Section 4. Lung and Airway Disorders

Chapter 52. Pleural Disorders

Topics: Introduction | Pleurisy | Pleural Effusion | Pneumothorax

Pneumothorax

A pneumothorax is a pocket of air between the two layers of pleura, resulting in collapse of the lung.

Normally, the pressure in the pleural space is lower than that inside the lungs. If air enters the pleural space, the pressure in the pleural space becomes greater than that in the lungs, and the lung collapses partially or completely. Sometimes most or all of the lung collapses, leading to immediate and severe shortness of breath.

A pneumothorax may occur for no identifiable reason; doctors call this a spontaneous pneumothorax. Spontaneous pneumothorax usually occurs when a small weakened area of lung (bulla) ruptures (primary spontaneous pneumothorax). The condition is most common in tall men younger than age 40. Most incidents of primary spontaneous pneumothorax do not occur during exertion. Some occur during diving or high-altitude flying, apparently because of pressure changes in the lungs. Most people recover fully; however, primary spontaneous pneumothorax recurs in about 30 to 50% of people regardless of the person's relation to sea level.

Spontaneous pneumothorax also occurs in people with extensive lung disease (secondary spontaneous pneumothorax). This type of pneumothorax most often results from the rupture of a bulla in older people who have emphysema, but it also occurs in people with other lung conditions, such as cystic fibrosis, Langerhans' cell granulomatosis, sarcoidosis, lung abscess, tuberculosis, and pneumocystis pneumonia. Because of the underlying lung disease, the symptoms and outcome are generally worse in secondary spontaneous pneumothorax; the recurrence rate is similar to that of primary spontaneous pneumothorax.

A pneumothorax may also follow an injury or a medical procedure that introduces air into the pleural space, such as thoracentesis. Ventilators can cause pressure damage to the lungs (barotrauma) that leads to a pneumothorax--most often in people with severe acute respiratory distress syndrome (see Section 4, Chapter 56).

Symptoms and Diagnosis

Symptoms vary greatly depending on how much air enters the pleural space, how much of the lung collapses, and the person's lung function before the pneumothorax occurred. They range from a little shortness of breath or chest pain to severe shortness of breath, shock, and life-threatening cardiac arrest. Most often, sharp chest pain and shortness of breath and occasionally a dry hacking cough begin suddenly. Pain may also be felt in the shoulder, neck, or abdomen. Symptoms tend to be less severe in a slowly developing pneumothorax than in a rapidly developing one. Except with a very large pneumothorax or a tension pneumothorax, symptoms usually subside as the body adapts to the lung collapse, and the lung slowly begins to reinflate as the air is reabsorbed from the pleural space.

A physical examination can usually confirm the diagnosis if the pneumothorax is large. Using a stethoscope, a doctor may note that one part of the chest does not transmit the normal sounds of breathing, while tapping (percussing) the chest produces a hollow, drumlike sound. A chest x-ray shows the air pocket and the collapsed lung outlined by the thin inner pleural layer. A chest x-ray can also show if the trachea (the large airway that passes through the front of the neck) is being pushed to one side because of a collapsed lung.

Treatment

A small primary spontaneous pneumothorax usually requires no treatment. It usually does not cause serious breathing problems, and the air is absorbed in several days. The full absorption of air in a larger pneumothorax may take 2 to 4 weeks; however, the air can be removed more quickly by inserting a chest tube into the pneumothorax.

A chest tube is needed if the pneumothorax is large enough to impair breathing. The chest tube is inserted through an incision in the chest wall and is connected to a water-sealed drainage system or a one-way valve that allows the air to exit without allowing any air to get back in. A suction pump may have to be attached to the chest tube if air keeps leaking in from an abnormal connection (fistula) between an airway and the pleural space. Occasionally, surgery is necessary. Often the surgery is performed using a thoracoscope inserted through the chest wall and into the pleural space.

A recurring pneumothorax can cause considerable disability. For people at high risk--for example, divers and airplane pilots--surgery is considered after the first episode of pneumothorax. Usually surgery involves repairing leaking areas of the lung and firmly attaching the inner layer of pleura to the outer layer. For people who have a pneumothorax that will not heal or a pneumothorax that has occurred twice on the same side, surgery, often using a thoracoscope, is performed to eliminate the cause of the problem. In secondary spontaneous pneumothorax with a persistent air leak into the pleural space or with a recurring pneumothorax, the underlying lung disease may make surgery hazardous. Often, the pleural space can be sealed by administering a talc mixture into the space or by giving the drug doxycycline through a chest tube that is draining air from the space.

See the sidebar What Is Tension Pneumothorax?