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On Wed, 7 Jun 1995, Richard Pyle wrote:
>
> > The question we should be discussing is not 'why should we do a deep air
> > course before trimix?', but, 'Should we not establish several years of
> > experience using air (or nitrox) at depth before learning trimix?'
? I guess that effeciency of communication is not
> among my strengths.
oh contrare rich....
on deep air before mix:
there have been alot of responses on this subject that hit close to home.
in our training we speak of "mental stamina" when relating to the focus
it takes to keep your ass out of serious trouble when task loading becomes
a problem.
Rob was right on when he
was relating to his experience with narcosis.. YOU NEVER KNOW how you will
be affected. some divers are affected differently on almost every dive.
some are caught only once in a while by a change.. but the one thing for
sure is that NARCOSIS IS NOT (totally) PREDICTABLE.
A diver that goes from "advanced open water" to trimix may
not know what it's really like to get slammed at depth. and there are other
factors that can come out of no where even on a trimix dive.. trimix is not
a majic gas that cures narcosis. you can get slammed just as hard while
diving mix as air.... (which could catch you off gaurd if you were not
feeling any narc two minutes before) you have CO2, and O2 narc, and who
knows what else to consider. if a diver hasn't ever been slammed at 170fsw
or deeper then, imho, that diver is a considerable risk diving any gas at
depth.
if you don't agree go buy a can of whip cream and let it set on the
counter for
a couple of hours, then exhale and without turning the can over breath the
propellent (make sure it's nitrous oxide first). take a good long breath
and hold it for about a minute.. :-) You might want to be sitting down or
at least leaning on something or someone first.. after you inhale wait
thirty seconds and try to open a combination lock... good luck. that's
pretty close to what a good narc feels like at 180-190fsw. now, imagine
having a minor problem at depth and having to deal with it (like a stuck
overpressure valve on a wet suite,)... you get my point i think.
you can
get blasted anytime your respiration increases ya know, and that can come
from a million places (currents, sharks, work, problems...). i want a
buddy or a student or any diver to be prepaired for the possiblity of this
slam before it happens.... and except for the whip cream (shut up george)
i don't know any other way except deep air training. the skill training
goes without saying, but even if you have gone over the emergency skills
a thouand times, if you don't know what a serious narc is like you could
**still** not deal with it correctly, and as rich points out.. you don't
have alot of time (on the bottom or on left on deco) to figure out
what's up.
one last point.. i have seen a very well trained deep diver with lots
of deep air and mix dives under his weight belt that is
usually not affected (is that afected or effected) at all by narcosis
get caught in a mild current, experience narc for the the first time in
months due to his mix diving and completely forget to monitor his depth,
gas and time. (on this dive he dropped to 1.7ata o2 and after his buddy got
his attention and got him to the backup stage bottle at 130fsw he had
200psi
in his bottom mix tanks, if it wasn't for his buddy he would **still** be
enjoying the buzz to this day)
narc isn't always scary when it jumps on you from behind.
once again you have to have mental stamina, which comes from experiencing
the narc. we do intermintent deep air dives (never past 220.. period) to
keep our edge, or narc conditioning if you will...
... just in case.
aloha,
dennis
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