According to pulseox.info, oxygen saturation (SpO2) is a measure of how much oxygen the blood is carrying as a percentage of the maximum it could carry. In the unit where I worked, when the patient has lower than 95% of SpO2, we start oxygen inhalation at 2 Lpm via nasal cannula while waiting for the anesthesiologist. If lower SpO2 persists, then we refer them to a physician. The equipment used for monitoring SpO2 is the use of a finger pulse oximeter.