Jim,
what you referred to is more or less what everybody knows( should
know,pardon). It is , so to speak , an answer referring to the quality
of symptoms.

Chris' question was one concerned with -quantity-.

That is , dependency of symptoms in relation to time and partial
pressure.
I suspect it as common knowledge, too, that these dependencies deal with
gravity of symptoms, their time dependant reversability, and their
evidence, if at all , in diving. 

What does your biblio have to offer for that ?
We also know the OSHA/ NOAA Limits , I suppose.

What does a student want to know from you, when he asks, which ppo2 is
safe ?
The evident answer seems to be, do not surpass a value of 1.x pp,certain
time limits,  a cns level of yy percent,avoid getting cold, high
workload, and you will not get ( whatever).

This answer is "wrong".
The correct answer would be , if you keep within the limits ( x,y) , the
hypothesis "nothing will happen" cannot be falsified.
Or , if your surpass limits (r,z) , the hypothesis "something is likely
to happen to you" has some undeniable statistical background.

In between those limits lies a zone which says " supply more data".

It is this zone Chris supposedly assumed you wanted to say more about.

The data I have seen do not represent statistical relevant hits below a
ppo2 of 1.7, so some restraint is advisable, but subject to the time/
workload/ cold/ stress  factor. 
No lineaar functions implied.

Lung tox , which you referred to , is of concern only for very long
exposures, which neither are everybodies cup of teanor general practice,
nor being apt to generalisation.

So, to enable you to give a more definite answer, the question should be
modified/ split up a bit.

" Industry-wide ban", to my point of you, smells like " quit thinking
about matters which WE think you are not able to understand .
This is a dead end street, in diving and in general.

regards
-Matthias

Jim Cobb schrieb:
> 
> Chris-
> 
> Welllll, let's see here. Ah, here we go, Chapter 8 of Diving Medicine, some
> tidbits of a very interesting (or maybe depressing) article:
> 
> "oxygen toxicity is caused by the production of free radical intermediates
> in excessive concentrations during exposure to increased oxygen pressures"
> 
> "the pathological response of the lung to oxygen toxicity can be
> differentiated into two overlapping phases of progressive deterioration. The
> fires is an acute exudateive phase consisting of interstitial and alveolar
> edema, intra-alvelolar hemorrhage, fibrinous exudate, hyaline membranes,
> swelling and destruction of capillary endothelial cells, and destruction of
> type I alveolar epithelial cells" (Christ that's just phase one)
> 
> "Changes in pulmonary function which have been measured in humans during and
> after prolonged exposures to oxygen pressures of 1.0 at or higher include
> decrements in inspiratory and expiratory lung volumes and flow rates, carbon
> monoxide diffusing capacity, and lung compliance." (that's at 1.0, folks)
> 
> So, Chris, I don't think you can always measure damage by the number of
> stiffs floating around in Her Royal Majesty's Waters. The question you have
> to ask is fucking up your lungs permanently worth a few minutes of saved
> deco? You are much better off exposing your lungs to the high PP02s when you
> are at deco resting and can give your lungs low PP02 intervals from your
> back gas. I think you high PP02 nitrox hounds ought to think things over a
> bit more carefully.
> 
>    Jim
>  -------------------------------------------------------------------
>  Learn About Trimix at http://www.cisatlantic.com/trimix/
> 
> > From: Chris Stenton <jacs@gn*.co*.uk*>
> > Date: Tue, 10 Oct 2000 19:26:26 +0100
> > To: cobber@ci*.co*
> > Cc: "dmdalton" <dmdalton@qu*.ne*>, dwiden@ho*.co*,
> > donburke56@ne*.ne*, "'Paul Braunbehrens'" <Bakalite@ba*.co*>,
> > techdiver@aquanaut.com
> > Subject: Re: rec trimix
> >
> >
> >> I know this is going to piss off a lot of rec divers but I believe that
> >> increasing your bottom PP02's for the purpose of avoiding a deco obligation
> >> is
> >> a really stupid idea. It is typical of our sport that this principle is
> >> embraced by almost everybody. Even to the point of calling potentially
deadly
> >> hyperoxic mixes "safeair".
> >
> >> I think there should be an industry-wide ban of bottom or working PP02's of
> >> anything over 1.2.
> >
> > Jim,
> >
> > Give us some statistics or physiology  to back this up. I haven't seen one
> > report of a recreational "no stop dives" diving  death or oxtox hit
attributed
> > to using Nitrox at a ppO2 of 1.4 or below here in the UK.
> >
> > Far more important surely is getting the people "at risk" out to do some
more
> > exercise. How about removing people cert cards who can't run a 6min mile;
far
> > more likely to reduce the work load of the emergency services than some
> > arbitrary ppO2 limit of 1.2.
> >
> >
> > Chris
> >
> > --
> > 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'.
--
Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.

Navigate by Author: [Previous] [Next] [Author Search Index]
Navigate by Subject: [Previous] [Next] [Subject Search Index]

[Send Reply] [Send Message with New Topic]

[Search Selection] [Mailing List Home] [Home]