What could be a consequence of a tension pneumothorax in a casualty with an open chest wound?

A tension pneumothorax occurs when air enters the pleural space and cannot escape, leading to increased pressure that can collapse the lung on the affected side and compress surrounding structures. A casualty with an open chest wound is at risk of developing a tension pneumothorax, especially if the wound acts like a one-way valve, allowing air to enter during inhalation but preventing it from escaping during exhalation.

When this pressure builds up in the pleural cavity, it can lead to several critical consequences. The collapse of the lung on the affected side occurs because the expanding air pushes against the lung tissue, causing it to deflate. Additionally, the increased pressure can push the mediastinum—where the heart and major blood vessels are located—toward the opposite side, which leads to compression of the heart and large vessels. This can impair normal cardiovascular function, reduce venous return, and decrease cardiac output, potentially leading to shock and other severe complications.

Therefore, in the scenario described, the development of a tension pneumothorax can result in collapsing the right lung (if the right side is affected), compressing the opposite lung (the left lung, due to mediastinal shift), and compressing the heart and blood vessels.