Respiratory failure is called respiratory failure when the partial pressure of oxygen is less than 60 mmHg in the resting state without oxygen. If it is also accompanied by a partial pressure of carbon dioxide greater than 50 mmHg, it is called type II respiratory failure. The difference between type 1 and type 2 respiratory failure is that type 1 respiratory failure only has an oxygen partial pressure less than 60 mmHg and a normal carbon dioxide partial pressure. Type I respiratory failure is mostly seen in acute pulmonary edema and ARDS (acute respiratory distress syndrome), while type II respiratory failure is mostly seen in patients with chronic bronchial disease, emphysema, and pulmonary heart disease. The treatment is also different. High-flow oxygen inhalation is recommended for type 1 respiratory failure, while low-flow oxygen inhalation is recommended for type 2 respiratory failure.