not at all

Steve Schultz wrote:
> 
> George,
> How does the sample profile affect repetitive dives later that same day?
> 
> thanks
> steve
> 
> On Wed, 29 Dec 1999 kirvine@sa*.ne* wrote:
> 
> > I ignore the first dive - in this case you have mushed the bubbles
> > anyway. After enough time, I ignore any first dive other than as regards
> > the oxygen exposure - that is where the risk lies.
> >
> > Shimell, David (shimell) wrote:
> > >
> > > George
> > >
> > > Here's another question.
> > >
> > > Say you do your 220' for 25 and then ascend to do a multi-level dive to
say
> > > 90' for 25.  How would you calculate the deco for this?  I recall you once
> > > talked about superimposing one table on another but I had it on my list of
> > > things to look at.
> > >
> > > David Shimell
> > > Email: shimell@se*.co* <mailto:shimell@se*.co*>
> > > Project Manager, IBM NUMA-Q, Sequent Computer Systems Limited,
> > > Weybridge Business Park, Addlestone Road, Weybridge, Surrey, KT15 2UF, UK
> > > registered in England and Wales under company number: 1999363, registered
> > > office as above
> > >
> > > -----Original Message-----
> > > From:   kirvine@sa*.ne* [SMTP:kirvine@sa*.ne*]
> > > Sent:   Friday, December 24, 1999 12:43 PM
> > > To:     QUEST@GU*.CO*
> > > Cc:     techdiver
> > > Subject:        SAMPLE DECO DIVE - 220 FOR 25
> > >
> > > Let's run through a sample dive. I will throw out the parameters and
> > > the standeard deco on one side, and my changes and why on the other ,and
> > > then we can discuss it.
> > >
> > >  We can then build the dive into a longer dive, a deeper dive and we can
> > > add more gasses and more stituations, and then the equipment to do it.
> > >
> > >  Let's start with this and get the discussion going that way. I need all
> > > questions, no matter how sophisticated, so we can get out the rock.
> > >
> > > ***PROFILE 220 FOR 25                   CHANGES
> > > ***GAS 16% OXYGEN  50% HELIUM   1.2 PPO2
> > >                                 85 AED
> > >
> > >          REASON FOR GAS CHOICE: the more heluim, the better . It is
> > > easier to breathe at depth, and it is easier to decompress from,
> > > contrary to what you have been told elsewhere. The reduced narc is
> > > obvious. I chose the 50% heliuum for this , but the more the better. The
> > > oxygen ppo2 should be kept intentionally low. The reason is that you do
> > > not want to unnecessarily deplete brain chemistry to pick up "perceived"
> > > deco advantage, expescially in light of the fact that we have boosted
> > > the helium which reduces the nitrogen damage and loading, and thus the
> > > deco requirement. While inert gas is inert gas for purposes of this
> > > discussion ( or said another way, the oxygen window is the oxygen
> > > window) the reality is that helium changes the physiological factors
> > > that are as real in deco as the straight compartment loading and
> > > unloading factors. Very important to us in our diving, and more so as
> > > the dives get more severe or repetitive. We also do not want to burn the
> > > shit out of our lungs with high PPO2's either, and keep in mind that
> > > depending on the bottom time, we are going to be forced to expose
> > > ourselves ot elevated oxygen to decompress.
> > >
> > > It is critical in multiday exposure that you reduce the oxygen dose, and
> > > we will show how to do that in each decompression.
> > >
> > > STANDARD DECO FROM A PROGRAM            REAL LIFE DECO
> > >
> > > DEPTH   TIME    GAS                     DEPTH   TIME    GAS
> > >                                         160-120 1 MINUTE EACH ON BG
> > > 110     1       16/50                   110     1
> > > 100     3                               100     1
> > > 90      4                               90      1
> > > 80      5                               80      1
> > > 70      3       50/50                   70      5       50/50
> > > 60      4                               60      2
> > > 50      5                               50      3
> > > 40      9                               40      5
> > > 30      11                              30      8
> > > 20      17      OXYGEN                  20      13      OXYGEN
> > > 10      26                              20-0    8
> > >
> > > TOTAL 88                                TOTAL   60
> > >
> > >                     REASONS FOR CHANGES
> > >
> > > 1) we start our deco at 80% of the profile in atmospheres, or in this
> > > case , around 160 feet. We are not changing gases yet, so no reason to
> > > sit on these stops. The ascent rate is 30 fpm, or the equivalent of a 20
> > > second stop every ten feet from the bottom, so we are really only adding
> > > 40 seconds per "stop" from 80% of the profile. This actually "maxes out"
> > > at about 5 minutes per "deep stop" in anything approaching saturations,
> > > which I call 150 minutes for the purposes of decomprssion reality as
> > > opposed to trying to decompress a whale. In a long dive, we also use the
> > > first deco gas at 80% of the profile . Not in play here.
> > >
> > > 2) moving up we do not extend these stops per Bulhmann, since we have
> > > already moved the "ceiling" quite a long ways above us, and are not yet
> > > really pressing the gradient ( in percentage or relative terms, ie the
> > > ratio of the atmospheric change deep a opposed to shallow). We need to
> > > get to a deco gas first and spend some time, so......
> > >
> > > 3) we "SIT" on the 70 foot stop for quite a bit longer than is suggested
> > > by theory. The reason is we want to use that wide open oxygen window for
> > > all it is worth down there to both clear the slate as much as possible,
> > > and to move that ceiling again quite a bit so that we can abbreviate the
> > > stops above as their ppo2 declines, rather than lengthening them as
> > > either Bulhmann or bubble mechanics would indicate - real life says we
> > > are correct. In fact, I have SKIPPED up to 100 minutes of our 40 foot
> > > stops with no repercussions, and Lucy Ho can vouch for me on this ( and
> > > the doppler says so). The other reason is that we want to give the blood
> > > a chance to totally circulate with the new gas. While it hits the key
> > > body parts immediately ( spine, heart, brain), it takes a couple of
> > > minutes to get to everything properly. We do not want to hammer high
> > > popo2's, we want to use them to our advanntage.
> > >
> > > 3) since we have done our deep stops and our high ppo2's, both moving
> > > our ceiling and shortening our upper time, we can go ahead and press the
> > > gradient as it condenses, and shorten the next few stops and get to that
> > > oxygen.
> > >
> > > 4) the oxygen does not have to be hit too ahrd. I like 12-13 minute
> > > stints with 6-8 minutes off. The reasons are that it takes almost no
> > > time to saturate with oxygen at any ppo2 once the immediate offgassing
> > > slows - a few minutes - and the damage starts to accrue after about
> > > 16-20 minutes in our experience, depending of course on the dosages
> > > already taken on the way up to this point.  The swelling of the lung
> > > tissue picks up after a few minutes, and the gas transfer process is
> > > severely hampered. Vasoconstriction gets worse, and you are pissing in
> > > the wind honking on the oxygen. You need to break to back gas, or in
> > > this case , just move up and get out.
> > >
> > > 5) slow final ascent - the last move up to the surface is one of the
> > > most critical. No matter how long you sit on a stop with the window wide
> > > open, there will still be gas that will not be displaced by this method.
> > > When you increase the gradient by trying to surface, the last of the gas
> > > comes out rapidly and does so in bubble form. You must do a slow ascent
> > > to reduce the risk of this, and for long dive it is one foot per minute
> > > to the surface, for this dive it is more like 2.5 - 3 fpm.
> > >
> > > 6) at the surface, sit still for a bit and try not to exert for about 30
> > > minutes thereafter. Bubbles forming at this time will now grow as they
> > > pick up offgassing nitrogen ( the helium is long gone) and will become
> > > problematic later, and severely so if you have a shunt that can then be
> > > opened by the in increasing pressure on the cappillary beds of the
> > > lungs.
> > >
> > > OK - let's take it from here and get the discusion going.  Please do not
> > > copy back the whole message or it will become a mail bonb - just cut and
> > > paste the parts you want to discuss, and lets discuss one item per
> > > email, SVP. When we expand this to a long dive, then I will cross copy
> > > it to WKPP@eg*.co*, and we will bring in the big guns ( Rose, Mee
> > > ,et al).
> > >
> > > Let's go .
> > >
> > > --
> > > 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]