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Rose has that one cornered. I experimented that day and surfaced from 30 with no stops and showed grade 4 for 20 minutes, then fell to zero to the suprise of the doctors. They said they had never seen that. Otherwise it was the same schedule that John used, and from that point forward I do the 30 or 20 to 0 at 40 fpm average so as not to take the unnecessary last bit of offgassing in bubble form. Interesting that this could be done, supporting what John is saying. colin harrison wrote: > > You wouldn't care to be more specific as to the actual deco times at the > three depths and the timing and duration of the breaks on bottom gas, would > you? Sounds very interesting. > > Colin Harrison > Aquarius Diving, Didcot, Oxon, UK. OX11 8AE. > DUI Main Distributor > Tel: 00 44 (0)1235 512056, Fax: 00 44 (0)1235 815352 > <http://www.aquarius-diving.co.uk/> > > -----Original Message----- > From: John R. Rose [mailto:rose@CS*.SC*.ED*] > Sent: 28 July 1999 15:07 > To: Bill Mee > Cc: kirvine@sa*.ne*; techdiver@aquanaut.com; rose@CS*.Sc*.ED* > Subject: Re: "trimix" worthless? > > Choosing between empiracle data and theoretical tables is fairly easy. > As I am sure both Bill and George remember, the Navy doppler exams > that were performed on us after extended bottoms times in Wakulla > last year. They quantitatively demonstrate the utility of helium in > deco gasses. After performing a 150 minute true bottom time dive > (not Rich Pyle bottom time) the doppler showed ZERO bubbles in my > system. That's right folk, ZERO. The Navy doctors refused to believe > that I had done a dive that day. Finally they were willing to entertain > the idea that perhaps I have been a safety diver in the basin, > but no way could I have spent 150 mintes at 280'. > > Now the really interesting point is that my combined actual time at > 10', 20', and 30' was only 180 minutes. The trick was using bottom mix, > i.e., 10/60 for gas breaks. Put that in your theoretical model and see > how bent you get. Obviously, no deco program generated my deco profile. > To give you an idea of how radical 180 minutes is with respect to deco > software, Decom suggest 288 minutes even with the N2 and He fudge > factors set to zero. > > Bottom line: helium in deco gas ==> no bubbles as verified by doppler. > > -John > > > George, > > > > Frankly, I would have to completely agree. You can come up with > theoretical > > tables all day long to predict decompression from trimix dives, but you > are > > probably just fooling yourself. Any kind of serious exposure to trimix > and > > you simply cannot decompress without some type of sub clinical > physiological > > damage. You and I and the others have done our share of these kinds of > dives > > and there is no hiding the fact that no matter how good shape you're in > > there is a tangible "beating" factor. I'm sick of it. > > > > My guess is that the real problem is nitrogen and that the effect is not > so > > much partial pressure dependent as it is simply pressure dependent. It is > > well known in chemical engineering that many reactions require external > > pressures to occur. For instance certain polymerization reactions are > > pressure dependent. > > > > Really, who knows what nitrogen is doing. We do know that it affects the > > mechanical characteristics of erythrocytes (red blood cells). The ability > of > > erythrocytes to deform is critical to their passage through some of the > > capillary beds and who would argue that gas transfer at the microcapillary > > level is not relevant to decompression? > > > > Heliox seems to give far superior results and this should not be > surprising > > since the commercial dive industry has compiled an historically impressive > > safety record for saturation diving. > > > > I don't know what this will mean for technical diving, but I guess it will > > ceratinly help the market for booster pumps when everyone realizes that > > "trimix" is a bust. > > > > At least with the rebreathers you can operate at much lower drive gas > > pressures; however I am not recommending that everyone run out and buy > > rebreathers as these devices pose all sorts of other risks. As you know I > > have been using straight heliox for the 120ft and 70ft deco gases with the > > Halcyon with drive gas pressures of 2000-2400 and had lot's of gas left > > over, even with the 40cf bottles after long decos. I have also jacked the > > bottom gas to 75% helium with great results. > > > > Where do we go from here? > > > > Bill > > > > > > -----Original Message----- > > From: Katherine Irvine <kirvine@sa*.ne*> > > To: techdiver@aquanaut.com <techdiver@aquanaut.com> > > Cc: rose@cs*.sc*.ed* <rose@cs*.sc*.ed*>; wwm@sa*.ne* <wwm@sa*.ne*> > > Date: Tuesday, July 27, 1999 3:14 PM > > Subject: Deco not working? Could be the gas....is "trimix" worthless? > > > > > > >I get questions all of the time as to recommendations for improving > > >deco that others are not satisfied that they are doing advantageously. > > >Many times it is obvious as to wrong shape of the deco or wrong gas, but > > >lately it is less clear. > > > > > > For my own account I have been more interseted than ever in > > >minimizing damage and maximizing my available workout time since I am > > >training for an Iron Man this fall - I can't have any down time from > > >training since I have to work three disciplines and workout twice per > > >day . My teammates have become more interested in marathons, bike > > >races, swim races, triathelons and in more conditioning, and have taken > > >the same attitide that I have taken, and that is we do not want diving > > >to get in the way of our training, even though diving was why we started > > >training in the first place. > > > > > > You have seen the progression of our deco, and may have noticed that > > >we started incorporating helium into the deco gasses, and increasing the > > >amount of helium in the mixes. As we got higher and higher on the helium > > >percentage , the truth has become clearer and clearer - nitrogen is the > > >problem, and "trimix" as we knew it is basicly worthless. > > > > > > Sure, I can walk away from most trimix dives, but I run away from > > >helium dives. We may have to revamp our entire structure on this issue. > > >Heliox may in fact be the correct gas for diving, and the answer to > > >deco, not anything more or less. > > > > > > The Navy asked us about loss of vital capacity. We can measure that > > >on the track , in the pool, and on the speedometer in one word ; > > >nitrogen. > > > > > > > > > > > > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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