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> On 22 September 1999 21:05, Huw Porter wrote:
>
> > A question (actually two) related to long thread on enriched air and
> depth.
> >
> > a)  If a diver in an emergency at depth switched to a too-high-PPO2 mix,
> > would the effects of oxygen toxicity kick in immediately or is there a
> > brief period of 'grace' - and if the latter, what factors influence this?
 
> Hi, Huw!  That's a 'Six-Million Dollar' question!  And the answer is:
> Yes/No - and more factors than wot you can poke a stick at! :-)  (As far as
> I'm aware there's still no formula for predicting when, where or why a 'hit'
> will happen!  It's been suggested that CO2 build-up; diet; fitness;
> emotional state; water temperature; work-load, etc. all play a role.)
 
You forgot the phase of the moon, the tide, and how good a time you
had the night before :^)
 
> The easiest answer is to say that even in the same individual, it varies
> from day to day and situation to situation!  In terms of trialing it until
> your luck runs out, it's probably on a par with Russian Roulette - with
> three chambers loaded!  :-)
 
And then not spinning before trying again :^) :^) :^)
 
OR - playing russian roulette with a gun that has a clip :^)
 
> > b)  Does oxygen narcosis relieve immediately on ascent to an appropriate
> > depth in the same way that nitrogen narcosis does?
 
> In the case of oxygen toxicity, (in the case of O2, it's toxicity - not
> narcosis!), it usually requires longer convalescence (Sp?) time - if you're
> fortunate enough to survive!
 
Interesting question.  The narcotic effect of O2 has been a topic that
has been debated.  Traditional thinking is that the narcotic effect of
nitrogen is due at least partially to its lipid solubility.
According to this, O2 at least in theory, should have roughly the same
narcotic effect as Nitrogen.  Of course, the difference is that Nitrogen
is an inert gas while the O2 is metabolized.
 
Interesting - but don't discount the possiblity of O2 narcosis...
 
Carl