Is it time to sink the CESA?

[dmaziuk]

I would think such practice can be done from 6 or 7 meters with the instructor staying at the bottom and observing the bubbles from slow exhale as the trainee ascends.

According to e.g. this: Can you feel a lung over-expansion injury happening? – Divers' Blogs 0.1 atm can be enough to blow a lung, so anything deeper than 1 metre is not entirely safe (though at 1m you'd have to really "pack" your lungs to blow them I expect).

 

[boulderjohn]

It is probably useful for students to practice sufficient number of CESA from minimal depths to get the feel of their lungs expanding if they hold their breath. It is trying to hold breath (a basic instinct underwater) that is likely to cause serious injury during ascent. I would think such practice can be done from 6 or 7 meters with the instructor staying at the bottom and observing the bubbles from slow exhale as the trainee ascends.

So let's say that you are an instructor staying at the bottom at 7 meters and observing the bubbles from the slow exhale as the trainee ascends, but you notice that there are no slow bubbles because the trainee is not exhaling. What do you do at that point? There will be no way for you to intervene, so the only thing you can do is start planning for possible consequences.

So what are the possible consequences?

About a decade or so ago, an SSI instructor was teaching a class for the University of Alabama. (It may have been the wife of the instructor, IIRC.) She had the class practice a ditch and don exercise that is not normally a part of training. The students were to descend to the bottom of the 4.5 meter/15 foot pool, take off their gear, ascend to the surface, swim back down, put the gear on again, and return to the surface. She was not with the students as they did the ascents after ditching the gear, so it was the same thing as you describe, only from a shallower depth. One of the students held his breath on the ascent and died on the surface.