Key messages

• Spontanous pneumothorax is generally due to subpleural blebs. It often occurs in chronic obstructive pulmonary disease, cystic fibrosis, and AIDS.

• Tension pneumothorax is associated with severe impairment of gas exchange and cardiac function.

• Barotrauma/pneumothorax occurs in 4 to 15 per cent of patients on mechanical ventilation, but in up to 60 per cent of patients with acute respiratory distress syndrome.

• Diagnostic methods include chest radiography and auscultation. Introduction

Pneumothorax is defined as a pathological collection of extra-alveolar air in the pleural space between the visceral and parietal pleura. It is generally due to alveolar or airway injury, but can also be caused by penetrating injury of the chest wall. It can be classified as spontaneous pneumothorax or pneumothorax of traumatic and/or iatrogenic origin. Common causes and mechanisms of pneumothorax and other forms of extra-alveolar air are summarized in Table 1.

table 1 Common causes and pathways of extra-alveolar air

Owing to the retracting forces of the lung tissue, the pleural pressure is more negative than the alveolar or the ambient pressure. If the integrity of the alveolar wall and the visceral pleura or the thoracic wall and the parietal pleura is broken, the air follows the pressure gradient and causes pneumothorax. Subsequently, depending on the amount of gas in the pleural space, the ipsilateral lung collapses. Lung volume decreases and oxygenation deteriorates due to an increased intrapulmonary shunt. If the gas inflow is limited, the lung collapse is not progressive and no mediastinal shift will occur. Without further inflow the pleural air will be reabsorbed within a certain time. Uncomplicated pneumothorax is usually well tolerated in otherwise healthy individuals. However, in patients with decreased pulmonary reserve, such as those with severe chronic obstructive pulmonary disease or acute respiratory distress syndrome, deterioration of oxygenation can be critical with even a small pneumothorax.

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