What is pneumothorax?

Pneumothorax refers specifically to the presence of air in the pleural cavity, which can occur as a result of a puncture in the lung or the chest wall. This condition leads to the collapse of the lung on the affected side due to the loss of negative pressure that is essential for lung expansion.

Understanding this condition is crucial because it can arise spontaneously, from trauma, or be introduced during medical procedures. The accumulation of air in the pleural space prevents the lung from fully expanding, which can lead to difficulty breathing and decreased oxygenation in the body.

In contrast, the other options describe different pathological states. Fluid accumulation in the lungs typically refers to conditions such as pulmonary edema. An infection of the pleura relates to pleuritis or pleurisy. Lastly, swelling of lung tissues pertains to inflammation rather than the presence of air in the pleural cavity. Thus, the definition of pneumothorax is accurately captured by the correct choice, emphasizing the significance of recognizing this condition in clinical practice.