Which condition could potentially lead to unconsciousness if left untreated?

The condition that could potentially lead to unconsciousness if left untreated is arterial gas embolism. When gas bubbles enter the bloodstream, typically from rapid ascent or injury while diving, they can obstruct blood vessels and disrupt blood flow to critical areas, including the brain. This lack of adequate blood supply can cause hypoxia, which may rapidly lead to unconsciousness.

Arterial gas embolism is particularly dangerous because the presentation of symptoms can vary, and they may progress quickly. Time is of the essence in treating this condition, as the longer the brain and other organs are deprived of oxygen, the more severe the consequences, including the potential for permanent damage or death.

Each option represents a serious diving-related condition, but the mechanisms and the immediacy of their consequences vary. Hypercapnia, hypothermia, and pneumothorax all present significant risks as well but do not have the same rapid progression to unconsciousness as arterial gas embolism does when untreated. For safe diving practices, recognizing and addressing the signs of these conditions promptly is crucial in preventing severe outcomes.