Chronic bronchitis is a chronic nonspecific inflammation of the trachea, bronchial mucosa and surrounding tissues. Clinically, the main symptoms are repeated attacks of cough, sputum or wheezing, which last for 3 months each year for more than 2 consecutive years. The early symptoms are mild, often occurring in winter and relieved in spring and summer. In the late stage, due to the aggravation of inflammation, the symptoms may exist all year round. Its pathological characteristics are bronchial gland hyperplasia and increased mucosal secretion. The disease progresses slowly and progressively, often complicated by obstructive emphysema. In severe cases, pulmonary hypertension and even cor pulmonale often occur.