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As a result of inattention on my part, I ended up with a fill of 28% Nitrox, instead of the usual 32% I've breathed for years. I dived it at Ginnie today, and noticed a palpable difference in nitrogen narcosis as evidenced by increased anxiety. I also incurred a significantly longer decompression obligation. It's tempting to go back to partial pressure fills for a 36% mix, still under 1.6 PO2 for the local popular spots, but necessitating a closer eye on the CNS clock.
I've never noticed a difference in narcosis, I narc about the same on 32 as I do on air.
I can't imagine 4% would make any noticiable difference, what about other factors, fatigue, increase in flow/work, different reg etc etc.
I'm also in the camp that o2 has narcotic effects
just my observations and opinions, I'm not paid to know these things.
IMHO pushing the PO2 in high flow cave is asking for trouble.
I don't narc easy but my wife does. At 90' in a cave on air, she should not be there. She is 100% fine on 32%. It makes a lot of sense - less nitrogen being absorbed = less narcosis effects. From what I understand while oxygen does have narcotic effects it is significantly less at the shallower depths that most divers are operating at. There is absolutely zero science behind my observations but the results are very real for her at least.Quote:
Originally Posted by fixxervi6
I agree!! The reason 32% is standard in Cave Country now is because of an accident at Devil's Eye. The standard back then was 34%. Someone had a little too hot mix, around 36%, and toxed.Quote:
Originally Posted by chimie007
That's the kicker. PO2 of 1.6 is not smart at depth in a high flow environment and is not worth the little difference that 4% might make. The working portion of your dive should never be higher than 1.4 PO2, IMHO.Quote:
Originally Posted by chimie007
Perhaps it was the anxiety of diving a new mix that was the trip. Keep the PO2 low as practical. Don't kid yourself, one day a high PO2 might just clean your clock. FWIW, a few years back, we did some tests at 42MSW switching between Nx 5/95, air, and Nx 36/64. There was no discernible difference in the narcosis level between them!! A little more deco won't hurt you unless you dive dry w/o a pee valve.Quote:
Originally Posted by Rick Palm
Dive Safe
Dale
You don't want to be increasing the O2 content to lower N2 %. You will eventually kill your self and possibly your buddy doing this. (assuming you find a buddy that will dive a plan like that with you).
Use helium to decrease narcosis. Bottom line.
12 years ago 36% (and even 38%) was the norm at Ginnie,but fortunately we got a lot smarter. There is too much CO2 build up to justify high PPO2 in a high flow cave system
Never underestimate the power of suggestion. Not to disparage anyone, but if you think you'll be less narced, you'll probably feel less narced.
When nitrox made its way into the recreational realm in the mid-90s, there were a number of "benefits of nitrox" touted. You'll feel less tired after a dive. You'll feel less cold during a dive. You'll be less narced during a dive. As time went by, each of these were disproved in blind tests.
The only proven benefit of nitrox is shorter decompression time/longer no-decompression time. As was mentioned, the standard nitrox mix in cave country used to be 34%. Now it's 32%, and I have started using 31% in Jackson Blue. The extra several minutes of deco is worth it to keep the PO2 a couple of points lower. I'm old, and I want to get older.
Just plan your dives to a 1.2 - 1.3 PO2 with 1.6 (100% o2) for deco. Depending on your average and max depth, your mix will vary. I use between 30% and 32% for Ginnie Diving.
Safe Diving
I just had this explained to me the other day... But what if you were told that O2 is more narcotic then N2? Not by much, but it is....
http://upload.wikimedia.org/wikipedi...ic_potency.gif
Apart from helium, all gases that can be breathed have a narcotic effect, which is greater as the lipid solubility of the gas increases
As a fellow 1958 model, I cling to the idea that "geezer gas" reduces fatigue! Don't go bursting my (Nitrox) bubble!Quote:
Originally Posted by Slüdge
I forget who said it - "The great tragedy of science - a beautiful theory destroyed by an ugly fact."
Mike
I agree. I've been moving down to 1.3 max PO2s. Just seems safer and isn't that much different for deco.Quote:
Originally Posted by Mike Edmonston
I agree, as another 1958 model. :)Quote:
Originally Posted by MORGAN
I notice a significant difference, especially on multiple dives a day. It could be an individual physiology thing, as most gas related issues are.
Forrest hit the nail on the head about the 34% a few years back. There was a death at Devil's and I believe a few other incidents, not death's, at Little River in the same period. It may not have been necessary for everyone to switch from 34 to 32, but it seemed like the prudent thing to do. I had some friends who backed down to 32 % for LR. For some reason, I never had a problem at Ginnie, but I had some O2 issues at LR on 34%, long O2 deco's.
All of these points are well-taken. It doesn't make sense to trade nitrogen for oxygen for a dubious decrease in narcosis, and less deco time: The complications of O2 toxicity are certainly a lot worse than N2 toxicity. My bet is that even helium has some narcosis associated with it: that's the way it seemed to me in the back of DiePolder III several years ago. With limited PO2 and PN2, that was the only explanation.
Of course, perhaps it is all because I have a lower mental status to begin with!
But I agree with all of the assessments above: better to put up with the inconveniences of a higher PN2, than risk a potentially fatal O2 hit. I'll stick with 32%.
(Incidentally, I don't consider the Devil's Ear/Eye system a "high flow" system, if you know where the sweet spots are!)
My friend Ron and I were discussing this several years ago. I was wondering where this "myth" started, and he actually had an answer. He said some tests were done where divers would make a dive and deco on air, then the same dive on nitrox with deco on oxygen. The longer the dive/deco, the more pronounced the difference between how tired the divers felt.Quote:
Originally Posted by MORGAN
Of course, he didn't provide any references...
Looks like i'd like to brew up a little xenonox for the next galaxy dive at ginnie...if i could only afford that...a little pink floyd (comfortably numb) on the uw ipod and a dive to remember (maybe).Quote:
Originally Posted by TonyDCaver
Now people will be huffing Xenon bulbs.Quote:
Originally Posted by wingman
Simply spending more time in the water, as with air, might have something to do with perceived "tiredness" as well.Quote:
Originally Posted by Slüdge
With these qualities who can resist..."Xenon is non-toxic, although it does dissolve in blood and belongs to a select group of substances that penetrate the blood-brain barrier, causing mild to full surgical anesthesia when inhaled in high concentrations with oxygen." Stolen from Wikipedia.Quote:
Originally Posted by Jay
Try some Trimix 30/30, and see if it helps at Devil's Eye.Quote:
Originally Posted by Rick Palm
After an apparent 02-induced seizure and fatality @ Devils several years ago, my team discussed what %02 we felt comfortable diving, and decided to dial back to 31% for that system, for an extra buffer at depth. So many variables go into determining a "safe" level of 02 exposure at depth that we thought as GWB1 would say, this was "prudent".
Didn't Sheck decide even Argox was WAY too narcosis-inducing? Xenonox would be about ten times as bad, right?Quote:
Originally Posted by wingman
Seems like Argox would be the mix of choice.
I think that 99% of felt nacrosis is state of mind, if you go in thinking, I"m on 32 I won't narc as much, you won't, if you go in on air thinking, damn I'm gonna narc, your gonna narc. I've seen people totally go blitzo at 80 feet on nitrox - and it was their state of mind that did it to them, you can tell who is gonna freak before you even get in the water sometimes.
Usually its the hoovers (from what I've observed) that narc out to the point you have to grab them because their pupils do that cartoon thing, so my non professional opnion about that is, they are hoovering due to discomfort/anxiety mix that with a touch of narcosis and flipzoid
I can tell "something is up" as shallow as 60 feet, my complex mental math skills (not that I have many to start with) start to be affected around 60 feet, when I get to 90 - 100 ish I can tell when I've hit the depth just by "how I feel".
Around 150 feet my motor skills start getting impacted, so I've decided that was my max depth on air that I would do, ever, just because my hands don't work as well, I have to move real slow working clips etc so I figure thats deep enough, espeically with helium now.
On trimix I count o2 as narcotic, my buddy I dive mix with doesn't.
I've dove 30/30 in Devils and I thought it was a perfect mix for the dive
Dark Eternal - I'd be curious how your wife would feel if you slipped her some 21 and told her it was 32 :-) obviously not a good idea, but the results would be interesting, it would rule out the placebo affect.
First time I took my wife down to 120 on air in a nasty lake, I asked her how she did when it was over, she was like, everything was fine I couldn't tell a difference, I said, thats becase you were narcin, if you are at 120 and you "are not narcing" and feel 100% normal, that means your narced :-)
"The great tragedy of Science - the slaying of a beautiful hypothesis by an ugly fact."Quote:
Originally Posted by MORGAN
Thomas Henry Huxley
This thread has got me thinking, i always wondered why i was so addicted to diving, it's the nitrogen. Nitrogen is your friend. I am going to start trying varios hypoxic bimixes (maybe just hypoxic nitrox works as a term as well). Maybe a nice nitrox 16.
Come by one of the shops where I work and I'll fill your cylinder with normoxic nitrox for six bucks!
Actually Bill, you're not too wide of the mark. Narcosis and anesthesia are just different points on the same spectrum. In the early days of dental anesthesia for children, it was common practice to give them 100% nitrous oxide, as the hypoxia helped get them asleep faster. A little oxygen (maybe 10%) would be dialled in when they got really blue!Quote:
Originally Posted by wingman
Andy
It actually happened the other way around. Every time she had been past 90' on 21 she had gotten narced. We were at JB and at the end of the dive she was like "I was not narced at all - that was a great dive" She thought she was breathing 21 but had in fact had grabbed the tank with 32%. I guess there is an argument for labeling your tanks better than we did. Like I said - not scientific at all but now she only dives 32% in the mill pond and is fine. Maybe its placebo - but it works for her. Personally I cant tell a difference between air and 32% up to MOD of the 32%.Quote:
Originally Posted by fixxervi6
No matter how low the ppO2 limited is dialed there will still be the occasional unexplained death.
OxTox has a time and dosage based limit. It's not about picking a particular number and calling that "safe". As dives get longer ppO2 needs to drop. 1.6 on a 15 minute dive is less risky then 1.4 on a 90 minute dive. On a long enough dive 0.5 is probably the ppO2 limit (just based on O2 tollerance if not Tox)
We are at a point where ppO2 is still an issue but other factors are probably becoming hidden contributors in the OxTox risk. CO2, physical stresses (cold tired), drugs, other gases in the mix or released from materials hoses, regulators - maybe even what one ate.
Some of the OxTox blamed deaths have been nowhere near any time-dose limit anyone has proposed following. Far enough to call into doubt that OxTox was actually the cause.
People still convulse and die walking around on the surface breathing air for reasons completely unrelated to OxTox. Until someone comes up with a new theory to explain mysterious diving deaths OxTox will be blamed for the majority of these events - until long after it has ceased to be the problem.