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Carlos, I should add that we are religious in taking backgas breaks every 12-18 minutes which is shorter than what the 'agencies' recommend. In addition, our breaks are 6-8 minutes long, again, not quite what the 'agencies' recommend. I should also mention that we are not doing `air breaks' but instead are taking breaks on gas with very little oxygen, i.e., ~10%. No one knows how much breaks back off the CNS clock. One may reasonable expect that breaking to something like 10/60 or 10/75 is more efficacious than something with greater oxygen content. -John > Carlos, > > As you say, we 'blow the CNS clock sky-high'. I am not aware of anyone > in our group having convulsed during deco. Certainly this has not > happened during the four years that I have been a member of the WKPP. > > In contrast, during the WAK II circus, Jason Richards went to 90 feet > on O2, convulsed, drowned, and was brought back to life at the surface > as documented by the National Geographic Special. > Of course that wasn't deco, nor was it anyone that we would let near > any dive site that we control. > > -John > > > > John, > > There's one thing I'm very curious about. You say you use oxygen in the > > habitat at 30'. > > And it's a well known fact that you guys blow the so-called "CNS clock" > > sky-high. > > All this begs the question: has anyone ever convulsed during deco? > > Thanks, > > Carlos > > > > > > > > > > > > > > > > "John R. Rose" <rose@CS*.SC*.ED*> on 07/28/99 12:30:36 > > > > To: colin@aq*.de*.co*.uk* (colin harrison) > > cc: rose@CS*.Sc*.ED*, wwm@sa*.ne*, kirvine@sa*.ne*, > > techdiver@aquanaut.com (bcc: Carlos Accioly/Ipanema/isa) > > Subject: Re: "trimix" worthless? > > > > > > > > > > Colin, > > > > There really isn't much to be more specific about. In Wakulla where we > > have habitats at 30' and can deco out of the water, the 10', 20', and > > 30' stops are combined and done on oxygen with breaks to bottom mix. > > The 288 minute time that I quoted for DECOM is predicated on all three > > stops being performed on O2, but not at 30'. > > Time on oxygen is limited to 12-18 minutes at a time with 6-8 minute > > breaks to bottom mix. Before leaving the habitat and reentering the > > water, at least 10 minutes is spent on bottom mix or 190' gas. > > >From 30' we perform a slow ascent at an effective rate of one foot > > per minute to the surface. > > > > Obviously, at other sites where we do not have habitats, the 30' stop is > > not performed on oxygen. At those sites, the 10' and 20' stops are > > combined and done at 20' on oxygen with similar back gas breaks. > > > > -John > > > > > 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'. > > > > > > > > > > > > -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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