SpO2 stands for peripheral capillary oxygen saturation. It is a measure of the oxygen saturation level in the blood and is usually expressed as a percentage. The measurement is typically obtained using a pulse oximeter, which is a non-invasive medical device that clips onto a finger or other part of the body and uses light to measure the amount of oxygen in the blood. A normal SpO2 reading is typically between 95% and 100%, and values below 90% may indicate a need for medical attention, as low oxygen saturation levels can lead to serious health problems.