Inclusion Criteria:  1. <60 years old;  2. Smoking ≥ 10 pack years.  3. With any of the following anomalies: a. Post-bronchodilator FEV1/FVC< 0.7. b. CT image abnormalities: emphysema, air trapping or bronchial wall thickening; c.Rapid decrease of FEV1 (>60 ml/yr).  Exclusion Criteria:  1. With other known chronic lung diseases, including bronchiectasis, interstitial pulmonary disease, tuberculosis, and pulmonary vascular disease (CTEPH).  2. With severe pleural disease and/or lesions of the sternum or ribs.  3. Suffering from serious uncontrolled other systemic diseases, including chest and abdominal surgery, heart attack (angina pectoris, myocardial infarction, malignant arrhythmia, etc.) and cerebrovascular disease (stroke) within 3 months, as well as kidney disease (AKI), cirrhosis, and any malignant tumor except lung cancer.  4. Suffering from severe cognitive impairment.  5. With active tuberculosis or are taking anti-tuberculosis treatment.  6. Pregnancy or lactation.  7. Previous lung surgery.  8. Acute upper and lower respiratory system infection within 4 weeks.