A pneumothorax (collapsed lung) results from a buildup of air in the space between the lung and the chest wall (pleural space). This prevents the lung from expanding properly when the person tries to breathe in, causing shortness of breath and chest pain.

A pneumothorax is usually caused by an injury to the chest, such as a broken rib or a puncture wound. It may also occur suddenly without an injury (spontaneous pneumothorax). Spontaneous pneumothorax can result from damage to the lungs caused by conditions such as chronic obstructive pulmonary disease (COPD), asthma, cystic fibrosis, and pneumonia. Spontaneous pneumothorax can also occur in people who don't have lung disease.

Symptoms of pneumothorax often include:

• Shortness of breath (dyspnea), which may be mild to severe, depending on how much of the lung is collapsed.
• Sudden, severe, and sharp chest pain on the same side as the collapsed lung.

A small pneumothorax may improve without treatment. But a more serious pneumothorax usually is treated by inserting a needle or a chest tube into the chest cavity. This relieves the pressure on the lung and allows it to re-expand.