200' on air for 5 min bottom time?

[Abdullah]

And kirby had hundreds of those dives, and it nearly killed him.

He had hundreds of those dives that didn't nearly kill him. So, what was different on the ONE dive that nearly killed him?

 

[DCBC]

Late to this party, but I'm calling b.s. on the "Adaptation" argument. ...As a practical matter you can yap all you want about narcosis adaptation, but I'm not buying it as being practical.

You of course are entitled to your opinion Lamont. My experience however, has caused me to come to a different conclusion. Adaptation does in-fact occur.

Adaptation has been experienced in various hyperbaric testing scenarios. I've been personally involved in such tests on a number of occasions, while I was stationed at DCIEM. One such test that I recall, involved the testing four Navy Divers (experienced) and eight Graduate Students from the University of Toronto. Testing was accomplished on the surface and at depth in the areas of convergent visual orientation and convergent thinking.

The experienced divers had a surface test score 12% lower than the average inexperienced subjects. At depth however, experienced test subjects outscored most inexperienced test subjects. The reaction times of both groups were approximately the same. Personally, my test results at depth (200 FSW) actually increased on the second day of testing.

Other testing has taken place since this time. Dr. Kevin Hamilton from DCIEM has written a few papers on the topic. One entitled "Subjective and Behavioral Effects Associated With Repeated Exposure to Narcosis (1992)" stated "While the results revealed no clear cut changes in global perceptions of narcosis across days, several symptoms from an adjective checklist showed unequivocal signs of adaptation."

That does not mean that using Deep-Air isn't hazardous; it is. Anything that impairs a Diver's ability increases risk. Risk is also increased by using a CCR or entering an overhead environment (for example). It's up to the individual diver to assess the risk and dive only when the risk is acceptable to him.

 

[supergaijin]

Me, I'm rather partial to narcosis- I start to feel it at around 4ata.... but I'm also looking for it; Seek and ye shall find. I dive that deep all the time and it doesn't seem to go away. No shame in that at all. Cousteau also used to 'get' narcosis much shallower than some of his other team members. Falco OTOH seemed to be a machine who dived regularly deep on air.

In the Philippines we regularly dived to 5ata and I rarely noticed narcosis. It was riding shotgun without a doubt however I wasn't looking for it, and so didn't notice it.

Ignore narcosis at your peril.

 

[Tortuga68]

The inherent risk with psychological/procedural adaptation to narcosis is that it does not account for stressor and physiological variables that the diver may encounter on any given dive.

One could equally say that's the risk with narcosis itself

I think the other DD summed it up pretty well; yes there's some degree of adaptation if you dive deep air regularly, but that doesn't mean narcosis won't bite you in the ass one day. And if you don't respect it that day will come sooner rather than later.

Same can be said of a lot of things in diving, gas switches for example...

 

[DCBC]

... yes there's some degree of adaptation if you dive deep air regularly, but that doesn't mean narcosis won't bite you in the ass one day. And if you don't respect it that day will come sooner rather than later..

Absolutely. This is why anyone using Deep-Air, CCR, entering a Cave, Wreck, or other OH environment, should seek training beforehand. Everyone will be affected by IGN after 50 FSW. Most divers don't think they're affected at this depth, but they are. That's the sinister thing about narcosis; you're affected and you don't realize it. Because the intensity of IGN varies, you have to monitor yourself and know how this is done. Only in this way, can a deeper dive be accomplished in a safe manner. Sometimes it's necessary to scrub the dive and ascend to a depth where the effects of narcosis are diminished.

 

[Ste Wart]

As with most deep air arguments, those most vocal against it are the ones that have never had an END higher than 30m.

 

[danvolker]

As with most deep air arguments, those most vocal against it are the ones that have never had an END higher than 30m.

Probably true....but sometimes people try to learn from the mistakes of others, rather than having to learn the "hard way" themselves.
In my case, George Irvine, Bill Mee and I dove pretty much every single deep reef and wreck between Jupiter and North Miami, from 170 feet to 280 feet deep, in the years between 1991 and 1995--all on deep air.... We tried to use the best plans, with the highest safety factors on these dives ( our DIR buddy system from WKPP--just concentrated list of what works, invented/discovered by other people, including guys like DCBC--meaning we wanted to use history, learn from it, and apply it for all team members, on all dives).

While we had no deaths in our ocean dives that our team was doing, individuals that had done dives with us, that went out and broke protocol on deep air dives, did die...and many many divers in the deep air fraternity DID DIE in this period between 91 and 95...Usually you could attribute the accident to mistakes heavily contributed to by the effects of deep air....

While I did hundreds of deep air dives, it would only take one critical mistake due to narcosis, to die... I do remember one of my first deep air dives with George and Bill....I was spearfishing with them at 280 feet, they were about 50 feet away from me with their own little mission, each of us had agreed that at 25 minutes we would all be back at the hooked off line, and all would do "Blow and Go" at the same time, in a group. When I had begun this hunt, I had no trouble checking my air supply, then my elapsed time on the dive, then looking for a fish to shoot...I was great and sharp with these 3 tasks, at 280 feet on air....the problem was when a 4th task was added....so 10 minutes or so into the dive, I was getting "Wagon-Trained" by about 20 big groupers in the 25 to 30 pound size range....they kept circling me at about 7 feet away from me, right after I had shot the first one....getting the first one on the stringer, should have been simple from a coordination standpoint, should have been seconds....and I distinctly remember being frustrated that I had to get this damn fish into the stringer, get the spear loaded, and shoot several more of these groupers as fast as possible....and fas as possible was turning out to be taking me forever with each fish! By the time I had 3 big fish, I felt a hand on my shoulder, George had grabbed it, and was smacking his finger on his computer, showing me we were at 25 minutes, and looking at me like --"what the H*ll...why was I not collecting at the line.." So due to the extra tasks to juggle, I had managed to forget to check elapsed time for quite a while....something like this "could have" caused an OOA or dangerously LOA issue without the Team based checks and balances we had.... Over the course of the next few years, I had occasion to return this favor for a number of quite prominent and amazing divers--of course due to the task loading effects and the deep air, in some of the extreme exploration environments we would get into.

I did like "Blow and Go"...it was lots more fun that the Trimix ascent...... 2 or 3 teams of us would collect at the hook, un hook once ready, then at the same moment, each would fully inflate their BC/wing.....In the next moments, you are rocketing upwards. Your OPV is literally Screaming as it dumps air with the rapid ascent and volume increase.... Immediately below your feet was this amoeba shaped monster of bubbles, hurtling upwards in pursuit, threatening to engulf you at any moment.....the scream of the overpressure valves was deafening, and the two key tasks all team members were intent on, was watching your buddies, and watching your depth gauge to begin a 100% dump at about 120 feet deep, so that by 100 feet deep, we would be at a dead stop...where we could collect and chill for a couple of minutes, prior to a slow ascent to the first stop at 50 feet. The narcosis would still be with us....the feeling of adrenaline and ecstasy from 280 feet was still alive and well, and it would live on through the entire 50 foot stop, beginning to wane somewhere in the middle of the 40 foot stop.

I have many fond memories of the deep air dives, and of the adventures...but the reality was, when George got us to try trimix in around 96, our first dive on it on the RB Johnson/Cory"n Chris, was different from any dive we had ever done on it before. Everything was easier....we each saw so much more than we had ever seen before--stuff we would talk about for hours afterward....the ease of the team functions, of the skills --whether stringing a fish, or of running a line in a passageway...every thing was sooo eaassyy.....How could we plan more huge explorations, in the sites we had dreamed about exploring--the places so challenging that few if any had ever contemplated them on air....how could we even imagine doing these sites on air, when trimix made them so much easier...and potentially, so much safer.
So we switched for good, and our diving just got much easier, no matter how deep.

 

[Peter Guy]

stu wrote

those most vocal against it are the ones that have never had an END higher than 30m.

And you know that how?

There really are some of "us" who have dived "deep air" (although NOT as DCBC has, more like the "average" recreational diver, that is, on rare occasions) -- who have "danced with the devil" and concluded it isn't such a good thing.

Unlike Lamont I am quite ready to believe people can adapt to the impairment -- that is, recognize that they are impaired and be able to continue to be somewhat (emphasis on somewhat) rational while impaired. But, as DCBC has written from his experience (both experimental and practical) the level of impairment may change on a whim and without notice and if/when the diver doesn't recognize the decreased impairment, trouble may well be the result -- as it was in Kirby's (the diver Lamont knows) case.

 

[Ste Wart]

As with most deep air arguments, those most vocal against it are the ones that have never had an END higher than 30m.

stu wrote

And you know that how?

There really are some of "us" who have dived "deep air" (although NOT as DCBC has, more like the "average" recreational diver, that is, on rare occasions) -- who have "danced with the devil" and concluded it isn't such a good thing.

Unlike Lamont I am quite ready to believe people can adapt to the impairment -- that is, recognize that they are impaired and be able to continue to be somewhat (emphasis on somewhat) rational while impaired. But, as DCBC has written from his experience (both experimental and practical) the level of impairment may change on a whim and without notice and if/when the diver doesn't recognize the decreased impairment, trouble may well be the result -- as it was in Kirby's (the diver Lamont knows) case.

Peter, calm down and accept the fact that everything posted on this board is not aimed at you. Neither was I commenting on DCBC's statement. I have however read enough 'deep air' threads on various forums and the same personas shout down deep air time and time again.. Personally I think a thread poll should be run to see what the balance is on this board. But I can already guess the results will confirm my suspicions.

 

[dumpsterDiver]

stu wrote

And you know that how?

There really are some of "us" who have dived "deep air" (although NOT as DCBC has, more like the "average" recreational diver, that is, on rare occasions) -- who have "danced with the devil" and concluded it isn't such a good thing.

Unlike Lamont I am quite ready to believe people can adapt to the impairment -- that is, recognize that they are impaired and be able to continue to be somewhat (emphasis on somewhat) rational while impaired. But, as DCBC has written from his experience (both experimental and practical) the level of impairment may change on a whim and without notice and if/when the diver doesn't recognize the decreased impairment, trouble may well be the result -- as it was in Kirby's (the diver Lamont knows) case.

I don't know that impairment is a function of a whim... (and I'm sure you meant increase impairment, not decreased..)

However impairment it is VERY much a function of exertion level. CO2 levels build much faster and are much harder to recover from due to the density of the gas. This inability to perform a high level of work makes an "in shape" diver a weakling who has much less strength/ (cardio capacity) reserves to "muscle out" of a situation. This is a physical impairment and adds a lot to the danger.

In addition, the Co2 build up further impairs mental function, causes discomfort and makes bad decisions and panic more likely.

I think part of the acclimation is similar to freedivers, who must learn to move smoothly and efficiently and strive to keep their emotions under control. This type of ability takes time to acquire.