O2 convulsion

jhaaja · 20th October 2005, 05:41

Thanks everyone for the info and thoughts!

JH
Finland

smekke · 20th October 2005, 09:32

Quote: (Originally Posted by saturation)

PN2 provides some protection against 02 convulsions. When this is replaced by He, the risk for oxtox increases. The risk in increasing order is ~ air > nitrox > trimix > heliox.

Didn't know that. I assumed adding He is good because it's more easy to breath (better ventilation, less chance for CO2 buildup).
Any references to studies or experiments which indicate the positive pN2 impact on oxtox ?

Many Thanks
Peter

***jradomski*** · 20th October 2005, 09:45

Quote: (Originally Posted by smekke)

Didn't know that. I assumed adding He is good because it's more easy to breath (better ventilation, less chance for CO2 buildup).
Any references to studies or experiments which indicate the positive pN2 impact on oxtox ?

Many Thanks
Peter

What saturation is talkng about is studies and dives that have been acomplished on very high pn2 loads.

N2 has the effect of slowing down the nervous system (retarding xmission fro the neurons), which is probably why this effect has been seen... while He allows the neuorons in the brain to communicate more easily...

This also is probably the reason why someone switching to an oxygen rich deco mix, is much more likely to tox than someone diving air very deep...
There have been air dives to over 450fsw with little problems other than SEVERE narcosis, but someone swicthing to oxygen at 60fsw is much more likely to tox at the same oxygen exposure..

A helox based deco mix will also have ahigher risk of toxing than a nitrox deco mix..
More helium isnt always better.. I have also discussed this matter many times with an HSE hyberaric chabmer trainer, and he told me that the incidence of tox effects is definately higher when they use heliox 50 for their schedules over the same exposures with oxygen only.

saturation · 20th October 2005, 17:20

Quote: (Originally Posted by smekke)

Didn't know that. I assumed adding He is good because it's more easy to breath (better ventilation, less chance for CO2 buildup).
Any references to studies or experiments which indicate the positive pN2 impact on oxtox ?

Many Thanks
Peter

Concur full with jradomski summary.

Here are some links as references:

'Prolonged latency' implies some 'resistance' to initiating seizures.

http://www.ncbi.nlm.nih.gov/entrez/q...063&query_hl=3

'Kindling' is an experimental attempt to 'mimic' seizures.

http://thedecostop.com/forums/showpo...3&postcount=54

http://www.scubaboard.com/showpost.p...2&postcount=18

Flying K · 8th November 2005, 07:51

I am glad you are alive and well. I think the O2 hit was related to CO2.

Thanks for posting your expeience

Kenny Schneider

Nick uk. · 10th December 2005, 18:28

Perhaps it's so obvious and that's why nobody has asked, but what was the condition of the sofnolime, time elapsed on it pre-dive and total time on it to the time of the incident?

RebreatherDave · 7th May 2006, 06:43

Your dive buddy rocks! And he is an OC weenie to boot! Pretty impressive how he knew exactly what to do and kept his cool....

jhaaja · 7th May 2006, 08:07

Quote: (Originally Posted by Nick uk.)

Perhaps it's so obvious and that's why nobody has asked, but what was the condition of the sofnolime, time elapsed on it pre-dive and total time on it to the time of the incident?

The lime was fresh for the dive and RT at the time of the accident was 75mins. I think it is unlikely that CO2 had anything to do with the seizure.

JH

Barfab · 20th September 2006, 21:42

Quote: (Originally Posted by jhaaja)

Here comes a clarification about the calibration that I did before the dive. I use 99,5% pure oxygen and when I calibrated I input to the handset that O2 percentage is 98%. Hope this clears this issue.

Thanks for the palpations explanation. Now I am even more sure that it was diaphgram contractions, because I can remember those quick inhale spikes during the contraction.

That's the right way to calibrate Inpiration reb, as 98% is referred non to the tank's FO2 but the FO2 into the head after flushin' with oxygen.
Apart the little differenc anyway.
It may be interestin to understand more about scopolamine, as I've heard that saturation divers can't use else that a bit aspirine!
Anyway Hyperoxia has very variable limits: when I was younger in '70 years, dove often with oxygen rebreathers deeper than 40' and did have no problems, also if the workload was at lower levels, it was a lot dangerous anyway!
Just once I was workin' in the shallow waters of an harbour did see some flashes, I surfaced "as a rocket" with no conseguences.
Now I'm terrible afraid about I did at that time and we must remenber that the lot of parameters involved to lead into cns convulsion cannot give absolutely safe limits.
Fabio Bartolucci

B N Coleman · 22nd September 2006, 17:10

Hi guys I have been doing deep CCR dives on the YBOD, and decided some time ago, following some long stories, to reduce the PPo2 down to 1.1 for any dive deeper then 60msw and longer then 15min. Plus I have buddies take NO seasickness tablets/patches as tests show these do have an effect, although they can not be specific, with high O2 over prolonged exposure. So far So Good todate !

20th October 2005, 05:41	#31 (permalink)
jhaaja Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Mar 2005 Location: Finland Posts: 867	Thanks everyone for the info and thoughts! JH Finland
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20th October 2005, 09:32	#32 (permalink)
smekke New Member Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: Oct 2005 Posts: 1	Quote: (Originally Posted by saturation) PN2 provides some protection against 02 convulsions. When this is replaced by He, the risk for oxtox increases. The risk in increasing order is ~ air > nitrox > trimix > heliox. Didn't know that. I assumed adding He is good because it's more easy to breath (better ventilation, less chance for CO2 buildup). Any references to studies or experiments which indicate the positive pN2 impact on oxtox ? Many Thanks Peter
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20th October 2005, 09:45	#33 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Home Build Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Home Build Join Date: Mar 2005 Location: "Da" Bronx Posts: 2,817	Quote: (Originally Posted by smekke) Didn't know that. I assumed adding He is good because it's more easy to breath (better ventilation, less chance for CO2 buildup). Any references to studies or experiments which indicate the positive pN2 impact on oxtox ? Many Thanks Peter What saturation is talkng about is studies and dives that have been acomplished on very high pn2 loads. N2 has the effect of slowing down the nervous system (retarding xmission fro the neurons), which is probably why this effect has been seen... while He allows the neuorons in the brain to communicate more easily... This also is probably the reason why someone switching to an oxygen rich deco mix, is much more likely to tox than someone diving air very deep... There have been air dives to over 450fsw with little problems other than SEVERE narcosis, but someone swicthing to oxygen at 60fsw is much more likely to tox at the same oxygen exposure.. A helox based deco mix will also have ahigher risk of toxing than a nitrox deco mix.. More helium isnt always better.. I have also discussed this matter many times with an HSE hyberaric chabmer trainer, and he told me that the incidence of tox effects is definately higher when they use heliox 50 for their schedules over the same exposures with oxygen only. __________________ Joe Radomski CCR Trimix Instructor Trainer ANDI Instructor Trainer Director #10 All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.
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20th October 2005, 17:20	#34 (permalink)
saturation New Member Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: Sep 2005 Location: Philadelphia, PA, USA Posts: 53	Quote: (Originally Posted by smekke) Didn't know that. I assumed adding He is good because it's more easy to breath (better ventilation, less chance for CO2 buildup). Any references to studies or experiments which indicate the positive pN2 impact on oxtox ? Many Thanks Peter Concur full with jradomski summary. Here are some links as references: 'Prolonged latency' implies some 'resistance' to initiating seizures. http://www.ncbi.nlm.nih.gov/entrez/q...063&query_hl=3 'Kindling' is an experimental attempt to 'mimic' seizures. http://thedecostop.com/forums/showpo...3&postcount=54 http://www.scubaboard.com/showpost.p...2&postcount=18
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8th November 2005, 07:51	#35 (permalink)
Flying K New Member Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Feb 2005 Location: CA Posts: 4	Re: O2 convulsion I am glad you are alive and well. I think the O2 hit was related to CO2. Thanks for posting your expeience Kenny Schneider
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10th December 2005, 18:28	#36 (permalink)
Nick uk. Made in England. Current Rebreather/s: Inspiration Classic Azimuth Other Rebreather/s: Azimuth Join Date: Nov 2005 Location: Viale C.Colombo 75 Marina di Carrara. MS 54036 Italy Posts: 579	Re: O2 convulsion Perhaps it's so obvious and that's why nobody has asked, but what was the condition of the sofnolime, time elapsed on it pre-dive and total time on it to the time of the incident? __________________ If it aint broke....don't fix it, and if it is.............well......get another one! divechief2000@hotmail.com
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7th May 2006, 06:43	#37 (permalink)
RebreatherDave Maximum **** Current Rebreather/s: Inspiration Classic Other Rebreather/s:** Join Date: May 2005 Location: L.A., where the debris meets the sea Posts: 227	Re: O2 convulsion Your dive buddy rocks! And he is an OC weenie to boot! Pretty impressive how he knew exactly what to do and kept his cool....
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7th May 2006, 08:07	#38 (permalink)
jhaaja Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Mar 2005 Location: Finland Posts: 867	Re: O2 convulsion Quote: (Originally Posted by Nick uk.) Perhaps it's so obvious and that's why nobody has asked, but what was the condition of the sofnolime, time elapsed on it pre-dive and total time on it to the time of the incident? The lime was fresh for the dive and RT at the time of the accident was 75mins. I think it is unlikely that CO2 had anything to do with the seizure. JH
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20th September 2006, 21:42	#39 (permalink)
Barfab New Member Current Rebreather/s: Inspiration Classic Megalodon Ouroboros Ray Azimuth Other SCR Other Rebreather/s: Ray Azimuth Other SCR Join Date: Feb 2005 Location: Italy Posts: 50	Re: O2 convulsion Quote: (Originally Posted by jhaaja) Here comes a clarification about the calibration that I did before the dive. I use 99,5% pure oxygen and when I calibrated I input to the handset that O2 percentage is 98%. Hope this clears this issue. Thanks for the palpations explanation. Now I am even more sure that it was diaphgram contractions, because I can remember those quick inhale spikes during the contraction. That's the right way to calibrate Inpiration reb, as 98% is referred non to the tank's FO2 but the FO2 into the head after flushin' with oxygen. Apart the little differenc anyway. It may be interestin to understand more about scopolamine, as I've heard that saturation divers can't use else that a bit aspirine! Anyway Hyperoxia has very variable limits: when I was younger in '70 years, dove often with oxygen rebreathers deeper than 40' and did have no problems, also if the workload was at lower levels, it was a lot dangerous anyway! Just once I was workin' in the shallow waters of an harbour did see some flashes, I surfaced "as a rocket" with no conseguences. Now I'm terrible afraid about I did at that time and we must remenber that the lot of parameters involved to lead into cns convulsion cannot give absolutely safe limits. Fabio Bartolucci __________________ World is a....Rebreather! Last edited by Barfab : 20th September 2006 at 21:44.
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22nd September 2006, 17:10	#40 (permalink)
B N Coleman New Member Current Rebreather/s: Inspiration Classic Other CCR Dolphin Ray Other Rebreather/s: Inspiration Classic Inspiration Vision Evolution Other CCR Dolphin Ray Join Date: Apr 2006 Location: Scottburgh South Africa Posts: 6	Re: O2 convulsion Hi guys I have been doing deep CCR dives on the YBOD, and decided some time ago, following some long stories, to reduce the PPo2 down to 1.1 for any dive deeper then 60msw and longer then 15min. Plus I have buddies take NO seasickness tablets/patches as tests show these do have an effect, although they can not be specific, with high O2 over prolonged exposure. So far So Good todate ! __________________
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