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> > A previous posting (which I can't find now, but I don't think=20
> >anyone argued against it) indicated that increased ppO2 will=20
> >tend to block the Nitrogen molecules from coming out of the=20
> >cells by osmosis.
>=20
> I will argue against it - that is not the way. There is no=20
> osmosis by
> gas. Gas can go freely on each side of the membrans of the cells.=20
> So there is no osmosis. Osmosis occurs, when a part of the=20
> fluid can=B4t pass the membran of the cell.
>=20
> > The only beneficial effect of the additional O2 that I can=20
> >see is that (again from a previous Bill Wolk posting) "the=20
> >additional osmotic pressure forces O2 into the surrounding=20
> >tissue,
>
> That has nothing to do with osmosis but with diffusion.
>=20
> > Is that the only benefit of the higher ppO2, or is there=20
> >something other way in which it aids off-gassing N2?
>=20
> Yes - I explained it up there.
> The models of diffusion work with the DIFFERENCE between the=20
> pressure of the gass inside the bubble and the pressure in the=20
> blood. And this pressure is maximal, when the pressure in the=20
> bubble is maximal and the pressure in the surrounding plasma is=20
> nearly zero. And this nitro-zero-pressure can be made with any=20
> nitrogen-free gass (heliox (see COMEX-deco-tables), oxygen etc.).
>=20
> HTH
>=20
> Bjoern
>=20

I think there are some terms stirred up here.
AFAIR (but I'm not an expert)=20
the process, when some stuff (soluted gas, salt or other)=20
spreads in a _homogene_ medium by the gradient of concentration,
is called diffusion.

If there is a membrane within the direction of the flow, jamming
the process, then it is called osmosis.

When a part of the fluid can't pass the membrane of the cell, then
it is a _semipermeable_ osmosis.

Am I right with that, or totally off track?

OTOH, that was a good explanation of the 'ox window'.
/Thomas.
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