What is a pneumothorax?

A pneumothorax is air that is trapped between a lung and the chest wall. The air gets there either from the lungs or from outside the body.

What are the causes?

Primary spontaneous pneumothorax

This means that the pneumothorax develops for no apparent reason in an otherwise healthy person. This is the common type of pneumothorax. It is thought to be due to a tiny tear of an outer part of the lung – usually near the top of the lung. It is often not clear why this occurs. However, the tear often occurs at the site of a tiny bleb or bullae on the edge of a lung. These are like small balloons of tissue that may develop on the edge of a lung. The wall of the bleb is not as strong as normal lung tissue and may tear. Air then escapes from the lung but gets trapped between the lung and the chest wall.

Most occur in healthy young adults who do not have any lung disease. It is more common in tall thin people.

About 2 in 10,000 young adults in the UK develop a spontaneous pneumothorax each year. Men are affected about four times more often than women. It is rare in people over the age of 40. It is also much more common in smokers compared with non-smokers. Cigarette smoke seems to make the wall of any bleb even weaker and more likely to tear.

About 3 in 10 people who have a primary spontaneous pneumothorax have one or more recurrences at some time in the future. If a recurrence does occur it is usually on the same side and usually occurs within three years of the first one.

Secondary spontaneous pneumothorax

This means that the pneumothorax develops as a complication (a secondary event) of an existing lung disease. This is more likely to occur if the lung disease weakens the edge of the lung in some way. This may then make the edge of the lung more liable to tear and allow air to escape from the lung. So, for example, a pneumothorax may develop as a complication of chronic obstructive airways disease (COPD) – especially where lung bullae have developed in this disease. Other lung diseases that may be complicated by a pneumothorax include: pneumonia, tuberculosis, sarcoidosis, cystic fibrosis, lung cancer, and idiopathic pulmonary fibrosis.

Other causes of pneumothorax

An injury to the chest can cause a pneumothorax. For example, a car crash or a stab wound to the chest. Surgical operations to the chest may cause a pneumothorax. A pneumothorax is also an uncommon complication of endometriosis.

What are the symptoms of a pneumothorax?

  • The typical symptom is a sharp, stabbing pain on one side of the chest, which suddenly develops.
  • The pain is usually made worse by breathing in (inspiration).
  • You may become breathless. As a rule, the larger the pneumothorax, the more breathless you become.
  • You may have other symptoms if an injury or a lung disease is the cause. For example, cough or fever.

A chest X-ray can confirm a pneumothorax. Other tests may be done if a lung disease is the suspected cause.

What happens to the trapped air and small tear on the lung?

In most cases of spontaneous pneumothorax, the pressure of the air that leaks out of the lung and the air inside the lung equalises. The amount of air that leaks (the size of the pneumothorax) varies. Often it is quite small and the lung collapses a little. Sometimes it can be large and the whole lung collapses. If you are otherwise fit and well, this is not too serious, as the other lung can cope until the pneumothorax goes. If you have a lung disease, a pneumothorax may make any existing breathing difficulty much worse.

The small tear that caused the leak usually heals within a few days, especially in cases of primary spontaneous pneumothorax. Air then stops leaking in and out of the lung. The trapped air of the pneumothorax is gradually absorbed into the bloodstream. The lung then gradually expands back to its original size. Symptoms may last as short as 1-3 days in cases of primary spontaneous pneumothorax. However, symptoms and problems may persist longer, especially in cases where there is an underlying lung disease.

Tension pneumothorax

This is a rare complication. This causes shortness of breath that quickly becomes more and more severe. This occurs when the tear on the lung acts like a one-way valve. In effect, each breath in (inspiration) pumps more air out of the lung, but the valve action stops air coming back into the lung to equal the air pressure. The volume and pressure of the pneumothorax increases. This puts pressure on the lungs and heart. Emergency treatment is needed to release the trapped air.

What is the treatment for pneumothorax?

No treatment may be needed

You may not need any treatment if you have a small pneumothorax. A small pneumothorax is likely to clear over a few days. A doctor may advise an X-ray in 7-10 days to check that it has gone. You may need painkillers for a few days if the pain is bad.

Aspirating (removing) the trapped air is sometimes needed

This may be needed if there is a larger pneumothorax or if you have other lung or breathing problems. As a rule, a pneumothorax that makes you breathless is best removed. It is essential to remove the air quickly in a tension pneumothorax. The common method of removing the air is to insert a very thin tube through the chest wall with the aid of a needle. (Some local anaesthetic is injected into the skin first to make the procedure painless.) A large syringe with a three-way tap is attached to the thin tube that is inserted through the chest wall. The syringe sucks out some air, the three-way tap is turned, and the air in the syringe is then expelled into the atmosphere. This is repeated until most of the air of the pneumothorax is removed.

Sometimes a larger tube is inserted through the chest wall to remove a large pneumothorax. This is more commonly needed for cases of secondary spontaneous pneumothorax when there is underlying lung disease. Commonly, the tube is left place for a few days to allow the lung tissue that has torn to heal.

Note: it can be dangerous to fly if you have a pneumothorax. Do not fly until you have the ‘all clear’ from your doctor following a pneumothorax. Also, do not go to remote places where access to medical care is limited until you have the ‘all clear’ from a doctor.

Treating recurrences

Some people have repeated episodes of spontaneous pneumothorax. If this occurs, a procedure may be advised with the aim of preventing further recurrences. For example, an operation is an option if the part of the lung that tears and leaks air out is identified. It may be a small bleb on the lung surface, which can be removed. Another procedure that may be advised is for an irritant powder (usually a kind of talc powder) that can be put on the lung surface. This causes an inflammation which then helps the lung surface to stick to the chest wall better.

A lung specialist will be able to give the pros and cons of the different procedures. The procedure advised may depend on your general health, and whether you have an underlying lung disease.

If you are a smoker and have had a primary spontaneous pneumothorax, you can reduce your risk of a recurrence by stopping smoking.

References and Disclaimer | Provide feedback


  • Bascom R et al; Pneumothorax, eMedicine, Feb 2009
  • Alhameed FM et al; Pneumothorax (Radiology perspective), eMedicine, Dec 2008
  • Pleural Disease Guideline, British Thoracic Society (September 2010); Includes guidance on: pleural infection; pleural effusion; pneumothorax; insertion of a chest drain and other procedures.
  • Kelly AM; Treatment of primary spontaneous pneumothorax. Curr Opin Pulm Med. 2009 Jul;15(4):376-9. [abstract]


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