Thoracentesis mainly refers to thoracentesis, followed by pulmonary puncture, which has diagnostic and therapeutic roles: I. Diagnostic thoracentesis: In cases where the cause of pleural effusion is unknown and the nature is difficult to determine, thoracentesis can extract pleural effusion for physical and chemical examination to clarify the physical and chemical nature of pleural effusion, so as to further clarify the cause of pleural effusion. Second, therapeutic puncture: In cases where the symptoms of pleural effusion are heavy, extraction of pleural effusion can reduce the symptoms of pressure on tissues such as lungs and heart, and thoracentesis can also inject drugs into the chest cavity to reduce the exudation of pleural effusion. Another puncture is pulmonary puncture, which is actually a further penetration of thoracic puncture. The puncture needle enters the chest cavity and continues to puncture into the lung tissue, mainly for the diagnosis and treatment of conditions such as unexplained pulmonary nodules and pulmonary cavities.