What setpoint for 100m+ diving do you use?

mattmexico · 13th February 2008, 13:56

Quote: (Originally Posted by Mixaddict)

What about OTUs over multiple days?

yo

With OTU I have seen signs of pulmonary ox tox after 5 hours in the water exiting with a CNS clock of over 150 % and then into a chamber for 12 hours deco at a po2 beyond what we do in the water. CNS ox tox at this point no concern anymore as I would just bounce around inside the can instead of drowning. The pulmonary signs where distinct as I would have smoked 2 large cigars and inhaled the smoke instead of puffing .... diving the next day was out of the question as my throat felt a bit raspy even the next day.

On OC wreck diving stuff I have broken regulary through my OTU ceiling but never had a problem there.

Only time with an issue where these very extreme exposures.

A health triggered pulmonary issue manifested itself some years back. I went diving CCR deep with a 1 1/2 hour last stop on 6 mtr which I did on a 1.4 without air breaks. The week prior to that dive I had a chest cold, slight bronchitis, which is basicaly inflamed lung tissue, which was not gone 100 %. During the long deco at 1.4 setpoint I could feel a slight difficult breathing issue. As I came to the surface it got worse, ending in signs of pulmonary tox. At some point I got dizzy and had respiratory problems, spastic diaphragm and the feeling to faint. Four hours after the dive I arrived at the chamber to get a checkup and the doc said I might have a inner ear hit and gave me a ride in the chamber. I was fine the next day without any residual problems.

The only time I had OTU related problems was with a less then 100% pulmonary fitness. Any other time I was fine.

greetings
Matt

jiseson · 13th February 2008, 15:42

Is not the issue that if on a dive u end with high levels-and for some reason need to go to a chamber- it limits their schedules with O2?

silent running · 13th February 2008, 17:05

Quote: (Originally Posted by jiseson)

Is not the issue that if on a dive u end with high levels-and for some reason need to go to a chamber- it limits their schedules with O2?

Hello jiseson, it is my understanding that the OTU tables allow for 800 OTUs above the stated exposure limits in case of the need for hyperbaric treatment. This is why I don't worry about going a little over the max per day OTUs on my long dive trips, Had no issues even after 12 days diving. -Andy

Gobfish1 · 13th February 2008, 19:14

Quote: (Originally Posted by silent running)

Hello jiseson, it is my understanding that the OTU tables allow for 800 OTUs above the stated exposure limits in case of the need for hyperbaric treatment. This is why I don't worry about going a little over the max per day OTUs on my long dive trips, Had no issues even after 12 days diving. -Andy

The standard A6 table used for a chamber ride need 650 OTU ,, i read ,,, some place ,,

i never worry about OTU ,,

dteubner · 13th February 2008, 20:02

The rat paper actually supports Mike's argument about He being worse than N2. The time to first EEG evidence of O2 toxicity was significantly shorter with the He experiments than the N2 ones.

That said, the issues in deep dives are more complex. One the one hand there are theoretical reasons why N2 should be protective against O2 seizures, narcosis works in a similar way to drugs - like benzodiazepines, which clearly do help with these fits. The rat study sort of showed this in the 'bimodal' response to N2 - implying some protection at inspired N2 at 2-6ATA.

On the other hand, N2 is much more dense than He so the higher the N2 the higher the work of breathing. High WOB produces more CO2 and makes CO2 elimination less effective. Narcosis also causes CO2 retention independantly of WOB. CO2 retention is almost certainly much more important than inert gas effects.

So whilst high He may be more likely (in and of itself) to be assosciated with CNS O2 toxicity, high N2 will cause more high CO2 which is a bigger problem.

Gobfish1 · 13th February 2008, 20:09

Quote: (Originally Posted by dteubner)

The rat paper actually supports Mike's argument about He being worse than N2. The time to first EEG evidence of O2 toxicity was significantly shorter with the He experiments than the N2 ones.

That said, the issues in deep dives are more complex. One the one hand there are theoretical reasons why N2 should be protective against O2 seizures, narcosis works in a similar way to drugs - like benzodiazepines, which clearly do help with these fits. The rat study sort of showed this in the 'bimodal' response to N2 - implying some protection at inspired N2 at 2-6ATA.

On the other hand, N2 is much more dense than He so the higher the N2 the higher the work of breathing. High WOB produces more CO2 and makes CO2 elimination less effective. Narcosis also causes CO2 retention independantly of WOB. CO2 retention is almost certainly much more important than inert gas effects.

So whilst high He may be more likely (in and of itself) to be assosciated with CNS O2 toxicity, high N2 will cause more high CO2 which is a bigger problem.

i think Mike has said this in some other thread on Rebreather World ,, he got a bit mixed up and did talk a small amount of bollox in this thread ,,

but he new that all along ,, and said so

Richard Harris · 13th February 2008, 21:54

Nicely summarised Dave!
you see Mike, now you can go back to your position of never having been wrong!

jiseson · 13th February 2008, 22:36

this seems all nice for shorter dive times but....
so from here i learn i can just toss out all i have been taught about OTU and ... ok great!

mattmexico · 13th February 2008, 22:43

Quote: (Originally Posted by jiseson)

this seems all nice for shorter dive times but....
so from here i learn i can just toss out all i have been taught about OTU and ... ok great!

yo

you are welcome

Matt

Drmike · 13th February 2008, 23:33

Quote: (Originally Posted by Richard Harris)

Nicely summarised Dave!
you see Mike, now you can go back to your position of never having been wrong!

ah all is right with the world once again

(It wasnt this Rat paper I was thinking of specifically - but damned if I can find it). I do have referances to point to higher inspired ppINERT (for fixed PPO2) being contributors to o2 tox (which would support the argument against high setpoints at depth - only in practice its hard to reduce setpoint without increasing ppINERT lol!

)

As previously mentioned by Dave I guess the increased CO2 due to increased WOB (associated with increased ppINERT could well be the cause)

Nice avatar btw - see you went the Nova way too

13th February 2008, 13:56	#41 (permalink)
mattmexico Rebreather World Writer Current Rebreather/s: Megalodon Classic Kiss Optima RB80 / Clone Other Rebreather/s: Inspiration Classic Evolution Prism Topaz Sport Kiss RB80 / Clone Join Date: Aug 2005 Location: Mexico, Q.Roo, Playa del Carmen Posts: 752	Re: What setpoint for 100m+ diving do you use? Quote: (Originally Posted by Mixaddict) What about OTUs over multiple days? yo With OTU I have seen signs of pulmonary ox tox after 5 hours in the water exiting with a CNS clock of over 150 % and then into a chamber for 12 hours deco at a po2 beyond what we do in the water. CNS ox tox at this point no concern anymore as I would just bounce around inside the can instead of drowning. The pulmonary signs where distinct as I would have smoked 2 large cigars and inhaled the smoke instead of puffing .... diving the next day was out of the question as my throat felt a bit raspy even the next day. On OC wreck diving stuff I have broken regulary through my OTU ceiling but never had a problem there. Only time with an issue where these very extreme exposures. A health triggered pulmonary issue manifested itself some years back. I went diving CCR deep with a 1 1/2 hour last stop on 6 mtr which I did on a 1.4 without air breaks. The week prior to that dive I had a chest cold, slight bronchitis, which is basicaly inflamed lung tissue, which was not gone 100 %. During the long deco at 1.4 setpoint I could feel a slight difficult breathing issue. As I came to the surface it got worse, ending in signs of pulmonary tox. At some point I got dizzy and had respiratory problems, spastic diaphragm and the feeling to faint. Four hours after the dive I arrived at the chamber to get a checkup and the doc said I might have a inner ear hit and gave me a ride in the chamber. I was fine the next day without any residual problems. The only time I had OTU related problems was with a less then 100% pulmonary fitness. Any other time I was fine. greetings Matt __________________ N 20' 37.617' W 87' 04.693' www.andreaswmatthes.com
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13th February 2008, 15:42	#42 (permalink)
jiseson DSIX/O2PTIMA Current Rebreather/s: Optima Other Rebreather/s: Join Date: Jun 2006 Location: long island,ny Posts: 454	Re: What setpoint for 100m+ diving do you use? Is not the issue that if on a dive u end with high levels-and for some reason need to go to a chamber- it limits their schedules with O2? __________________ *Jonathan D Iseson*
(Online)

13th February 2008, 17:05	#43 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,778	Re: What setpoint for 100m+ diving do you use? Quote: (Originally Posted by jiseson) Is not the issue that if on a dive u end with high levels-and for some reason need to go to a chamber- it limits their schedules with O2? Hello jiseson, it is my understanding that the OTU tables allow for 800 OTUs above the stated exposure limits in case of the need for hyperbaric treatment. This is why I don't worry about going a little over the max per day OTUs on my long dive trips, Had no issues even after 12 days diving. -Andy
(Online)

13th February 2008, 19:14	#44 (permalink)
Gobfish1 Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other Rebreather/s: Inspiration Classic Inspiration Vision Evolution Join Date: Apr 2005 Location: Manchester UK Posts: 352	Re: What setpoint for 100m+ diving do you use? Quote: (Originally Posted by silent running) Hello jiseson, it is my understanding that the OTU tables allow for 800 OTUs above the stated exposure limits in case of the need for hyperbaric treatment. This is why I don't worry about going a little over the max per day OTUs on my long dive trips, Had no issues even after 12 days diving. -Andy The standard A6 table used for a chamber ride need 650 OTU ,, i read ,,, some place ,, i never worry about OTU ,, __________________ Steve G Apparently not the only gay diver in the village http://drinkingliberally.org/blogs/o...nzee-glock.gif http://www.scubatunes.com/audio/vol01/mp3/HiTech.mp3
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13th February 2008, 20:02	#45 (permalink)
dteubner Pedant Current Rebreather/s: Sport Kiss Classic Kiss Other Rebreather/s: Join Date: Mar 2005 Location: Adelaide, Australia Posts: 216	Re: What setpoint for 100m+ diving do you use? The rat paper actually supports Mike's argument about He being worse than N2. The time to first EEG evidence of O2 toxicity was significantly shorter with the He experiments than the N2 ones. That said, the issues in deep dives are more complex. One the one hand there are theoretical reasons why N2 should be protective against O2 seizures, narcosis works in a similar way to drugs - like benzodiazepines, which clearly do help with these fits. The rat study sort of showed this in the 'bimodal' response to N2 - implying some protection at inspired N2 at 2-6ATA. On the other hand, N2 is much more dense than He so the higher the N2 the higher the work of breathing. High WOB produces more CO2 and makes CO2 elimination less effective. Narcosis also causes CO2 retention independantly of WOB. CO2 retention is almost certainly much more important than inert gas effects. So whilst high He may be more likely (in and of itself) to be assosciated with CNS O2 toxicity, high N2 will cause more high CO2 which is a bigger problem. __________________ Dave T Hanlon's Razor - Never attribute to malice that which can be adequately explained by stupidity.
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13th February 2008, 20:09	#46 (permalink)
Gobfish1 Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other Rebreather/s: Inspiration Classic Inspiration Vision Evolution Join Date: Apr 2005 Location: Manchester UK Posts: 352	Re: What setpoint for 100m+ diving do you use? Quote: (Originally Posted by dteubner) The rat paper actually supports Mike's argument about He being worse than N2. The time to first EEG evidence of O2 toxicity was significantly shorter with the He experiments than the N2 ones. That said, the issues in deep dives are more complex. One the one hand there are theoretical reasons why N2 should be protective against O2 seizures, narcosis works in a similar way to drugs - like benzodiazepines, which clearly do help with these fits. The rat study sort of showed this in the 'bimodal' response to N2 - implying some protection at inspired N2 at 2-6ATA. On the other hand, N2 is much more dense than He so the higher the N2 the higher the work of breathing. High WOB produces more CO2 and makes CO2 elimination less effective. Narcosis also causes CO2 retention independantly of WOB. CO2 retention is almost certainly much more important than inert gas effects. So whilst high He may be more likely (in and of itself) to be assosciated with CNS O2 toxicity, high N2 will cause more high CO2 which is a bigger problem. i think Mike has said this in some other thread on Rebreather World ,, he got a bit mixed up and did talk a small amount of bollox in this thread ,, but he new that all along ,, and said so __________________ Steve G Apparently not the only gay diver in the village http://drinkingliberally.org/blogs/o...nzee-glock.gif http://www.scubatunes.com/audio/vol01/mp3/HiTech.mp3
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13th February 2008, 21:54	#47 (permalink)
Richard Harris Dr Harry Current Rebreather/s: Classic Kiss MK 15.X Other Rebreather/s: Join Date: Jul 2005 Location: Adelaide, South Australia Posts: 118	Re: What setpoint for 100m+ diving do you use? Nicely summarised Dave! you see Mike, now you can go back to your position of never having been wrong! __________________ "Harry" www.divedoc.net
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13th February 2008, 22:36	#48 (permalink)
jiseson DSIX/O2PTIMA Current Rebreather/s: Optima Other Rebreather/s: Join Date: Jun 2006 Location: long island,ny Posts: 454	Re: What setpoint for 100m+ diving do you use? this seems all nice for shorter dive times but.... so from here i learn i can just toss out all i have been taught about OTU and ... ok great! __________________ *Jonathan D Iseson*
(Online)

13th February 2008, 22:43	#49 (permalink)
mattmexico Rebreather World Writer Current Rebreather/s: Megalodon Classic Kiss Optima RB80 / Clone Other Rebreather/s: Inspiration Classic Evolution Prism Topaz Sport Kiss RB80 / Clone Join Date: Aug 2005 Location: Mexico, Q.Roo, Playa del Carmen Posts: 752	Re: What setpoint for 100m+ diving do you use? Quote: (Originally Posted by jiseson) this seems all nice for shorter dive times but.... so from here i learn i can just toss out all i have been taught about OTU and ... ok great! yo you are welcome Matt __________________ N 20' 37.617' W 87' 04.693' www.andreaswmatthes.com
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13th February 2008, 23:33	#50 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,128	Re: What setpoint for 100m+ diving do you use? Quote: (Originally Posted by Richard Harris) Nicely summarised Dave! you see Mike, now you can go back to your position of never having been wrong! ah all is right with the world once again (It wasnt this Rat paper I was thinking of specifically - but damned if I can find it). I do have referances to point to higher inspired ppINERT (for fixed PPO2) being contributors to o2 tox (which would support the argument against high setpoints at depth - only in practice its hard to reduce setpoint without increasing ppINERT lol! ) As previously mentioned by Dave I guess the increased CO2 due to increased WOB (associated with increased ppINERT could well be the cause) Nice avatar btw - see you went the Nova way too __________________ Get a girlfriend you sad twat - a Rebreather is an unfaithful mistress - dont blind yourself to her faults just because she goes down on you Last edited by Drmike : 13th February 2008 at 23:35.
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