Rebreather World - View Single Post - What setpoint for 100m+ diving do you use?

Drmike · 13th February 2008, 04:40

Quote: (Originally Posted by mattmexico)

yo

On the described 120 meter - 400 foot dive I did not do air breaks but have done so before and after. Feeling is you can do very high CNS exposure well over 100 % and be safe if you do air - low po2 breaks.

Matt

Hey Matt,

Yes air breaks lower risk of toxing and help maintain lung off gassing ability.

Personally I suspect the way we look at CNS is wrong. I wonder if it is really as cumulative as its presented.

I believe its the instantaneous ppo2 and the situation at that time that is far more critical. I can imagine a circumstance where someone with a CNS of 50% toxes because they are swimming hard with high ppHe and high setpoint, where as someone with a CNS of 200% sat on deco doing nothing with same setpoint is safer.

My point is I don't really worry about the CNS (as its traditionally measured) I concern myself with what my ppo2 is at a given time and given circumstance. There may well be a cumulative effect - but I suspect this is masked by the fact we are usually well into restful deco by the time the CNS creeps that high.

I don't like doing final stop on 1.6 as I find I feel like I'm suffocating after a while - air breaks temp relieve this feeling for me. But if i deco out on 1.4+ I feel no sense of choking up and as Im on on a lower setpoint I suspect the lungs are less effected, risk of toxing is reduced (exponentially for small changes in ppoo2)

for the deep dives im doing, often the advantage of decoing out on 1.6 over 1.45 is negliable to non existant

(Personally on a big dive Id rather to an extra 45mins of deco with setpoint 1.45 than deco out on 1.6 faster)

13th February 2008, 04:40	#29 (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: 3,323	Re: What setpoint for 100m+ diving do you use? Quote: (Originally Posted by mattmexico) yo On the described 120 meter - 400 foot dive I did not do air breaks but have done so before and after. Feeling is you can do very high CNS exposure well over 100 % and be safe if you do air - low po2 breaks. Matt Hey Matt, Yes air breaks lower risk of toxing and help maintain lung off gassing ability. Personally I suspect the way we look at CNS is wrong. I wonder if it is really as cumulative as its presented. I believe its the instantaneous ppo2 and the situation at that time that is far more critical. I can imagine a circumstance where someone with a CNS of 50% toxes because they are swimming hard with high ppHe and high setpoint, where as someone with a CNS of 200% sat on deco doing nothing with same setpoint is safer. My point is I don't really worry about the CNS (as its traditionally measured) I concern myself with what my ppo2 is at a given time and given circumstance. There may well be a cumulative effect - but I suspect this is masked by the fact we are usually well into restful deco by the time the CNS creeps that high. I don't like doing final stop on 1.6 as I find I feel like I'm suffocating after a while - air breaks temp relieve this feeling for me. But if i deco out on 1.4+ I feel no sense of choking up and as Im on on a lower setpoint I suspect the lungs are less effected, risk of toxing is reduced (exponentially for small changes in ppoo2) for the deep dives im doing, often the advantage of decoing out on 1.6 over 1.45 is negliable to non existant (Personally on a big dive Id rather to an extra 45mins of deco with setpoint 1.45 than deco out on 1.6 faster) __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment Last edited by Drmike : 13th February 2008 at 04:45.
(Offline)