Dave:

    I'm not sure about the number, but it sounds about right.  If 15% of the
oxygen is carried by the plasma, then the other 85% is carried on
hemoglobin.

    Obviously there is some correlation with increased PO2s and problems
associated with oxygen, as can be seen with O2 toxicity.  The thought I put
forward yesterday would indicate that, if the blood system is the only way
O2 can get into and affect the body, then higher PO2s would not have any
effect since no more O2 can get in there anyways. This is obviously not the
case.

    Your point made me realize an error in my thinking yesterday.  Following
Henry's Law (regarding solubility of a gas in liquid increasing as the
partial pressure of that gas increases), at higher PO2s, more oxygen would
dissolve into the plasma and thus more would be transported to the tissues.
This might explain effects of higher PO2s.  I don't know if higher PO2s
would affect the saturation point of hemoglobin, but I see no reason that it
would, unless high pressure acting on the hemoglobin itself cause
conformational changes that might increase (although it would more likely
decrease) its O2 carrying capacity.

Interesting point.  What's the name of that book?

Ben

David Shimell (shimell) wrote:

> Ben
>
> > I have a typical human oxygen equilibrium
> > curve infront of me, and our blood becomes saturated with oxygen at a
> PO2 of
> > around 120 mmHg (oxygen bound to hemoglobin, and dissolved in
> hematocrit).
> > Now unless my math is wrong....  100% oxygen at sea level is at a PO2
> of 1
> > atm, which is equal to 760mmHg.  Even a normoxic mixture has a PO2 of
> around
> > 160mmHg.  This would indicate to me (again unless my math is wrong)
> that
> > breathing gases with higher PO2s will allow for no physiological or
> > biochemical mechanisms of increased gas exchange since no more oxygen
> can
> > physically get into our systems.
>
> I read in John Lipman's book that says that 15% of O2 is transported by
> Plasma.  Unfortunately, this was about the point I put the book down!  I
> have no idea whether this transport mechanism would play a greater role
> with increasing ambient pressure.
>
> Dave
> --
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