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Sorry, did not read this correctly the first time . Deco is still the same amount of time, only now you go to the 50% and do a 70.60.50 for a couple of minutes or so and then the same 40 , 30 , 20. The interlude at 90 really shuts the deco down to nothing. We do dives like this where we go there and then to 55 feet and this pretty much wipes the deco right out. 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'. > > --------------------------------------------------------------------- > To unsubscribe, e-mail: quest-unsubscribe@gu*.co* > For additional commands, e-mail: quest-help@gu*.co* -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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