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this should've gone to the list ---------- Forwarded message ---------- Date: Sun, 13 Feb 2000 10:50:11 GMT From: Edward Watson <ted.watson@ze*.co*.uk*> To: Steve Schultz <se2schul@un*.ma*.uw*.ca*> Subject: Re: In water recompression. (FWD) (FWD) <snip legalities bit, not interested in that> > The first assumption is that the worst thing the "omitter" has > effectively done is move up the last 20 feet and out of the water too > fast. By this I mean that if any of us do this at any point in any deco > proper or improper, we are foaming out that last pressure gradient that > NO amount of deco will remove. Only a slow ascent to the surface will > allow that last bit of gas to come out in solution. Jumping up 20 feet > will bring it out in bubble form, no matter what. > So now the guy is out and foaming, but only the doppler knows this - > he is asymptomatic. We know from our doppler experience and endless > studies that this bubbling will actually INCREASE with time after the > diver is out of the ater, and will peak some 20 minutes to an hour > later, and hold at that level for up to hours. So assuming ommitted deco, the idea that the first 30 minutes or so post dive is effectively a surface deco stop is incorrect, it should be much longer? > Now, we have two choices - do nothing ( which includes breathing > oxygen on the surface ), or tell him to go back and do some deco , and > then ascend slowly. What do you mean 'some deco'?- just repeat what was omitted exactly, or go a bit deeper and start again, or add in extra time at the ommitted stops/faster ascent > Now we have to look at the profile - how deep , how long, how > serious could this omission be? How deep do we have to get this guy to > reduce the bubbles to where we can get them into solution or at least > managable enough to offgas through the lungs or get small enough to pass > by way of the circulatory system to the lungs where we can work on them > with oxygen. > Generally, if you can keep the guy alive, and stay on him, and that > goes for a may-be-nothing situation to a real blowout, getting him down > and getting him on oxygen ( or the correct max PPO2 gas for the depth) > are both a must if he is going to not be brain damaged. > The general best bet in the three situations you describe are to > take your chances by going back in, finding the starting point that is > reaonable and will not take to long to ascend from, and redoing that > part of the deco, with special emphasis on taking the last 30 to 20 feet > very slowly all the way up. How do you decide what starting point is reasonable in a given situation, or is just a best guess thing > Pain hits are not so big of a deal as an annoyance and a dive trip > ruiner as they are not going to go away completely. For one, the bubble > traped most likely seeded much deeper , and only grew to pain size > later. You can tell the depth at which it shrinks when the pain goes > away, and do the math to figure how deep it reasonably cound have seeded > at. It is a waste of time to go back to that depth since the damage is > done and you will feel the pain of the damage long after the bubble has > been reabsorbed. The better bet is to reduce it somewhat and give it a > chance to diminish ( they generaly grow first, but you have > receompressed it somewhat) and then try to overcome it with oxygen in > the slow ascent. realistically a pain hit is going to be much easier to sort out in the field than one involving paralysis etc. What we need to know is how best to deal with it if there's going to be a reasonable delay in evacuation to a chamber. Obviously it's always going to be a balance with hypothermia, gas volumes possibly sea-sickness all being considerations. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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