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I have been following the narcosis discussion with much interest, and I would now like to add a few comments of my own. I do not claim to any particular expertise, just experience and the fact that I have done some reading. If anyone remains in a head down position for several minutes, either in the water or out of the water, and then suddenly moves to a head up position, he will experience vertigo. It is a transient phenomenon and passes in a few seconds. It is obviously caused by a delay in the adjustment of the blood flow to the brain necessitated by the change of position. Most people seldom, if ever, remain long in a head down position out of the water, so many experience it for the first time in the water where we are often in a head down position, descending, looking for lobsters under rocks, etc. It has absolutely nothing to do with narcosis, but some people seem to be confusing it with narcosis. I myself have experienced it many times and learned to ignore it. We are told that inert gas narcosis is related to the solubility of the inert gas in lipids. It should then be obvious that it takes time for the gas to be transported by the blood stream to the tissues involved. We are concerned with nerve tissues which have short half times, so the time will be just a few minutes, but the effect will not be immediate. Therefore people who think they feel narcosis at the start of the dive must be experiencing something else. Did they descend head down and then raise their heads when they got to the bottom? Little was said in the discussion about the psychological effects of being in a strange environment. They must be considerable and difficult to distinguish from the physiological effects of narcosis. Certainly diving in cold turbid water will have a detrimental psychological effect. Is the diver rested? Is he worried about his equipment or something else? These and many other factors will have a significant effect. A diver making a dive much deeper than he has been before will not know what to expect from narcosis or how to handle himself. The proper way to learn about narcosis it to increase the depth of the dives gradually and learn how to handle yourself as you go. A diver who has never been deeper than 50 ft. who makes a dive to 150 ft. is certainly asking for trouble. A number of years ago I made a series of dives in warm, clear tropical water to 190 ft. for 7 minutes (surface to start of ascent). Although I am sure I had some affects of narcosis, they were minimal and did not bother me. I was confident and in control at all times. The ideal conditions, the short duration of the dive, and the fact that I had been deep before all worked in my favor. On letter mentioned narcosis which had a long term effect: minutes, hours, even days after returning to normal pressures. These effects must be caused by something much more serious than mere narcosis. The very long term effects are similar to the effects described by people who have undergone general anesthesia, especially protracted general anesthesia. In the latter cases it has been blamed on at least some degree of hypoxia to some part of the brain. I cannot, however, think of any reason for the similarity. Does any one have any ideas? Bruce Gerhard
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