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> 
> >What effect does hyperoxic concentrations in the blood have on restriction
> >of bloodflow?  I understand oxygen is a vasoconstrictor - shouldn't
> >excessively elevated dissolved PPO2 result in constricted perhipheral
> >vessels & consequently a build-up in CO2? 
> 
> Except that CO2 is a vasodilator so you get into a hyperoxia=vasoconstriction
> hypercarbia=vasodilation cycle keeping blood flow at some satisfactory 
> level.  Also remeber that maximally constricted blood vessels are not going 
> to stop the flow of blood.


It seems to me (I'm just talking off the top of my head right now...) that
the oxygen concetration at an inspired PPO2 of 2 ATM is high enough above
"normal" that it would lead to a vascular constriction effect that could
only be countered by proportionally high CO2 concentrations (i.e., CO2
buildup).  Also, blood flow wouldn't have to stop entirely to result in a
buildup of CO2 in the tissues - it would just have to slow enough that CO2
is not eliminated from the tissues at rate equal to or exceeding its
production by metabolism.

Yes? No? Maybe?

Aloha,

Rich

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