CESA Training

[TMHeimer]

[QUOTE="The Chairman, post: 9276322

That's the only way I teach it anymore. They get the mechanics down and it's on the surface. I repeat it a few times, even if they get it right the first time. Those who do it once from depth get all the danger and fear and often never ever do it again. IOW, they get an experience but not any real training.[/QUOTE]


************************************************


Understandable and a good idea to just teach it horizontally in the pool. But in order to practice it that way after certification, the diver must either go to a pool or just do it horizontally in open water near the surface. I suppose one could do that (if one thinks of it).

 

[rick00001967]

You might like to review this video of the US Navy training.

thats awesome

 

[Scraps]

The problem with the horizontal confined water CESA is that the buoyancy dynamics are the opposite of a vertical CESA.


In a vertical CESA, once a diver begins ascending, the expanding air in the bcd and lungs and wetsuit cells make it easier to ascend to the point that the diver needs to bleed out air from the bcd in addition to exhaling so as not to ascend too quickly.

In a horizontal CESA, a neutrally buoyant diver who exhales slowly for 30+ seconds will lose altitude as the lungs empty. That’s why so many OW students end up bumping along the bottom as they approach the finish line, struggling not to take another breath.

It may be good practice to develop the ability to exhale a single breath slowly, but it’s an unrealistic simulation of an ascent and its sensations. As an unintended consequence, it may actually reduce new divers’ confidence that they can get to the surface on a single breath.

 

[TMHeimer]

The problem with the horizontal confined water CESA is that the buoyancy dynamics are the opposite of a vertical CESA.


In a vertical CESA, once a diver begins ascending, the expanding air in the bcd and lungs and wetsuit cells make it easier to ascend to the point that the diver needs to bleed out air from the bcd in addition to exhaling so as not to ascend too quickly.

In a horizontal CESA, a neutrally buoyant diver who exhales slowly for 30+ seconds will lose altitude as the lungs empty. That’s why so many OW students end up bumping along the bottom as they approach the finish line, struggling not to take another breath.

It may be good practice to develop the ability to exhale a single breath slowly, but it’s an unrealistic simulation of an ascent and its sensations. As an unintended consequence, it may actually reduce new divers’ confidence that they can get to the surface on a single breath.

Agree. Practicing it vertically IMO is the only way to practice it for it to mean something. And if you're gunna do that, it should be done that way once in the OW course. Or don't do it at all anywhere.

 

[Dody]

My thoughts on the original post:

As divers who know we need air and don’t want to die pursuing our hobby, we continuously work to identify, evaluate, and mitigate risks.

Effective mitigation strategies either reduce the likelihood of the contingency under consideration or provide a means of making that contingency a non-emergency—or both.

Therefore, if one is concerned about an OOA emergency at 30 meters, practicing CESA from that depth seems like an ineffective mitigation strategy because it neither reduces the likelihood of the event nor does it make the event a non-emergency.

What do you if? And your answer is "if will not happen'.

 

[Gareth J]

What do you if? And your answer is "if will not happen'.

I think the answer has been given, a redundant air source.

The simplest is a pony cylinder, especially for relatively shallow recreational diving.

I have always reckoned that most people can make a swimming ascent from 20m (66ft) with a reasonable chance of success. Beyond that things start to stack up against you.

The only time I dive without a redundant air source is on some overseas holidays. I really don't like diving without some form of redundancy, on blue water holidays, I accept the additional risk.

 

[Scraps]

What do you if? And your answer is "if will not happen'.

The obvious answer is that if you find yourself OOA at 30 meters with no buddy and no redundant air source, you do what you can to get to the surface.

I submit to you, however, two things:

First, whatever 30 meter CESA you’ve practiced, the actual emergency won’t be the same as your practice. You won’t start with a deliberately full breath, you won’t manage your ascent rate well, and you will be extremely lucky to reach the surface alive, unbent, with no water in your lungs, and without an embolism.

Second, there are very good reasons no training agency prescribes CESA’s from deeper than 10 meters. It is an inherently risky maneuver, intended to be resorted to only emergencies that divers are diligently trained to avoid. You need to know it’s there the same way a fighter pilot needs to know his seat can eject: he knows ejecting will probably bust him up a bit, but it increases his chance of surviving an imminent crash.

Practicing CESA from 30 meters just in case you put yourself in that emergency is akin to practicing jumping out of a third story window just in case you find yourself in a house fire without a ladder nearby.

I’m in the redundancy camp. I carry a pony that I’ve practiced with and know is sufficient to get me and a buddy to the surface safely.

 

[boulderjohn]

You won’t start with a deliberately full breath

Just a reminder about the US Navy training video posted earlier---the trainees are required to exhale fully before beginning the ascent.

 

[Dody]

The obvious answer is that if you find yourself OOA at 30 meters with no buddy and no redundant air source, you do what you can to get to the surface.

I submit to you, however, two things:

First, whatever 30 meter CESA you’ve practiced, the actual emergency won’t be the same as your practice. You won’t start with a deliberately full breath, you won’t manage your ascent rate well, and you will be extremely lucky to reach the surface alive, unbent, with no water in your lungs, and without an embolism.

Second, there are very good reasons no training agency prescribes CESA’s from deeper than 10 meters. It is an inherently risky maneuver, intended to be resorted to only emergencies that divers are diligently trained to avoid. You need to know it’s there the same way a fighter pilot needs to know his seat can eject: he knows ejecting will probably bust him up a bit, but it increases his chance of surviving an imminent crash.

Practicing CESA from 30 meters just in case you put yourself in that emergency is akin to practicing jumping out of a third story window just in case you find yourself in a house fire without a ladder nearby.

I’m in the redundancy camp. I carry a pony that I’ve practiced with and know is sufficient to get me and a buddy to the surface safely.

I will find myself the lightest, trimmest, easy to strip down (my life is a journey) pony bottle.

 

[uncfnp]

I will find myself the lightest, trimmest, easy to strip down (my life is a journey) pony bottle.

That would be the Spare Air.