Pneumothorax

In pneumothorax, air or gas accumulates between the parietal and visceral pleurae. The amount of air or gas trapped in the intrapleural space determines the degree of lung collapse.

In a tension pneumothorax, the air in the pleural space is under higher pressure than air in adjacent lung and vascular structures. Without prompt treatment, a tension or a large pneumothorax results in fatal pulmonary and circulatory impairment.

Causes

Air leaks occur when the alveoli (tiny air sacs) become overdistended and burst. Pressure of the air delivered by mechanical ventilators (breathing machines) is the most common cause. Meconium aspiration (inhalation of the first stools passed in utero) can also trap air and lead to over distention (the lungs expand too much) and air leaks. Air leaks often occur in the first 24 to 36 hours when lung disease is at its peak. Some otherwise healthy babies can develop a "spontaneous" air leak that does not cause symptoms or distress.

Signs and symptoms

The cardinal features of pneumothorax are sudden, sharp, pleuritic pain (exacerbated by movement of the chest, breathing, and coughing); asymmetrical chest wall movement; shortness of breath; and cyanosis. In moderate to severe pneumothorax, profound respiratory distress may develop, with signs of tension pneumothorax: weak and rapid pulse, pallor, neck vein distention, and anxiety. Tension pneumothorax produces the most severe respiratory symptoms; a spontaneous pneumothorax that releases only a small amount of air into the pleural space may cause no symptoms.

Diagnosis

Sudden, sharp chest pain and shortness of breath suggest pneumothorax. Chest X-ray showing air in the pleural space and, possibly, mediastinal shift confirms this diagnosis. In the absence of a definitive chest X-ray, physical examination occasionally reveals:

• on inspection: over expansion and rigidity of the affected chest side; in tension pneumothorax, neck vein distention with hypotension and tachycardia .
• on palpation: crackling beneath the skin, indicating subcutaneous emphyserna (air in tissue) and decreased vocal fremitus
• on percussion: hyperresonance on the affected side
• on auscultation: decreased or absent breath sounds over the collapsed lung.

If the pneumothorax is significant, arterial blood gas findings include pH less than 7.35, partial pressure of arterial oxygen less than 80 mm Hg, and partial pressure of arterial carbon dioxide above 45 mm Hg.

Treatment

Treatment is conservative for spontaneous pneumothorax in which no signs of increased pleural pressure (indicating tension pneumothorax) appear, lung collapse is less than 30%, and the patient shows no signs of dyspnea or other indications of physiologic compromise.

Such treatment consists of bed rest; careful monitoring of blood pressure, pulse rate, and respirations; oxygen administration; and, possibly, needle aspiration of air with a largebore needle attached to a syringe.

If more than 30% of the lung is collapsed, treatment to reexpand the lung includes placing a thoracostomy tube in the second or third intercostal space in the midclavicular line, connected to an underwater seal or low suction pressures.

Recurring spontaneous pneumothorax may be treated by instilling a sclerosing agent through a thoracostomy tube or during thoracostomy. Thoracotomy and pleurectomy are also procedures to prevent recurrence by causing the lung to adhere to the parietal pleura. Traumatic and tension pneumotho­races require chest tube drainage; traumatic pneumothorax may also require surgical repair.

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.