Pneumothorax

 
Definition
A pneumothorax is air between a lung and the chest wall
 
Radiographic Appearance
 On a chest x-ray there is an area of the chest contents devoid of lung markings and normally denser separated from the area with lung markings by a fine line, most small pneumothraces are apical.
A film on inspiration and expiration with demonstrate the dynamics and may help to visualise a small pneumothorax seen on an inspiratory film
 
Pathology

What are the causes of pneumothorax?

Spontaneous pneumothorax - means that the pneumothorax develops for no apparent reason. This typically occurs in young, thin adults who do not have any lung disease. Men are affected 4 times more often than women. It is thought to be due to a tiny tear (rupture) of an outer part of the lung - usually near the top of the lung. It is not clear why this occurs. Air then escapes from the lung but gets trapped between the lung and the chest wall. About 1 in 10 people who have a spontaneous pneumothorax have one or more recurrences sometime in the future, usually on the same side.

Injury - to the chest such as from a road traffic accident or a stab wound to the chest.

Lung diseases - pneumothorax is an uncommon complication of some lung diseases such as asthma, emphysema, pneumonia, etc

The pressure of the air that leaks out of the lung and the air inside the lung equalises in most cases of spontaneous pneumothorax. 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 or 'rupture' that caused the leak usually heals within a few days. 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.

Tension pneumothorax - 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.

 
Treatment:
No treatment may be needed for a small pneumothorax. It 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. Painkillers may be needed for a few days if the pain is bad.

Draining the air may be needed if there is a larger pneumothorax or if you have other lung or breathing problems. As a rule, a pneumothorax that causes shortness of breath is best drained. It is essential to drain a 'tension' pneumothorax quickly. The air is removed by inserting a small tube through the chest wall and sucking out the trapped air. This is done under local anaesthetic.
 
Images

Tension Pneumothorax
 

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