Mailing List Archive Mailing List Archive
--_=_=_=IMA.BOUNDARY.HTML_4998384=_=_=_ Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit John, if you are using 80/20 at 30 feet, then the PPO2 is 1.53. If you are worried about having a PPO2 of 1.6 and moving in the water column due to surge, etc., then do your oxygen stop at 18 feet or so. Keep in mind that 1.6 is just an arbitrary line in the sand, not a value at which you die. By using oxygen and doing this, you take maximum advantage of the oxygen window to achieve the decompression, rather than relying on the gradient, as well as having all the other benefits of having the oxygen on you. To minimize the toxicity risk, you drop the PPO2 of your bottom gas according to the exposure, and use back gas breaks on the oxygen stops. (The other stops are not really worrisome, since you are starting a high PPO2 gas after completing a break that was effectively achieved on the previous gas). Gas switching is one reason not to use the FFM. Switching to an FFM on the 20 foot stop might be a good idea, but you still need to be able to break to the low PPO2 gas. In cold water, mask switches like that are very uncomfortable. You say you have read this stuff, but it doesn't appear to have been absorbed... The "Baker's Dozen" post alone adresses a number of safety issues which warrant using the oxygen. Think this through. -Sean --Original Message Text--- From: Johnscha@ag*.co* Date: Thu, 19 Jul 2001 13:21:14 -0400 Sean I have read these and yes I agree it is more efficient and I use 02 totally resting on a log at 15' in the cave. I just believe, that in the open ocean, I don't care how good you are at buoyancy control you are going to bob and you are already at PO2 1.6. ) On 80/20 you are at 1.28. In my mind a much safer margin. If we assume that 02 at 20' is the standard then I believe the full face mask should also be SOP. John -----Original Message----- From: Sean T. Stevenson [mailto:ststev@un*.co*] Sent: Thursday, July 19, 2001 1:11 PM To: techdiver@aquanaut.com; John Schachleiter Subject: RE: The Seizure John, I copied this post to techdiver for the benefit of anyone following the thread. I have never used Decom, so cannot comment on the profiles it produces, but for any given profile can certainly comment as to the effectiveness of using the correct gases. First off, read and thoroughly understand each of the points listed in the "Baker's Dozen" post. Then, do some reading on decompression theory, specifically the application of the oxygen window for maximizing deco effectiveness. I think this topic is discussed in both David and Elliot's book, and in Weinke's. The toxicity risk created by using oxygen is minor, and is mitigated by the correct application of low PPO2 back gas breaks. Eddie Brian also has posted some good stuff on this. I can't see how using oxygen at 20 fsw imposes any greater risk than using 80/20 at 30 fsw, but I do see a lot of advantages to using the oxygen. Read the literature, then come back and tell us why you disagree. -Sean --Original Message Text--- From: Johnscha@ag*.co* Date: Thu, 19 Jul 2001 12:53:13 -0400 Sean I can only say what works for me. I try to limit my diving to around 200' on a light Trimix of 25% He or less keeping the END at 130' and PO2 1.4 . Total bottom time between 20 - 25 min. I deco using Decon MS Dos 6. something. Deep stops and no 10' stops. Yes, I am on 80/20 from 30'. I add 5 min. at 20' for my age, 55. After 30+ years of flying and diving I have never crashed or drowned myself. What works, works. Thanks John --_=_=_=IMA.BOUNDARY.HTML_4998384=_=_=_ Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: 7bit <HTML> <FONT FACE="MS Sans Serif" DEFAULT="FACE"><FONT SIZE="1" POINTSIZE="8" DEFAULT="SIZE">John, if you are using 80/20 at 30 feet, then the PPO2 is 1.53. If you are worried about having a PPO2 of 1.6 and moving in the water column due to surge, etc., then do your oxygen stop at 18 feet or so. Keep in mind that 1.6 is just an arbitrary line in the sand, not a value at which you die. By using oxygen and doing this, you take maximum advantage of the oxygen window to achieve the decompression, rather than relying on the gradient, as well as having all the other benefits of having the oxygen on you. To minimize the toxicity risk, you drop the PPO2 of your bottom gas according to the exposure, and use back gas breaks on the oxygen stops. (The other stops are not really worrisome, since you are starting a high PPO2 gas after completing a break that was effectively achieved on the previous gas). Gas switching is one reason not to use the FFM. Switching to an FFM on the 20 foot stop might be a good idea, but you s till need to be able to break to the low PPO2 gas. In cold water, mask switches like that are very uncomfortable. <BR> <BR> You say you have read this stuff, but it doesn't appear to have been absorbed... The "Baker's Dozen" post alone adresses a number of safety issues which warrant using the oxygen. Think this through.<BR> <BR> -Sean<BR> <BR> <BR> --Original Message Text---<BR> <B>From:</B> Johnscha@ag*.co*<BR> <B>Date:</B> Thu, 19 Jul 2001 13:21:14 -0400<BR> <BR> <FONT COLOR=0000ff><FONT FACE="Arial"><FONT SIZE="2" POINTSIZE="10">Sean<FONT COLOR=000000 DEFAULT="COLOR"><FONT FACE="MS Sans Serif" DEFAULT="FACE"><FONT SIZE="1" POINTSIZE="8" DEFAULT="SIZE"><BR> <FONT COLOR=0000ff><FONT FACE="Arial"><FONT SIZE="2" POINTSIZE="10">I have read these and yes I agree it is more efficient and I use 02 totally resting on a log at 15' in the cave. I just believe, that in the open ocean, I don't care how good you are at buoyancy control you are going to bob and you are already at PO2 1.6. ) On 80/20 you are at 1.28. In my mind a much safer margin. If we assume that 02 at 20' is the standard then I believe the full face mask should also be SOP.<FONT COLOR=000000 DEFAULT="COLOR"><FONT FACE="MS Sans Serif" DEFAULT="FACE"><FONT SIZE="1" POINTSIZE="8" DEFAULT="SIZE"><BR> <FONT COLOR=0000ff><FONT FACE="Arial"><FONT SIZE="2" POINTSIZE="10">John<FONT COLOR=000000 DEFAULT="COLOR"><FONT FACE="MS Sans Serif" DEFAULT="FACE"><FONT SIZE="1" POINTSIZE="8" DEFAULT="SIZE"><BR> <BR> <BR> <FONT FACE="Tahoma"><FONT SIZE="2" POINTSIZE="10">-----Original Message-----<BR> <B>From:</B> Sean T. Stevenson [mailto:ststev@un*.co*]<BR> <B>Sent:</B> Thursday, July 19, 2001 1:11 PM<BR> <B>To:</B> techdiver@aquanaut.com; John Schachleiter<BR> <B>Subject:</B> RE: The Seizure<BR> <BR> <BR> <FONT FACE="MS Sans Serif" DEFAULT="FACE"><FONT SIZE="1" POINTSIZE="8" DEFAULT="SIZE">John, I copied this post to techdiver for the benefit of anyone following the thread. I have never used Decom, so cannot comment on the profiles it produces, but for any given profile can certainly comment as to the effectiveness of using the correct gases. First off, read and thoroughly understand each of the points listed in the "Baker's Dozen" post. Then, do some reading on decompression theory, specifically the application of the oxygen window for maximizing deco effectiveness. I think this topic is discussed in both David and Elliot's book, and in Weinke's. The toxicity risk created by using oxygen is minor, and is mitigated by the correct application of low PPO2 back gas breaks. Eddie Brian also has posted some good stuff on this.<BR> <BR> I can't see how using oxygen at 20 fsw imposes any greater risk than using 80/20 at 30 fsw, but I do see a lot of advantages to using the oxygen. Read the literature, then come back and tell us why you disagree.<BR> <BR> -Sean<BR> <BR> <BR> --Original Message Text---<BR> <B>From:</B> Johnscha@ag*.co*<BR> <B>Date:</B> Thu, 19 Jul 2001 12:53:13 -0400<BR> <BR> <FONT COLOR=0000ff><FONT SIZE="2" POINTSIZE="10">Sean<FONT COLOR=000000 DEFAULT="COLOR"><FONT SIZE="1" POINTSIZE="8" DEFAULT="SIZE"><BR> <FONT COLOR=0000ff><FONT FACE="Arial"><FONT SIZE="2" POINTSIZE="10">I can only say what works for me. I try to limit my diving to around 200' on a light Trimix of 25% He or less keeping the END at 130' and PO2 1.4 . Total bottom time between 20 - 25 min. I deco using Decon MS Dos 6. something. Deep stops and no 10' stops. Yes, I am on 80/20 from 30'. I add 5 min. at 20' for my age, 55. After 30+ years of flying and diving I have never crashed or drowned myself. What works, works.<FONT COLOR=000000 DEFAULT="COLOR"><FONT FACE="MS Sans Serif" DEFAULT="FACE"><FONT SIZE="1" POINTSIZE="8" DEFAULT="SIZE"><BR> <FONT COLOR=0000ff><FONT FACE="Arial"><FONT SIZE="2" POINTSIZE="10">Thanks<FONT COLOR=000000 DEFAULT="COLOR"><FONT FACE="MS Sans Serif" DEFAULT="FACE"><FONT SIZE="1" POINTSIZE="8" DEFAULT="SIZE"><BR> <FONT COLOR=0000ff><FONT FACE="Arial"><FONT SIZE="2" POINTSIZE="10">John <FONT COLOR=000000 DEFAULT="COLOR"><FONT FACE="MS Sans Serif" DEFAULT="FACE"><FONT SIZE="1" POINTSIZE="8" DEFAULT="SIZE"><BR> <BR> <BR> <BR> <BR> <BR> </HTML> --_=_=_=IMA.BOUNDARY.HTML_4998384=_=_=_-- -- 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]