-----Original Message-----
From: Taylor, John <john.taylor@cs*.co*.uk*>
To: 'Dan Volker' <dlv@ga*.ne*>
Date: Thursday, March 05, 1998 2:52 AM
Subject: RE: Why Obesity in deep tech diving is a contraindication---gas
exchange, revisited.



>Dan,
>
>(serious question!)
>
>Is the converse true, i.e. that an obese diver will exchange LESS gas
>during the dive time, and therefore have a lower deco obligation on some
>dives due to this poor exchange?

>John Taylor, Marketing and Trading Systems, IT Development

Hi John,
The setting where this is most relevant  is in the cave or reef environment,
at extreme depth and 23 minute or more duration. In this cave or reef
setting, you will want to cover lots of ground, so you will be predisposed
to use a scooter. The fat diver will have no efficiency in pumping
blood---he will run a relatively higher heart rate, than the ultra fit
diver. Someone like George Irvine will scooter  along the 250 foot ledge, at
a heart rate of about 45 bpm. His fat ,slobish, Gilliam like counterpart
will run closer to 90 bpm (my guess, but a fair one) and will not be
physiologically capable of efficiently powering the critical functions of
his body without a much higher heart rate than George. The Yoga concept that
Tom Mount has preached about, is another tool that can help a diver like
George, a great deal more than one like Giliam. George will have relaxed all
non-essential muscles, to the point that the blood flow is nearly shunted
away from them, and only minimal flow needed for critical life systems will
continue. In this way, his helium and nitrogen ingassing will be much
slower. The Gilliam style diver will have no where near the fitness level to
successfully relax enough muscle mass, and slow his heart rate much below 80
or 90 bpm.  If they both had to swim, George would exert next to no energy
to move, still maintaining a heart rate in the 65 to 75 area, while the
Gilliam type diver may be well into the 120's or well above that.
On ascent, George will increase his heart rate and exertion level, to
increase the volume of blood exposed at the alveoli, to gradient ---this
speeding off-gassing. If he raises his HR to 130, which is still not a level
which can feel like "work" to him, the volume of blood he moves will
increase dramatically.  The Gilliam style diver will not be able to raise HR
significantly without discomfort, and since regardless of his heart rate,
the flow has so much more body mass to travel through, so much more volume
that has to be "flushed", the fat guy would need two or three times  the
heart pumping  power which George has, just to move as much blood through
all his body tissues, in the same time unit. But he has only a fraction of
George's cardiac power.

Another analogy for this. George's body is a 25 gallon aquarium that has to
have 100% of its water volume filtered --( totally recirculated through a
pump and filter )every minute. The Gilliam diver is a 150 gallon aquarium,
that needs to have 100% of its water  recirculated through a filter by a
pump. Do you think you can use the same pump in both aquariums??? Realizing
that  George trains as a competitive swimmer, this gives him a heart that
would be the right size for the 150 gallon aquarium, while the sedentary,
pot smoking Gilliam diver has a heart that would recirculate at a rate
appropriate for a 5 gallon aquarium.  So if the George aquarium needs to
filter something out, it has exponentially more flow capability to do this
filtering, than the Gilliam diver does.  And this model completely ignores
the tissue saturation issue, which becomes extremely critical with helium in
an obese diver, at 300 feet, after 25 or 30 minutes.... suddenly this
enormous fat reservoir is full of helium, and its off gassing rate is going
to cause far more time to be spent  at each deep stop, to allow it to
offgass.  The obesity issue continues to compound itself into worse and
worse contraindications for deep diving.  The issue may realistically
become, how deep can an obese diver dive, before the exponential compounding
of problems begins to occur??? It may be at 150 or 180 for 12 minute
durations on trimix----I have no real idea---only special testing will
determine this.
Regards,
Dan Volker

>
>> -----Original Message-----
>> From: Dan Volker [SMTP:dlv@ga*.ne*]
>> Sent: Thursday, March 05, 1998 1:29 AM
>> To: techdiver
>> Cc: TOM.MOUNT@wo*.at*.ne*; RMC; Bill Mee; GIRVINE@bl*.ne*
>> Subject: Why Obesity in deep tech diving is a
>> contraindication---gas exchange, revisited.
>>
>> There still seems to be too much controversy over fitness standards
>> needing
>> to be created. This can only stem from a misunderstanding by many of
>> the
>> unfit divers, as to "WHY" they are at risk. My example below, is
>> another
>> attempt to explain the concept.  Anyone else want to jump in to this?
>>
>>
>> Ability to exchange gasses faster, as in an elite level athlete with a
>> high
>> VO2 max, will translate into exposing more blood in the body, to the
>> gradient in the lungs, in a given period of time. This could translate
>> into
>> a cross country skiing ( they traditionally have the highest VO2 max
>> scores
>> of any Olympic athletes) tech diver having the ability to offgas
>> helium and
>> nitrogen almost 4 to 5 times as fast as an obese  diver would be
>> capable of.
>> Since the effects of hypothermia and the challenge of supporting a
>> tech
>> diver begin to become more pronounced after several hours of deco,
>> this will
>> make a huge difference, if the elite diver
>> needs a full hour to do deco from a 270  foot dive, for 23
>> minutes. The fat diver may find even more deco obligation than five
>> times
>> the athlete's , because his longer stop requirements ( say 5 times as
>> long
>> at each stop) at 180, 170, etc., will
>> incur more deco obligation from the deep deco part of the dive----they
>> will
>> have to do more deco, just from their deep deco stops alone. This
>> could
>> create exponential increases in deco time at 50, 40, 30, 20, and 10
>> foot
>> stops.  Instead of this being 4-5  hours of deco , as would be
>> suggested by
>> their slower gas exchange rate ( versus the 1 hour for the
>> athlete), they may "really" need 10 hours or even more.  Statistics on
>> fat
>> tech divers
>> getting bent after deep long duration dives are horrifying, giving
>> much
>> credence to these
>> ideas here.
>> Dan
>>
>>
>>
>> --
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>

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