Oxygen saturation is the proportion of hemoglobin saturated with oxygen to all hemoglobin in the flowing blood, and is a very important physiological indicator, as well as a very important indicator of vital signs. The normal value of oxygen saturation should be above 95%. In normal people, the value of oxygen saturation monitoring is mostly in the range of 95%-99%, and can also reach 100%. Oxygen saturation monitoring can detect problems related to pulmonary ventilation and air exchange. If there are respiratory or cardiac problems, the oxygen saturation will be directly affected and hypoxemia will occur. In severe cases of hypoxemia, the patient will present with facial cyanosis and hypoxia. Hypoxia itself is a very important blow to the organs and can cause major organ dysfunction and failure. Thus, hypoxemia can lead to respiratory failure, cardiac failure, abnormal liver failure, abnormal renal failure, and it can also affect the brain, with alterations in mentation and consciousness. Therefore, oxygen saturation monitoring for critically ill patients can effectively reflect the level of blood oxygen in order to facilitate early detection of problems.