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Rich
I agree with you and it is likely an early dose of HPNS , I also have 
had this it most likely reduced nutrition to the brain due to the 
helium effct on the membranes ( the bases of hpns)but who knows. The 
rate of compression is of course a factor that for us in tek diving is 
hard to deal with as we have limited gas supplies.
Tom
You wrote: 
>
>> I suspect you'll get other such requests, but could you hit
>> the high points (cliff notes version) of the down sides of
>> heliox.  Guess I should find the time to read "Mixed Gas" which
>> I bought back around xmas....
>
>It's not in there.  In fact, it's not published anywhere.  When I 
first 
>encountered it, I thought I was weird, but George and others have told 
me 
>in private they've encountered the same thing:
>
>When breathing very low PN2 at depth, it's hard to concentrate.  You 
feel
>"wired" - spastic.  It's like narcosis in reverse - you're nervous and
>jittery.  I believe this state of being is not safe, and is very
>unproductive beause you can't concentrate on anything. Perhaps this is
>some sort of pre-HPNS thing (it seems worst at depths in excess of 
about
>250 feet), but the books will tell you that HPNS is not an issue until
>depths in excess of about 500 feet.  But then again, I wonder what 
sorts
>of compression rates the books base their conclusions on.  Maybe its 
just
>psychology -- "What the f--- am I doing here?!?!" -- a clarity of mind 
and
>ability to rationalize that the narcosis always used to mask.  On one 
of
>our early trips to Christmas Island, the sharks were so intense that 
we
>would get down to 200 feet as quickly as we could - not because there 
were
>fewer sharks, but because we didn't care about them as much.  Maybe 
it's 
>the same sort of thing - with no narcosis, you're actually WORRIED 
about 
>how deep you are.....
>
>A bit of narcosis - like 90-130 feet worth, helps you stay calm and
>relaxed.  I believe that you can actually think more clearly when calm 
and
>relaxed.  I also think you're less likely to panic.  Obviously, too 
much
>narcosis can also lead to panic, and certainly impairs your ability to
>think clearly.  In my experience, the best ratio is somewhere around
>90-130 feet of narcosis, depending on how well you deal with narcosis. 

>
>Now, bear in mind I say "you" (in the generic sense), only on the 
>assumption that what I experience is similar to what most people would 

>experience.
>
>Hope that helps,
>
>Aloha,
>Rich
>--
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>

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