A chest tube is a medical device used to remove air, fluid, or pus from the space around the lungs, known as the pleural cavity. It is typically inserted through the chest wall and connected to a drainage system. This procedure helps to re-expand the lung and improve breathing in patients with conditions such as pneumothorax or pleural effusion. The insertion of a chest tube is usually performed in a hospital setting by a healthcare professional. The tube can remain in place for several days, depending on the patient's condition, and is monitored to ensure proper drainage and prevent complications.