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> Rich,
> You're on your anecdotal evidence soap box again.
> Sorry, it just does not hack it. Concrete data that provides with the minimum
> of conjecture is what we need. Anecdotal evidence can be downright
misleading.
> Hey sometimes statistically valid material can be misleading also, but the
former
> have more shortcomings.
Of COURSE we need concrete data! The problem is, we have VERY little of
it when it comes to the diving practices were doing. If we limited
ourselves to diving within the bounds of what we know from so-called
concrete data, we'd do only air, and maybe nitrox dives in shallow water,
would do only heliox dives in deep water, would never do IWR under any
circumstances whatsoever, etc. etc. The point I've been trying to make
is that we DON'T HAVE all the concrete data we need! So our options then
are:
1) not dive outside the bounds of our existing concrete data;
2) dive outside the bounds with blinders on and hope for the best;
3) dive outside the bounds using our collective experience
(= anecdotal evidence) as a guide
Of COURSE anecdodal evidence can be misleading - moreso than "concrete"
data - that's why it has to be taken with a grain of salt. But it sure as
hell isn't worthless.
Here's an example - oxygen narcosis.
To my knowledge, there has been only one controlled study on the role of
oxygen in causing narcosis. The study was very preliminary, with a
restricted sample size, and the very tentative conclusion was that oxygen
should be considered about equipotent for narcosis as nityrogen. My body
of anecdotal evidence (personal experiences and discussions with others)
is that oxygen seems to be equal to or slightly less narcotic than
nitrogen when the PO2 is less than about 1.4; and slightly or
considerably more narcotic when the PO2 is more than about 1.7. I was
telling this to Dr. Hugh Greer last week, and he not only found it
fascinating, but he'd never heard of that effect before. He didn't seem
to doubt me at all.
So, when I'm diving along with a rebreather at a constant depth and I
start to feel increased narcosis do I:
a) Incorporate the anecdotal evidence and check to see if my PO2 is
getting to high; or
b) Ignore it because there's no concrete evidence to support the notion
that increased PO2 can contribute to narcosis?
I know this is probably not a fair question, but my point is, concrete
evedince will only get us so far. If we want to push beyond the bounds
of concrete evidence, we need to take WHATEVER sources of information we
have, look at such evidence in the context of what we "know" from the
concrete data, and blend it all together using a great deal of
intelligence, a handful of salt, and extraordinary prudence.
Aloha,
Rich
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