How deep can you do a CESA and survive?

[Footslogger]

That is amazing.

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All I can say is that my lungs were in great shape back then and I was lucky. Been a long time but I broke the surface like a Trident sub at flank speed and then pulled the arming lever on my CO2 cartridge that inflated my horse collar. Sure glad the collar inflated cause I was way too tired to tread water at that point.

It was a dumb mistake that forced me into that situation in the first place but at least I lived to learn from it.

 

[jbd]

Practicing the CESA is a very bad idea, much like practicing cutting your main chute and opening the reserve. You can kill yourself while youre practicing. You may exceed a safe ascent rate, not control your airway properly, or drown. I also disagree that students should be taught to actively open their airway while ascending. This is basic psychology. We want a student to easily recall a muscle memory during a panic situation. Making an ahh sound is much easier to remember than controling your airway.

The lesson you should come away with in regards to the CESA is that you should never have to do it. If you do, you have already screwed up royally by diving solo, losing your buddy, or not monitoring your air. Your first response in an out of air emergency should be to notify your buddy and try a normal breathing ascent. If that is not possible, share air and ascend.

I disagree almost completely with this post.:shakehead
Making an ahhing sound is the wrong thing to do. By its very nature you are restricting the flow of air from the lungs. Charlie99 has it right and has given a very good description of what should be happening.

The whole ahhing thing comes from trying to teach CESA while moving horizontally through the water, which does not address the situation at all. CESA is moving vertically in the water column with a resulting decrease in ambient pressure which makes it necessary to allow air to flow freely from the lungs. Moving horizontally through the water does not result in changes to ambient pressure, therefore one must force the air out of the lungs by exhaling to prove to an instructor that the airway is open. The rational behind this is incorrect.

 

[cudachaser]

Oh wow...didn't think of the horizontal thing

 

[Charlie99]

Going aaaaaahhhh guarantees that you have an open airway. The extra air that you needlessly expel doing this limits the effective depth of a CESA.

Clearly there are advantages of teaching the "aaaaaaaahhhhhh". The instructor can easily verify that the airway is open both by sound and by seeing bubbles. It is also an easy to teach, relatively foolproof method of keeping the airway open. For an initial cert class, these are reasonable tradeoffs compared to the downside -- the shallower depth from which a CESA can be performed.

Practicing a CESA obviously has dangers involved, and one has to balance the risks and benefits. In my case, since I often solo in the 40' range (and occasionally deeper) without rendundant air source, I had a significant incentive to really understand and optimize my performance of a CESA.

When I did the CESA in 2002 everyone kept telling me that I was crazy and that I had to keep exhaling. I looked at the biophysics and disagreed. I had enough faith in my "open airway is sufficient" theory that I was willing to test it out. My CESA was done at the very beginning of a dive dive, in warm clear waters of Cozumel, with the DM knowing my intentions. It was an immediate descent and immediate ascent, with my reg out of my mouth from 90' up to about 30' just to keep from cheating. I figured that my N2 loading was negligible -- not much more than a typical freediver. I also minimized the DCS risk by halting the ascent at 15' and staying there. The only real risk was lung barotrauma / embolism.
Once was enough. I haven't repeated the drill.

 

[jviehe]

I disagree almost completely with this post.:shakehead
Making an ahhing sound is the wrong thing to do. By its very nature you are restricting the flow of air from the lungs. Charlie99 has it right and has given a very good description of what should be happening.

The whole ahhing thing comes from trying to teach CESA while moving horizontally through the water, which does not address the situation at all. CESA is moving vertically in the water column with a resulting decrease in ambient pressure which makes it necessary to allow air to flow freely from the lungs. Moving horizontally through the water does not result in changes to ambient pressure, therefore one must force the air out of the lungs by exhaling to prove to an instructor that the airway is open. The rational behind this is incorrect.

Well just have to disagree. I prefer my students practice how they would do it, and that means making the ahhh sound to remind them to keep an open airway. Again, its pyschology. In a emergency you should stop, think, and then act. Thinking about the best way to conserve air on the way to the surface does not help. Anyone can go from 30 to the surface while saying ahhh. I dont see where making a noise has anything to do with horizonatal. The only reason we do horizontal as all is becuase the pool isnt 30ft deep. I have to err on the side of professional education system designers here.

And regardless, as I said, you should never have to do a CESA. How you expel air on the way is negligible to your safety as long as you have an open airway. Do it as your taught, and avoid having to do it in the first place. Keep it simple.

 

[victor]

The chamber is pressurized with air in about 30 seconds - never mind the ears, this is life or death time. As the chamber pressurises, narcosos will make you pass out.

Ouch!!!!!! If the narcosis does not make you pass out the squeeze would.
I don't fancy being the poor sailor who get to test this system from that depth.