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Doug,

>Some of the posts are suggesting a physiologic phenomenon which occurs
>at altitude due to the higher percentage of O2 in Nitrox which causes
>a hypoxic condition after the dive. If this was true, you would think
>it would also occur at sealevel with Nitrox, and it very well may as
>there are many physiologic processes which occur during dive that are
>not well understood, especially by layman. I certainly don't know.

*Obviously* if you're hypoxic before a dive you'll be hypoxic after
the dive (at some point).  The whole point of this was a post by Joan
asking about using Nitrox at altitude and if it would contribute
toward hpoxia moreso than air at that same altitude.  Her statement is
based on a single paragraph on PP 413 of Deepr into Diving by Lippman
which says

"A diver surfacing from a dive at altitude is moving from a breathing
gas which contains a high oxygen partial pressure, to an atmosphere in
which the oxygen levels are lower than normal.  As a result, the diver
may experience symptoms of hypoxia and breathing difficulties for a
period after the diver.  This will be accentuated if the diver has
been exerting himself.  In this situation, blackout after ascent could
occur.  A diver must anticipate this problem and minimize exertion
after ascent."

You know this *exact* same paragraph is also in "The Essential of
Deeper Sport Diving" - I should have saved my money...

Unfortunately this paragraph is useless as it stands and the
references at the end of the chapter will be difficult for me to get
my hands on.  The question remains and while some have offered
potential hypothesis dealing with blood perfusion/etc but, I have come
to believe that the answers to these questions just do NOT exist. 

-Carl-

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