Recurrent pulmonary atelectasis indicates partial or complete airlessness of the lungs with volume atrophy. Recurrent atelectasis is a sign, not a name, so the cause of the recurrent atelectasis needs to be sought. Pulmonary atelectasis refers to a constricted and airless state of the whole lung or part of it. It may be acute or chronic, and in chronic cases there is often a combination of pulmonary atelectasis, infection, bronchiectasis, tissue destruction and fibrosis. In adults, the main cause of acute or chronic atelectasis is obstruction in the bronchial lumen, commonly due to mucus plugs of mucousy bronchial secretions, tumors, granulomas or foreign bodies. Pulmonary atelectasis can also be caused by narrowing or twisting of the bronchi, or by exogenous compression of the bronchi by enlarged lymph nodes, tumors or hemangiomas, or by exogenous compression of lung tissue by fluids and gases such as pleural effusion and pneumothorax. Radiological examination is the most important means of diagnosing pulmonary atelectasis. The presence and location of lobar or segmental atelectasis can usually be clarified by conventional chest plain films. The upper lobe opacification can be mistaken for mediastinum widening, the encapsulated effusion is also similar to pulmonary opacification, and a large amount of pleural effusion can conceal the lower lobe opacification. 2.Bronchoscopy Bronchoscopy is one of the most valuable diagnostic tools for pulmonary asplenia and can be used in most cases. In most cases, obstructive lesions can be seen directly under the microscope and biopsies can be taken, and if a rigid bronchoscope is used, the stenosis can be dilated and exogenous foreign bodies or endogenous stones can be removed. 3, sputum and bronchial aspirate examination sputum bacterial smear examination sputum bacterial culture because the coughing up of secretions mainly from the lung that does not occur, can not reflect the pathological process that causes bronchial obstruction, so sputum examination has little significance for the diagnosis of pulmonary atelectasis, should be made for bacterial, fungal and tuberculosis mycobacteria smear examination and culture, and routine cytological examination, allergic Aspergillus infection sometimes can be cultured Aspergillus, but it should be noted that the laboratory often has Aspergillus. But need to pay attention to the laboratory is often contaminated with Aspergillus, if cough up sputum bolus, and microscopically found a large number of mycelium, you can establish the diagnosis. 4, lymph node biopsy and extrathoracic biopsy histopathology if pulmonary atelectasis caused by bronchopulmonary carcinoma or lymphoma, subxiphoid and mediastinal lymph node biopsy is very helpful for diagnosis, while fibrinoscopic biopsy is often negative, if there is a clear hilar or mediastinal growth, lymph node biopsy often has positive findings, if radiological changes only distal lung tissue atrophy, it is difficult to obtain positive results, nodular disease, tuberculosis, fungal In cases of pulmonary atelectasis caused by nodular disease, tuberculosis, fungal infection, subxiphoid and mediastinal lymph node biopsies are occasionally positive. 5.Pleural effusion examination and pleural biopsy There are various reasons for the formation of pleural effusion in pulmonary atelectasis, pleural effusion may mask the radiological signs of pulmonary atelectasis.