What immediate action should be taken if a diver presents with symptoms of DCI?

Providing oxygen is the immediate action that should be taken if a diver presents with symptoms of Decompression Illness (DCI). Administering supplemental oxygen helps increase the amount of oxygen available to the tissues and assists in reducing the size of nitrogen bubbles formed in the bloodstream or tissues. This can significantly aid in alleviating the effects of DCI and can help stabilize the diver while preparing for further medical intervention, such as transport to a hyperbaric facility.

Supplemental oxygen facilitates faster elimination of nitrogen from the system, enhances tissue repair, and can improve symptoms in the short term until advanced medical care is available. Immediate access to oxygen therapy is a priority in managing symptoms of DCI because it directly addresses one of the key physiological issues caused by the illness: the presence of excess nitrogen in the body.

Other potential actions, while beneficial in different contexts or for different medical conditions, do not provide the same level of urgent and effective treatment in cases of DCI. For example, cold water could lead to hypothermia, elevating the legs does not directly address the underlying issue of nitrogen bubbles, and shaking a diver to keep them alert could cause further injury or distress.