When oxygen saturation drops, treatment is determined by the degree of the drop. If the drop is mild, the patient’s underlying disease can be treated, including anti-inflammatory, antispasmodic and asthma, cough and phlegm, etc., while if the drop in oxygen saturation is more pronounced, especially below 90%, oxygen therapy is required. The oxygen concentration of oxygen therapy depends on the specific condition of the patient. If it is type I respiratory failure, medium and high flow oxygen can be applied, and if it is type II respiratory failure, continuous low flow oxygen is required. If oxygen saturation does not improve through oxygen inhalation, mechanical ventilation is required for treatment, either through noninvasive ventilation or intubation for invasive ventilation, depending on the specific characteristics of the patient’s condition to determine the treatment measures.