What happens to the pressures in the thorax during a tension pneumothorax?

In the case of a tension pneumothorax, air enters the pleural space and cannot escape, leading to an accumulation of air that puts increasing pressure on the thoracic cavity. This pressure increase is significant because it compresses the lung on the affected side, leading to its collapse. As more air enters with each breath, the pressure continues to rise, further compromising lung expansion and function. The increase in pressure can also push the mediastinum (the space between the lungs that contains the heart and major vessels) to the opposite side, potentially affecting blood flow to the heart and leading to cardiovascular instability. Therefore, the correct understanding of the process is that the pressures in the thoracic cavity significantly increase, resulting in the collapse of lung structures and severe respiratory distress.