Chronic respiratory failure occurs on the basis of existing lung diseases, such as chronic obstructive pulmonary disease, severe pulmonary tuberculosis, pulmonary interstitial fibrosis, pneumoconiosis, chest lesions and chest surgery, trauma, extensive pleural thickening, chest deformity, etc. The most common cause is COPD. In the early stage, it may manifest as type I respiratory failure. As the disease gradually worsens, lung function becomes worse and worse, and it may manifest as type II respiratory failure. In the stable stage of chronic respiratory failure, although PaO2 decreases and PaCO2 increases, patients can stabilize within a certain range through compensation and treatment, and patients can still engage in general work or daily life activities. Once the respiratory tract infection worsens or other inducements occur, it may manifest as a significant decrease in PaO2 and a significant increase in PaCO2. This can be called an acute attack of chronic respiratory failure, which is the most common type of chronic respiratory failure in clinical practice in my country.