The main indicators measured by a pulse oximeter are pulse rate, oxygen saturation, and perfusion index (PI). Oxygen saturation (SpO2) is one of the most important basic data in clinical medicine. Oxygen saturation refers to the percentage of bound O2 in the total blood volume.
The oxygen consumed by the human body mainly comes from hemoglobin (there are four types of hemoglobin in normal blood: oxyhemoglobin (HbO2), deoxyhemoglobin (Hb), carboxyhemoglobin (CoHb), and methemoglobin (MetHb)). Deoxyhemoglobin reversibly binds oxygen, while carboxyhemoglobin and methemoglobin do not. The oxygen content in the blood is usually referred to as the amount of oxyhemoglobin in the blood, and the physical quantity of blood oxygen saturation is used to describe changes in the oxygen content of the blood.
