Max Depth for CESA

[billt4sf]

What is the maximum depth that one can do a CESA ?

Assuming a regular breath has been taken, is there a practical limit from which it's too deep for a CESA (meaning you're gonna drown without using someone else's air)? Assuming you're under the NDL limits, what is realistic to expect?

In my OW class, we practiced CESA in the pool, and maybe in the ocean as well -- I don't recall. Never practiced it since -- should I?

- Bill

 

[ScubAtlanta]

I'd like to know, too. In my OW class, we did one from around 25', if I remember correctly. I'm in decent shape, but I was concentrating hard on blowing out air and making sure I didn't ascend too fast -- and my lungs were screaming by the time I surfaced. I wonder what the safety considerations are re: practicing this skill (by that I mean, is it considered risky?). I'm a complete newb, so I'm not offering any opinions -- just asking the question along with you.

 

[TSandM]

In my personal opinion, practicing good buddy skills and learning gas management is far more important than practicing CESAs. After all, what do you need to have to do a CESA? You need to be out of gas AND have lost your buddy. Prevent either, and you don't get that far down the incident pit.

I believe there are documented CESAs from 100 feet. Blood oxygen isn't a problem, because you've got four times as much of it in your lungs as normal; the problem is suppressing the hypercapnic drive to breathe for the time it takes you to get to the surface. At 60 fpm (which is a fast ascent rate) that's over 2 minutes. Most people can't hold their breath that long without some kind of training and practice.

 

[Peter_C]

If performing a CESA the chances of a regular breath are slim to non or you wouldn't be doing a CESA. I know some people practice it as a normal part of their diving when they run out of air, but I wouldn't recommend it. Remember the story of Mago the DM from Jack's Dive Locker running out of air?


Much better to practice air management and buddy skills. That way you never need to do a CESA. (For me it is too hard on my ears ascending quickly.)

 

[billt4sf]

In my personal opinion, practicing good buddy skills and learning gas management is far more important than practicing CESAs.

the problem is suppressing the hypercapnic drive to breathe for the time it takes you to get to the surface. At 60 fpm (which is a fast ascent rate) that's over 2 minutes. Most people can't hold their breath that long without some kind of training and practice.

Great points - we do practice sharing air and even buddy breathing.

I am glad I asked because I never thought of that problem of suppressing the drive to breathe even when you have enough air!

 

[DevonDiver]

I don't think drowning is an option. From any recreational depth, inside NDL, I think most people could get up from 30-40m... provided they don't panic and really showed some willpower to survive. Next best option would be to exceed the max ascent rate - better alive with DCS than drowned. Last option would be to ditch ballast/weights and float up - passing out en-route and you'll still hit the surface, with much better chance of survival. Keep the regulator in your mouth... it'll help defeat the urge to breath... sucking on a dry tank is a lot better than sucking up the ocean..

Allegedly, a former SEAL managed a ~32m CESA in my neck of the woods not to long ago...(after squeezing out of a wreck port-hole sans equipment).

 

[knotical]

In training you normally have the imposed condition that you must exhale continuously.
But in real life, in a simple out of air situation, you’ll be able to take a few more breaths (inhalations) as the ambient pressure decreases during your ascent. This effect is more pronounced as you get closer to the surface.
Also in real life, you could increase your ascent rate, thereby increasing your possible maximum starting depth. But that would likely increase DCS risk.

I would only consider practicing CESA in conditions similar to training, i.e. with a buddy&#8217;s air close at hand. <or at least a pony>

 

[dumpsterDiver]

What is the maximum depth that one can do a CESA ?

Assuming a regular breath has been taken, is there a practical limit from which it's too deep for a CESA (meaning you're gonna drown without using someone else's air)? Assuming you're under the NDL limits, what is realistic to expect?

In my OW class, we practiced CESA in the pool, and maybe in the ocean as well -- I don't recall. Never practiced it since -- should I?

- Bill

I used to commonly practice ditching my tank at 60 feet or so and then swimming up without it and then snorkeling back down to put it back on. It is not difficult if you are calm, and your heart rate is slow and you are relaxed and don't over-exert yourself.

However, the way you state the question makes no sense at all..... in what type of emergency are you going to take a normal breath and THEN begin an emergency ascent?

Answer: NEVER! (probably) A really bad emergency with the scuba unit is probably going to be detected AFTER you exhaled and you discover there ain't no mo air when you try to suck... so in this scenario, your lungs are nearly empty. Your ability to fight the urge to breath is VASTLY reduced when your lungs are empty.. the Co2 concentration builds much, much faster and it will burn and you will feel very uncomfortable very quickly.

If you don't believe me,,, try this.. exhale completely and then run up 2 flights of stairs.. what does that take 20 seconds or less? Unless you are superman, you will be hurting at the top. The discomfort is not from lack of oxygen (for 20 seconds) but a very elevated Co2 level in your lungs, since there is no air to dilute it... (more or less).

So if you are really trying to figure out how far you can ascend with no air from the tank, you better figure it after an exhalation.

The other absolutely critical issue is your metabolic state when the emergency occurs. If you have been swimming and exerting yourself and your breathing rate is elevated and then instantly cut off, your ability to function is reduced to a several seconds.. Don't beleive me? Try jogging for 5 minutes, then keep running and just exhale and see how far you get with empty lungs? Do it on the grass....You won't make 20 strides

In reality, most OOA situations are not non-functioning tank.. they are a tank that his been run down to a very low pressure.. This means that the tank will still deliver air slowly on the ascent, and as long as you are calm and not fighting a lot of negative buoyancy, you cany gently fin up and float up at 60 feet per minute from over 120 feet... Anyone can do this, IF they are calm and are not already out of breath when they start the ascent. They may also get bent, but they CAN do this.

I always carry a pony bottle below 60 feet, because I just feel much more relaxed and comfortable knowing that if a hose explodes, I can still make it to the surface without any rush or urgency at all.

 

[DBailey]

I would only consider practicing CESA in conditions similar to training, i.e. with a buddy&#8217;s air close at hand. <or at least a pony>

Having the buddy's air close at hand or a pony bottle is irrelevant. Since you are only practicing, you should have plenty of air in your tank. Also, the regulator should say in your mouth on a proper CESA. Worst case scenario should be that you take a breath, and start over.

For me, it is a self rescue tool that is part of my total diving toolkit. It should be practiced, but I will say other skills should receive more practice (dive planning, gas monitoring, buddy skills, air sharing, etc).

 

[ScubAtlanta]

As long as you keep your reg in your mouth (so at worst, you're sucking on a dry tank and not sucking water), is there a real danger of blacking out, since as TSandM says, blood oxygen isn't a problem? Is it just an issue of dealing with your body screaming at you to "breathe!" when you don't really need to? I'm not asking this well . . . I guess what I'm asking is, if blood oxygen isn't a problem, and the only real problem is severe discomfort on being unable to breathe in, shouldn't you still arrive up top conscious and in decent shape, assuming your depth (<60') and ascent rate aren't excessive?