Functioning with high CO2

Genesis · 14th December 2006, 03:52

That's a fair question, actually.

Could you manage a CO2 hit by exhaling through your nose, then hitting the manual add (assuming its on the inhale C/L) while inhaling? That would give you (mostly) clean diluent - but how many of those cycles does it take before you calm down, and can you manage the actions necessary (which are more complex than twisting a knob) when screwed by the hit?

That's the part I don't know...... the BOV is clunky compared to a regular mouthpiece, but if its the difference between a successful bail and not if you take a CO2 hit, well.......

Mike · 14th December 2006, 04:07

Quote: (Originally Posted by dteubner)

In your experiment it is very unlikely that your CO2 was at all high - it may even have been a bit low.

The sensation of dyspnoea (shortness of breath) with exercise is not related to an elevation in CO2 (hypercarbia), it is not well understood but relates to a whole host of factors.

Dyspnoea post exercise is also not related to hypercarbia.

Dave T

Dave - you've just made my head explode as that's completely different from what I've understood for a good many years.

My understanding was that, simplistically, Aerobic exercise was where you were performing at a level that your cardio-pulmanary system could keep up the exchange of O2 / CO2, and Anerobic was where you can't. You had the Krebs cycle in your cells producing ATP by convering sugar and O2 into CO2 and water, when there isn't enough O2, you produce lactic acid through incomplete respioration of sugar, rather than going through to CO2

I understood the breathing response to be regulated by carboxyllic acid sensors in the brain reacting to elevated levels in the blood (with a few people having this not work so well so they actually react to low O2)

If CO2 removal is a bunch more efficient that O2 uptake, then I can understand that during exercise you could be in O2 debt without the corresponding CO2 buildup - but if they are approximately equal, then it doesn't make much sense to me.

Mike
BTW - in lieu of the OC DSV I do practice open loop on the prism from time to time to try and have it as the first response to any dodgy feelings. It's not as permanent a solution as the OC DSV, but it's probably quicker.

Mike · 14th December 2006, 04:16

Quote: (Originally Posted by Skipbreather)

Hi Mike-

I appreciate that you’ve gone to considerable effort to get some insight to the CO2 issue, but DUDE- with respect- they were great efforts, but bear little resemblance to what you might expect to go thru in an underwater hypercapnia event. A closed breathing loop w/ limited scrubbing ability combined with elevated ambient pressures make it an entirely different game.

Ken

Umm - it wasn't much of an effort to hold my breath for 20 seconds... the rest of it I was doing anyway. And one thing about swimming training - it gives you a bunch of time to think.

I figure it must be different, but rather than just asserting it's so and giving an anecdote, how about some explanation of the physiology that makes it so?

Sometime when I've got a doctor type sitting around home I'll give the prism a breathe sans scrubber to see how different it feels to me.

Mike

**nigelh** · 14th December 2006, 07:37

Quote: (Originally Posted by Mike)

Both 2 and 3 should be analogous to any anerobic exercise - you are getting rid of some, but not all, the CO2 each breath. Therefore CO2 will build up to uncomfortable levels over time - but it should take a minimum of 90 seconds to get to the dehibilitating stage, and that should be long enough to recognise and react?

I've posted my run in with CO2 before so I won't rerun the sordid details again but the snag was that I didn't notice. Automatic systems in my head just gently wound up the breathing rate and the alarm only sounded when I couldn't breath any more and by then swapping off the loop was impossible. The BOV means that if ever, grief I hope never, that happens again I snap the valve and I'm off the loop.

I've overdone it badly freediving occasionally but this was far worse. I was breathing but it wasn't doing me any good. However the automatic systems that won't let you 'choose to die' had cut in and the reg in my hand that I knew was OK was light years away.

dteubner · 14th December 2006, 08:31

Quote: (Originally Posted by Mike)

Dave - you've just made my head explode as that's completely different from what I've understood for a good many years.

I understood the breathing response to be regulated by carboxyllic acid sensors in the brain reacting to elevated levels in the blood (with a few people having this not work so well so they actually react to low O2)

If CO2 removal is a bunch more efficient that O2 uptake, then I can understand that during exercise you could be in O2 debt without the corresponding CO2 buildup - but if they are approximately equal, then it doesn't make much sense to me.

Didn't mean to make your head explode mate.

The "breathing is a response to hypercapnea" business does not explain what happens in esercise. Hyperventilation in exercise starts without the CO2 changing. There are many many inputs to the respiratory centres and large muscle movements are themselves enough to make you breathe harder.

The concept of oxygen debt is about the lactate. As you said, lactic acid is the end point of anaerobic metabolism as energy is derived from the conversion of sugar to lactate, without oxygen being required. Once there is available oxygen again then the lactate needs to be converted all the way through to CO2 - which requires oxygen. My understanding is that it's this use of oxygen to get rid of lactate which represents the 'debt'.

Body cells need a relatively normal pH to function efectively. Anaerobic exercise produces lactic acid, which makes the blood acidic. If you add hypercarbia (which also makes the blood acidic) on top of this, the pH falls quite dramatically and normal function becomes impossible.

Dave T

Edit - some evidence apart from "I reckon this" Entrez PubMed

Mark Chase · 14th December 2006, 08:57

A few points from my perspective:

1: I know two people who have had Co2 hits both experienced deep divers one is an instructor. Both said they couldn't force them selves to take the loop out of their mouths. They were breathing to fast to allow them selves to switch over. One solved the problem by doing a rapid ascent on loop. He was at 20m on the shot. The other dill flushed until he got confident enough to bailout which was apparently immediately after he ran out of diluent

2: Breathing elevated PP02 can delay the onset of symptom of a C02 hit so you don't realize you have a problem till its too late.

3: A BOV will make you more inclined to bailout early because its simple. We loose the habit of reg switching on CCR and we don't like re filling bailout cylinders. As a result we are less likely to switch to OC when a problem occurs. Having made this fundamental error a couple of times I opted for a BOV plumbed into a large off board cylinder.

ATB

Mark Chase

decoweenie · 14th December 2006, 09:20

I have over-breathed the different units at time when working very hard, it was very difficult to bring it under control.

However, I have seen someone passed out completely u/w from hypercapnia. He is a strong and experience diver, yet unable to finish making the signal before passing out completely. And he didn't remember a lot until back on the boat.

Looking back, I am not 100% sure if he could even switch the BOV if he had one. And that scares me...

Mike · 14th December 2006, 09:37

Quote: (Originally Posted by dteubner)

Didn't mean to make your head explode mate.

Edit - some evidence apart from "I reckon this" Entrez PubMed

Thanks Dave
Appreciate that you followed up with a reference. I'll do some more reading I think - interesting to have something I've believed I understood demonstrated to be wrong.

Have you considered the breathing limitation imposed by swimming though?

Distance swimming, now that I've been educated

, I'll believe does not involve a rise in CO2.

Dynamic apnea or freediving clearly must, almost by definition.

Sprinting, I'd still consider falls somewhere in between. Being somewhat oldschool, I consider that breathing slows you down. (Neil Brooks was once quoted as saying "30 seconds? I can hold my breath that long, why breath?)

Even if we are to just consider dynamic apnea, why don't we see the same CO2 hit symptoms there? Or perhaps that's part of what a Samba is? But doing apnea stuff I get really recognisable symptoms like diaphram contractions before really needing to breath. If it only happened in dynamic apnea I'd be suggesting that it could be due to the other exercise related breathing triggers, but as it happens in static apnea as well, that doesn't seem likely.

Perhaps I need to get someone to take some blood samples at the pool...

Oh, and Mark Chase, do you have an idea why you think your no.2 happens, as I though that the body's reaction to high CO2 wasn't influenced by O2 levels?

Mike - learning stuff today!

CharlieT · 14th December 2006, 10:16

Thank you Mike for starting this educational and very relevant post.

This is the bad one for us CCR divers, worse than the possibility of an O2 hit.

I have a great fear of overbreathing my scrubber so stop and rest if I have over-exerted myself.

A BOV must, as several have said, be the quickest way of the loop in the instance of an impending CO2 hit.

Might not save you in the worst instances, as Phi relates, but sound as good a counter-measure as is available.

Mark, a rapid ascent from 20m sounds a bit scary! Finger pressed on O2 button, I hope?

Mike, this post has helped me make the decision to buy a Golem BOV for my Vision.

Charlie

decoweenie · 14th December 2006, 10:38

Quote: (Originally Posted by CharlieT)

Might not save you in the worst instances, as Phi relates, but sound as good a counter-measure as is available.

Yes, and also allowing a buddy-rescue a lot easier instead of having to attempt to replace DSV-to-reg on an unconscious diver.

14th December 2006, 03:52	#11 (permalink)
Genesis Bubbless Box of Death Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: Oct 2005 Location: Sunny Florida Posts: 1,453	Re: Functioning with high CO2 That's a fair question, actually. Could you manage a CO2 hit by exhaling through your nose, then hitting the manual add (assuming its on the inhale C/L) while inhaling? That would give you (mostly) clean diluent - but how many of those cycles does it take before you calm down, and can you manage the actions necessary (which are more complex than twisting a knob) when screwed by the hit? That's the part I don't know...... the BOV is clunky compared to a regular mouthpiece, but if its the difference between a successful bail and not if you take a CO2 hit, well....... __________________ "A venturesome minority will always be eager to get off on their own, and no obstacles should be placed in their path; let them take risks for Godsake, let them get lost, sunburnt, stranded, drowned, eaten by bears, buried alive under avalanches - that is the right and privilege of any free American." http://www.denninger.net http://www.diversunion.org/liability.htm - Fix the Diving Cert racket
(Offline)

14th December 2006, 04:07	#12 (permalink)
Mike Prism 'prentice Current Rebreather/s: Prism Topaz Other Rebreather/s: Inspiration Classic Evolution Join Date: Feb 2005 Location: Melbourne Posts: 332	Re: Functioning with high CO2 Quote: (Originally Posted by dteubner) In your experiment it is very unlikely that your CO2 was at all high - it may even have been a bit low. The sensation of dyspnoea (shortness of breath) with exercise is not related to an elevation in CO2 (hypercarbia), it is not well understood but relates to a whole host of factors. Dyspnoea post exercise is also not related to hypercarbia. Dave T Dave - you've just made my head explode as that's completely different from what I've understood for a good many years. My understanding was that, simplistically, Aerobic exercise was where you were performing at a level that your cardio-pulmanary system could keep up the exchange of O2 / CO2, and Anerobic was where you can't. You had the Krebs cycle in your cells producing ATP by convering sugar and O2 into CO2 and water, when there isn't enough O2, you produce lactic acid through incomplete respioration of sugar, rather than going through to CO2 I understood the breathing response to be regulated by carboxyllic acid sensors in the brain reacting to elevated levels in the blood (with a few people having this not work so well so they actually react to low O2) If CO2 removal is a bunch more efficient that O2 uptake, then I can understand that during exercise you could be in O2 debt without the corresponding CO2 buildup - but if they are approximately equal, then it doesn't make much sense to me. Mike BTW - in lieu of the OC DSV I do practice open loop on the prism from time to time to try and have it as the first response to any dodgy feelings. It's not as permanent a solution as the OC DSV, but it's probably quicker. __________________ Open ....... Closed Mind ........ Loop
(Offline)

14th December 2006, 04:16	#13 (permalink)
Mike Prism 'prentice Current Rebreather/s: Prism Topaz Other Rebreather/s: Inspiration Classic Evolution Join Date: Feb 2005 Location: Melbourne Posts: 332	Re: Functioning with high CO2 Quote: (Originally Posted by Skipbreather) Hi Mike- I appreciate that you’ve gone to considerable effort to get some insight to the CO2 issue, but DUDE- with respect- they were great efforts, but bear little resemblance to what you might expect to go thru in an underwater hypercapnia event. A closed breathing loop w/ limited scrubbing ability combined with elevated ambient pressures make it an entirely different game. Ken Umm - it wasn't much of an effort to hold my breath for 20 seconds... the rest of it I was doing anyway. And one thing about swimming training - it gives you a bunch of time to think. I figure it must be different, but rather than just asserting it's so and giving an anecdote, how about some explanation of the physiology that makes it so? Sometime when I've got a doctor type sitting around home I'll give the prism a breathe sans scrubber to see how different it feels to me. Mike __________________ Open ....... Closed Mind ........ Loop
(Offline)

14th December 2006, 07:37	#14 (permalink)
nigelh New member Current Rebreather/s: Inspiration Vision Other CCR Other Rebreather/s: Inspiration Classic Other CCR Join Date: Mar 2005 Location: Brighton, Sussex, UK Posts: 883	Re: Functioning with high CO2 Quote: (Originally Posted by Mike) Both 2 and 3 should be analogous to any anerobic exercise - you are getting rid of some, but not all, the CO2 each breath. Therefore CO2 will build up to uncomfortable levels over time - but it should take a minimum of 90 seconds to get to the dehibilitating stage, and that should be long enough to recognise and react? I've posted my run in with CO2 before so I won't rerun the sordid details again but the snag was that I didn't notice. Automatic systems in my head just gently wound up the breathing rate and the alarm only sounded when I couldn't breath any more and by then swapping off the loop was impossible. The BOV means that if ever, grief I hope never, that happens again I snap the valve and I'm off the loop. I've overdone it badly freediving occasionally but this was far worse. I was breathing but it wasn't doing me any good. However the automatic systems that won't let you 'choose to die' had cut in and the reg in my hand that I knew was OK was light years away. __________________ nigelh
(Offline)

14th December 2006, 08:31	#15 (permalink)
dteubner Pedant Current Rebreather/s: Sport Kiss Classic Kiss Other Rebreather/s: Join Date: Mar 2005 Location: Adelaide, Australia Posts: 221	Re: Functioning with high CO2 Quote: (Originally Posted by Mike) Dave - you've just made my head explode as that's completely different from what I've understood for a good many years. I understood the breathing response to be regulated by carboxyllic acid sensors in the brain reacting to elevated levels in the blood (with a few people having this not work so well so they actually react to low O2) If CO2 removal is a bunch more efficient that O2 uptake, then I can understand that during exercise you could be in O2 debt without the corresponding CO2 buildup - but if they are approximately equal, then it doesn't make much sense to me. Didn't mean to make your head explode mate. The "breathing is a response to hypercapnea" business does not explain what happens in esercise. Hyperventilation in exercise starts without the CO2 changing. There are many many inputs to the respiratory centres and large muscle movements are themselves enough to make you breathe harder. The concept of oxygen debt is about the lactate. As you said, lactic acid is the end point of anaerobic metabolism as energy is derived from the conversion of sugar to lactate, without oxygen being required. Once there is available oxygen again then the lactate needs to be converted all the way through to CO2 - which requires oxygen. My understanding is that it's this use of oxygen to get rid of lactate which represents the 'debt'. Body cells need a relatively normal pH to function efectively. Anaerobic exercise produces lactic acid, which makes the blood acidic. If you add hypercarbia (which also makes the blood acidic) on top of this, the pH falls quite dramatically and normal function becomes impossible. Dave T Edit - some evidence apart from "I reckon this" Entrez PubMed Last edited by dteubner : 14th December 2006 at 09:02. Reason: A bit of evidence
(Offline)

14th December 2006, 08:57	#16 (permalink)
Mark Chase RBW Member Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,858	Re: Functioning with high CO2 A few points from my perspective: 1: I know two people who have had Co2 hits both experienced deep divers one is an instructor. Both said they couldn't force them selves to take the loop out of their mouths. They were breathing to fast to allow them selves to switch over. One solved the problem by doing a rapid ascent on loop. He was at 20m on the shot. The other dill flushed until he got confident enough to bailout which was apparently immediately after he ran out of diluent 2: Breathing elevated PP02 can delay the onset of symptom of a C02 hit so you don't realize you have a problem till its too late. 3: A BOV will make you more inclined to bailout early because its simple. We loose the habit of reg switching on CCR and we don't like re filling bailout cylinders. As a result we are less likely to switch to OC when a problem occurs. Having made this fundamental error a couple of times I opted for a BOV plumbed into a large off board cylinder. ATB Mark Chase __________________ See my "Doing It Chasey" video where I'm locked into a padded room, naked, with two ball bearings and within an Hour, I manage to lose one and break the other!!! Kevin Juergensen 16/11/08 [/quote]
(Offline)

14th December 2006, 09:20	#17 (permalink)
decoweenie Crash Test Dummy Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Cairo Posts: 5,487	Re: Functioning with high CO2 I have over-breathed the different units at time when working very hard, it was very difficult to bring it under control. However, I have seen someone passed out completely u/w from hypercapnia. He is a strong and experience diver, yet unable to finish making the signal before passing out completely. And he didn't remember a lot until back on the boat. Looking back, I am not 100% sure if he could even switch the BOV if he had one. And that scares me... __________________ "...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..." - Rebreather World PM
(Offline)

14th December 2006, 09:37	#18 (permalink)
Mike Prism 'prentice Current Rebreather/s: Prism Topaz Other Rebreather/s: Inspiration Classic Evolution Join Date: Feb 2005 Location: Melbourne Posts: 332	Re: Functioning with high CO2 Quote: (Originally Posted by dteubner) Didn't mean to make your head explode mate. Edit - some evidence apart from "I reckon this" Entrez PubMed Thanks Dave Appreciate that you followed up with a reference. I'll do some more reading I think - interesting to have something I've believed I understood demonstrated to be wrong. Have you considered the breathing limitation imposed by swimming though? Distance swimming, now that I've been educated , I'll believe does not involve a rise in CO2. Dynamic apnea or freediving clearly must, almost by definition. Sprinting, I'd still consider falls somewhere in between. Being somewhat oldschool, I consider that breathing slows you down. (Neil Brooks was once quoted as saying "30 seconds? I can hold my breath that long, why breath?) Even if we are to just consider dynamic apnea, why don't we see the same CO2 hit symptoms there? Or perhaps that's part of what a Samba is? But doing apnea stuff I get really recognisable symptoms like diaphram contractions before really needing to breath. If it only happened in dynamic apnea I'd be suggesting that it could be due to the other exercise related breathing triggers, but as it happens in static apnea as well, that doesn't seem likely. Perhaps I need to get someone to take some blood samples at the pool... Oh, and Mark Chase, do you have an idea why you think your no.2 happens, as I though that the body's reaction to high CO2 wasn't influenced by O2 levels? Mike - learning stuff today! __________________ Open ....... Closed Mind ........ Loop
(Offline)

14th December 2006, 10:16	#19 (permalink)
CharlieT Custom Title Allowed! Current Rebreather/s: Inspiration Vision Other Rebreather/s: Join Date: Nov 2005 Location: London Posts: 449	Re: Functioning with high CO2 Thank you Mike for starting this educational and very relevant post. This is the bad one for us CCR divers, worse than the possibility of an O2 hit. I have a great fear of overbreathing my scrubber so stop and rest if I have over-exerted myself. A BOV must, as several have said, be the quickest way of the loop in the instance of an impending CO2 hit. Might not save you in the worst instances, as Phi relates, but sound as good a counter-measure as is available. Mark, a rapid ascent from 20m sounds a bit scary! Finger pressed on O2 button, I hope? Mike, this post has helped me make the decision to buy a Golem BOV for my Vision. Charlie
(Offline)

14th December 2006, 10:38	#20 (permalink)
decoweenie Crash Test Dummy Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Cairo Posts: 5,487	Re: Functioning with high CO2 Quote: (Originally Posted by CharlieT) Might not save you in the worst instances, as Phi relates, but sound as good a counter-measure as is available. Yes, and also allowing a buddy-rescue a lot easier instead of having to attempt to replace DSV-to-reg on an unconscious diver. __________________ "...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..." - Rebreather World PM
(Offline)

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode