Medically SpO2 refers to blood oxygen saturation, which is a frequently monitored component in emergency department tests. Oxygen saturation includes arterial oxygen saturation, venous oxygen saturation, and is the volume of oxygenated hemoglobin bound by oxygen in the blood as a percentage of the volume of all hemoglobin, i.e. the concentration of blood oxygen in the blood. Therefore, oxygen saturation is an important physiological parameter of respiration and circulation, and the level of oxygen saturation is a direct measure of whether the human body is hypoxic or not, and an important indicator of lack of oxygen. In human venous blood, the oxygen saturation is 75%, and the arterial blood should reach 98% or more. If in hypoxic and hypoxic diseases, both arterial and venous oxygen saturation, i.e. SpO2, are significantly reduced.