C02 Retention / Decay times

Bobnob

womble

That makes sense.
So why do they teach dil flushes as the first-line-of-defence measure??

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diverreb

Not all do. My first reaction is to go to bail out. See if a few breaths clears the situation, then get back on the loop & flush. Monitor it from there. If it comes back, stay on bail out & turn the dive. If you feel fine, it's up to you... stay or go.

Richie

Simon Mitchell

Because many instructors fail to understand that not all CO2 problems arise from the loop (ie scrubber failure).

Having said that, dil flushes may facilitate staying on the loop in the face of CO2 tranisently breaking through the scrubber, eg during heavy over-exertion. In this setting, dil flushing and rest may fix the problem. But if you've got the cause wrong it probably won't.

The only intervention for CO2 toxicity that is never wrong (provided you have the gas and your regs are performing well) is bailing out onto open circuit. As Mike has implied earlier, you can sort the problem out from there, with a cautious return to the loop being indicated in some circumstances.

Warm regards,

Simon M

Mark Chase

I do both


However, i note some of the flapper valve checks i used to do on the Classic i can no longer do on the KISS with cooper hoses.

ATB

Mark

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tibby

I can see how a simple dil flush won't address the retained CO2 issue but I was taught to do a dil flush/open loop which is simply using your CLs and ADV as a second stage while exhaling offboard. If you press a meg ADV it seems to be very efficient in delivering ample fresh gas volume to ventilate your lungs providing you are not rebreathing it. Then, bail out. The only problem I see with this is that if this skill is not second nature it may take more physical effort (to keep CLs from over inflating, becoming buoyant) thus adding to the CO2 production. Of course, I'd rather switch a knob on a BOV if I had one but that expense will come after cave training. Gotta' mind priorities.
I have seen what a retained CO2 hit does and I'm not sure I would have enough judgment left to safely bail out on a reg if the hit is serious.
Really apreciate this discussion.
Tibby

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Does the voice of reason change when you add helium to the mix?...hmm

Drmike

there are of course different degrees of 'hits' Personally I think one of the most important things we can do as Rebreather divers is develop a very sensitive nose when it comes to recognising very early signs of being on the CO2 spiral. Doing that should go some way to ensure we never allow ourselves to get to the stage where we are completely debilitated. Like being bent our worst enemy is often denial (I am not having CO2 hit!)

But I fully agree prevention is better than cure.

But I suspect for deep divers retained CO2 is a far greater risk and something that cant be prevented pre dive (other than by being fit, deciding to use a scooter) For retained CO2 I believe we need to employ some of the techniques being discussed here (such as learning to id signs of increasing CO2 and best recovery techniques) to avoid and manage

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Drmike

If you are having a CO2 hit with elevated breathing rates the last thing you want/can do is anything that may increase your WOB or require you to pause breathing (even for a second)

I think its important when looking at CO2 recovery techniques to bare that in mind.

This is why its vital your BOV (or OC bail 2d stage) breathes well at depth. if it doesnt you can easily accelerate your trip up the CO2 spiral!

If you get to the point where you feel you cant recover from the spiraling CO2 induced breathing rate, even though you have bailed, because increasingly you cant get enough gas in your lungs - I suspect at that stage your only hope of survival maybe to purge your 2nd stage whilst breathing form it, youll waste gas but your likley going to die at that stage anyway if you dont.

as mentioned earlier - prevention is better than cure, develop a nose for inceasing RMV/CO2 issues, be always on the look out for them and manage them before they get to a degree where they are hard/impossible to manage.

Personally I dont believe you can realy do much to help anyone recover from a retained co2 hit. They will either be before that part of the spiral which will mean they are still able to self recover or they will be beyond that point which means they will likely panic (because they feel they cant breathe and the CO2 induced panic feelings) and take you with them!



poo - not fun stuff to discuss

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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

tibby

It really is a bummer and didn't mean it was fun, just very useful knowledge.
Thanks for the reply. It sure puts things in perspective.
Tibby

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Does the voice of reason change when you add helium to the mix?...hmm

doug allen

Let's see....a $35 scrubber....or your life.....hummmmm......I'm thinking I'll go for a new scrubber.

It is great to know that the scrubber will last longer than 3 hours......but dang.......when it is used up...it is gone...lights out....spend a few bucks and save your life.

JMHO