Hypoxemia can be determined by history, symptoms, and laboratory tests. 1. Medical history: Generally, patients with hypoxemia have a history of asthma, pulmonary edema, pulmonary embolism, and cardiac insufficiency. 2. Symptoms: For patients with hypoxemia, if the PaO2 drops to about 60mmHg, inattention, mild decrease in intelligence and vision may occur. If PaO2 falls to about 40~50mmHg or below, headache, disorientation and memory impairment, drowsiness and other symptoms may occur. If PaO2 is less than 30mmHg, the patient may experience loss of consciousness or even coma. If PaO2 is less than 20 mmHg, it can lead to irreversible damage to nerve cells within minutes. In addition, patients may be accompanied by cyanosis, chest tightness, palpitations and other symptoms. 3. Laboratory examination: patients with hypoxemia can also determine hypoxemia through arterial blood gas analysis, blood routine, pulmonary function tests and other laboratory tests. If patients are suspected of suffering from hypoxemia, they should go to the hospital in time to improve the relevant examination and clarify the cause of the disease, so as to carry out the corresponding treatment in time.