Max depth for CESA?

[Mr Carcharodon]

It seems the people who have done CESA from below 100 fsw have had some training. They were told it is possible. Or they have simply been told there is no limit. it is surely the case that CESAs have been done from well below 100 fsw before. We know that thousands of people (Sam Miller speak up here) have done it from 100 fsw sucessfully. Could most people CESA from 40 msw or 131 fsw maybe yes. That said fast ascents make me feel really bad and the bubble models suggest why, even for repeated acents from shallow depths. Violating the decompresion guidelines may be bad, and yet drowning is surely worse.

 

[TMHeimer]

You're supposed to CESA at a safe speed--theoretically no faster that 60/30' per minute depending on the agency. When I did it taking the OW course, the instructor said that I was really fast. Looking way back to that, I know that wasn't good. Going up a lot faster than the recommended speed really amounts somewhat to a buoyant ascent, except you didn't drop your weights.
Going up at the recommended speed means you are not getting any 02 intake. I'm sorry I compared that to breath holding and hope no one ever does that. It IS the number one rule in the OW course. I assume, perhaps wrongly, that everyone here knows that.
I can do a CESA fine from 30' and practice it now & again. But when I near the surface, it feels like I really don't want to try this from deeper, as I am very ready to take a breath. That's why I compared it to breath holding. Either way, there's no new O2 intake whether your lungs are expanding or not, airway open or not. Now, there may be some benefit from expanding air in the lungs replacing the air that you are expelling with the open airway. If so, perhaps someone in the know can explain. Is it possible that all of the expanding air in the lungs doesn't get exhaled when you are ascending, and that some of it goes the other way through the system and into tissues? My physiology knowledge is limited to the DM course.
When I finish my CESA from 30' at the recommended speed I FEEL like I've been holding my breath. I am sure that if I exceeded the recommended speed I could easily do it from quite a bit deeper.
When I practice CESA I start with only half full lungs, as opposed to the way it is taught with full lungs (I had one instructor that told students to take a few deep breaths before starting--in effect hyperventilating, a term no longer used by PADI). I figure that if I have enough air in the tank to get enough air to fill my lungs then I probably have enough to begin my ascent as a "normal" ascent rather than a CESA. Perhaps starting with half full lungs is why I'm ready for a good breath upon reaching the surface.

 

[charlier]

I hope some of the people reading this realize that when you do a CESA from depth, you should not hold your breath. You should exhale all the way up. Once you start exhaling, the air will come out pretty well for the rest of the way--it is not like doing it horizontally in the pool without the benefit (or threat) of expanding air. Please, please, please everyone! If you ever have to do a CESA from deep, do NOT hold your breath! You do not have to be a champion freediver to exhale all the way to the surface because of the fact that the air in your lungs is expanding rapidly as you ascend.

I have yet to read the complete thread - but everyone should remember that free divers "breathe up" at the surface before their decent. Since lung volume changes during depth and on ascent, a surface breath hold from free diving is unlikely to result in AGE. As a free diver, I something think about a scuba CESA from 30 or 40 m. John is 100% correct that air in your lungs are expanding rapidly from your last breath at depth, say at 30m. As a free diver, I do not exhale while ascending and after much training this ingrained to my muscle memory. With scuba, these techniques are not appropriate and are dangerous.

 

[Sam Miller III]

I have found a new diving friend, Mr Carcharodon,

Going gradually deeper is extending the range.
Speaking from the perspective

LA County training ADP did CESAs from 30-40 fsw and UICC did CESAs from 100 fsw.

Years ago the classes were 100 plus people, certainly 1000 plus people over the years, with no adverse affects that I know of. But no one was expected to do a CESA from 100 fsw on day one, or under stress. In a sense this is like doing a S drill air share. We used to do those at the end of dives until it became routine. When the actions to resolve an emergency become routine it is not an emergency any more.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Some may recall post #5 to this thread

1) George Bond USN made a free ascent from 300+ feet
2) Dick Bonin, founder of SCUBA Pro, while in USN testing regulator performance with/for Doug Fane made a free ascent from 200+ feet under the ice cap
3) LA County UW instructions association UICC (the first and most difficult civilian training program) required a free ascent from 33 feet followed by free ascent from 100 feet.
The LA County basic program required a free ascent from 30 feet
4) I have made a free ascent from "considerable depths "

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
to expand a bit
1) George Bond was a USN Doctor and father of the US "Man in the sea program." He was affectionately know as Poppa topside during the programs short life. There is a book of the same name probably available on Amazon

2) Dick Bonin was a USN officer during the Korean war. Spent a lot of time testing SCUBA equipment, specifically regulators for *Doug Fane prior to the USN adapting SCUA in October 1954. As I recall a Northhill regulator was the one that froze while he was at 200 feet-- he chose to make a free assent.
After Korea Dick worked for Divemaster in his naïve Chicago and is credited with designing and marketing via Divemaster the worlds first dive log .
In 1963 he was the cofounder of SCUBA Pro
* Dough wrote a book The Naked Warriors which was made into a Hollywood movie. Zale Parry was his daughter -( I have an inscribed copy of Dough's book)

3) LA Co Underwater instructors program UICC was and is the most difficult and demanding civilian program in the world. It was based on demonstrable performance and knowledge not money and time in grade.

To be accepted in to the program was an honor to graduate was a huge honor. Many applied, a few were accepted and a precious a few were certified.

All were water men and women with years of water experience

During UICC many assents were made; one test was a D&R (D&D) from 33 feet. Remove tank & regulator, surface breathe up, dive down and replace (Oh the horror of it all !)

At one of the 2 day Catalina weekends or on a boat trip a 100 foot free assent. No problems - the students were all long term watermen and it was just a minor requirement of the intensive 3 months long program

The LA Co Advanced Diving Program was also 3 months of intensive training - every Thursday night a 3 hour lecture by an expert in diving, Saturday 2 training dives, every third week end it was Saturday and Sunday training dives -- and yes a 33 feet free assent was part of the training

In both programs the participants were required to maintain an LA County UW instructors dive log, developed by Tom Ebro and the second dive log in the world .

All this occurred prior to the creation of the rest of the organizational alphabet

And that is the way it is..

Sam Miller, 111

 

[Akimbo]

IMHO, doing one CESA or free ascent during Scuba 101 is of marginal value in terms of instilling confidence, which makes panic less likely. Free ascents need to be reflexive and that requires habituation. The reflexive component automatically extends to all high-stress situations that could result in an embolism.

... Violating the decompresion guidelines may be bad, and yet drowning is surely worse.

Part of my personal habituation journey includes instilling this decision tree so I don't waste critical time with mental debates:

Avoid drowning, embolism, and getting bent... in that order.​

 

[wheeledgoat]

Yeah.... well.... I'm only speaking for myself but I LONG ago stopped believing a single thing Brett Gilliam said or wrote.... In terms of personality he comes across to me like the Donald Trump of scuba diving.

So glad to see other skeptisism of that tale. Just doesn't smell right to me. Why is it relevant that it was Rod's left leg the shark swallowed? Details like that are abound, and are meant to personalize the experience for the reader to increase the shock value.

"I could see Robbie about 100 feet above us looking on in horror" - absolutely amazing that he can discern Robbie's facial expressions and emotions from 100' away, esp given his circumstance.

The whole story has a proper narrative story arc, 1st, 2nd, and 3rd act, complete with tension and relief points ("hopes soared upon realizing that he was still alive...") and way, way too many adjectives like "grimly fought" and "mutilated torso".

If I were charged with making that story MORE exciting and scary, I'm not sure I could; not a single opportunity was missed to insert an emotionally charging or shocking adjective or description. No doubt it is powerfully written, but if it were a true accounting, it would seem to me the survivor/writer wouldn't feel the need to use such embelishments.

 

[dmaziuk]

Is space an extreme pressure or just one atmosphere less than we have at sea level?

Professor Farnsworth: Good Lord! That's over 5000 atmospheres of pressure!

Fry: How many atmospheres can the ship withstand?

Professor Farnsworth: Well, it was built for space travel, so anywhere between zero and one.

 

[RayfromTX]

A brilliant deduction my dear Watson.

 

[TMHeimer]

IMHO, doing one CESA or free ascent during Scuba 101 is of marginal value in terms of instilling confidence, which makes panic less likely. Free ascents need to be reflexive and that requires habituation. The reflexive component automatically extends to all high-stress situations that could result in an embolism.



Part of my personal habituation journey includes instilling this decision tree so I don't waste critical time with mental debates:

Avoid drowning, embolism, and getting bent... in that order.​

Agree completely, that's why I do practice it from my usual 30' dives. If you dive deeper regularly it makes sense to practice from those depths--perhaps gradually deeper each time is a good idea. I was shown how to administer 02 in Rescue & DM. If I didn't review the steps I wrote down then, I would be useless as I don't own an O2 bottle.

 

[dmaziuk]

A brilliant deduction my dear Watson.

Sadly, my google-fu failed me this time.
I meant to post this: Bad google, no cookie.