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>... >Both times narcosis set in at about 120 feet. Both times were while >diving Gilboa Stone Quarry. The puzzling thing is that I've been past >120 numerous times at other places without problems. I know narcosis >doesn't follow very well defined rules, but is this normal? Probably... see text below. >It concerns me because I'm not one of those who gets happy or euphoric. > I get pretty paranoid, and my buoyancy control goes right out the >window. This last occurance was just this past weekend. I was fine >right up to 120 feet. Or at least that's when I recognized it. I >realized that I was very nervous, and decided to head for the down line. > By the time I hit the line, only a few feet away, I had ascended 17 >feet and set off the ascent alarm on my computer. >... >What kinds of things contribute to Narcosis? Are there any steps I can >take to reduce my risk of Narcosis? Is it normal to hit it at 120 one >day and not at 140 the next? Eric, The following are all contributor to Nitrogen Narcosis: It is normal that you don't feel narked at the same depth every day or in every situations. Nervosity, cold, CO2, speed of descent, position during descent, lack of visual references, reduced visibility, stress (caused by complexity of dive, situation or time). If you do a slow descent, narcosis will 'hit' you less (you'll have a better capability of detecting the first symptoms). At the first symptoms, remember to SLOW DOWN. You can have quite a good control of yourself, but not at the same speed. Think about your breathing, especially the exhalation (often, this alone will solve the problem). You should not be doing physical effort at depth. The previous advice will help you acheiving a dive when everything is going well. However, your response in case of an emergency or an unforeseen situation is nearly unpredictable. If your intention is to go at depths where you get narced, it is required to overlearn any skills that may be required in an emergency. There are various theories about adaptation to nitrogen narcosis. Kevin Hamilton, M.-F. Laliberte and B. Fowler did a research on dissociation of the behavioral and subjective components of nitrogen narcosis and diver adaptation. This study was conducted at the Defense and Civil Institute of Environmental Medecine (DCIEM). They found that the global estimate of narcosis (subjective evaluation - how we feel) showed adaptation on day 3. On the other hand, the behavioral component (how we react) did not show any adaptation. This seems to provide us with a false sense of security. The global estimate was made of subjective evaluation of several adjectives (able to concentrate, able to think clearly, fuzzy, etc). The study revealed that judgments about work capability can be differentiated from judgments about body sensations (work capability judgment showed few signs of adaptation). Note: in the text above, I implicitely state that nitrogen is the sole contributor to narcosis. This is believed to be false by many specialists today. It is tought that oxygen is as much narcotic as nitrogen (may be a bit more). >Incidentally, I'm planning on taking courses next year in Technical >Nitrox and Trimix. Will trimix help solve the narcosis problem at >depths beyond Nitrox's shallower limits? With trimix, you can ajust your END (equivalent nitrogen depth) as you wish. Michel Therrien m.therrien@ne*.qc*.ca*
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