HOW DEEP WOULD YOU GO ON AIR while SOLO DIVING IN A CAVE?

[BillGraham]

Personally, I don't breathe air unless there's nothing else available and I don't care for solo diving because it's less fun than having someone along so I normally won't do either of these things.

[bullfrog]

The only time I've been badly narced like this was at 90' but it was due to extreme exhertion. Used to help Frank on the Spree drilling moorings for the Flower Gardens. Carrying an extra 50 lbs to the drill site can work an old man hard. I remember once getting to Franks feet at the site and looking up at him smiling as I let go of the 50 lbs. He grabbed my ankle as I went by (heading to the surface) and after I got the air dumped out of my wing he just stood there and shook his head. Gotta respect being narced, it'll kill ya.

The mental image of this really made me laugh. Glad frank grabbed ya. It is a good example of narced. you probable thought you were fine didn't you?

[mdax]

100'
When people tell me they have "adapted" or "acclimated" to diving air deep i view them in the same light as drunks who believe they can drive or do complex tasks just as well when tanked.

[OH]

An hour? Was that in a chamber or so?
Full face mask?

There is no "normal". There have been hits at 1.6, and Jim Miller survived over an hour at around 3, before his hit. 300' on air is just over 2.1.

[FW]

An hour? Was that in a chamber or so?
Full face mask?

No, it was in the water. I think everyone else is surprised too.

[rjack]

I wonder if the same mechanism that causes narcosis would increase the seizure threshold, thus delaying or preventing convulsions due to oxygen toxicity...

There is some speculation that this is true. Liz Halbach toxed at ~1.4-1.5 IIRC with 25% helium in her mix. Jim Miller, with the same 25% helium in his mix, lasted an hour before toxing at roughly double the ppO2. Actually seizing is too erratic to genuinely know.

[NorthWoodsDiver]

200'+/- a few feet. After numerous "deep" air dives in cold, dark, wrecks I wouldn't hesitate to take it to 200. However, if helium was available...

[apitkin]

There is some speculation that this is true. Liz Halbach toxed at ~1.4-1.5 IIRC with 25% helium in her mix. Jim Miller, with the same 25% helium in his mix, lasted an hour before toxing at roughly double the ppO2. Actually seizing is too erratic to genuinely know.

Actually, for many years the opposite was believed to be true, based on work that Lanphier did in 1955. Based on some scant experimental data, he concluded in his work for the US Navy that increasing the PN2 at a given PO2 increased the likelihood of CNS symptoms. He may not have adequately controlled for the effects of CO2. Kenneth Donald, who did more work on human subjects in oxygen toxicity than any other researcher, concluded that the PN2 had no effect on susceptibility, either positive or negative.

[floridakid]

Being that many of the popular theories atribute narcosis to antagonism of NMDA receptors and agonism of GABA receptors, narcosis would decrease the likelihood of convulsions. However, there are many other factors at play when determining of when convulsions due to O2 tox will occur. If narcosis does in fact involve stimulation of GABA receptors, I would be shocked to find out elevated pN2s did not to some extent prevent convulsions.

That would be a really cool study for someone with access to a chamber to do, hint hint

[Sludge]

I dived air to 192' once in Bonaire on the Windjammer because I couldn't get any helium. I remember the basic details of the dive, but time was WAY accelerated (about a minute into the dive I looked at my computer only to find that seven minutes had gone by). Conditions were perfect - 82° water, 100' vis, no current - so we made the decision to do the dive on air. Would I do it again? Maybe. But I wouldn't recommend it to someone else.

In a cave? No way.