>Hi Dan,
>
>A question on gas exchange. How does VO2 max figure into this discussion?
Is
>not VO2 max calculated at the extreme high end of exertion?

Actually, it gets calibrated using progressive resistance and exertion, and
requires the low exertion baseline in the first part of its measurement.
Yes, at the extreme limit of work output, you find your VO2 max, but the
larger gas exchange components of VO2 max, will be apparent in exchange
occurring at 80 % of max HR, at 70 % of max, and  at 55% of max.  As it
falls below this, exertion is so low that exchange can be limited by further
slowing of the heart rate ( which controls the amount of blood exposed to
the inert gas gradient in the alveoli).

How does gas
>exchange vary in people with different levels of conditioning while at
rest?

You could find a point where exchange would be similar, but it would require
the very fat person to run a very heigh exertion rate, while the elite
athlete was quite relaxed. Since perfusion will suffer durring major 80 to
90% of max HR exertions, this will complicate the offgassing for the very
fat, who have poor perfusion any way.

>Are not the dives you describe performed by George, performed in a state of
>suspended animation ( referring to your comments on his physiological
control
>through Yoga techniques) deep penetration scooter dives, drift dives? Where
is
>the effort, and high end exertion that would bring VO2 max into play?

On deco, George will begin mild exertion, and will drastically increase his
bloodflow by elevating his heart rate. He has no need to hit "high" heart
rates,  for him to reach even 125 or 130, given a max for him of around 195
HR, this would be easy, comfortable exertion, but with an exponential
increase in the volume of blood being exposed to gradient.


If gas
>exchange is not substantially different at rest at sea level, between the
>various stages of conditioning in the control group, would it not be
>proportionally the same at rest at 8?9?10? atmospheres?.

Much better question!
The 2 issues are CO2 processing and Helium/nitrogen offgassing. First, the
CO2 issue: If they remain at rest, and no exertion or fear/excitement
reactions occur, then there will be NO CO2 issue for these two
extremes....On the flip side,.... At 10 atmospheres, a fit diver and very
unfit diver, hover over a deep wreck. Both are fine, both are maintaining
low HR's, though low for the unfit dive will not be below 80, and low for
the fit diver will be 45 bpm. Suddenly, a 25 foot GW Shark swims toward
them. The fit diver experieinces a heart rate spike to 170 bpm, while the
unfit diver hits about the same. One of them shits his pants---we won't say
which this was.  After the GW circles for 20 seconds, the high CO2 levels
the high respiration rate each stationary diver ( each is hiding behind a
bulkhead )  is experiencing, is overloading the unfit diver, who begins to
pass out. Luckily, the GW leaves, and the fit diver then has to worry about
how to revive the unfit diver. The GW example perhaps is extreme, so if you
prefer, replace this with a 12 foot bull shark,  circling for several
minutes--and this DOES happen on out deep North Palm reefs and wrecks.

As to helium/nitrogen offgassing, the exchange rates have huge gradients at
10 atmospheres, and no appreciable  gradients at sea level ( assuming no
dives in the last 24-48 hours. Having 4 times the blood exposed to gradient
on offgassing, the very fit diver will lose helium and nitrogen much faster
than the unfit. At sea level, with no gradient, there would be no offgassing
for either.


Who dives to 250" and
>rides a bike?

Me.

>  Swims laps?
George
...All the WKPP divers engage in elite level cardiovasular sports or
training.
Regards,
Dan


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