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Mike · 13th December 2006, 23:01

How much of the problem with CO2 is driven by the primary effects of CO2 (imperative to breath), vs the secondary effects (Narcosis, increased sensitivity to O2)?

So far, I've decided that a OC BOV isn't worth the complexity it introduces - but I'm not 100% convinced.

So I try to play around with increasing CO2 in me, and seeing what sort of effect it has, and what effective capability I have. Last night I was in the pool, swimming laps, trying to recapture a bit of fitness. After a bit of distance I did a sprint set of 10 by 50m sprints, with minimal recovery time between sprints. At the end of this set, I normally have a pulse rate in the 200 to 220 range, and my breathing is, umm, rather rapid.

At this point I took a medium breath and submerged, looking at my watch and taking my pulse. Pulse averaged 180 over the 20 seconds I managed to hold my breath for, and I was able to adjust my goggle strap one handed at the same time.

Now - it's a pretty inexact measure, but I'm willing to bet that my CO2 levels were pretty high at that point - my breathing had been pretty shot on the last break, I had a stitch etc. But, while I had the reasurance of the surface being 50cm away and wasn't mentally stressed, I was still able to do a 20 second breath hold and function pretty normally. My reasoning is that 20 seconds is plenty of time for me to get a bailout reg in my mouth, even including turning the tank on or doing some basic untangling.

Afterwards, it took me a few minutes to recover afterwards, and my SAC would have been over 100 litres/minute for a couple of minutes - but I'd been well aware of rapid breathing for a good 5 minutes prior, and there is no way I wouldn't have noticed the condition I was in for the last couple of sprints way earlier and done something about it.

All this is giving me a (false?) sense of confidence about CO2 - that I will recognise it well before I get to the point where I'm not able to do anything about it.

However, I also know that this is not the experience of people who have had CO2 issues, so what's the difference?
Can we, through exercise, push our CO2 levels high enough to experience the sort of symptoms of a CO2 hit?
Is experiencing CO2 at the surface completely neglecting some other important variables such as narcosis?
Does a scrubber breakthorugh (for instance) evidence as an insiduous increase in CO2 until some tipping point is reached where we go from not noticing to incapacitated in a couple of seconds? (this is the one that I don't quite believe, and hence the basis for thinking I don't need an OC DSV)

Mike

13th December 2006, 23:01	#1 (permalink)
Mike Prism 'prentice Current Rebreather/s: Prism Topaz Other Rebreather/s: Inspiration Classic Evolution Join Date: Feb 2005 Location: Melbourne Posts: 325	Functioning with high CO2 How much of the problem with CO2 is driven by the primary effects of CO2 (imperative to breath), vs the secondary effects (Narcosis, increased sensitivity to O2)? So far, I've decided that a OC BOV isn't worth the complexity it introduces - but I'm not 100% convinced. So I try to play around with increasing CO2 in me, and seeing what sort of effect it has, and what effective capability I have. Last night I was in the pool, swimming laps, trying to recapture a bit of fitness. After a bit of distance I did a sprint set of 10 by 50m sprints, with minimal recovery time between sprints. At the end of this set, I normally have a pulse rate in the 200 to 220 range, and my breathing is, umm, rather rapid. At this point I took a medium breath and submerged, looking at my watch and taking my pulse. Pulse averaged 180 over the 20 seconds I managed to hold my breath for, and I was able to adjust my goggle strap one handed at the same time. Now - it's a pretty inexact measure, but I'm willing to bet that my CO2 levels were pretty high at that point - my breathing had been pretty shot on the last break, I had a stitch etc. But, while I had the reasurance of the surface being 50cm away and wasn't mentally stressed, I was still able to do a 20 second breath hold and function pretty normally. My reasoning is that 20 seconds is plenty of time for me to get a bailout reg in my mouth, even including turning the tank on or doing some basic untangling. Afterwards, it took me a few minutes to recover afterwards, and my SAC would have been over 100 litres/minute for a couple of minutes - but I'd been well aware of rapid breathing for a good 5 minutes prior, and there is no way I wouldn't have noticed the condition I was in for the last couple of sprints way earlier and done something about it. All this is giving me a (false?) sense of confidence about CO2 - that I will recognise it well before I get to the point where I'm not able to do anything about it. However, I also know that this is not the experience of people who have had CO2 issues, so what's the difference? Can we, through exercise, push our CO2 levels high enough to experience the sort of symptoms of a CO2 hit? Is experiencing CO2 at the surface completely neglecting some other important variables such as narcosis? Does a scrubber breakthorugh (for instance) evidence as an insiduous increase in CO2 until some tipping point is reached where we go from not noticing to incapacitated in a couple of seconds? (this is the one that I don't quite believe, and hence the basis for thinking I don't need an OC DSV) Mike __________________ Open ....... Closed Mind ........ Loop
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