Oxygen saturation below 90 indicates that the body is in a state of hypoxia, and hypoxemia will occur, which needs to be treated immediately according to the cause of the disease. Normal people’s blood oxygen saturation is generally above 95, when the blood oxygen is lower than 90, it means that the body’s arterial blood can not provide enough oxygen to human tissues, thus leading to insufficient oxygen supply to human tissues and organs, which may lead to impaired function of tissues and organs, and may lead to serious organ failure and other situations. Generally, when the vital signs are unstable and the cardiopulmonary function is seriously impaired, there will be a drop in blood oxygen saturation, leading to coma, shock, confusion and other symptoms, and in serious cases, respiratory failure, circulatory failure and other symptoms or even death. Oxygen therapy, respiratory stimulants, and symptomatic treatment of the original disease are needed immediately, and respiratory and circulatory support therapy is also needed if necessary. Therefore, if the above symptoms occur, it is important to go to the hospital in time and follow the doctor’s instructions.