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A pleural tap is a procedure in which a sample of fluid is removed from the space between the lining of the lungs and the chest wall. The lining of the lungs is a double layer of membranes called the pleural membranes, which surround and support the organs. A pleural tap is performed as part of a diagnostic process or as a treatment to remove fluid from the lungs. This procedure is also called a pleural fluid aspiration, thoracentesis or thoracocentesis.
In healthy lungs, there is very little fluid between the layers of the pleural membranes. Excess fluid generally is caused by trauma or some kind of disease process, such as cancer, infection or heart failure. In such cases, a pleural tap is a diagnostic measure in which a sample of fluid is drawn and tested for the presence of bacteria, viruses or other clues to indicate the cause of the fluid build-up.
This procedure also can be used for treating symptoms of certain diseases. For example, a type of cancer called pleural mesothelioma causes fluid to build up between the pleural membranes. This fluid build-up, called pleural effusion, causes discomfort and makes breathing difficult. The pleural tap procedure is used as a treatment to remove fluid and to help the patient breathe easier.
To prepare for the procedure, the patient usually will sit on a chair or on the edge of a bed. The patient must lean over a table and rest his or her arms, chest and head on the top of the table. The patient's back is washed and sterilized to help prevent infection, and a local anesthetic is then injected into the site where the tap will be performed.
During the pleural fluid tap, a long, thin needle is inserted through the skin into the pleural space between the membranes. A sample of fluid is drawn into the needle. When the needle is in place, it is very important that the patient not move, cough or breathe deeply, in order to prevent sudden movements that might result in lung injury. If the test is being carried out as part of a diagnostic process, the fluid sample is tested in a laboratory for malignant cells, microorganisms and proteins that provide diagnostic clues.
There are several risks associated with the pleural tap procedure. The most common risks are of coughing or fainting during or after the procedure. Uncommon risks include pain in the lung, a collapsed lung and fluid build-up in the lung. Very rare risks include damage to nearby organs, such as the spleen or liver, and bleeding into the chest cavity. Generally, someone who has this procedure will undergo a chest X-ray immediately afterward, to ensure that the lungs have not been damaged by the needle.