Posted by Eins on October 17, 2001 at 17:52:12:
In Reply to: Long response attached posted by MHK on October 16, 2001 at 10:08:14:
I sent the following to MHK by e-mail (the board was down) but want to post it here as well in case one of you guys has got some good ideas to contribute. Thx.
Thank you and I appreciate your response which I consider a successful approach to familiarize a layman with the decompression models and the underlying theory. No ifs and buts. Patrick would, as I mentioned, apply nutritional insights to scuba diving to make diving safer. At this point, I think that Patrick would not need to dig into that much of a background and would better understand the scope of his (nutritional) task if he got some information along these lines (and this is a first draft):
>>A human bodyís tissues will load with inert gas (N2 in air) if subjected to increased pressure. A descending scuba diverís tissues will therefore load up more and more, the longer and deeper this diver stays underwater, until a saturation point is reached (which is specific for each depth). To ascend safely and without causing decompression sickness (DCS), this diver must ascend not faster than allowed by the specific tissue groupís off gassing properties. I.e., the diver must avoid that the loaded gas forms bubbles before it off gasses through the lungs. Compare it to a soda bottle which, if opened very slowly, will hardly bubble and will not overflow but which, if opened too fast, will form masses of large bubbles and will overflow. Bubbles are what causes DCS. They stop flow in blood vessels thinner than the bubbleís diameter and cause either undersupply of blood (= oxygen) or pinch on nerves at narrow passages. The fact that the body consists of tissue groups with different on- and off gassing properties (speeds) complicates the issue.
To reduce risk of DCS, a diver must, amongst other things,
a) ascend slowly (the current recommendation is 30 fpm) and possibly stop ascent and remain at certain depths to allow off gassing before advancing to lower water pressures
b) hydrate sufficiently to keep tissues hydrated which improves off gassing; hydration also improves the bloodís properties to carry away off gassed N2
c) avoid exertion before, during and after the dive to prevent actions of the metabolism that are adverse to preventing DCS
d) maintain proper thermal insulation to prevent hypothermia which would support DCS
e) follow all these rules with even tighter tolerances, the older the diver is, as the aging body is less equipped to function in a desirable manner.
In more extreme cases, divers willingly expose themselves to conditions that require many hours of decompression stops underwater. As long as they follow proven concepts of decompression theory, they run a good chance to surface without any symptoms of DCS. On the other hand, it happens too often that divers who have not even subjected themselves to extreme situations and who have followed the protocol, nevertheless suffer from DCS and need hyperbaric treatment to resolve the symptoms.
It would be very beneficial, if harmless nutritional substances could help the tissues to off gass the loaded N2 quicker and with less risk of causing DCS. <<
I think this is as far as the synopsis needs to go to kick things off. Please feel free to correct, to add helpful facts or to re-write in order to make more sense. Thanks for all your help.
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