Respiratory failure can be divided into type I, type II, or acute and chronic according to different typing criteria, as follows: 1. Type I: accompanied only by hypoxemia, with arterial partial pressure of oxygen below 60 mmHg and normal or low partial pressure of carbon dioxide; 2. Type II: partial pressure of carbon dioxide higher than 50 mmHg, accompanied by low partial pressure of oxygen; or chronic respiratory failure patients with partial pressure of oxygen higher than 60 mmHg and partial pressure of carbon dioxide higher than 50 mmHg; 3. Acute: can cause functional damage to important organs in a short period of time; 4. Chronic: chronic process, without serious damage to important organs.