Oxygen exposure has cumulative risks and spike risks, as well as temporary
and longer-lasting damage risks. The basic ways to minimize these is to 1)
reduce ppo2 for longer dives while increasing helium content, reduce
overall ppo2s for repetitive or multiday diving, including starting deco
gases at a shallower depth than usual, 2) interrupting exposure with breaks
to a gas that gives the lowest breathable ppo2 on regular intervals, and 3)
using the correct gasses at deeper deco stops to as to reduce the need for
longer times at shallower stops.

Keep in mind that bends risk is in now way equivalent to death risk. keep
in mind that spiking ppo2s on top of an extended exposure to already
borderline ppo2s is deadly. keep in mind that jumping to a high ppo2 gas
deep is idiocy and absolutely unnecessary.

Oxygen in higher ppo2s causes the body to try to defend itself, and those
defensive mechanisms include adding cell layers to the interface,
vasoconstriction to reduce transmission, swelling of the lung tissues and
fluid accumulation to defend, and other immune responses, all of which are
counterproductive to gas exchange. These reactions onset within 12 minutes
and in no more than 20 minutes to some degree or other. Preventing them is
easier than reversing them.

When you 'toggle" the gasses back and forth, you are reducing these
responses and actually increasing the ability to eliminate unwanted gasses,
while at the same time allowing brain chemistry to keep up with the
stresses, thus postponing any critical event that might cause a tox.

We do these things on a carefully prescribed basis. Only one of our dive
sites allows for a habitat, and at that site we are merely able to do a
higher ppo2 with a 12 on, 6 off protocol, then a 10 minute cleanup break,
then an ascent to the surface at 1 foot per minute on no greater than 50%
gas for the first 12 feet. We have safety divers on each decompressing
diver. We are also getting a huge advantage being in air for that part of
the deco, rather than in water.

For the rest of our sites, we are doing conventional inwater deco. There we
really have to be meticulous about exposure. On any of the long dives, we
do the entire last step of a gas on backgas ( ie, the 120 bottle would be
used from 120-90 and then the 80 stop would be on back gas). We also take a
20 minute cleanup break at 50 feet on backgas and finish the stop on 50%.

15 years of WKPP experimentation with protocol and gases went into our
methods, and we validate them with bloodwork and doppler, not to mention
results.

Aside from Rule Number One violations, the most dangerous aspects of diving
are 1) driving to the site, 2) decompression on high ppo2s.

Separately,---

I see this drooling idiot JT has weighed in on the discussion. This person
is a total idiot, and so are his dive buddies. They want so badly to be
recognized - well they are - as morons. They can't dive, they know nothing,
they have big mouths and big egos ( undeserved, they have no real
experience, no methods worth discussing, no validation of anything but
stupidity, and they are extremely dangerous. Avoid these people at all
costs. My best advice, and you all know when I was last wrong about
something like this - never. these guys are monkeys with an attitude. There
are only two or three of them left with the "captain", and my bet is that a
more serious form of attrition will eventually prevail.


From: "The McLeods" <rmmacleod@ac*.ca*>
Subject: O2 exposure
Date: Wed, 4 Sep 2002 18:11:32 -0300
    Now that all the bantering has ended,I have a serious question for
George regarding O2 exposure.After following all of G's instruction on how
to deco properly,my deco's are going very well,I feel much better when
getting out of the water.My question is this:when using O2 for deco,how


-----Original Message-----
From: The McLeods [mailto:rmmacleod@ac*.ca*]
Sent: Wednesday, September 04, 2002 5:12 PM
To: techdiver
Subject: O2 exposure


    Now that all the bantering has ended,I have a serious question for
George regarding O2 exposure.After following all of G's instruction on how
to deco properly,my deco's are going very well,I feel much better when
getting out of the water.My question is this:when using O2 for deco,how do
the cave guy's control their O2 exposure on those incredibly long
dives.Using deco-planner for instance,it does not take long to exceed max O2
limits,even when taking into account the back gas breaks.How is this
accomplished safely,aside from using a habitat?

Randy

--
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]