Definitely got much, MUCH worse (I don't want to admit how much exactly
).
I need to make a conscious effort to limit the SAC when say training BO or things get silly.
However - I am happy about it and I make sure my reflexes are "SAC high" on CCR.
From speaking to divers and instructors ten times more knowledgeable than I will even be - they think a lot of unexplained fatal accidents where very experienced divers, in perfect conditions and without any apparent reason just "freaked out" - were caused by CO2 induced "dark narc".
To the best of my knowledge CO2 retainer induced dark narc hasn't been researched much, but two things verifiably help with reducing CO2 risks - mix density and... breathing pattern.
When kept within reason of course - breathing deep and a lot is simply safer (and more relaxed, no feeling of restriction).
You can put pure heliox in your dil but it won't help you much if you breathe too slow and/or shallow to remove all CO2 in time.
There's another aspect of it - where sofno starts losing efficiency due to loss of temperature in very cold waters if hot gas and CO2 is not delivered to it fast enough. Again more pondering than being able to point to research papers.
From personal experience I can recall a very weird dive which we had just after certification. Water temp was 6-8C, outside temp -2C (after a walk to the water the scrubber was probably quite cold even with prebreathe), we were chilling shallow around 15m hanging by a wall and relaxing.
First and last time in my life I suddenly had a hard to explain bout of stress and feeling of danger, without any reason at all.
It's hard to explain, not full "out of control" panic, but really, really bad "knot in the stomach, hair raising on the neck" dread.
I also clearly recall the feeling of "needing to get out of here".
I managed to control myself and it passed. In retrospective my best guess (after just being crazy
) is that when relaxing I started breathing around 12-14 SAC and maybe shallow as it was true bliss to finally relax on CCR, which cooled the sofno past the efficiency limit, didn't vent the lungs enough and caused blood CO2 buildup.
From other situations I know I'm a retainer sadly.
Stress panting removed it when dread hit me and allowed me to control the situation.
Luckily there was no deco, but if it continued at big deph/deco I dread what could have happened if it started building up more and more.
Apologies for a long rambling, but I thought that other responses while completely valid missed the point that on CCR the OC obsession with lowering the SAC is not only pointless, but may kill you.
Breathe away compadres!
