What is the deepest you can do an OOA?

[H2Andy]

If you are breathing out, you are removing CO2 from your system. As long as you are breathing out, the CO2 level continues to reduce ...

i'll take it on faith... seems counter-intuitive ... i would guess that if you are deep enough, you will reach a point that your body has so much CO2 that you can't avoid taking a breath in simply by slowly exhaling

 

[Blackwood]

I can easily hold my breath for about 1 min, maybe 2 if my life depended on it, and even if I blacked out, maybe I could still get a minute or two in of unconscious ascent with an inflated BC.

I betcha you'd breathe in once you lost consciousness.

 

[cerich]

i don't think this is correct

the urge to breathe in depends on the amount of CO2 in your system, not how full your lungs are or not

actually Andy as you go up you are very consious of the feeling of having no more air to breath out, then just as it starts to get really noticeable the feeling goes away and you find you have plenty of air to breath out.
Breath out nopw untill you feel it in your lungs, it'll only take you a few seconds, now rest a few mins and just hold your breath, the need to breath comes much later the second way. The first way you didn't build up much CO2 but you did run out of air to breath out.

 

[cerich]

i'll take it on faith... seems counter-intuitive ... i would guess that if you are deep enough, you will reach a point that your body has so much CO2 that you can't avoid taking a breath in simply by slowly exhaling

don't forget that just like the PPO2 is dropping as you assend so is the PPCO2

 

[H2Andy]

what i am saying is that it seems to be that if you start out too deep or with not enough air in your lungs, there will come a time as you ascend that the buildup of CO2 can not be overcome by breathing out slowly

don't forget that just like the PPO2 is dropping as you assend so is the PPCO2

ah!

that makes sense

 

[Blackwood]

i'll take it on faith... seems counter-intuitive

I agree.



Let's say you dump everything. That is: you breathe out hard enough to exhale even your ERV. In theory, that's all she wrote. All the CO2 you can possibly dump by a single exhale (i.e. not an inhale-exhale cycle) is gone.

Can you now refrain from breathing indefinitely (i.e. until you pass out)? Or do you still have the urge to inhale? I'd bet dollars to donuts you still have enough CO2 pulling your trigger to make you want to breathe. Same goes with a long exhale facilitated by the expansion of residual air in your lungs, or so it would seem to me.

??

 

[cerich]

I agree.



Let's say you dump everything. That is: you breathe out hard enough to exhale even your ERV. In theory, that's all she wrote. All the CO2 you can possibly dump by a single exhale (i.e. not an inhale-exhale cycle) is gone.

Can you now refrain from breathing indefinitely (i.e. until you pass out)? Or do you still have the urge to inhale? I'd bet dollars to donuts you still have enough CO2 pulling your trigger to make you want to breathe. Same goes with a long exhale facilitated by the expansion of residual air in your lungs, or so it would seem to me.

??

The ONLY way you will dump everything (air) is if you replace it with water, otherwise you have air in your lungs that expands as you assend.

Folks, I've DONE this MANY times, I find it easy and even guys that hate doing it and indeed are afraid of it manage quite well.

 

[Blackwood]

The ONLY way you will dump everything (air) is if you replace it with water, otherwise you have air in your lungs that expands as you assend.

So a complete exhale is impossible?

 

[cerich]

So a complete exhale is impossible?

can you breath out enough to create a vacuum and collapse your lungs?

Otherwise a complete exhale of all the air in your lungs is impossible.

 

[fweber]

I have to agree with everyone that has stated, it would be best to plan your dives in a manner that would prevent ever needing a CESA. That said, I can see some value in the OP's question. How many people have ever practiced an CESA other than the once during class? The level of misunderstanding and misinformation suggest not many. Having an improved level of knowledge in this regard could prevent someones situation from turning into panic and subsequently costing their life.

The breath reflex as I understand it, is triggered by PP CO2, not lack of O2. There is still plenty of O2 in your lungs when your brain is screaming at you to breath. The exception to this would be free divers who train themselves to breathhold. As you ascend the decreasing pressure results in expansion of the gas in your lungs. Allowing and demanding that you exhale continually as you ascend and allowing a reasonable ascent rate with minimal increase in the urge to breath. Most of the tables are based on safe ascent rates of 60 ft/min. Slower is certainly better from a safety standpoint, but 60 ft/min is certainly unlikely to get you bent if you're still within NDL. Higher ascent rates are definately possible, without getting bent, in an emergency. And as others have said, better bent than drowned.

Personal experience is that 60 fsw is certainly doable by someone who is not extremely fit nor a waterman of the first order. It wasn't what I woulf refer to as comfortable, but also wasn't reason to panic. I imagine I could do one from considerably deeper, but don't really want to. Similarly, I've witnessed ascents by freedivers that have borrowed breaths from as deep as 120'(incredibly unsafe, don't try this at home, etc,etc,) They certainly weren't overly stressed.

So,... plan your dives so you never have to perform a CESA. But, by all means go practice once or twice in a controled environment, from some depth greater than 10'. It might prevent the panic that could kill.