Re: RC: Re: Climate and Altitude changes

[Ben Turner <bturner@ida.org>]

On Thu, 7 Sep 2000 15:06:51 -0600, "Susan Garlinghouse"
<suendavid@worldnet.att.net> wrote:

>> what about higher altitude changes? would that not effect the horses
>oxygen?
>> How can you get past the slower recovery times since the oxygen would be
>> somewhat thinner than what they are used to?
>
>
>The oxygen is NOT thinner at altitude, there is just as much of it at 20,000
>ft as there is at sea level.  The difference is that there is less
>*pressure* at altitude to help drive it across the lung membranes and into
>circulation.  OK, enough useless trivia. <g>
>
>The research at Cal Poly demonstrated that horses are very good at adapting
>to altitude changes, semi-instantly.  There are long-term changes as well,
>but you have to start looking harder to see them.

     Ah, a subject near and dear my distant long and distant past
--dissertation research addressing biophysics of pH and
2-3-diphosphoglycerate regulation of oxygenation of hemoglobin (relevant
to both adaptation to altitude changes and to loading and unloading
between lung and peripheral tissue).  Crank rusty pedantic neurons and
produce:  

     Actually, unless augmented by artificial means, there is in fact less
O2 per given volume at higher altitude.  The relative proportion of O2, N2
and the residual gases does not vary dramatically as overall pressure
drops over the altitude ranges of interest for athletic events conducted
without auxilliary breathing apparatus (dry air relative composition
remains roughly constant up to about 25km, *).  

     The "driving force" for specific gas transport across permeable
membranes is related to the partial pressure of the gas in question.  The
partial pressure of O2, (PO2) can be reduced by either lowering the
proportion of O2 at constant overall pressure or by reducing the overall
pressure while maintaining the same relative proportion of O2.  

     I used to use the first case (reducing the proportion of oxygen at
constant pressure to lower PO2) to generate different states of hemoglobin
oxygenation in the lab.  It is the latter case (reducing overall pressure
with roughly constant relative composition) that exists at higher
altitudes.  Therefore, it is not probably not misleading to view higher
altitudes as having "thinner" oxygen.

     As Susan indicates, this is but trivia to the more important clinical
and practical observations of the species specific adaptation where it
seems that she and ti have different responses (shocking, shall we alert
the media?)   ;->

On Thu, 7 Sep 2000 13:06:41 EDT, Tivers@aol.com wrote:
>You can't That takes time. And an exercise challenge or two. Weeks.

     As I return to my normal lurk mode, to await the resolution, I
extend my thanks to all who share their experience, intellect, and
wit in this forum.  Although I do not compete nor participate in
endurance, my horses and I benefit from my reading an active, stimulating
ridecamp.

Best,
Ben Turner
bturner@ida.org


*More information than you want to know (pressure, temperature, ideal
composition, etc. at altitudes approaching 1,000,000 meters) can be found
in such references as the U.S. Standard Atmosphere of 1976 (U.S. Committee
on Extension to the Standard Atmosphere (COESA)) which "consists of single
profiles representing the idealized, steady-state atmosphere for moderate
solar activity. Parameters listed include temperature, pressure, density,
acceleration caused by gravity, pressure scale height, number density,
mean particle speed, mean collision frequency, mean free path, mean
molecular weight, sound speed, dynamic viscosity, kinematic viscosity,
thermal conductivity, and geopotential altitude."