Final answer:
A thoracentesis is the medical procedure used to drain excess fluid from the pleural cavity to treat a pleural effusion and restore normal lung function.
Step-by-step explanation:
The procedure for draining a pleural effusion, which is the accumulation of excess fluid in the pleural cavity, is called a thoracentesis. During this procedure, a needle or a small tube (catheter) is inserted through the chest wall into the pleural space to remove the fluid. This can help to alleviate symptoms like shortness of breath and chest pain associated with the effusion. The balance of fluids in the pleural cavity is crucial; too much fluid can compromise lung function by preventing the lungs from fully expanding.
Normal intrapleural pressure is negative, which aids in keeping the lungs inflated. This negative pressure is disrupted when excess fluid accumulates, necessitating the thoracentesis to restore normal lung function. This procedure is carefully performed to prevent complications such as a collapsed lung (spontaneous pneumothorax) or infection.