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It seems Zplan adds conservatism as time rather than Pgas, am I right?
That's the approach I like since it's closer to addressing the real
parameter. Perfusion varies with thermal comfort and workload. Further, for
short duration deep mix diving a slight increase in bottom time affects your
gas uptake a lot more than a slight increase in depth/Pgas. Typically all
"events" will take place on the bottom. That's when blood flow is optimal,
which also means maximum ongassing. Unless you have exciting decos, the rate
of perfusion during offgassing will tend to be less.

So, diving to a given depth with a high rate of perfusion makes you pick up
more gas faster -- it does not make you dive deeper than planned. Revving up
the timer makes more sense than assuming a higher Pgas.

Anyway, a broader look at conservatism would be interesting. What kind of
conservatism is productive? For instance, I believe more in adding deep
stops than in prolonging a 10' stop. Also, it's common to pad a helium
algorithm more than a nitrogen algorithm. For trimix, this "playing it safe"
may be elusive if nitrogen elimination is your greater problem rather than
helium. Thus, adding factors that look good may not do much for you.

This forum may help us get first things first. We've got Pyle or WKPP deep
stops that have proved their value in the field. Conversely, we've got deep
air profiles that can't be patched up at 20' and 10' no matter what time you
add. Starting out right is crucial. Theoretically various deco gases may
come out the same, yet there are indications that some combinations are more
productive. So, I invite anybody to post hunches/educated guesses,
procedures that work as well as those that don't. Science done correctly is
boring but one shouldn't frown at practical indications and field
experience. Seeing a pattern to what works is a prerequisite for asking the
right questions.

regards,

Hans



 

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