What is a pneumothorax?

A pneumothorax occurs when air enters the pleural space, which is the area between the lung and the chest wall. This accumulation of air leads to a collapse of the lung on the affected side. The presence of air in the pleural space disrupts the normal negative pressure that is essential for lung expansion during breathing. As a result, the lung tissue cannot properly inflate, leading to symptoms such as sudden chest pain and shortness of breath.

In contrast, the other options describe different pulmonary or pleural conditions. Fluid accumulation in the lungs refers to pulmonary edema, which is a buildup of fluid in the air sacs that can impair respiration. Inflammation of lung tissue relates to conditions like pneumonia or bronchitis, which involve an immune response that can lead to symptoms of infection and difficulty breathing. Swelling of the pleura around the lungs can occur in conditions like pleuritis (pleurisy), which involves pain and inflammation but does not involve the entry of air leading to lung collapse.