe or nose-bridge of the patient for pulse measurement.