When you notice symptoms of CNS oxygen toxicity, what should you do immediately?

When experiencing symptoms of CNS (central nervous system) oxygen toxicity, the most appropriate action is to conduct a controlled ascent together. CNS oxygen toxicity can manifest through symptoms such as visual disturbances, ringing in the ears, changes in consciousness, or muscle twitching. These symptoms can pose significant risks, especially if they lead to a loss of motor function or consciousness.

Ascending to a shallower depth allows the partial pressure of oxygen in the breathing gas to decrease, which reduces the risk of further complications from CNS toxicity. A controlled ascent ensures safety for both the diver experiencing symptoms and their buddy. By ascending slowly and methodically, both divers can monitor each other and maintain consistent communication, thereby enhancing safety.

Diving deeper would increase the risk of exposure to higher oxygen pressures, exacerbating the situation. Buddy breathing and using an alternate air source may not effectively address the immediate need to alleviate CNS toxicity symptoms and could introduce additional risks during an emergency situation. Therefore, conducting a controlled ascent together is the most responsible and effective course of action.