We know this, that is why we go 12 minutes on , 6 minutes off where we are
breathing 10-12% ox / high HE. So what? We also limit our max oxygen time to
150 minutes for a saturation dive. We found that you have to toggle back and
forth and keep pressing the gradient. Old Hat for us. Our experiments are
dynamic, not fixing one variable and our results prove it. We have the
fastest decompression schedules in diving and the most clean deco at the
same time. JJ and I did 7 HOURS at 285-300 and 8.5 hours deco, of which 150
minutes was the oxygen regime done above at 2.0 in a dry habitat. The rest
of these guys are playing "pin the tail on the donkey" with these one sided
experiments that don't mean jack  unless you can put it all together like we
do.

-----Original Message-----
From: David Reinhard [mailto:reinhard@oc*.co*.au*]
Sent: Thursday, October 19, 2000 6:50 AM
To: Scott Hunsucker; techdiver@aquanaut.com
Subject: Re: Nitrogen elimination and oxygen



I have managed to get hold of the abstract for this paper. I do appreciate
that it is only an abstract. I offer it without further comment since I am
sure there are many on the list who would better understand just what they
have done than I would.

Dave.

"TITLE:  O2 pressures between 0.12 and 2.5 atm abs, circulatory function,
and N2 elimination.
AUTHORS:  Anderson D; Nagasawa G; Norfleet W; Olszowka A; Lundgren C
AUTHOR AFFILIATION:  Hermann Rahn Laboratory of Environmental Physiology,
State University of New York, Department of Physiology, School of Medicine,
Buffalo 14214.
SOURCE:  Undersea Biomed Res 1991 Jul;18(4):279-92
CITATION IDS:  PMID: 1887516 UI: 91361444
ABSTRACT:  To study the effects of inhaled oxygen pressures on N2
elimination, 72, 2-h washouts were performed in 6 subjects at oxygen
pressures of 0.12, 0.2, 1.0, 2.0, and 2.5 atm abs using a closed circuit
system that supplied an O2-argon mixture and collected the N2 off-gassed.
Hypoxia induced a significant (9.4%, P less than 0.05) increase in nitrogen
eliminated as compared to normoxia. Pure oxygen breathing induced a small,
insignificant (3.5%) decrease in nitrogen yields, but further increases in
oxygen pressure induced significant decreases in nitrogen yields (-8.9%
and -16.9% for 2.0 and 2.5 atm abs, respectively). Heart rate, cardiac
output, skin perfusion and leg blood flow decreased, whereas mean arterial
pressure increased with increasing oxygen pressure. We conclude, therefore,
that perfusion-dependent N2 elimination decreases secondary to
vasoconstriction induced by increasing oxygen pressures. Changes in inhaled
oxygen pressures during different phases of compression-decompression may
induce alterations in the rate of inert gas uptake and elimination. Although
not currently quantifiable, such alterations would imply added uncertainties
in the computation of decompression schedules. Oxygen breathing during
decompression should be performed at the lowest possible ambient pressure
compatible with freedom from pathogenic bubble formation.








At 08:39 AM 10/17/00 -0500, Scott Hunsucker wrote:
>Dave,
>    Do not take one article about anything involving medicine or physiology
>as a good source for information.  If this study were repeatable and found
>its way into accepted thinking within the practicing community, then maybe
>it would be worth considering.
>    The study also deals with breath hold diving and DCS not SCUBA
>diving.  This may or may not make a difference with being exposed to a
>larger amount of nitrogen with SCUBA.
>    One can manipulate medical studies and statistics to say whatever one
>desires.  Most people would be horrified if they knew what was studied and
>reported inside medical journals.
>    Thanks for bringing this up, when I get a chance I will pull the
>references and take a look at it.
>Scott Hunsucker
>
>This seems to be challenging one of the fundamental principles of using
>>high O2 mixes...I would like to know more!!
>>" Dr. Claes E. G. Lundgren from the Department of Physiology at the State
>>University of New York at Buffalo has done extensive research on the
diving
>>physiology of breath-hold diving and decompression sickness.
>>The common treatment of oxygen breathing during decompression should be
>>performed at the lowest possible ambient pressure. Dr. Lundgren and his
>>team found that nitrogen elimination decreased as inhaled oxygen pressure
>>went up. What does this bode for 'Nitrox' diving?
>>References;
>>Anderson, D., G. Nagasawa, W. Norfleet, A. Orszowka, and C.E.G. Lundgren.
>>1991. O2 pressures between 0.12 and 2.5 atm abs, circulatory function, and
>>N2 elimination. Undersea Biomedical Research 18(4): 279-292.
>>
>>Anderson, D.J. George, and C.E.G. Lundgren 1993. Moderate hypercapnia:
>>cardiovascular function and nitrogen elimination. Undersea & Hyperbaric
>>Medicine 20(3): 225-232. "
>
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