A pulse oximeter is a medical device for measuring the oxygen saturation in the blood.
The device works on the basis of light absorption by the blood. It sends a beam of light through the tissue and measures the amount of light absorbed. Oxygen-rich blood absorbs light differently than oxygen-poor blood. By measuring the absorption of red and infrared light, the pulse oximeter can calculate and display the oxygen saturation in the blood.
The readings are usually expressed as a percentage of the maximum oxygen binding capacity of haemoglobin in the blood, which is called oxygen saturation (SpO² value).
A pulse oximeter primarily measures the oxygen saturation of the blood, but can also provide other important information such as pulse rate and perfusion index. The perfusion index (PI) is a measure of blood flow in the area where the pulse oximeter is located. It is expressed as a percentage and can be an indicator of circulatory disturbances or vasoconstriction.
