(See also Introduction to Chest Injuries.)
Tension pneumothorax occurs when air accumulates between the chest wall and the lung and increases pressure in the chest, reducing the amount of blood returned to the heart.
In an ordinary pneumothorax, injury to a lung allows a certain amount of air to enter the space between the lung and the chest wall (pleural space). Typically, the air stops accumulating. However, in tension pneumothorax, air continues to enter the pleural space as the person breathes and pressure rises inside the chest. The rise in pressure reduces the amount of blood returning from the body to the heart because the blood cannot force its way into the chest and back to the heart. As a result, the heart has less blood to pump to the body, resulting in shock. These effects can occur rapidly, particularly in people using a mechanical ventilator. Tension pneumothorax can rapidly be fatal.
Doctors diagnose tension pneumothorax based on the person's history, symptoms, and examination results. For example, one side of the chest may bulge (be distended), and doctors may hear a hollow sound when they tap it. When they listen to the chest with a stethoscope, they may not hear any air flowing to the lung.
Because tension pneumothorax is an emergency, doctors begin treatment immediately rather than doing tests.
Doctors immediately insert a large needle into the pleural space to remove the air (called needle decompression). Then a chest (thoracostomy) tube is inserted to continue to drain air and allow the lung to reinflate (see Chest Tube Insertion). Usually local anesthesia is used.