Liveaboard fatality - Caymans

[boulderjohn]

In the event of of oxygen toxicity, the diver often--but not always--has a warning sensation prior to unconsciousness or seizure. Those warnings are usually listed with the acronym VENTID.

V=visual disturbances
E=Ear issues, like ringing in the ear
N= Nausea
T= Twitching; Tingling
I= Irritability
D= Dizziness

Some people add "Con" (ConVENTID) for "convulsions, but I don't consider convulsions to be a good warning sign--I think you are already there in that case.

If people experience any of those feelings and realize they are at risk for toxicity, the two options are to get on a safe gas supply immediately or ascend immediately. In either case, if you are too late applying the remedy, you will experience the effects of toxicity anyway. If you experience it while ascending, you will go all the way to the surface, and you will do it quickly. It will not be good.

 

[Ayisha]

Some people add "Con" (ConVENTID) for "convulsions, but I don't consider convulsions to be a good warning sign--I think you are already there in that case.

If people experience any of those feelings and realize they are at risk for toxicity, the two options are to get on a safe gas supply immediately or ascend immediately.

True, if they're experiencing convulsions, they're already there, but I think "Con" is also included as a sign the buddy can observe, whereas the others are symptoms the victim experiences and the buddy may not be aware of, but may sense something is "off".

If someone is having a seizure, the buddy should keep in mind that they should not ascend with the victim until after the tonic-clonic phase of the seizure to avoid the victim suffering from an Arterial Gas Embolism (AGE). The rescuer should try to keep the victim at the same depth because the glottis may close during the tonic-clonic phase. The victim will then likely become unconscious after a seizure, and then they can be brought up at a "safe" rate of ascent.

 

[boulderjohn]

If someone is having a seizure, the buddy should keep in mind that they should not ascend with the victim until after the tonic-clonic phase of the seizure to avoid the victim suffering from an Arterial Gas Embolism (AGE). The rescuer should try to keep the victim at the same depth because the glottis may close during the tonic-clonic phase. The victim will then likely become unconscious after a seizure, and then they can be brought up at a "safe" rate of ascent.

That issue is hotly debated. Some agree with you; some do not. The courses I teach are non-committal, talking about the issue and saying the matter is not settled. A recent workshop on this concluded that bring the diver to the surface was the most important goal, so the rescuer should take the diver to the surface under all circumstances.

 

[kelemvor]

tonic-clonic phase

What is that?

 

[boulderjohn]

What is that?

The first two parts of a grand mal seizure are the tonic and clonic phases--those are the parts we think of when we think of a seizure. These are usually followed by the postictal phase, which is a sleep-like state.

 

[Storker]

A couple years ago in South Florida, a diver mistakenly believed he had air in a set of doubles that had been sitting around full for a number of months, and he went on a dive where he was likely at about 160 feet for 20 minutes or so. (I talked with his buddy.) He actually had 36% in those tanks.

With the risk of derailing the thread: This is why my standard MOA is to always analyze my tanks on-site, just before attaching my 1st stage. I store my tanks filled, ready for diving, and even if they're properly marked with % O2 and MOD, I prefer to have that extra layer of safety.

I don't trust myself 100% since I know I've made errors before; I can still remember that incident back in '84...

 

[Ayisha]

That issue is hotly debated. Some agree with you; some do not. The courses I teach are non-committal, talking about the issue and saying the matter is not settled. A recent workshop on this concluded that bring the diver to the surface was the most important goal, so the rescuer should take the diver to the surface under all circumstances.

Could be. A coroner for a local diving accident here a number of years ago gave the information that I summarized earlier. The information was followed up with DAN and they gave the same but more detailed information.

In this local case, the cause of death was listed as "Air Embolism due to Barotrauma in a scuba diver with Acute Oxygen Toxicity". The coroner and a DAN medic recommended trying to keep a convulsing diver at the same depth until they stop seizing, then beginning an ascent at a recommended rate to avoid barotrauma.

 

[boulderjohn]

I have attached the study to which I refereed earlier. It is a 2012 UHMS paper, and its authors include key members of DAN's leadership. In rereading it, I see that my memory of it was inexact. The recommendation depends upon the status of the diver at the start of the rescue.

Is the regulator in the mouth? If no, then the diver should be taken to the surface in a hurry. If yes, then the regulator should be held in place and the diver kept at depth until the clonic phase subsides.