What physical finding is most likely in a patient with a tension pneumothorax resulting from a knife wound?

In the case of a tension pneumothorax, the accumulation of air in the pleural space leads to increased intrathoracic pressure, which causes the affected lung to collapse and can also push the mediastinum towards the opposite side. One of the key physical findings associated with a tension pneumothorax is hyperresonance upon percussion of the affected side.

When percussing the thorax, normal lung and pleural tissue produce a dull or resonance sound. However, when air is trapped in the pleural space, as in a tension pneumothorax, the sound becomes hyperresonant. This occurs because the presence of excess air creates an abnormal resonance that is more pronounced than that of normal lung or fluid-filled structures, indicating that there is a significant amount of air present.

The degree of hyperresonance can vary depending on the amount of air trapped, but it is a classic finding associated with this condition and helps clinicians differentiate it from other thoracic issues. This characteristic sound is why hyperresonant percussion is the correct choice in this scenario.