CESA Training

[TMHeimer]

1) You do need to exhale. Try holding your breath and you will see.
3) I know the theory. However, how long can you exhale without the urge to inhale if you start your ascent right after a full exhale?
Try that, you will see.

You don't need to exhale, as dmaziuk says. You keep the epiglottis open (the thing that opens & closes the airway from mouth to lungs-- physiology experts can explain it better). Same idea as you don't have to exhale through your nose when maskless-- you also can close that off internally (with the soft pallet, I believe), so water only goes in as far as the back of your nostrils area, but not down to your lungs. Some advise students to exhale a bit to prevent water from going into the nostrils, but that won't hurt you and exhaling is not needed. This situation is probably why some students have trouble with the "no mask" skills. It's all about airway control.
Now, I believe someone once told me that there are a tiny % of people out there who really have physical (not mental) problems opening and closing those airway "doors". Don't know if that's true, but makes sense as there is usually an exception to the rule.

As he said, instructors require you to exhale saying "ahhhhh" during the CESA so they KNOW your airway is open (and you're not holding your breath by closing it). So no lung injuries for students. I do exhale when practicing CESA (but no "ahhhh"), because I know I can make it from 30 feet. As well, I then don't have think at all about making sure my airway is in fact open. You wouldn't want to inadvertently close it off on the way up, say, if you get distracted.

 

[johndiver999]

As a practical matter, if a diver has to perform a “real CESA” then I don’t think it would make sense to initially exhale. If the diver is in a neutral condition, (immediately before the event) then exhaling is going to make them heavy. Why would a diver not want to, at a minimum, preserve the neutral advantage when they begin swimming? Dumping all the air from your lungs at depth can make the diver 4-5 lbs heavier.

Who wants to swim up 5 lbs extra in a life or death emergency? Chances are, they have some air in a BC and that will undergo expansion (as will any exposure suit), but perhaps these factors may not be at play in certain circumstances. So utilizing the buoyancy of lung volume seems to make sense, especially at the start.

I think it makes sense to BEGIN to exhale very slowly at depth. This keeps the airway open and should allow the diver to remain neutral and reduce the strenuousness of the ascent (which could be critical). Also, the rate of gas expansion is relatively slow at depth, so there is no need to exhale fast. Once you are on your way up and have made it to 20 feet or so, it is probably a good idea to really begin to exhale more fully/faster.

If there is still some air in the tank, then you might be exhaling 1/2 of the lung volume and then try to do a gentle and slow inhalation which would be somewhat consistent with natural, non-emergency breathing.

 

[John C. Ratliff]

I just ran across this description of a CESA from our Vintage Scuba website.
Well, for some reason I cannot paste it here. I'll try again later.

 

[TMHeimer]

As a practical matter, if a diver has to perform a “real CESA” then I don’t think it would make sense to initially exhale. If the diver is in a neutral condition, (immediately before the event) then exhaling is going to make them heavy. Why would a diver not want to, at a minimum, preserve the neutral advantage when they begin swimming? Dumping all the air from your lungs at depth can make the diver 4-5 lbs heavier.

Who wants to swim up 5 lbs extra in a life or death emergency? Chances are, they have some air in a BC and that will undergo expansion (as will any exposure suit), but perhaps these factors may not be at play in certain circumstances. So utilizing the buoyancy of lung volume seems to make sense, especially at the start.

I think it makes sense to BEGIN to exhale very slowly at depth. This keeps the airway open and should allow the diver to remain neutral and reduce the strenuousness of the ascent (which could be critical). Also, the rate of gas expansion is relatively slow at depth, so there is no need to exhale fast. Once you are on your way up and have made it to 20 feet or so, it is probably a good idea to really begin to exhale more fully/faster.

If there is still some air in the tank, then you might be exhaling 1/2 of the lung volume and then try to do a gentle and slow inhalation which would be somewhat consistent with natural, non-emergency breathing.

I like the process you describe. Maybe even at some point stop exhaling and just keep the airway open? I won't be experimenting with this from deep depths.

 

[Blackcrusader]

Over breathing is a big problem today, my resting breath rate is 7 breaths a minute, have a look at the book I mentioned.

I took 5 breaths in 77 seconds in taking this video at 26m depth. Inverted on my back facing the surface was trying a new video light and dang the lion fish did not seem bothered by it and swam down towards me.

 

[Blackcrusader]

As a practical matter, if a diver has to perform a “real CESA” then I don’t think it would make sense to initially exhale.

It makes sense if you use your BCD inflator hose and exhale the air into your BCD which you can then rebreathe. On the ascent if you get any extra air from your regulator fine. Of course if you had no air left in the tank due to first stage o ring failure or free flow from regulators then that BCD sure does become quite useful. I've done it this way from 40m to surface but do not suggest others try it unless they have a clean bladder in their BCD. Knowing how to do CESA and practicing it are two different things. Same for rebreathing air from your BCD.

I'd rather rebreathe the air from my BCD from depth than attempt a CESA. I already have a low SAC rate and am comfortable with knowing how my brain works when managing that feeling of needing to breathe when you really don't need to just want to. I find diving to be very relaxing. I've managed to remain calm when others have been stressed to near panic. I feel more stress now that I cannot undertake my usual dive vacations several times a year.

This thread has had some good conversations apart from scuba spear fishing and some other off topic discourse.

 

[John C. Ratliff]

Here's the text I spoke about earlier.

I just got out of the pool this morning after trying out my newly-adjusted Scubapro Pilot/Mk VII combo, and it not only breathed superbly, but also without any of the annoying "popping" that I had before. I have three Mk VII first stages, and this one was a friends (Lynn Herbert) that he gave me; I understand from talking to Paul Schoresman at the Northwest Diving History Meeting yesterday that this first stage (first generation) was not originally mated to the Pilot, but that's okay, as I simply wanted a test platform for the second stage. WOW! What a nice-breathing regulator.

In our meeting yesterday, another pioneer diver, Brent Budden, said that he nearly died while using a Pilot, but from a very unusual circumstance. He was making a professional dive in a cow pond to unplug a large pipe, and a large discharge from the pipe hit the Pilot just perfectly to lift up the diaphragm, and deposite a bunch of "stuff" (including pieces of hay) into the regulator. He tried to inhale, and only got cow $#%&* and "stuff." But he was only in about twenty feet of water, and made his way to the surface. He said he told himself,

"Now, don't panic, you're only twenty feet away from air. Just swim over there and surface." And that's what he did. He did like his Pilot regulator.

This would have happened with the A.I.R. I too, as they have the same basic design. Moral of the story, don't try diving a Pilot in a pipe containing...(well, maybe don't dive there at all).

Paul's brother, Keith, whom I worked with at Etec Systems, Inc., used to be a Pilot regulator technician, and he loved that regulator. He could tune it to a very high efficiency, apparently.

Now, I really like my Pilot, and will be using it in open water later this spring.

John
https://vintagescuba.proboards.com/thread/4963/scubapro-pilot-regulator-came?page=2

This happened many years ago, and he was not recreationally diving. But I don't think he wanted to try any safe second/octopus either.

SeaRat

 

[Edward3c]

...
He was very surprised to report that he was able to do a pretty much normal ascent and even completed some portion of a safety stop on the dwindling air supply.

...

So perhaps this is one more "example" of a CESA that will never be counted or recorded by any agency?

That’s stretching the definition of a CESA a bit.

 

[Celt]

I took 5 breaths in 77 seconds in taking this video at 26m depth. Inverted on my back facing the surface was trying a new video light and dang the lion fish did not seem bothered by it and swam down towards me.

That’s exceptional, does it come natural to you? people who dive all their lives seem to have an exceptional oxygen transfer rate, do you know of any studies done on it.

 

[johndiver999]

That’s stretching the definition of a CESA a bit.

Perhaps. Especially since the diver (in this case) had a redundant supply available. Is it an emergency situation when a diver is at 90 feet and it begins to get hard to inhale from the tank and there is no redundancy available? I don't know.

You've indicated that one organization has not collected even one incident of a CESA in 10 years, yet most of us know of divers who have been irresponsible and run their tank down way too low. So perhaps there would be more CESA's recorded, if the definition were defined more clearly or broadly?

Is there an agreed upon definition of CESA's?