Bronchitis is a lung disease in which there is increased secretion of mucus from the bronchi and trachea and is caused by both infectious and non-infectious factors. Patients who smoke have a much greater chance of developing bronchitis than those who do not smoke. The clinical symptoms of bronchitis are: (1) coughing, most patients show white foamy mucous sputum; (2) coughing, acute bronchitis patients have an acute onset and usually show a dry cough, coughing too often may also cause sternal pain, chronic patients have a long cough that is easily repeated; (3) shortness of breath, commonly seen in patients in the acute phase. Patients with bronchitis may also have systemic symptoms, such as fever and headache, but they usually do not last long. Early symptoms are mild and usually have no obvious symptoms. Bronchitis has a long and slow and continuous course, and in the late stages it can affect physical health and lung function. Early lung auscultation may not be abnormal, or coarse breath sounds may be heard, and then scattered dry rales may be heard as the disease progresses. White blood cell counts are usually normal in laboratory tests, and the diagnosis is more significant by chest x-ray. In addition, smoking is an important cause of the disease, so it is important to stop smoking.