Bronchoscopic applications: 1. Direct observation: fiberoptic bronchoscopy can observe the upper and lower airways, and direct observation can diagnose a variety of congenital anatomical abnormalities; 2. Bronchoalveolar lavage: bronchoalveolar lavage fluid culture and cellular component examination can provide pathogenic and cytological basis for disease diagnosis, while therapeutic lavage can treat pulmonary atelectasis by removing secretions that obstruct the airways; 3. Bronchial endothelium Biopsy: for histopathology, immunohistochemical analysis and microbiological culture. Indications for bronchoscopy: 1. trachea, bronchopulmonary dysplasia and malformations: tracheal and bronchial achondroplasia, tracheal cricoid cartilage, tracheo-oesophageal fistula, congenital malformations of trachea, bronchus and lung; 2. pulmonary atelectasis: x-ray findings of persistent lobar or segmental atelectasis and pneumonia should be treated by bronchoscopy and even require multiple lavage treatments; 3. hemoptysis or blood in sputum: hemoptysis has many causes, such as pulmonary tuberculosis, Bronchial tuberculosis, inflammatory lesions of the lung (bronchitis, bronchiectasis, lung abscess and granuloma, etc.) and tumors. The pathogenic and pathological examination can be done by bronchoscopy; 4. Chronic cough and recurrent respiratory infections: can be caused by various factors such as asthma, foreign bodies, gastro-esophageal reflux and tracheal developmental abnormalities, etc., which need to be differentially diagnosed. 5.Limited stridor: This syndrome suggests localized narrowing of the large airways, which may be caused by inflammation, tuberculosis, tumors, foreign bodies in the bronchi, or by enlarged parabronchial lymph nodes, enlarged thyroid glands behind the sternum, or mediastinal masses compressing the airways, and needs to be differentiated; 6.Lung mass lesions: including masses, abscesses, tuberculosis, and parasites, etc. 7, diffuse lung disease: including interstitial lung disease, idiopathic pulmonary fibrosis, nodular disease, eosinophilic pneumonia, alveolar protein deposition and other chronic lung diseases need to be differentially diagnosed; 8, removal of airway foreign bodies: bronchoscopy to remove larger foreign bodies is not as convenient as hard bronchoscopy. The effect of bronchoscopy on the removal of deep bronchial foreign body is exact; 9, tracheobronchial laceration or rupture: trauma to the chest, suspected tracheobronchial laceration or rupture, bronchoscopy can often be a clear diagnosis; 10, tracheal intubation: for children with neck disorders and difficulty in posterior elevation, which can not apply direct laryngoscopic intubation, bronchoscopy can be used to guide the tracheal intubation; 11, before, during and after thoracic surgery Diagnosis and auxiliary diagnosis.