Pneumothorax

Pneumothorax is characterized by an accumulation of air or gas between the parietal and visceral pleurae. The amount of air or gas trapped in the intrapleural space determines the degree of lung collapse. The most common types of pneumothorax are open, closed, and tension. Many factors contribute to pneumothorax.

Causes

The following conditions and procedures can trigger pressure changes that cause open, closed, or tension pneumothorax.

Open pneumothorax

• Penetrating chest injury, such as a gunshot or knife wound
• Insertion of a central venous catheter
• Chest surgery
• Transbronchial biopsy
• Thoracentesis or closed pleural biopsy

Closed pneumothorax

• Blunt chest trauma
• Air leakage from ruptured, congenital blebs adjacent to the visceral pleural space
• Rupture of emphysematous bullae
• Rupture resulting from barotrauma caused by high intrathoracic pressures during mechanical ventilation .
• Tubercular or cancerous lesions that erode into the pleural space
• Interstitial lung disease such as eosinophilic granuloma

Tension pneumothorax

• Penetrating chest wound treated with an airtight dressing
• Lung or airway puncture by a fractured rib associated with positive-pressure ventilation
• Mechanical ventilation (after chest injury) that forces air into the pleural space through damaged areas
• High-level positive end-expiratory pressure that causes alveolar blebs to rupture
• Chest tube occlusion or malfunction

Signs and Symptoms

There may be no symptoms if the pneumothorax is small (a small amount of air in the pleural space) or there may be shortness of breath if a large amount of air is in that space. If a physician suspects a pneumothorax, a chest x-ray may be taken to confirm the diagnosis and to determine the amount of air present.

Diagnostic tests

Chest X-rays reveal air in the pleural space and, possibly, a mediastinal shift, which confirms the diagnosis.

Pulse oximetry results may show early decline. Arterial blood gas studies may show hypoxemia, possibly accompanied by respiratory acidosis and hypercapnea. Levels of arterial oxygen saturation may decrease initially but typically return to normal with­in 24 hours.

Treatment

Typically, treatment is conservative for spontaneous pneumothorax with no signs of increased pleural pressure (indicating tension pneumothorax), with lung collapse less than 30%, and with no dyspnea or other indications of physiologic compromise. Such treatment consists of bed rest, careful monitoring (blood pressure and pulse and respiratory rates), oxygen administration and, possibly, aspiration of air with a large-bore needle attached to a syringe or insertion of a Heimlich valve.

If more than 30% of the lung collapses, treatment to reexpand the lung includes placing a thoracostomy, tube in the second or third intercostal space in the midclavicular line. The thoracostomy tube then connects to an underwater seal or to low-pressure suction.

Recurring spontaneous pneumothorax requires thoracotomy and pleurectomy. These procedures prevent recurrence by causing the lung to adhere to the parietal pleura. Traumatic and tension pneumothorax require chest tube drainage; traumatic pneumothorax may also require surgical repair. Analgesics may be prescribed.

Prevention

Stopping smoking will decrease the risk of developing severe lung disease that may lead to pneumothorax. Controlling lung diseases such as asthma may lower the risk of pneumothorax.