Underwater Convulsions and how to handle – From Deco Stop Article.

  1. Stabilize the convulsing diver. Control her position in the water column by making physical contact (either with her person or a piece of equipment.) Do not ascend while she is in shock and convulsing.
  2. Do your best to hold the regulator in her mouth (certainly the gas she is breathing MAY be causing the convulsions, and the ideal action would be to have the stricken diver breathe from YOUR gas supply; however, breathing any gas is better than breathing water).
  3. Signal to other team members that you need assistance
  4. Do not attempt to ascend until the diver's body relaxes and the convulsions cease.
  5. When convulsions cease, check the level of diver's consciousness. If she is awake, signal her to switch regulators to a gas YOU KNOW is appropriate for your current depth. If they are breathing but are unresponsive (likely) you may not be able to switch regulators. MAKE SURE THAT WHICHEVER REGULATOR IS IN USE IS ATTACHED TO AN ABUNDANT GAS SUPPLY! Monitor gas levels for the stricken diver often.
  6. Adopt recovery position** and begin ascent KEEPING HER AIRWAY OPEN AND REGULATOR IN PLACE. Use her buoyancy compensator to control ascent for you both. (Open the automatic vent on her dry suit and yours.) If you have another team member helping, sandwich the stricken diver between the two of you.
  7. If possible, blow a signal marker to tell your surface support that you have an in-water emergency.
  8. Complete your decompression schedule. You may choose to accelerate it if circumstances dictate, but DO NOT risk DCI to get the stricken diver to the surface... Remember, she has the same obligation as the rest of her team!
  9. Be prepared for a second series of convulsions.
  10. Bring diver to surface and secure and remove gear (inflate wings, clip to equipment line, cut harness), get diver to surface personnel or on boat or on shore.
  11. Activate EMS. Note: The correct call to the Coast Guard in this situation would be a pan pan and NOT a mayday.
  12. Monitor. Document. Follow Instructions from EMS or Coast Guard. Reassure. Treat for Shock. Watch for signs of DCI. Set diver's gear aside for inquiry... Either one among your team or group, or more formal.

* Oxygen Toxicity may present itself underwater in the form of a clonic-tonic convulsion. However, a convulsing diver may or may not be experiencing a CNS toxicity episode. You cannot diagnose precisely what's going on, so always deal with the situation in a structured way and resist the temptation to second-guess the situation.

Do check to see if the MOD of the gas the stricken diver was breathing when they convulsed corresponds to the depth they were at. Do get them on a leaner mix or get them higher in the water column, as swiftly as is possible without compromising other safety protocols. Do Watch your own gas switches.

** Recovery position = anything that works! Essentially, you will ride the stricken diver through the water column making sure you have control of their BC, their airway (keep it open) and the regulator (in their mouth). I find it difficult to completely control venting gas in a stricken diver's drysuit (and my own in these circumstances) if I maintain a horizontal trim. I find I do better if I present them and myself in a semi-vertical attitude. I also prefer to be able to monitor the stricken diver's eyes. And so prefer to be facing them rather than being behind them. Try threading your right arm under their left arm, around their shoulder holding their BC inflator in your right hand. Use your left hand to hold their regulator in place. Do your best and remember that style takes a back seat to function... Use any fixed aid -- such as an anchor line or wall -- to assist and arrest your ascent. This is one of the few exercises on your training course where you are "allowed" to hold onto ascent lines and walls, and where you will not be "penalized" for being vertical in the water!