Chronic bronchitis refers to repeated bronchial infections with a course of more than 2 years and an annual attack time of more than 2 months. There are four major symptoms: cough, wheezing, inflammation, and sputum. X-ray chest films show changes such as interstitial chronic bronchitis and emphysema. Other diseases with such symptoms should also be ruled out, such as tuberculosis, lung abscess, heart disease, bronchiectasis, bronchial asthma, and chronic nasopharyngeal diseases. If children with acute bronchitis cough and expectoration for more than 2 to 3 weeks, it can be considered to enter the chronic process. In recent years, many experts have also believed that it is more appropriate to define persistent cough with or without expectoration for more than 3 months as chronic bronchitis.