High carbon dioxide in the body is called carbon dioxide retention, which is generally known by blood gas analysis of arterial blood, and elevated carbon dioxide in the body indicates that there is a certain obstacle in the ventilation function and gas exchange function of the lungs. The following causes are common: 1. short expiratory time due to thoracic, neurological and muscular lesions, insufficient pulmonary ventilation, insufficient exhaled carbon dioxide, resulting in carbon dioxide retention in the body, common thoracic deformities, chest trauma, poisoning, etc. 2. chronic inflammatory airway diseases, airway obstruction causing airflow restriction, resulting in carbon dioxide retention. 3. lung diseases, such as pulmonary fibrosis, silicosis and other diseases 4.Severe cardiovascular diseases, such as coronary heart disease, mitral stenosis and other cardiovascular diseases cause severe heart failure, and pulmonary edema causes pulmonary ventilation and ventilation dysfunction, which can also lead to elevated carbon dioxide in the body.