>As I stated before being fit is better.
>
>A fit diver would be able to do a lot more workl either at the surface or
>depth before incapacitation. CERTAINLY
>
>But back to the real world of diving.  The Pressure gradient is THE driving
>force that causes you to ongas inert gasses. But it takes TIME for the gas
to
>pass into the body. This is based on the physics of gas exchange NOT
overall
>fitness. George will be able to move more Gal / Min of blood than the fat
guy
>True !! but blood does not off gas by merely racing thru the alveoli it
takles
>a certain amount of time for the transfer to take place.

Wrong Assumptions!

The issue is the amount of gradient, that works upon a given unit of blood.
With much  more blood volume being exposed to gradient in a given time, the
gradient has more opportunity to cause gas  exchange to occur. Equally
significant, with the far better perfusion and vascularization of the George
Irvine "clone",  all tissues within the Irvine clone's body will experience
a larger gradient, in the process of diffusion with  dissolved gasses.

In the hypothetical, HUGE OBESE tech diver clone, gradient in the distant
realm of fatty tissues in his back side, as well as across the great realm
of his enormous swelled pot belly, will be slow to react to ascent changes,
and diffusion rates of inert gases will be relatively slow. Dissolved
Helium, in these distant regions, will not have good egress to the main
circulatory system, so while the circulation which carries its more readily
acquired inert gasses from fast tissues, travels slowly across the exchange
area in the lungs, requiring much more time than the Irvine clone, to expose
each unit of blood to enough gradient to sufficiently offgass it,  the
helium "sinks" which spread across the enormous swelled pot belly, the huge
backside, and around most of the body of the HUGE OBESE tech diver clone,
still have enormous reservoirs  of dissolved Helium, acting as waves of
multiple time bombs, which will explode later if not given the additional
time to slowly make their way out of the poorly perfused and non-vascular
fatty tissue, out into the slowly recirculating, main cardiovascular system.

You suggest in your example that the alveoli have a set rate of gas
exchange, and that faster circulation of blood will NOT increase gas
exchange rate---essentially, suggesting that higher volume of blood exposed
will equal less exchange, because you think that it will be moving too fast
for exchange to continue at the optimal exchange rate, which you felt was
achieved at a much slower  blood volume movement. .

If this were true, the tendency of an athlete to increase the volume of
blood they pump with each heart beat during intense exertion, and the
drastic increase in the  number of heart  beats per minute---pumping more
volume of blood all around the body per unit of time, would NOT succeed in
allowing the athlete to attain higher power outputs ( run faster, swim
faster, carry a heavy load, etc.) . In fact, the increased volume of blood
moving, recirculating at a much faster rate, is what promotes the better gas
exchange which allows the greater exertion rates.  The "gradient" is applied
to the delivery system of the red blood cells, and with greater and greater
volume of bloodflow, greater and greater gas exchange rates occur.
I do NOT expect the amount of  inert gas dissolved in the blood fluid to
exchange at the same rate as oxygen and CO2, which is assisted by its own
transport system. However, for the same reason that gradient drives O2 and
CO2 exchange, and more is exchanged by movement of much larger blood
volumes,  much larger blood volume movement will drive more inert gas
diffusion out of the alveoli by providing more gradient action to each unit
of blood.

I am suggesting chamber  testing with lab animals of differing VO2max
levels, to corroborate this,  and potentially Doppler studies on humans in
the chamber, to corroborate VO2max  levels as related to gas exchange rates
for helium and nitrogen.   I do NOT say this is FACT right now. It is the
experience of WKPP in the exposures it has had, versus the cave community at
large, that differences in personal gas exchange rates "seem" to be rooted
in fitness levels. Intuitively, this would appear to be the most reasonable
answer. This is why we need testing to take place, to determine if this is
the underlying cause of individual differences in functional  decompression
rates.   Ultimately, this should provide guidelines, that can be used to
attain much higher levels of safety,  for individuals looking to pick a
depth and duration limit, for their specific body, at its present gas
exchange rate. .




Regards,
Dan Volker


The blood that comes
>in contact with the alveoli will have a lower PP of inert gas AFTER
passing
>than just before.  If the fat guys blood was circulating so slowly as to
>completely off gas before passing thru the lung the guy would be dead.
>
>The duration of the blood to the alveoli would not be greater. The time
would
>be the same (hang time) The exact same piece of blood would pass thru 4
times
>as often for george, but the blood goes by so quickly it woulsd not have
>enough time to dump all its inert gass load.
>Lets say you had a convyer belt full of buckets that gathered water from a
>lake & moved over a garden to dump out & water the plants.  The buckets
hold
>5 gal of water each the fat convyr moves 50 buckets per minute. The george
>convyer 200 / min. These buckets are not dumped on the plants, but leak out
>slowly through holes in the bottom. Now these buckets can only release
their
>water when they are actually OVER the plants. The water flows out of the
>buckets at 2 .5gal / min  the dwell time of each bucket on the convyer over
>the garden is one minute for the fat convyer but only 15 sec for the george
>convyer because it is going 4 Xs faster. Both convyers would dump the same
>amout of water.
>
>fat one 50 Bucket /min X  2.5 Gal/min X 1min = 125 gal
>
>George one 200 Bucket/min X 2.5 Gal/Min X .25 Min = 125 gal.
>
>The blood does not get to dump all of it's inert gas load each time it
passes
>thru the lung. only part of it. How much of it is determined by the
pressure
>differential & the physics of the gas transfer thru the alveoli.
>
>If you blood was able to dump it's full load each time thru the lungs it
would
>only take a few circuts of the blood on pure o2 to completly cleanse the
blood
>of inert gas.
>
>While it is true that I have over simplified the gas transfer, you get my
>drift
>
>Captain Zero
>--
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>

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