Blood hypoxia refers to the reduction of partial pressure of oxygen in the blood and the reduction of oxygen saturation, resulting in a series of hypoxia symptoms in the body, common symptoms include: First, the central nervous system hypoxia symptoms, because the central nervous system is most sensitive to the lack of oxygen, hypoxia, the patient will appear dizziness, headache, tinnitus, insomnia and forgetfulness, and even serious cases of emotional and mental changes. Second, the symptoms of the respiratory circulatory system, due to the lack of oxygen, respiration will appear compensatory acceleration, manifested as shortness of breath, chest tightness and other sensations, and the heart will appear compensatory acceleration of the heartbeat, the patient will feel panicky, and even induced angina pectoris, the feeling of chest pain. Third, the symptoms of limb muscles, due to the lack of oxygen in the blood, the muscles of the limbs get less oxygen supply, there will be symptoms of limb weakness, the patient has difficulty in walking, and even turn over and need help.