What condition is characterized by the buildup of air and pressure in the thoracic cavity?

The condition characterized by the buildup of air and pressure in the thoracic cavity is tension pneumothorax. This occurs when air enters the pleural space and cannot escape, leading to increased pressure that compresses the lung on the affected side and can cause a shift of the mediastinum toward the opposite side. The pressure buildup can severely compromise respiratory function and hemodynamics, making it a life-threatening emergency that requires immediate intervention.

In contrast, pneumonia is an infection of the lungs that leads to inflammation and fluid accumulation but does not primarily involve air buildup. Atelectasis refers to the collapse of part or all of a lung due to various factors, including obstruction or lack of air; it does not specifically involve excess air in the thoracic cavity. Hemothorax involves the accumulation of blood in the pleural space, which can also lead to respiratory distress, but it specifically pertains to blood rather than air.