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This is necesary for reducing damage of all types, and as far as the CNS clock goes, all we know from commercial diving info is that good breaks seem to give you a fresh start. We don't take any chances with this. What we know from Navy is that repeated days of oxygen exposure increase the risk of tox. We also know from commercial diving that you don't get out of a seizure underwater. We get our exposure recommendations from Hamilton Research. John R. Rose wrote: > > 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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