Oxtox: Seeing it 1st hand

[Cave Diver]

I assume you guys were breathing EAN 21? I remember JC once saying that he had never heard of someone toxing on air (when talking about the Feldman death on U-869) and I have always had a vague belief that ppO2 is not the only determinant in toxing - absolute percentage of O2 played a part (hence why people can set staggering 'deep air' depth records without toxing).

Not saying for sure your friend toxed - as they say, a lot of the VENTID symptoms also reflect advanced narcosis symptoms. But just throwing it out there.

Yes it was air. And I'm not sure I buy the theory that you can't tox on air.

Oxtox (as I understand it) is a function of depth and time. The deeper you go, the faster you're racking up deco obligation and the faster you're burning through gas supply. You could spend a lot more time at 30' on a AL40 of 02 than you could on air at 240' and thus be more likely to tox shallow on higher percentages. That doesn't rule out (in my mind) the chance to tox deep on lower ones.

 

[TSandM]

There was a young man who died at around 250 feet in Monterey a year or so ago -- I believe he was observed to seize, and he was on air, if I recall correctly.

 

[rjack321]

Yes it was air. And I'm not sure I buy the theory that you can't tox on air.

Oxtox (as I understand it) is a function of depth and time. The deeper you go, the faster you're racking up deco obligation and the faster you're burning through gas supply. You could spend a lot more time at 30' on a AL40 of 02 than you could on air at 240' and thus be more likely to tox shallow on higher percentages. That doesn't rule out (in my mind) the chance to tox deep on lower ones.

I have a bit of a theory that CNS deression from N2 reduces the likeihood of convulsions on air at high ppO2 compared to the same ppO2 on trimix without the CNS depression. Its not really provable due to the vagueries of convulsions in the first place. But does potentially explain the capacity to do pretty substantial air dives with sleepiness being the overriding symptom instead of excitability, twitching or convulsion type stuff.

 

[Rhone Man]

And I'm not sure I buy the theory that you can't tox on air.

I would never say "can't" - saturation divers have toxed on mixes much leaner than 21%. But I do have this vague and highly unscientific sense that a lower percentage of oxygen for the same ppO2 would have a lower risk. If I have a slow day this week I may trawl through the Rubicon archives and see if I can find anything which might be relevant.

 

[Dsix36]

To the Op:

If a diver is lost and in zero vis, he might think that there is no chance of getting out alive and the thought of death may creep into the mind. I have had a couple of close calls where I got a mental vision (of my cat) that snapped me back to reality and is the main reason that I survived. There is NO reason to ever give up and accept death during a dive. NEVER GIVE UP, is a golden rule that should not be taken lightly. Taking time to write a note to loved ones or some crap like that is burning valuable moments that can make the difference between getting out alive or dieing.

Now if you enter the water with the intention of suicide (I have a living will and understand this option) then why not just dive with a hypoxic mix. You will just drift into sleep and drown while you are asleep. There will be no pain or mental stress over the whole breathing of water ordeal.

 

[Cave Diver]

I have a bit of a theory that CNS deression from N2 reduces the likeihood of convulsions on air at high ppO2 compared to the same ppO2 on trimix without the CNS depression.

That's an interesting take. Is that based on something tangible or is that just one of those little niggling thoughts in the back of your mind?

I'm not asking that to make light of it, just trying to understand if you've read something or seen some sort of anecdotal evidence that gives you those thoughts, or if it's just more like a "feeling."

 

[denisegg]

To the Op:

If a diver is lost and in zero vis, he might think that there is no chance of getting out alive and the thought of death may creep into the mind. I have had a couple of close calls where I got a mental vision (of my cat) that snapped me back to reality and is the main reason that I survived. There is NO reason to ever give up and accept death during a dive. NEVER GIVE UP, is a golden rule that should not be taken lightly. Taking time to write a note to loved ones or some crap like that is burning valuable moments that can make the difference between getting out alive or dieing.

Now if you enter the water with the intention of suicide (I have a living will and understand this option) then why not just dive with a hypoxic mix. You will just drift into sleep and drown while you are asleep. There will be no pain or mental stress over the whole breathing of water ordeal.

Damn...die for a cat...hell I swam over 400ft while going through an IPE to LIVE..a cat never entered my mind...

 

[Dsix36]

Damn...die for a cat...hell I swam over 400ft while going through an IPE to LIVE..a cat never entered my mind...

I have no family anymore. My cats are the closest thing to family that I have and they depend on me to take care of them. It gives me a VERY important reason to NEVER GIVE UP and always come home from a dive.

Other people might need to return in order to take care of their children or whatever else is important in their life.

 

[Rhone Man]

I think people overemphasize the "convulsions" part of the signs and symtoms of CNS toxicity, I have seen dizziness and facial twitching in the water in a buddy on deco as well. It was late in 20mins of deco and we surfaced uneventfully.

Doing some background reading in Rubicon's archives. Twitching seems to be the overwhelmingly preponderant symptom (at least in controlled experiments).

 

[Duke Dive Medicine]

Damn...die for a cat...hell I swam over 400ft while going through an IPE to LIVE..a cat never entered my mind...

You've had IPE? Have we talked to you yet?