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Oxygen Toxicity and Underwater Convulsions September 23, 2008

Posted by Chris Sullivan in Emergencies.
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In the DAN Technical Diving Conference session on CNS Oxygen Toxicity, Dr. Simon Mitchell and Dr. Bill Hamilton mention the appropriate method for handling convulsions under water. An underwater convulsion is a very dangerous thing, as the regulator will usually come out of the diver’s mouth as they convulse. Replacing the regulator is usually impractical, although if the convulsion is recognized by another diver at the onset it is possible that it can be held in place until the convulsions cease.

I have taken three courses on using enriched air (a.k.a. Nitrox) in diving. Enriched air has a higher percentage of Oxygen than atmospheric air and is usually implicated in Oxygen Toxicity, although it is also possible with air alone if the depths are great enough. These state the following:

  1. DSAT Tec Deep: “The general recommendation is to wait for the convulsion to cease and then bring the victim up, maintain a neutral head position that allows air to escape from the airway”
  2. IANTD Advanced Nitrox: “DO NOT: Raise the victim until the convulsion has ceased; There is a risk of embolism!”, etc.
  3. PADI Enriched Air Diver Specialty: “If the diver has the mouthpiece in place, hold it there; but don’t waste time trying to replace it if it’s not. Immediately bring the diver to the surface and check for breathing….”

Dr. Hamilton recommends bringing the diver to the surface immediately. His rationale is that while there is a small chance of an embolism, there is a certainty of drowning when the diver has no airway. Dr. Mitchell added that it is a misconception that the diver’s airway will spasm shut during a convulsion, which would prevent expanding air from escaping through the diver’s mouth or nose and thus precipitate an rupture of the lung tissue. According to Dr. Mitchell, this has been shown time and again not to be the case. So the latest information appears to side with the PADI.

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