A diver is suspected of having DCI. What is the first action that should be taken?

The initial action for a diver suspected of having decompression illness (DCI) is to have the diver breathe oxygen. Administering oxygen helps to increase the amount of available oxygen in the bloodstream, which is crucial for treating DCI. Oxygen can aid in the elimination of nitrogen bubbles that may have formed in the diver's tissues and bloodstream due to improper ascent or prolonged exposure to high pressure. It helps reduce symptoms and supports recovery until more advanced medical treatment can be provided.

While keeping the diver lying down, treating for shock, and monitoring vital signs are important components of first aid, they are secondary actions that follow the administration of oxygen. The priority is to begin oxygen therapy as quickly as possible to address the underlying issue of DCI effectively.