Nitrox - 1.40 or 1.60 PO2?

[Scuba-Stu]

The cause was unknown? The woman had a seizure underwater and drowned. That is both fact, and quite easy to understand. The coroner determined oxygen toxicity as the cause of the seizure. ALL the divers that participated said it was at 1.4 pp02.

So the only "maybe" here is the cause of the seizure. And that is pretty much conclusive itself.

Im not sure what article you read but "The medical examiner stated there was no way he could determine the actual cause of death, and we would likely never know for sure." There was no mention of any coroner determining oxtox as the cause of seizure.

I’m done arguing. You can chose to believe what you want from the article.
"So the only "maybe" here is the cause of the seizure." That was my point, the cause is unknown.

This is the artical I read: Divers4Life | Liz & Tim's Adventures

 

[Rhone Man]

Is not part of the problem that the physiology of O2 toxicity is not well understood.

Gene Hobbs has cited the example of a women who toxed (or may have toxed) at 1.3 ATA.

If you read Gary Gentile's Technical Diving Handbook, he talks about how the US Navy used to put people into chambers breathing oxygen at 2.2 ATA for half an hour (admittedly sitting at rest) without passing out.

There are just some fundamental unknowns. Risks may be small, but given that O2 toxicity at depth usually = death, you really need to think about how badly you feel you need those extra minutes at the bottom (or richer mix to cut your deco time).

Just make sure your spouse doesn't sue anyone if you get it wrong.

 

[Papa_Bear]

I guess some have a problem with the concept of discussion? I never stated my observations as fact, not once, and I pronounced them as antidotal! Who will I kill with my "Belief"? It was an observation that I expressed for comment... I am looking for information here for myself anyone interested in facts about Nitrox! To somehow twist that into my beliefs will kill someone, please educate me and everyone here with Science, but remember physiology is not science it is an art, because we are all different and no one can predict when, where, now much, or time of a hit unlike the escape velocity of earth orbit! So rather than dismiss my comments say you don't have the information or express your own opinion! I have been diving VooDoo gas a a long time with no apparent problems with my setting! If I am not getting the headaches that I got on Air, then explain the physiology better than I did with my observation! Simple? Right! This is called a discussion please keep it that way!

 

[Papa_Bear]

One more question needs to be asked! I understand from medical professionals that no one dies of OT, but the drowning! In chambers they simple take you up and you recover! Is that not the facts? That is way it is less a risk in a helmet or full face mask.... Just a question!

 

[Thalassamania]

Actually in a multiplace chamber (which is always pressurized with air or a normoxic mix, pure oxygen would be too dangerous) you breathe oxygen through a hood or a mask that dumps the exhalation overboard. If someone has a seizure the mask or hood is removed.

I don't know what the effect would be continuing to let some one seize, I don't expect it would be good.

 

[Papa_Bear]

In O2 therapy they take you up because the O2 is the point.... So they take you to a point where you can tolerate the O2..... I know how it is administered, not my point, but nice side bar for those who may not know!

 

[Anti-Hero]

Im not sure what article you read but "The medical examiner stated there was no way he could determine the actual cause of death, and we would likely never know for sure." There was no mention of any coroner determining oxtox as the cause of seizure.

I’m done arguing. You can chose to believe what you want from the article.
"So the only "maybe" here is the cause of the seizure." That was my point, the cause is unknown.

This is the artical I read: Divers4Life | Liz & Tim's Adventures

I didn't know we were arguing? Regardless, as research progresses and our understanding of the physiological effects becomes more clear, I'm sure there will be plenty more to argue about in the coming years.

 

[nereas]

Is not part of the problem that the physiology of O2 toxicity is not well understood.

Gene Hobbs has cited the example of a women who toxed (or may have toxed) at 1.3 ATA.

If you read Gary Gentile's Technical Diving Handbook, he talks about how the US Navy used to put people into chambers breathing oxygen at 2.2 ATA for half an hour (admittedly sitting at rest) without passing out.

There are just some fundamental unknowns. Risks may be small, but given that O2 toxicity at depth usually = death, you really need to think about how badly you feel you need those extra minutes at the bottom (or richer mix to cut your deco time).

Just make sure your spouse doesn't sue anyone if you get it wrong.

Now we are back to discussing deco time. That is akin to discussing CCR time.

During the planning phases of your O/C-deco or CCR-dive, you would indeed need to preplan your ppO2 levels based on the amount of time you are planning, both bottom time and deco time.

And then you would adjust your mix richness.

Increasing your richness to "decrease" your deco time would be making the problem worse.

A more feasible reaction on O/C would be to increase your "air" breaks (which you cannot do with a CCR). But a more feasible "plan" on either O/C or CCR would be to DECREASE the richness of your mix.

So your guess was backwards. A nice try, though.

The O/P was asking about NDL-recreational scuba, which does not last long enough to give you ox tox exposure, as long as you keep your ppO2 level at 1.6 ATAs or less.

 

[Anti-Hero]

Now we are back to discussing deco time. That is akin to discussing CCR time.

During the planning phases of your O/C-deco or CCR-dive, you would indeed need to preplan your ppO2 levels based on the amount of time you are planning, both bottom time and deco time.

And then you would adjust your mix richness.

Increasing your richness to "decrease" your deco time would be making the problem worse.

A more feasible reaction on O/C would be to increase your "air" breaks (which you cannot do with a CCR). But a more feasible "plan" on either O/C or CCR would be to DECREASE the richness of your mix.

So your guess was backwards. A nice try, though.

The O/P was asking about NDL-recreational scuba, which does not last long enough to give you ox tox exposure, as long as you keep your ppO2 level at 1.6 ATAs or less.

You have absolutely no idea what you're talking about.

 

[Charlie99]

If you read Gary Gentile's Technical Diving Handbook, he talks about how the US Navy used to put people into chambers breathing oxygen at 2.2 ATA for half an hour (admittedly sitting at rest) without passing out.

Far more common is the USN treatment Table 6 hyperbaric chamber treatment which is a couple of hours on O2 at 60' (2.8ata ppO2) with 5 minute air breaks every 20 minutes. Only a small percentage of patients have convulsions.

Of course, going into convulsions in a chamber is not likely to result in drowning , but convulsing underwater with a standard 2nd stage is likely to cause drowning. So I consider this sort of stuff only relevant to what I'm willing to expose myself to in a true emergency where a 1% risk of death is acceptable.