Emergency ascents

[Ice9]

I'm not certified yet, but this sounds like something I would practice.

Only at vshallow depths at first of course, but then increasingly deeper as confidence is gained.

Its right there in the acronym, the C part... Controlled, and how else one develope Control without practice eh? You Dont want your first CESA to be in a "have to" situation and I think one would gain a little psychological protection (panic reduction) by developing that Controlled part. I think maybe I'd shoot for goal of somewhere between 60-100'.

Does anyone practice these?

Once you go through the training, you'll understand why you probably don't want to practice CESA at any real depth. Personally, I hate to do it in training at 30 ft, but thats just me. If you find yourself in a situation that you have to do a CESA, you have probably screwed up in many different ways. Moral of the story: try not to screw up!

 

[Web Monkey]

It's a 70M download. Care to summarize it?

Terry

In case anyone is interested:

Samson RL, Miller JW (eds.) Emergency Ascent Training. 15th Undersea and Hyperbaric MedicalSociety Workshop. UHMS Publication Number 32WS(EAT)10-31-79. Bethesda: Undersea andHyperbaric Medical Society; 1977; 100 pages. RRR ID: 4260

 

[texdiveguy]

It's a 70M download. Care to summarize it?

Terry

Its from 1977 so you can probably find some 'Cliffs' notes....

 

[redacted]

I believe you can practice deep CESA without going deep. If you are comfortable with 30 ft, then start at 30 ft but slowstop at 5 to 15 feet for 30 or 40 seconds before you surface. That should be roughly equivelent to a 60 ft CESA - perhaps harder because you don't get the same air expansionin your lungs. Progress toward deeper starts and/or slower ascents using time rather than depth to practice.

 

[ReefHound]

Its right there in the acronym, the C part... Controlled, and how else one develope Control without practice eh?

And right afterwards is the E part... Emergency.

Decompression is not an exact science. We have tables and ascent rates that have shown to offer a reasonable level of safety most of the time, but people can exceed these limits and no get DCS and people can follow these limits and get DCS. So we try to be extra cautious, abide by slower than "allowed" ascent rates, and make "safety" stops. You are not doing this in a CESA.

I once saw an interesting article about Navy divers and questioning the training for sub escape using "blow and go". It pointed out the number of deaths and severe injuries from the training was greater than the number of mariners that had ever used this technique for real. In other words, the training was killing more people than it could ever save. I suspect if we had divers "practicing" 100' CESA's we would see the same result only far worse.

 

[TSandM]

To answer part of the original question: The two limiting factors on doing a CESA are maintaining enough arterial oxygenation to stay conscious, and tolerating the increasing CO2 which is occurring as a result of not being able to flush it out of the lungs.

If you have normal lung function (and divers probably do, or they couldn't do all the things they need to do to dive) your hemoglobin is about 99% saturated in room air. At depth, because of the higher ppO2 due to high ambient pressure, the hemoglobin will be saturated and there will be significant dissolved oxygen in plasma, too. On the surface, if we have preoxygenated someone with 100% O2, we have four to six minutes before their oxygen saturation even begins to fall. Obviously, nobody's doing a four minute CESA.

On the other hand, CO2 is our primary drive to breathe. Most people can tolerate about a minute of apnea (non-breathing) before they can't stifle the desire to inhale any longer. In an absolute emergency, my guess is that that time would be somewhat longer. At 60 fpm ascent rate, that's 60 feet or more of CESA that most people should be able to do. People with some CO2 tolerance (which has been documented in divers) can probably tolerate more time, and therefore more depth.

However, the discussion should be academic, because the number of things that have to go terribly wrong to end up doing a CESA from great depth is huge. You have to have lost your entire gas supply (and, if you're deep, you should have considered some degree of redundancy in that) AND your buddy/buddies, to be forced to CESA. That's a lot of mistakes, beginning with planning and finishing with execution, along with some extremely bad luck, to get into that situation.

 

[String]

If you're doing CESA then you've broken at least 3 or 4 cardinal rules of diving and therefore should not be diving in the first place. Its something strictly obsolete in the modern era.
Anyway that has to do one for real really should be forced to repeat basic training as obviously none of the lessons sunk in.

 

[MauiScubaSteve]

CESA used to be done from deeper depths, but similar to the sub escape training, there were more training injuries than real CESA attempts so shallower training depths evolved.

One of my classmates at instructor factory claimed his small third world island instructor required 60' CESA (PADI), in 1999. Just because some standards are max 30' does not mean all instructors are following said standards. Just like 100' max depth on AOW deep dive, some instructors will do it the old way they were taught.

Speaking of breaking cardinal rules, I have held my breath over 3 minutes at 9' deep from a breath off scuba, as did the 3 others in the pool with me. We were all experienced free divers and did the 4 breath hyper/saturation before holding. I give myself a better than 50/50 chance of bent survival from 130' (2 min 10 sec at 60'/sec), if I get a decent last breath. Remember to drop your weights before you pass out!

 

[Zieg]

If you're doing CESA then you've broken at least 3 or 4 cardinal rules of diving and therefore should not be diving in the first place. Its something strictly obsolete in the modern era.
Anyway that has to do one for real really should be forced to repeat basic training as obviously none of the lessons sunk in.

I guess I belong to a different church.

 

[waynel]

I keep reading about these Controlled Emergency (Swimming) Ascents. Some say the limit is about 30 feet and some say it's possible from about 60 feet. Seems to me that how much air you got on your last breath would determine the depth from which you would be able to make one. Personally, I would be looking for another diver with a spare regulator to commandeer rather than trying one at depth. I've practices a few with an instructor from 30 feet which worked out OK but haven't yet tried anything deeper. Comments?

Careful about your terminology. You try to "commandeer" one of my regs and you will drown. A diver grabbing at me can kill me as well...As others have suggested here, if you want to avoid ever being in that situation never dive without 4 available regs and two tanks. That's right, never do a deep dive alone. Notice I didn't say never dive alone. A 15 or 20 ft. reef dive? While the "book" says NO, unless you have a heart attack at that depth you could probably survive just about any emergency. You can still make a slow ascent from that depth with completely empty lungs and no gas.