Good topic...

> > Is there any proven value to the deeper stop?  I know that they're
> > recommended for deep decompression dives, by Richard Pyle et al, but these
> > were all no-deco dives.  Or was this just a means of slowing divers down
> for
> > the transition to the 5m/15' stop?  Or possibly a legal requirement?  It
> was
> > in Queensland, where there seems to be quite a bit more diving regulation
> > than my usual haunts.
>
> You mean scientifically proven?  Dunno, but I have proven to myself that the
> deep stops, work. I have been doing them for quite a while now, even on the
> no decompression dives. For me, it definitely makes a difference on how i
> feel after a dive. Spent the weekend cave diving with a friend who just
> moved back to Pensacola after living several years on the west coast. He was
> diving Trimix and his computer generated tables required him to do the deep
> stops. He would have done them anyway. I was diving various Nitrox mixes and
> using 50 percent and 100% deco gasses. We followed his deco schedules as his
> were the longest. I cut tables using Decoplanner but carried and used my
> computer also. I noticed that my computer cleard on each dive before I ever
> got to the 20' stop and a good 10 to 15 minutes before Rob's schedule was
> done. I attribute this to doing the deep stops. YMMV... :-)

The way people have been talking about "deep" stops in the newsgroup is
actually backwards from the ways/reasons they are being done.
First, "deep" deco stops are not done at some distance from the surface,
they are typically guaged from the max depth of the dive.  Since most
people dive relatively shallow this often turns out to be *close* to
the same thing anyway.

In any case, the idea behind deep deco stops is to help prevent the
growth of the microbubbles (I once said it's to help prevent the
formation of microbubbles but was told that pretty much any time
pressure gets lowered by a reasonable amount you will have some
microbubbles present).  Your first "deep" stop should be done no
shallower than 2 ATA from the bottom.  That is, if your max depth
was 130', do your first stop at 70'.  These stops only need to
be roughly 1 minute in duration.  I find it extremely interesting
that this just happens to be roughly the amount of time it
takes your blood to make one complete circuit in your body (i.e.
your lungs will scrub your entire blood supply once in this
time period).  Your 2nd stop would be another 2 ATA.  When you get
"shallow" (as is this 70' stop) then various people do
different things and, for the most part, they are pretty much close
to equivalent.  Some people would take half the distance to the
surface and stop at the next deeper 10' level (i.e. the next
stop would be 40' for one minute), etc...

For the most part, shallow deco as is prescribed by most profiles
is treating the bends that you already have.  The deep stops
are supposedly a *preventative* (not a curative).

Carl