Thoracentesis is a proof point of the chest wall puncture to extract liquid and / or air in the pleural space (external space of the lungs) using a thin hollow needle or a catheter. Normally the test is performed with the aim of analyzing a sample of fluid causing excessive pleural effusions, but also other causes such as lung cancer, pulmonary embolism, pneumonia, pancreatitis, etc. Thoracentesis no prior preparation is required, but the realization of a chest radiograph before and after the test. Besides, it is necessary that the patient does not cough or move during the process as this could cause damage to the lung. The test starts with the application of anesthesia in the back area where the pleural puncture takes place, which involves inserting the needle above the rib into the pleural space to remove a sample of the liquid to be analyzed in the laboratory. As the result, the treatment will be adapted to the pathology.