Max depth for CESA?

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A couple of decades ago, a UHMS workshop released the results of its study of training related incidents/fatalities. They determined that practicing emergency ascents like this was the number one cause of these fatalities.

Well, yeah, it is very labor intensive to teach effectively and dangerous as hell if you screw up!!! (for other readers rather than John) Free ascents also requires more watermanship skills than prerequisites demand today. It isn't an isolated skill like clearing a mask or attaching a regulator. It's just not compatible with training designed, timed, and priced for occasional warm water vacation divers. It is also a 20% instructor and an 80% self-teaching problem. Student motivation and self-reflection is critical.

It is actually much easier to teach buoyant submarine escapes because they are moving so fast and the ride is so short. We're basically talking about no-decompression dives from +/-300' on air. Personally, I have always suspected that part of the reason for the training is to show how important it is to prevent and manage crisis on the boat before facing an escape like this.
 
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I would like to add that some training may provide the wrong kind of familiarity... the namny kind of familarity that comes with being guided through every step. All things are announced so there are no actual surprises, no valve is actually turned off, etc...

Harassment dives are still part of US Navy training... talk about labor intensive and requiring a lot of student motivation! You can do a lot when you have 25 training days for a Scuba course like the USN.

Edit: Not to be confused with BUD/S training. Navy divers are not combat swimmers and they don't expect people trying to kill them... outside of bar fights anyway. :wink:
 
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Back in the bad old days martial arts training was apparently done full contact with real weapons. Enrollment paperwork included something to the effect of student's life being the teacher's to do with as he pleases -- to absolve everyone involved from legal responsibility in case stuff happened and the student didn't survive the lesson.

Nowadays I guess SEAL training would be as close as you can get.

Yeah, well, I get that "do or die" training works... but maybe by selection as much as by training...
The trick would be to do that or any form of training such that it is safe. Selection still can happen, not everything is for everyone, but it should happen safely and thus by choice - the instructors or the students, not by elimination due to injury or worse...
 
Yeah, well, I get that "do or die" training works... but maybe by selection as much as by training...
The trick would be to do that or any form of training such that it is safe...

IMHO, mutually exclusive forces are at work. "Selection" isn't in the recreational Scuba industry's self-interest, nor are:
  • Expensive, long, and demanding courses
  • Courses that emphasize the risks of diving as opposed to what some of us consider soft-peddling. Example: Never stop breathing versus the ugly, blunt, and physics-intensive long version. The object is not to scare customers away or into a competitor's shop.
  • High wash-out rates... which doesn't sell equipment, advanced courses, dive trips, or create that invaluable word-of-mouth sales force.
  • Investing time in skills that the majority of divers will never need or remember
  • Emphasizing self-rescue skills over risk avoidance
There's no clean migration path from casual recreational diver to hard-core diving zealot. Scubaboard probably attracts a higher percentage of hard-core types because it is a good place to intellectually explore diving, but isn't hostile to casual divers. The trick is finding a way to share information without giving just enough information to the self-preservation challenged among us to hurt themselves. [/SOAPBOX]
 
FWIW when I was certified in '76 we had to ditch our gear on the bottom except for mask and fins and make a free ascent from 30', then dive and recover our gear.
 
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Panic happens when you run out of ideas and don't know what to do next.

The two divers here were able to get to the share air part. What next? Fin to the surface rapidly or slowly? Who leads? Safety stop or not? What are the hand signals?

We can learn from this and I'm very glad that the OP posted this. It just goes to show that things can go wrong even if you're doing everything right and just don't know it.

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I asked my instructor years ago during AOW what to do if you had to CESA from say 80'. He said--you do (or I guess do a buoyant ascent and hope for the best). I regularly practise it from 20-30' since I almost always dive solo and almost always to those depths. I THINK 30' is about my personal limit, or at least close to it. A CESA is not holding your breath of course, but though your airway is open, it amounts to the same thing---not inhaling (though air in your lungs--and tank-- does expand SOME). I wouldn't want to have to do it deeper than that. But in those cases, I'm USUALLY with a buddy.
 
I asked my instructor years ago during AOW what to do if you had to CESA from say 80'. He said--you do (or I guess do a buoyant ascent and hope for the best). I regularly practise it from 20-30' since I almost always dive solo and almost always to those depths. I THINK 30' is about my personal limit, or at least close to it. A CESA is not holding your breath of course, but though your airway is open, it amounts to the same thing---not inhaling (though air in your lungs--and tank-- does expand SOME). I wouldn't want to have to do it deeper than that. But in those cases, I'm USUALLY with a buddy.
Air in tank does not expand...
 
A CESA is not holding your breath of course, but though your airway is open, it amounts to the same thing---not inhaling (though air in your lungs--and tank-- does expand SOME). I wouldn't want to have to do it deeper than that. But in those cases, I'm USUALLY with a buddy.

Air in tank does not expand...

Okay folks, time for an explanation.

The air in the lungs DOES expand. That is why you MUST exhale the entire way to the surface. If you do not, you can create a lung overexpansion injury. It is why you can do a CESA from depths most people would consider to be ridiculous. CESAs have been done successfully from 100s of feet. The math is simple. If your lungs are full at roughly 200 feet, the air in there will expand 7 times by the time you reach the surface.

The air in a tank DOES NOT expand. It is a rigid container that does not know it is under pressure. However, the reason you are supposedly out of air at depth is that the regulator can only deliver air to you at a pressure greater than the pressure you are under at the time you are attempting to breathe. If you cannot get a breath at one depth but ascend sufficiently, the regulator will be able to deliver air now that you are at a reduced ambient pressure.
 
Sorry guys, my fault on the tank air expansion. I know exactly what happens regarding the pressure/reg aspect, just misspoke. Getting sloppy in old age.

Well, to be ridiculous, I guess I could say I was thinking--- that because you have now ascended some, the reg is able to deliver you some air it couldn't before, so the tank air has now expanded into the reg....how's that for rationalisation of what I was thinking when I said that......
 
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