Nitrogen tolerance question

[dlarbale]

All,

Thanks for providing your opinions on this topic and also for the informative links (Yooper). I'm still not convinced but hey it's all based on what I've experienced so shifting that from my mind will take a while - the puzzels excercise might help in doing this, but I'm not too sure when I'll get the chance to try it as I live in Adelaide South Aus and your lucky to get 30m's!!

Yooper, can you start a new thread on reverse profiles with your info that you mention (when you've got the time of course).

Thanks - Dave.

PS// What are people's personal depth limits for air. Think I'll start a new thread with a poll.

 

[Rick Murchison]

Originally posted by Lost Yooper
Cripes, the last I heard, nobody even knows where or why reverse profiles became a bad thing.

It isn't very complicated - and really has nothing to do with DCS directly, but rather the nature of the Navy tables.
Allow me an example... I want to do two 50 minute dives - one to 40 feet and one to 60 feet. Using the Navy tables, if I do the 60 foot dive first, I can do the 40 foot dive whenever I want to after a 10 minute surface interval. But if I do the 40 foot dive first, I have to wait over seven hours to do the 60 foot dive and stay out of decompression.
That's a pretty practical reason to "do your deepest dive first."
With the advent of computers the "shallow first penalty" is less, but in the simulations I've played with it's still there - nowhere near the magnitude of the tables, but there nonetheless. (Using the Oceanic, for example, the penalty for doing the 40 foot dive first is a bit over an hour and a half vice the seven hours on the tables)
Rick

 

[Rick Murchison]

Narcosis, I believe, is pretty much independent of experience, and one gets just as narced after lots of experience as they did the first time. That doesn't mean you can't adapt, though - and improve your ability to handle narcosis.
For example - I know that at 130 feet it takes me longer to interpret what my SPG gauge reads than it does when I'm close to the surface, and my first few deep excursions (with an SPG) found me glancing at the SPG as usual, only later realizing that I'd looked at it ok, but I hadn't read what it said. After only a dive or two having to look back at the SPG again to really see what it said, I learned that at 130 feet, I have to take my time to read the gauge - the shallow water glance doesn't work. So I have adapted, even though my "tolerance" hasn't changed.
Rick

 

[buff]

I have dove a few times to 130' and have always felt like I do at 30'. I probably feel o.k. at 130' because I am already narced.

Repeated exposure to nitorogen narcosis is probably like alcohol intoxication-you don't become any less drunk you just know how to act "less drunk".

 

[Uncle Pug]

Originally posted by buff
you don't become any less drunk you just know how to act "less drunk".

Or you think you are acting less drunk....
Always entertaining to watch....

 

[padiscubapro]

Originally posted by dlarbale
I'm not too sure about this non-tolerance to N2.

I can recall a 2 month period in Indonesia where I was diving fairly deep all the time. Now the thing that I remember most is the first couple of dives to depth and the almost instant slap in the face from N2. After a few deep dives the effects were definately less - no question.

So did I dream all of this or what? What evidence has been supplied to undermine the theory of the diving greats?

Dave.

PS// Are reverse profiles really so bad? I've read some interesting articles from the WKPP boys on this and it would appear that they even encourage it, see -

http://www.wkpp.org/articles/Decompression/repetitive_dives.htm

I agree with some of the other response, you feeling better as the week went on is probably due to the fact that you were more relaxed and had much better breathing technique.. On your early dives you probably were aprehensive, stressed and possibly nervous and this in all likelyhood caused you have an inconsistent breathing pattern and either you would breathe shallow or overbreath your reg which would increase CO2 buildup within your blood and Co2 is highly narcotic.. So in escense you may have had less narcosis, but it was not less narcosis of nitrogen just the narcosis of CO2 wasn't present or greatly diminished.


I can relate 1 dive where CO2 definately came into play.. I was on my ccr and had a slight leak so the chemical was not working at optimum efficiency (it probably would have been fine except I looked under things a few times with a heads down orientation so I guess I got the chemical wetter than it should be) and I was working hard, The breathing loop was still intact.. All Of a sudden I had the feeling of impending doom, and just about every other narced symptom I could think of.. I went shallower (I was only around 110 to start )and symptoms didn't really subside..I did notice some symptoms of CO2 so I decided to to a compete loop flush while continuing to breath fresh gas within a few breaths the symptoms disappeared.. I was able to recognize the cause of the symptoms because of training..
Part of my CCR training (and the classes I teach) is to induce high CO2 in a controlled situation to aid in the identifcation of symptoms. I took it easy for the remainder of the dive (with no further problems) paying careful attention and found the problem after breaking down the unit.. The leak was my fault and I should have caught it... Without the hard work in all likelyhood I would have never noticed and would have found the leak, after changing the scrubber for the next dive..

 

[jamespitt]

come on dave, put that poll up because i have a PB at Batee Poep (Gla).
i have to say that when doing regular deep dives you definitely do know how to handle the N2 hit better than if you hardly ever get narced. perhaps kirks book of knots at depth would sort it out.
i found that at first 35msw was enough for me to first feel the effects of narcosis, but on later dives would only get that warm fuzzy, numb at the lips feeling at 42+msw.
maybe its tolerance or maybe its experience...
James

 

[dlarbale]

Ah Mr Pitt,

Wondered how long it would take B4 you chirped in.

Al I can say is that I witnessed exactly the same effect whilst in Bali. Only did 4 dives - progresively deeper and had a ball. The first dive to 42 was a tad heady but the subsequent 58 was fine. Oops shouldn't really be saying all of this people might start asking about what mix I was using, who my buddy was, what redundancy I had etc.

To all those people wondering this, just let it be said that I lived and had a fantastic time for very little money (4 dives for 40 US and accomodation at 2.5 US a night can't be bad).

Later - Dave.

PS// No I didn't get around to doing the math test. Maybe next time if I've got a slate.