There are requirements for the physician or nursing in terms of the concentration of oxygen inhaled. Because COPD patients are more significantly hypoxic, the oxygen saturation is usually <90%. However, the required oxygen concentration is between 1.5 and 2L/min. If the oxygen concentration is too low, the patient may not be able to correct the symptoms of hypoxia, but too high oxygen concentration will cause carbon dioxide retention, which will further induce pulmonary encephalopathy, cause coma and increase the patient's burden. Because this requires intubation on the machine, admission to the ICU may cause a great financial burden and mental suffering to the patient. Some patients may feel that when they enter the hospital, the oxygen flow should be higher so that it may be better and the hypoxic symptoms can be corrected faster, but in fact this is a very wrong approach and it is recommended to follow the hospital's rules.