CESA theory

[Dody]

I know that this subject has been discussed ad nauseam on SB (I have probably read all the related threads) but not in the way that I am searching. Out of all the diving skills that I have learnt, this is the one that worries me the most. Let me explain. We learn the skill no deeper than 9 meters or so because it is dangerous. I would then assume that it should not be considered below that depth. But some people claim that they practise it at 20 meters and other than they did it in real life from 30 meters. A « controlled » ascent from this depth would take at least 90 seconds following the old rule of 18m/ min and the double with the 9m/ min. No way would I be able to exhale during 90 minutes starting with my lungs empty. My question is: can someone explain step by step what happens during a deep CESA? At what depth should the air in the lungs expand so that you could inhale or continue to exhale? Can you do it only once? Is this whole thing true or should you be prepared to die if you can’t reach the surface with whatever air you already have in your body? I am not talking about OOA due to lack of air in the cylinder but more a 1st stage failure. Thank you.

 

[rhwestfall]

and the buddy is.....

 

[Dody]

and the buddy is.....

Sorry. I forgot to mention that I was not expecting out of context answers like buddy, pony bottle, doubles or whatever. The question is clear. Let’s assume that there is no other solution than CESA. Thank you.

 

[drk5036]

I have often thought about this; I wonder what it feels like! Usually when we exhale, there’s a limited amount of gas in our lungs. Just a normal exhale takes only a few seconds in regular breathing. But if you’re swimming up especially from a very deep depth…it must feel like you can just keep exhaling forever? Bizarre!

 

[CuzzA]

Here's the deal. If you are out of gas at 30 meters you have two choices. Stay there and die or head for the surface. All of your questions are irrelevant if you're 30 meters deep and out of gas.

Bottom line is keep your airway open on the way up. If you end up bent so be it. Rather be bent on the surface than dead on the bottom.

 

[rhwestfall]

I was certified in the era where buddy breathing and CSEA were part of the basic curriculum. I believe now each are no longer components of (at least) initial SCUBA training, thought to be too dangerous.

It is a tool in the toolbox, and basically a "last option". You are saying a "only option", and asking if you will survive? Well, if you don't try you obviously will not....

I've done it from 40' just once (skills work), and from 20' in a class. I dive in a manner that there are numerous other options to utilize before the swim to the surface.

The simple point is that you should be diving in ways that this is a practically impossible occurrence.

 

[Dody]

Here's the deal. If you are out of gas at 30 meters you have two choices. Stay there and die or head for the surface. All of your questions are irrelevant if you're 30 meters deep and out of gas.

Bottom line is keep your airway open on the way up. If you end up bent so be it. Rather be bent on the surface than dead on the bottom.

Agree on the (lack of) choice. But it does not hurt to try to understand what happens in your body, physiologically. Or explained differently if you have a chance to do it in a controlled manned or just surface as fast as possible.

 

[rhwestfall]

So try it.... Start at the bottom, and do a swim-up with the regulator in your mouth.... see what it feels like... you always have a regulator in your mouth and an air source.

I wouldn't do it a second time in a dive or at any time other than right at the beginning......

 

[Dody]

So try it.... Start at the bottom, and do a swim-up with the regulator in your mouth.... see what it feels like... you always have a regulator in your mouth and an air source.

I wouldn't do it a second time in a dive or at any time other than right at the beginning......

Once again, this is not the question and the answer is off topic. Like saying that no one should even be in a position to do a CESA from deep. The question is: when you do a CESA from deep, what happens in your body as far as the gas is concerned? I have no intention to try or experience it.

 

[rhwestfall]

what happens in your body as far as the gas is concerned?

Have you missed the part in your training on how gasses respond to changes in pressure? Do you understand why you don't hold your breath? You are asking questions that are basic principals...

You list your credentials as a DM....