Oxygen concentration in chronic obstructive pulmonary disease, usually given continuous low-flow oxygen, oxygen concentration of 35% or less, and not suitable for giving high concentration of oxygen. Because COPD is a chronic disease, hypoxia, if corrected quickly, can easily lead to an increase in synchronized carbon dioxide concentration, instead of inducing type II respiratory failure. COPD is prone to secondary respiratory acidosis, which is a respiratory change caused by increased carbon dioxide. If the oxygen flow is too high and easy to lead to carbon dioxide concentration is too high, resulting in type II respiratory failure and pulmonary encephalopathy, the occurrence of impaired consciousness, posing a threat to the patient’s life. Therefore, the flow rate of oxygen concentration in chronic obstructive pulmonary disease is mainly around 35%, which can satisfy the basic situation of patients.