Pneumothorax

Definition:

• Air in the pleural space

Causes:

• Trauma to the chest wall
• Spontaneous

Pathophysiology:

• Pneumothorax is localised if the visceral pleura has previously undergone adhesion to the parietal pleura, or generalized if the whole hemithorax contains air
• Normally, the pressure in the pleural space is negative but this is lost once a communication is made with atmospheric pressure
• The elastic recoil pressure of the lung then causes it to partially deflate
• If the communication between the airways and the pleural space remains (an open pneumothorax), a bronchopleural fistula is created
• It takes about 40 days for a 50% collapse of the lung to reabsorb completely once the pneumothorax is closed

Tension pneumothorax:

• A valvular mechanism may develop through which air can be sucked during inspiration but not expelled during expiration
• The intrapleural pressure remains positive throughout breathing, the lung deflates further, the mediastinum shifts and venous return to the heart decreases – with increasing respiratory and cardiac embarrassment
• A tension pneumothorax is very rare, unless the patient is on positive ventilation

Spontaneous pneumothorax:

• Usually occurs in young males (male:female is 6:1)
• It is caused by the rupture of a pleural bleb, usually apical and is thought to be due to congenital defects in the connective tissue of the alveolar walls
• Both lungs are affected with equal frequency
• Often these patients are tall and thin
• In patients >40 years, the usual cause is underlying COPD
• Clinical features:
• Sudden onset of unilateral pleuritic pain
• Increasing breathlessness

Treatment:

• Essentially involves aspirating the air in the pleural space
• If the air reaccumulates, insert an intercostal drainage tube with underwater seal for 2-3 days
• If the air reaccumulates after this, a pleurectomy is sometimes required