If oxygen is given at medium or high flow, the excitatory stimulation of the respiratory center will be weakened after the correction of hypoxia, which may aggravate carbon dioxide retention and cause respiratory depression or even coma, so oxygen should be given at low flow. Respiratory failure is divided into type I respiratory failure and type II respiratory failure. Type I respiratory failure is only hypoxic, oxygen partial pressure is generally <60mmHg, carbon dioxide partial pressure is normal, and oxygen can be administered at medium to high flow rate. Type II respiratory failure, in addition to oxygen partial pressure <60mmHg, is often accompanied by carbon dioxide retention, carbon dioxide partial pressure >50mmHg, and low-flow oxygen intake.