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We do the same, but the ratio is different ( 12-18  to 5-7 ) . We start
at depth with this, and count all of it as deco. We have to do this
since the cumulative oxygen is too much, even with the low ppo2 ( same
as yours ). Our dives have maxed out the deco, and probably are close to
our max bottom time as we get more efficient at covering ground. We now
know that the deco works, so we just have to be concentrating on making
it safer tox, whole body , and pulmonary wise. Less drag with more power
and reserve burn time are what we are working on now. 

You obviously have to execute your dives much faster and more precisely
due to the freezing water. Let me suggest that you study the usdct
compared to us to see what they are doing ( besides watchingCis Lunar 
TV while diving) that is slowing them down so severely, and continue to
do more of what you ar doing that is working so well.

Jason, to do what you are doing - long range deepo cave exploration - in
cold water is a real lesson in skill and execution. I will be honest
with you : I  have no reason to believe that I could pull it off
succcesfully, and would be hesitant to even try ( maybe a support dive ,
but not what you are doing). Knowing what I do know , it has to be
seriously difficult. You guys are good.

Jason Weisacosky wrote:
> 
> As the director of that project and the OCDA, I'll convey our 'break' method
> for that particular dive (even though most all of them are done virtually the
> same)
>     On the dives we conducted at Maramec (and all dives made up here by the
> OCDA), we use a very low PO2 for bottom gas (sometimes not even a 1.0) with a
> high He content (45%-55% depending).  Stage gas is the same *or* with a
> slightly reduced He content for shallower depth and deco situations.
>     Our deco gases are like this, O2, EAN50, EAN35, and Tmx 20-30.
>     If some Tmx is left over from the stage(s) following the 1st stages of
> deco, we also use it to 'break'  during the rest of deco (a good way to use
> the gas you'd drain afterwards anyway).  The 'break'  PO2 is very low and
> keeps the potential O2 problems to a minimum (as you know, the whole reason
> for breaking).  In the 'written' case, we had some 20-20 left and used it to
> break while saving the back gas/deep safety's ((We did the whole dive,
> incidentally, on stages with  minimal back gas usage ( 300psi)).
>     The longer type dives up here are currently limited by water temperature,
> and our dives are not nearly as long as  George, etc. are making.  Most of our
> methods, etc., are the result of direct consultation with George, too.
>      Also, our break intervals are 20 to 5 and we haven't had lung burning
> problems to date (duration may be the reason).
>     Finally, I really don't think the OCDA guys/gals are strokes.--Jason
> 
> kirvine@sa*.ne* wrote:
> 
> > Higher is better - easier to breathe. Remember you are also trying to
> > offset swelling and irritation. Also adding helium is preferable to
> > adding nitrogen at that stage, since it is less lkely to conribute to
> > bubble growth when you get out. I use the lowest oxygen that can be
> > breathed at the depth with the highest helium. The term "air break" is
> > generic for this action. Most people just don't get how to use oxygen -
> > look at the usdct web site for how NOT to do it. My personal bet is that
> > these strokes have french fried lungs after each dive based on the farm
> > animility with which they are conducting the deco. The correct intervals
> > are also far different from what these amateurs are doing.
> >
> > John E. Ivanic NACD#1648 wrote:
> > >
> > > I was just reading the latest edition of deep tech, and read the article
> > > on the boy's that were diving in merimac cave system.
> > > One of the fellows said he used 20/20 trimix for break gas, I was
> > > wondering what the advantages  or disadvantages are. I understand that a
> > > lower O2% would be good, but what about the 20% He?
> > >
> > > John Ivanic      comments:  ivanic@di*.ne*

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