Safely Practicing CESA

[DeepBound]

Since practicing CESA requires ascending at the max. rate of 60ft/minute, from 30ft or more usually, how can you safely do this drill? If you do it before you have much nitrogen loading, is bubble formation less of a problem? Would it be smarter to just do it once at the start of a skills practice dive rather than doing it a number of times in a row?

How do you practice CESA, or do you at all?

 

[Charlie99]

Considering the risk involved, I've only done two practice CESAs.

I was very unhappy with my (in)ability to do much of one during my OW cert class, because I was exhaling too much. I eventually realized that the standard advice to hum or blow bubbles was the problem. By simply keeping the airway OPEN, excess air will just naturally exit. Don't try that method, unless you have very good conscious control of your glottis.

On a trip to Cozumel about 5 years ago I did a couple practice ones.

In both cases to minimize N2 loading, I did it at the beginning of the dive day, and dropped right to the bottom, then back up.

On the 2nd day I dropped straight down to 90' at the beginning of the dive day, and then came back up, at just barely over 30fpm. For some extra safety, I halted my ascent at 15'.

Viz was good and both my buddy and others on the boat knew that I'd be doing that drill.

I have never done one for real, nor have I ever practiced it again, since, once I figured out how to do it right that one time, the risk wasn't worth doing extra practices.

 

[Knight1989]

While not exactly the same thing as a real situation, I practice mine on a horazontal level. Not that I do this very often at all, but I have in the past had a buddy swim 60ft or so away and then swim to him exhaling the whole time, using what I estimated to be a safe ascent speed.

 

[Charlie99]

While not exactly the same thing as a real situation, I practice mine on a horazontal level. Not that I do this very often at all, but I have in the past had a buddy swim 60ft or so away and then swim to him exhaling the whole time, using what I estimated to be a safe ascent speed.

The difference between a horizontal practice and doing the real thing is amazing. It was very strange to leave the bottom, slowly ascend while letting air bubble out (as opposed to forcing/actively exhaling), and reach the surface with the same amount or even a bit more air in my lungs.

 

[CompuDude]

We did one from 60 fsw during my early training in the 80s (I can't recall if it was OW or AOW anymore). Beginning of the dive. I see people cringe when I tell them that these days... I guess they really think that you gain the same experience doing it horizontally, which simply isn't the case. I agree, it is one of the oddest things ever to exhale for a full minute (recall this was during the 60 ft/min ascent days) and still have air! It really helps your confidence level to know just how well it works, though.

 

[SDAnderson]

If you're a PADI diver, you've already done a CESA drill with an instructor during your OW check-out dives - that should be enough. They really are dangerous and the risk of practicing them probably outweighs the benefit of becoming proficient at a "last option" skill. There are a lot of skills that new divers need to master (kick styles, buoyancy, mask removal & replacement, valve drills, etc.) and the CESA doesn't need to be one of them.

If you're determined to practice, however, I'd suggest that the best way to do it is just like you did it during your open water course - including finding an instructor to be your buddy, since instructors are trained to help with the drill. This is definitely not a skill for two new divers to be practicing with each other.

• Practice this in water between 20 and 30 feet deep. Deeper than 30' is not recommended.
• Limit the practice to a time when NO2 loading is light - like the first dive of the first day.
• Do not practice this skill more than once per day - bounce dives are a good way to fizz yourself and repeating them is asking for trouble.
• You'll need an ascent line that is securely anchored to the bottom and taught. The line should be at least 1/2" in diameter so that it can be gripped easily. Light boat anchors are usually not sufficient weight to securely anchor you to the bottom and should not be used.
• Keep your regulator in your mouth at all times.
• Do not drop your weights.
• Make the "ah" sound as you gently exhale all the way up. If you stop exhaling or stop making the sound, the drill is over and you should grab the ascent line and resume normal breathing.
• Kick gently to start the ascent and kick only as needed to maintain the ascent.
• Your buddy should have a solid grasp on you and the ascent line at all times. If he stops you for any reason, the drill is over and you should resume normal breathing.
• Do not grab the ascent line unless you feel yourself getting out of control. If you grab the ascent line, the drill is over and you should resume normal breathing.
• Have a hold on your deflator and vent air as you rise to control your ascent rate and buoyancy.
• Ascend no faster than 60fpm - 30fpm is better. Be careful to control your ascent all the way to the surface.
• When you get to the surface, orally inflate your BCD and signal your buddy that you're OK.

It bears repeating, however, that this is a skill I don't recommend practicing.

 

[Charlie99]

Making the "ah" sound will keep you safe and works even if you don't have voluntary control of your airway. OTOH, if you know how to keep your airway open, you can make a much, much, slower ascent by merely letting the air bubble out naturally.

This is an interesting post describing a 5 minute ascent from 100' at less than 20 feet per minute ascent rate, in a Submarine Escape Training Tower.

 

[Rich Courtney]

How do you practice CESA, or do you at all?

I don't bother, as I always have some form of redundancy.....

Safe diving,

Rich

 

[JimC]

I'm with Rich on this one.

 

[CompuDude]

I agree it's really not something you should practice on any sort of regular basis, but handled properly, I don't think it's horrendously dangerous.

I don't really like the new training method of swimming horizontal in the water. It's just not realistic, and won't give you the same confidence actually feeling the air expand does.

My wife is getting certified next month, and one of the things I will probably do is ONE real practice cesa with her from 30' (not the extra depth I learned it from), once she is certified (unless I can talk her instructor into doing a real one with her). First, and possible only, dive of the day, for that one. And once she has done it, I doubt I'll ever do another practice one again. It's just not necessary.