Definiton Also known as pleural fluid aspiration, the thoracic wall is punctured to obtain a specimen of pleural fluid for analysis or to relieve pulmonary compression and resultant respiratory distress. Locating the fluid before thoracentesis reduces the risk of puncturing the lung, liver, or spleen. The pleural cavity should contain less than 20 ml of serous fluid. Pleural effusion results from the abnormal formation or reabsorption of pleural fluid. Certain characteristics classify pleural fluid as either a transudate or exudates. Purpose To provide pleural fluid specimens to determine the cause and nature of pleural effusion. To provide symptomatic relief with