Deep CESA

[immersed]

I did a search on this but I confess that I didn't make it through examining all of the threads, mostly because it was always just mentioned in passing.

When I learned about CESA in OW I was familiar with Boyle's Law from high school Physics and it all made sense, but I still found myself amazed when I actually did one in the ocean - literally my first thought when I broke the surface was "wow that college boy junk actually worked!"

I've been curious ever since, though (and this is purely academic because my buddy and I keep close enough for it to not become first choice), how deep it would work. It would seem reasonable that there must be a point that while Boyle is still trying to help, the lungs would have extracted all of the oxygen that they could.

Speculations, first-hand knowledge?

 

[jagfish]

If I understand your question, "From how deep can someone do a CESA", I would think this would be limited by the amount of time someone could hold their breath, since they only have access to the air from a single breath.

I urge caution with this kind of experimentation, though, expecially if you are trying for deeper depths. It's fraught with all kinds of unpleasant possibilities, even with the presence of a buddy: shallow water blackout and DCI hit from sudden and rapid surfacing....

 

[jbd]

If memory serves, there have been a couple of posts that indicate that some people have done CESA from around 90 feet.

Regarding the O2 extraction, it might be that there is enough O2 in the blood due to the higher partial pressure at depth. At 99 feet you are breathing close to 80% O2. Could this create an excess of O2 in the bloodstream that would be available for metabolic activity? There have been something posted about this in the past.

Even from the the 90 to 100 foot range you would only need to be without the ability to breathe for around a minute or slightly more.

 

[Don Burke]

I've been curious ever since, though (and this is purely academic because my buddy and I keep close enough for it to not become first choice), how deep it would work. It would seem reasonable that there must be a point that while Boyle is still trying to help, the lungs would have extracted all of the oxygen that they could.

Speculations, first-hand knowledge?

People have died trying it from very shallow. People have survived it from below two hundred feet.

My speculation is that you are in mostly uncharted territory beyond about sixty feet.

 

[TwoBitTxn]

People have died trying it from very shallow. People have survived it from below two hundred feet.

What was the cause of death? My bet would be AGE.

TwoBit

 

[TwoBitTxn]

At the surface the air we exhale is about 19% O2. Most people can hold their breath 60-90 seconds without too much difficulty.

That being said, an ascent from 60 feet should take about 60 seconds and an ascent from 90 feet 90 seconds. Assuming keeping the throat open for gas escape, a 60fpm ascent should not encounter DCS issues in a diver who has not exceeded NDL's.

Shallow water blackout should not be an issue because you are only without air for generally no more than 90 seconds and the exertion is minimal.

The point will be to relax, don't panic, and realize that on the way up you will probably be able to get another breath from your cylinder.

TwoBit

 

[SwimJim]

I have personally done one from sixty feet. I would not want to repeat that adventure. I will also add that that was almost thirty years ago. I was using a single hose reg and a J valve(which had snagged and tripped) and no pressure guage. I added a pressure guage shortly after that dive I remember.

Jim

 

[Dragon2115]

It's used to be done from 100 fsw in submarine escape training with no ill effect. It should be noted though that the subject wasn't at that pressure long enough to build up nitrogen in their body. However, as was previously said, as long as the NDL for that depth hasn't been exceeded so that there is no deco obligation, there shouldn't be a problem if done properly.

 

[NauticalbutNice]

TBH if I am out of air at 90 feet/28ishm my first concern is not DCI. You drown faster than you get a bend.

While I would be concerned with ascending in a controlled manner (not a bolt for the surface) if my option is drowning or DCI in any form I choose the latter.

Nauticalbutnice :fruit:

warning the above contains sleep deprived personal opinon.

 

[Don Burke]

What was the cause of death? My bet would be AGE.

That or lung expansion injuries is what I have heard. I have never heard of anyone having a problem with shallow water blackout on a CESA.

As has been said here, there are chambers to fix bent. Omitted deco procedures are also an option.

There are no chambers that can fix drowned.