What is true about pneumothorax?

Pneumothorax is the presence of air in the pleural space, which can either occur spontaneously, or result from iatrogenic injury or trauma to the lung or chest wall. Primary spontaneous pneumothorax occurs in patients with no history of lung disease. Smoking, tall stature and the presence of apical subpleural blebs are risk factor. Secondary pneumothorax affects patients with pre-existing lung disease and is associated with higher mortality rates. The mean pleural pressure remains negative, spontaneous reabsorption of air and re-expansion of the lung occur over a few days or weeks, and infection is uncommon.