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> Date sent: Mon, 9 Oct 1995 13:10:37 -0700 > From: iantdhq@ix*.ne*.co* (IANTD ) > Subject: narcosis adaption > To: techdiver@terra.net > Narcosis & Adaptation > > Stepping into controversy is a sin for someone who wishes to avoid the > flames But--- > > I do believe there is a degree of adaptation to narcosis, based on > personal experience and having been a subject in different narcosis > studies. The "adaptation" that is perceived, is to a large extent an illusion. During any complex task that is carried out, the brain is continually making a choice between "speed" and "accuracy". The relationship between these characteristics is sigmoidal, and the precise placing of this line depends on the number of "active" synapses assigned to coping with this problem. Narcosis (aka anesthesia) reduces the number of participating synapses and shifts the curve to the left, i.e. we lose both accuracy and speed. HOWEVER, by making a conscious decision to sacrifice "speed", one is able to make up for some loss of accuracy. It was a common syndrome in the bad old days, when a drunk could "safely" drive home at 40 km/hour (15 mph) with one wheel in the gutter. They were making use of the same mechanism. HOWEVER, neither the drunk nor the narced diver has adapted to the level of narcosis (that's like adapting to a pO2 of zero), what they have done is shift their priorities to accuracy, and to shut down non- critical processing (peripheral inputs, etc). The range of pN2 that starts to cause discernable narcosis is not that wide, and is covered by the biological diversity of the population. Flame away! > > I. The first study was a behavioral modeling one: In this it was the > old approach of we will give you a free course if you will allow us to > screw with your mind and body; > > In this program we taught students form entry level diving in three > groups of folks as closely sex, personality education etc. related as > possible. > One group was taught you will be seriously narked at 100 or deeper > > A second group was approached that you may get a degree of narcosis but > you can cope with it > > The third group was taught that strong willed divers may deal with > narcosis to great depths. > > The subjects were progressed in OPEN WATER( I think that an open water > test will always vary from a chamber study from a behavior standpoint. > because your brain./mind is functioned to protect itself and behaves > differently in a stress environment than inn a non stress environment > such as a chamber. The chamber studies are valid in measurements except > they do not take into consideration the behavioral modifications of in > water survival that the brain will react to) > > In the above testgroup 1: All divers exhibited severe symptoms of > narcosis in the 100 to 150 foot range. One of these totally lost motor > function and had to be carried to shallower water including keeping his > regulator in his mouth. This person would have drowned without > assistance. > > Group 2 Adapted much better with several completing single factor > evaluations with minimal degradation as deep as 150 to 180 feet. > > Group 3 performed far better than the other groups with one female > actually improving on each dive even though on each dive depth was > increased by 20 feet. ( max depth 240) > > In this experiement each subject was accompanied by two staff deep > divers. The purpose of this was not to say one may or may not tolerate > narcosis but rather to see what the psychological attitude/mind set > would have on performance. The test used were the ball bearing test, > math function and pegboard. However only one test was given per dive. > There was no multitask problem solving evaluations in this drill as it > was not broad enough to test all aspects of narcosis. It did reflect > the importance of the mind set of the diver and individual > predisposition to narcosis. > > A second experiment was much more conclusive. In this program Dr. Dick > Williams and I were the subjects. We were convinced that experienced > deep air divers who maintained regular exposures to depth with no more > than a week between deep divers became highly tolerant to narcosis. > > The experiment began with Dick and I making five consecutive days of > deep dives to build our tolerance levels . At this point the test began > these were performed in the controlled environment of a chamber and due > to our experience and determination to prove our point I think we > actually scored better in the chamber than we would have in open water. > Plus the test would have been more difficult in open water. For five > days we dived to 300 feet and completed a performance objective. The > test were math function (I scored higher at 300 than at the surface), > Ball bearing test(in this test one takes twizzers and picks up steel > ball bearings and drops them through a close tolerance piece of > stainless steel tubing and the number achieved is compared to the > surface values, the purdue pegboard test was used, a short-term memory > evaluation was undertaken , a word association accompanied by hand > writing evaluation was also used. On all five days both Dick and I had > quite favorable results. To us we were proving our belief in our > tolerance. > > But our belief in tolerance was shaken when on the sixth day we were > told to select three test of our preference. These test were then > divided into three divisions each. During the dive we were to complete > part on of each of the three test then part two and then part three. > Dick and I both breezed through part one , however at part two of the > second test (we each had selected different test and the ones that > were common were sequenced differently from each other) both of us came > to a dead stop. After an additional 10 minutes of attempting our > problem solving abilities neither of us had been able to advance in the > test. > > This blew the tolerance theory, but did suggest a degree of adaptation. > If we were tolerant we would have been able to reason through the test. > With a degree of adaptation we were able to focus on single events. > > This test was a eye opener to me and was my first real step towards > becoming respectful of narcosis. Incidentally I have seen this test > performed on other divers at depths just over 200 feet with like > results. > > I I think when we as deep divers express our feelings of norm it is due > to an adaptation process. Your brain in its effort to make you survive > is adapting your behavioral response to a known depressant. But it does > not produce a reaction that yields total mental agility. Thus while a > diver may go quite deep and complete an objective. This same diver most > likely will not have the mental ability to do multi task problem > solving. > > George had made a statement about being lost in a cave which IAEll > extend to wrecks as well. From an adaptation standpoint one may do > routine functions and have a safe return to the surface(we all have). > However should the diver get lost and lets say it is compounded by > being in a siltout and away from the line(hopefully all of us use > lines on any extended penetration today in wrecks as well as caves)The > ability to reason all the survival needs , find line, determine > direction to surface etc./. The diver will most likely have great > difficulty in accurately and timely completing these life threatening > decisions. > > A comparison I think is like: Someone has had a wee bit to much to > drink, they get into the car and as they are driving a police car gets > behind them, as the driver is familiar with being intoxicated the brain > produces adaptive behavior that allows the car to be driven in a > straight line, perhaps even straighter than normal in this situation. > However fact is if a child ran out in front of the car the divers > mental and physical coordination/responses would most likely be slowed > to a point of not being able to avoid running over the child. > > I also think that we are not always aware of symptoms as adaptive > behavior also emplys we have become use to a degree of performance > degradation and no longer notice it. In my case my first tell tale sign > of narcosis is not how I feel (hell I feel great, I feel normal) it is > when I reach out to touch a line or something I miss it by several > inches. Usually at this point IAEm unaware of narcosis even though > obviously IAEm narked. This is one reason that narcosis may be life > threatening as to those of us who are used to it have sufficient > adaptation that we really do not recognize symptoms that to an > unadapted diver would be apparent. Yes I can and have taken great > photos at depth but that is comparable to doing the test Dick and I did > in the earlier test, one thing to focus on at a time. IAEm not sure that > if a complex situation occurred that I could reason my way through it. > This again is why I encourage divers to limit deep air to a max of 200 > feet and recommend 180 feet for air dives. It is also why in overhead > environments one may wish to reduce the narcosis level even more. > > I'm not telling anyone what to do, earlier I stated IANTD traing > practices. > > My personal philosophy follows the statement Gil Milner a psychriast > and former cave diving buddy made. > > "You have the responsibility to inform others of the risk of any > endeavor, and as an individual you must discover the risk of all > aspects of an objective , once the risk is FULLY UNDRERSTOOD and > accepted. Each fool has the right to kill or injure themselves as they > see fit, provided they do not entice others to take the same risk" > > Again I'm just stating my experiences and opnions and earlier in a past > post I stated IANTD's training policies. I do accept and subcsribe to > Gil Milners philosophy. Diving is risky business and the risk most > likely doubles for each ata depth increase. All gases and mixtures and > decompression models have limits. All technologies that we can use such > as trimix for depth also have their own risk benefit decisions one must > make. Nothing in life comes without a price and you must be the one to > determine the price you will pay for a given benefit. > > Past research, past experience, the process of accident analysis, and > determination of your own risk benefit projection are the tools we all > should use in making our decisions on deep diving, penetration diving > and use of all the various technologies available to increase our > performance. Just be sure you are making an informed decision, and that > you truly accept the risk of the event and that you are willing to pay > the maximum price that risk may demand. If you have done these things > GO FOR IT! JUST DON'T DO IT WITHOUT GOING THROUGH THIS PROCESS AND > DON'T EXPECT OTHERS TO ACCEPT YOUR PERSONAL RISK FACTOR AND TAKE > PRECAUTIONS NOT TO ENTICE THEM TO FOLLOW YOUR STEPS. > -- > Send mail for the `techdiver' mailing list to `techdiver@terra.net'. > Send subscription/archive requests to `techdiver-request@terra.net'. > Greetings Prof JG van der Walt Head: Dept. Physiology Veterinary Science University of Pretoria Onderstepoort 0110 Republic of South Africa Tel # + 27 12 529-8025 Fax # + 27 12 529-8305
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