The lungs are covered on the outer surface by a smooth thin membrane called visceral pleura which is continuous with a similar membrane – the parietal pleura which lines the inner surface of the chest wall. The space between the parietal and the visceral pleura is called the pleural cavity which in normal circumstances is a potential space only. The opposing surfaces of both the pleural membranes on the inside of the pleural cavity are moist so as to allow the smooth expansion of the lungs during breathing.
Normally, there is no air in the pleural cavity. Pneumothorax is the presence of air in the pleural cavity which can happen from a leak from the lung. Similar to the fluid in the pleural cavity, the presence of air causes compression of lungs (lung collapse) and produces breathlessness. Chest pain and a feeling of heaviness are other important symptoms.
Pneumothorax generally occurs as an acute and sudden phenomenon, frequently in a previously healthy individual. This is called “spontaneous pneumothorax”. Sometimes, the pneumothorax can also happen in a sub-acute or chronic fashion. Presence of fluid along with the air is referred to as “hydro-pneumothorax”.
Spontaneous pneumothorax presents with sudden onset of severe chest pain and breathlessness, which requires urgent treatment. Such an episode may sometimes follow a bout of exertion, while occasionally without any preceding event. It is commonly believed that a weak spot on the surface of lung may suddenly burst causing release of air into the pleural cavity. This is akin to a case of a balloon, which on inflation can burst at a point which is weak.
People with tall body habitus and Morphanoid features are prone to develop pneumothorax. Chronic tobacco smokers, patients with emphysema and some other chronic lung diseases are also more likely to have pneumothorax. Some of the secondary causes of pneumothorax include lung infections (such as tuberculosis), pneumonias and lung tumours. Chest trauma is another important cause.
Diagnosis of pneumothorax, suspected on history and clinical examination is established with chest x-ray. CT scan of the chest is required to look for the underlying lung. Treatment comprises of a pig-tail catheter drainage/ chest-tube insertion for drainage of air.
Pneumothorax can sometimes recur either on the same or the opposite side. An underlying lung disease should be suspected in such a case, although this may not be demonstrable in all cases. Treatment for recurrent pneumothorax also requires the air drainage with a tube. Small amounts of air can also be aspirated with a syringe.
The procedure of pleurodesis is useful for patients with recurrent pneumothoraces. Pleurodesis involves the adhesion of the two layers of pleural membrane induced by injecting some chemical substances in the pleural cavity after drainage of air. Pleurodesis is a fairly effective method for prevention of recurrences.
Occasionally, an acute pneumothorax can present with severe respiratory distress, cardiac compression and shock (sudden fall in blood pressure). Such an emergency called “cardiac temponade” should be handled immediately by establishing an urgent drainage procedure.