Mailing List Archive Mailing List Archive
Just to add a couple of things. The Navy tables are not useful for tech diving. The first thing the Navy manual says is that mixed gas diving should not be done unless there is a chamber on board the ship. In fact, the schedules assume that you will deco to 40 feet, then get lifted up to the ship, stripped of your gear and put in a chamber and recompressed within 5 minutes. This is important for military dive operations and is a hold over from caisson decompression where you had to move shifts of workers in and out of pressure every few hours. It was much more efficient to pull an elevator load up to the surface, rush them into a surface chamber as a group and decompress them that way. (We're talking late 18th early 19th century technology here). What is pretty clear from both Navy tables and straight Buhlmann calculations is that you are overpressuring the tissues, essentially causing sub clinical bends if you will, then "treating" with longer stays at shallower depths with higher O2 percentages. The first attempt to address this was Pyle's "deep stop" method. He is the first to tell you that this was just a rough guess, not based on any kind of science. Scientific work has been done by Baker and others, and the results are the so called Gradient Factors which modify Buhlmann calculations to address the overpressure problem when ascending from depth. There is also a fairly radical re-think called Variable Perfusion Modelling which is the first complete change in deco theory in half a century. Johnny is right about TDI. I just read their trimix manual last week and in it they basically say, get a good deco program, forget tables. The downside to using a computer program is not understanding what the theory is behind the program. You need to understand what the computer is doing, and if and how you need to modify it for your fitness, experience, dive conditions, etc. What the WKPP guys do is based on the fact that they self select people that are capable of doing extreme dives and deco. Thats not to say that with enough work and self discipline you can't do the same, but you can't just wander into the water after sitting behind a desk all week. Wendell >Hi Isaac > >3 years back I used to do dives that required 1-1½ hr on 80%. >On a couple of ocations I stayed 2½ hrs on 80% just to see when any >pulmonary symptoms would begin. No gas breaks done. In these exposures there >was really no significant symptoms. > >When I do pure O2 now, I get the symptoms after 30-40min. There I'm doing 15 >/ 3 gasbreaks (but using the 50% decogas to "break" on) > >From my chamber experience and talking to comercial divers, the inhalation >resistance on the O2 reg or mask, has a major influence on how your lungs >are going to feel afterwards. > >BTW, no agency is using Navy tabels anymore. I think even TDI stopped 2 or 3 >years ago. > >Regards > >Johnny Christensen > > >>From: "Isaac Callicrate" <icallicrate@ho*.co*> >>To: trey@ne*.co*, techdiver@aquanaut.com >>Subject: RE: Dr Black/ChamberHaters >>Date: Tue, 11 Dec 2001 12:48:16 -0500 > >-snip- > >>>Im interested to hear if any of the IANTD's on the list have done a >>long >>enough exposure to see pulmonary issues on 80/20? I hope Im not the only >>one >>getting something out of this. (Everyone take a turn squeezing more out of >>Trey while he is feeling generous) >>Thanks > > >_________________________________________________________________ >Chat with friends online, try MSN Messenger: http://messenger.msn.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]