Deep Air - Here we go again....

[Puffer Fish]

How about you read Bennett&Elliot Physiology of Diving and find an article where they researched the adaptation to narcosis?

For lazy people, here's a summary: adaptation does exists, is short term (read: after you don't get regularly narced for a week you back to square 1) and is most noticeable for simple tasks like hammering a nail. High complexity tasks show little to no improvement with practice.
Level of narcosis also varies for individual on a different days.

And you should probably top it of with another research quoted in Bennett&Elliot which ties gas density to work of breathing and lung ventilation, with WOB observed to be increasing exponentially in relation to depth when diving air below 100-130 feet, while efficiency of lung ventilation drops at the same time, promoting CO2 retention.

So for a price of airfill we get increased N2/O2 narcosis, increased CO2 narcosis (200 times more narcotic than N2) and increased likelihood of O2 tox (which is well proven to be precipitated by increased levels of CO2).

This is based on solid research not some anecdotal evidence "I dove to 190 yesterday and I'm fine" or "Commercial divers do it all the time". NASA was flying space shuttles for 20 years before they discovered they have issues with protective foam destroying thermal protection. Unlike some macho divers - they actually drew conclusions from incidents and changed their ways rather than "Uh... but we did it for 20 years".

But maybe I'm wrong and you actually do have something more than anecdotes to back your claims up. I would love to see them and correct my viewpoint.

Well, then the solution to deep diving is to only have problems that are like hammering a nail...and avoid those "complex" things altogether... problem solved.

or use trimix.. hummm, I vote trimix.

 

[Puffer Fish]

Come on...It gives you something to do.

Amazing as it might seem, I happen to be on your side in this one.

I did a trimix course this last summer.

 

[JeffG]

Amazing as it might seem, I happen to be on your side in this one.

I did a trimix course this last summer.

Not that amazing. I'm always right.

 

[Anti-Hero]

I'm just here for the chicks.

 

[LiteHedded]

Well, then the solution to deep diving is to only have problems that are like hammering a nail...and avoid those "complex" things altogether... problem solved.

or use trimix.. hummm, I vote trimix.

if only it were that easy.
I'm with you. I vote trimix

 

[DaleC]

I guess things won't really change until the old guard retire or are killed off by their own foolish practices.

Agree or disagree with deep air; that's perhaps the saddest thing I've read here in a while.

 

[Kevrumbo]

Moreover, our results suggest that experienced divers can discriminate between the behavioral and subjective components of narcosis. . .It has been proposed that the intensity of narcotic symptoms could be used by divers to gauge the extent of performance loss (10). The present results indicate that this advice is inappropriate for adapted divers because the two components of narcosis [behavioral and subjective] uncouple in a direction that could lead to an overestimation of performance capabilities --a potentially dangerous situation. On the other hand, the question arises as to whether adaptation confers any benefits on the diver, since performance efficiency is not directly improved and could be overestimated. In this regard, it could be argued that a reduction in symptom intensity reduces the possibility that attention will be focused on subjective sensations rather than the task at hand. [i.e. Subjective awareness vs. Situational awareness??]

p.9, Hamilton K, Laliberté MF, Fowler B. Dissociation of the behavioral and
subjective components of nitrogen narcosis and diver adaptation. Undersea Hyperb
Med. 1995 Mar;22(1):41-9. PubMed PMID: 7742709.
http://cradpdf.drdc.gc.ca/PDFS/zba24/p154358.pdf

Yep . . .in my experience, I can agree to that

 

[DCBC]

You appear to have a ton of in water experience. Unfortunately old school experience isnt that impressive to modern tech divers who as a whole are overly cautious and completely non-mucho. A few things have changed since 1984

Thanks for your comment. Yes, your description of the modern tech diver may well be accurate. I certainly don't however fault anyone for being over cautious.

I suppose some people think they can ridicule others after they have accumulated a couple of hundred hours underwater. Afterall, what is there to possibly know that they haven't mastered?

 

[DCBC]

It seems to me that everyone (even those who are 'proponents' of 'deep air') recognizes that there is a narcotic safety envelope beyond which using helium is advisable. The discord revolves around where that 'limit' is. And, like everything else, it's different from one person to the next.

I agree with your assessment, thanks.

 

[DCBC]

..But maybe I'm wrong and you actually do have something more than anecdotes to back your claims up. I would love to see them and correct my viewpoint.

There are many studies that have been undertaken over the years. Some of these I was personally involved with as a test subject when I was at DCIEM. I have gone into the results of some of these tests in previous postings and have outlined the affect that experience plays in narcosis. Individual adaption to narcosis is a fact. Note that I said adaption, not immunity (people seem to want to put words in my mouth).

The ability to dive to 150 or 200' on air is not necessarily something that a recreational diver needs to do. The ability to dive to 250 or 300' on trimix is not necessarily something a recreational diver needs to do. However, there will be those who dive for recreation that will undertake such dives.

For some, this is identified as a macho activity. Others identify diving air as macho and not deep diving trimix. Either way, the level of risk increases in both activities.

An interesting examination of Technical Diving and the added risks are itemized in a paper by Carl Edwards, SPUMS Journal Vol 27 No. 3 September 1997 and is available on-line here: http://rubicon-foundation.org/dspace/bitstream/123456789/6084/1/SPUMS_V27N3_15.pdf

My position is that:

1. Divers will continue to use air
2. Some divers will be seriously affected by Nitrogen Narcosis
3. Not all divers use trimix, nor will all divers ever use trimix
4. Trimix is not always available at all dive sites
5. For some divers trimix is cost-prohibitive
6. For those divers who elect to use air and dive deep, training and experience in using Deep Air will assist those who would not otherwise benefit from such training.

Because I've stated these things, I have been ridiculed as macho and a poor instructor. I understand that everyone has an opinion, even though they may not be qualified to give one. This is after all a public forum and I realize that some people get their kicks by throwing stones at people they don't have to look in the eye.

The following studies support my statements (the first two were undertaken at DCIEM):

Hamilton K, Laliberte M-F Heslgrave R.
Subjective and behavioural effects associated with
repeated exposure to narcosis. Aviation, Space and
Environmental Medicine 1992; 63: 865-869.

Hamilton K, Laliberte M-F, Fowler B. (1995).
Dissociation of the behavioural and subjective
components of nitrogen narcosis and diver
adaptation. Undersea Hyperb Med 1995; 22(1):
41-49.

Baddeley AD, De Figueredo JW, Hawkswell
Curtis JW, Williams AN. Nitrogen narcosis and
underwater performance. Ergonomics 1968; 11:
157-164.