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Scott,

Let me check, but I do not think that the statement:

>4) CO binding is so thermodynamically favorable that binding is, 
>practically speaking, permanent, essentially removing the bound 
>hemo site from the pool of available transport.

is quite accurate.  At sealevel, with only 0.21 ATA of oxygen partial
pressure, this statement is essentially true, but in the presence of
high enough partial pressures of oxygen, monoxide will unbind from
hemoglobin.  "Further more, it bind with about 230 times as much tenacity
as oxygen, which is illustrated by the carbon monoxide-hemoglobin
dissociation curve in Figure 41-12 (this is take from Guyton's "Textbook
of Medical Physiology", page 511 and 512).  This curve is almost identical
with the oxygen-hemoglobin dissociation curve, except that the pressures
of the carbon monoxide shown on the abscissa are at a level 1/230 of those 
on the oxygen dissociation curve.  Therefore, a carbon monoxide pressure
of only 0.4 torr in the alveoli, 1/230 that of the alveolar oxygen, allows
the carbon moxide to COMPETE equally wit# the hemoglobin and causes half to
the hemoglobin in the blood to become bound with monoxide instead of oxgyen."

"A patient severely poisoned with carbon monoxide can be advantageously
treated by administering pure oxygen, for OXYGEN at high alveolar pressures
DISPLACES carbon monoxide from its combination with hemoglobin far more
rapidly than can oxygen at the low pressure of oxygen present in atmospheric
air."

And, as it is stated in Mountcastle's "Medical Physiology", "The combination
of CO and Hb is freely reversible when the partial pressure of CO becomes
less in the alveolar air than it is in the mixed venous blood.  The most
rapid elimination of CO is accomplished by (1) reducing inspired CO to
zero by removing the victim from contact to CO to insure a maximum partial
pressure gradient for elimination of CO, (2)increasing alveolar ventilation
by any appropriate means NOT including CO2 administration, and (3)employing
high inspired Oxygen tensions to facilitate the dissociation of CO from
HB.  This is most effective if oxygen administration is accomplised in
a hyperbaric chamber, which allows alveolar oxygen partial pressure of
greater than 1.0 atmospheres absolute, up to a maximum of 2 - 3 ATA's
for short durations to accelerate the CO elimination.' (Mountcastle, "
Medical Physiology", volume 2, 14th edition.)

4) CO binding, still the one-way trip, is driven less by the 
>lowered pressure, but the bound molecules remain the same.

So, as you can see, CO binding is not the "one-way trip" as you described
it.

John
Submariner Research, Ltd.
(johncrea@de*.co*)

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