Indications for bronchoscopy: 1. Unexplained hemoptysis, especially over 40 years of age, hemoptysis lasting more than 1 week or blood in sputum; 2. Unexplained chronic cough; 3. Unexplained restricted croup; 4. Unexplained hoarseness; 5. Cancer cells or suspected cancer cells in sputum; 6. Abnormalities in chest X-ray or CT examination, suggesting pulmonary atelectasis, lung mass shadow, obstructive pneumonia, diffuse lung lesions, hilar and/or mediastinal lymph node enlargement, tracheobronchial stenosis and unexplained pleural effusion.