How much air for a CESA

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These "what if" questions present more than an interesting math problem: they can distract for focusing on prevention of the scenario presented. It is obvious that the scenario presented is completely preventable through safe and competent diving practices. For that reason, though I would be a little less sarcastic in communicating it, I fell like Greyhound does. But more importantly, herman makes a great point: you are not going to be "suddenly" out of air. So enjoy the math problem, but also always: plan and follow a safe dive profile, monitor your gauges regularly, stay close enough to you buddy so they can be a source of survival, check your gear thoroughly before every dive trip, and again before every dive. Know and recognize the signs of a low tank- you can feel it. It's fine to know the extremes of an emergency self rescue. It's better to never put yourself in a position where you have to do it.
DivemasterDennis

I do agree with your basic idea, but there are failure modes that could leave a diver suddenly and completely OOA on their primary tank. They are extremely rare but should not be completely ignored. The critical point is good planning and dive practices will render even these types of problems more a serious inconvenience rather than a hazard.

 

[Blue Sparkle]

I ... did a CESA from 50 ft ... ran out of lung air at one point, stopped to breath in from newly expanded air, then continued up exhaling.

...I suggest you hurry your ascent - but be careful about inhaling while ascending. I stopped for that.

Don,

I notice you mentioned that while you were in the middle of a CESA you stopped to inhale, and that one should be careful about inhaling while in motion upwards. I didn't know that. Is there something physiological about the moment when one switches from exhaling to inhaling that closes one's airway momentarily? Does that hold true even if holding the "optimal open" position? i.e. head angled back and lower jaw thrust outward?

Blue Sparkle

 

[DandyDon]

Don,

I notice you mentioned that while you were in the middle of a CESA you stopped to inhale, and that one should be careful about inhaling while in motion upwards. I didn't know that. Is there something physiological about the moment when one switches from exhaling to inhaling that closes one's airway momentarily? Does that hold true even if holding the "optimal open" position? i.e. head angled back and lower jaw thrust outward?

Blue Sparkle

I guess I erred in that statement. :blush: Let's just say avoid over expansion risks. I felt so dumb in my CESA and frantic with my ascent, I was trying to add some late caution to the event - but I guess that step was unneeded.

 

[RonFrank]

If one feels as if they are going to run out of air for some reason, and their buddy is going to abandon them I would suggest practicing CESA drills until they are not an issue. Start shallow maybe 30' and work to depth.

A better idea is don't run out of air, and if you do make sure your buddy is around, or you have a pony. I have never run out of air... never. I do not plan on starting but I have a buddy, or a pony. I prefer a buddy.

I am always surprised at these threads, but then again running out of air is the #1 cause for dive accidents. If you are a moron you best plan on running out of air without a buddy, so see paragraph #1.