Presence of air between the layers of the pleura, the two-layered membrane that separates the lungs from the chest wall
In a pneumothorax, air enters between the two layers of the pleura, the membrane that separates the lungs from the chest wall. A pneumothorax may cause the lung beneath it to collapse, which can then lead to chest pain and shortness of breath. The air that produces a pneumothorax can come from within the lungs or outside the body, depending on the cause. The condition often affects only one side of the chest.
The amount of air between the layers of the pleura may be small, and in such cases breathing is not severely affected. However, a large pneumothorax may cause severe shortness of breath. In a tension pneumo-thorax, air that enters between the layers of the pleura cannot get back out and causes the pressure inside the pleural layers to rise. This condition also causes severe shortness of breath and can be fatal. It requires immediate medical treatment.
In most cases, the cause of a pneumothorax is the spontaneous rupture of an abnormally dilated alveolus (air sac), known as a bulla, on the surface of the lung. Most bullae are present from birth. Rupture of a bulla is often caused by vigorous exercise but can sometimes occur at rest. A pneumothorax due to the rupture of a bulla occurs most frequently in tall, thin young men.
A pneumothorax may develop as a complication of lung disorders such as asthma and chronic obstructive pulmonary disease. Repeated pneumothoraces may be associated with Marfan’s syndrome, a rare inherited disorder that affects connective tissue and results in abnormalities of the bones, heart, and eyes.
Other possible causes of a pneumothorax include a penetrating chest wound that allows air to enter between the layers of the pleura from outside the body, fractured ribs that tear the lung beneath them, or surgical procedures performed on the chest.
Symptoms of a pneumothorax usually develop rapidly and may include:
Chest pain, which may be felt as sudden and sharp or may cause only slight discomfort.
Shortness of breath or a sudden worsening of pre-existing shortness of breath in someone with a long-term respiratory disorder.
Tightness across the chest.
In a tension pneumothorax, there is severe pain and shortness of breath. The high pressure caused by a tension pneumothorax prevents blood from returning to the heart from the lungs, which in turn causes low blood pressure, fainting, and shock.
If your doctor suspects that you have a pneumothorax, a chest X-ray will be carried out to confirm the diagnosis. A small pneumothorax usually disappears by itself over the course of a few days as the leak that created it heals and the air is gradually absorbed by the body. If the pneumothorax is larger or you have an underlying lung disorder such as asthma, you may need hospital treatment. The doctor will either withdraw some air with a needle or insert a drainage tube through the chest wall under local anaesthesia to enable air to escape (see Chest drain).
A tension pneumothorax is a medical emergency. It is treated by inserting a large, hollow needle directly into the affected side of the chest to allow air to escape. This procedure provides immediate relief of symptoms.
If an air leak persists or returns, a technique known as pleurodesis may be used to prevent further lung collapse. This procedure introduces a chemical irritant between the two layers of the pleura to make them stick together. However, pleurodesis is not always successful and, rarely, surgery may be required to repair the damaged area.
With appropriate treatment, most people with a pneumothorax recover completely. However, in 1 in 5 cases the condition recurs, usually within a year.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.