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Three things got my attention right away: 1. ArgOx is used. There is some research on that for use as a treatment mix. 2. PPO2 of .12atm, .2atm, 1.0atm, 2.0atm, and 2.5atm would seem to be too spread out. 3. There is no mention of the ambient pressures used, which makes me wonder if the percentages in the the breathing gas changed or if they pulled fourteen point something inches of vacuum to get the .12 atm PPO2. That would account for the jump in N2 offgassing. Don Burke Chesapeake, Virginia ----- Original Message ----- From: David Reinhard <reinhard@oc*.co*.au*> To: Scott Hunsucker <swhac@pc*.gu*.ne*>; <techdiver@aquanaut.com> Sent: 19 October, 2000 06:50 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. " > > > >-- > >Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > >Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. > > > > > > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. > ____________NetZero Free Internet Access and Email_________ Download Now http://www.netzero.net/download/index.html Request a CDROM 1-800-333-3633 ___________________________________________________________ -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. 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