CESA from 100 feet?

[friscuba]

If you got a full breath then how did you know you were out of air?

Joe

I ran a tank out once by accident - my fault, went down with a tank that only had 300PSI or so and didn't do a predive or descent check. Learned a good lesson that day, now I listen to my own advice on the BWRAF issues. I knew I was out on the third to last breath when the draw changed. I had someone right there and was only in 40' so there was no need for a CESA.

Just curious as to how many regulators out there that aren't noticeable 'til the last breath. The other thing is, you would somehow have to draw your final bit of usable air at the exact moment you finish inhaling not to have at least some air available on the next breath, the odds of that are low I'd think.

later,

 

[slingshot]

Re: Charlie99, from first page: uvula! Of course, the uvula doesn't really have anything to do with voluntary control of your airway. Mainly, as others have said, it is the glottis, which is part of your larynx (the main laryngeal cartilage forms the "adam's apple").

Feeling out of breath is not just a matter of how much air you have in your lungs. It also has to do both with the amount of oxygen and carbon dioxide you have in your blood, and thus, in the gas in your lungs.

Consider this: I can take in a full breath, hold it, and still feel a powerful need to breath in, say, a minute or two. I'm curious after a 90 second ascent (as mentioned in an earlier post) that there wasn't some oxygen hunger, despite having enough gas volume in your lungs. I know of course typical exhaled gas contains a significant amount of residual oxygen (which is in part why we bother to do rescue breathing).

Comments from those who have done this?

 

[String]

Its CO2 level that causes the breathing reflex not oxygen lack. This is why issues such as shallow water blackout are a problem for free diving and snorkellers if they purge their lungs too much before diving.

 

[Iruka]

Originally Posted by Sideband
If you got a full breath then how did you know you were out of air?

Hi Sideband....well, I was just practicing a CESA, so I DID have plenty of air. However, I've never yet experienced (in 5,460 dives) a situation where I didn't know I was almost out of air without any warning. I'm sure there might be some mechanical malfunction which might cause that, or a really good (ie "out of my price range) regulator might breathe normally until there's virtually no air left. Normally, at least in shallow waters (less than 10m/30') I can tell for a few MINUTES that I'm very low on air, just by the breathing resistance.

Anyhow, you & a few other people have given me something to think about....what IF I had to do a CESA "starting on empty." Not sure I'd want to practice that, though...I'd think the need for air would make someone more likely to ascend quickly (in order to take advantage of the air expansion & more available air.) Obviously, even if you can do a "practice" CESA from fairly deep, there'd be a lot more stress involved in doing it "for real." But I think knowing that I HAD practiced it already would make it a little less frightening.

 

[Dragon2115]

However "bent" can often be permanent and "embolised" is usually fatal.

Rather than do that its far better to eliminate any need for a free ascent by proper training and equipment.

I guess you missed the part about when "the only other option is dying".

But you're right, bent can be permanent. And embolized is usually fatal. But then again, the risk involved with either one is vastly preferrable to the permanency of being dead from drowning now isn't it?

As for eliminating the need, that would be nice, and in fact the odds are very low that a situation would arise in standard rec diving to need to do a CESA in the first place. However, places like NASA spend billions of dollars to minimize the risk in everything they do, and they still have catastrophic failures that they didn't predict.

And even though the odds are usually several million to one, people do still win the lottery. This is just one lottery where you hope your number doesn't come up.

 

[Charlie99]

I ahve a question for all of the people that say they have "practiced" this from the 90 to 100 foot range. How many did it starting with empty lungs?

Since I was doing this to test my limits, I purposefully chose to do it at the bottom of a normal exhale.

While it's NOT the recommended way to do it, I did it with the reg out of my mouth, face down, mouth slightly open. Since I WASN'T exhaling during the ascent, the fact that I started at the bottom of normal breathing cycle wasn't a problem. (Airway open, but not exhaling)

You'll have to decide for yourself if the risk of this exercise is worth it. I tried to minimize risk ...

clear warm, hi viz water of Cozumel.
right at the beginning of the first dive of the day
immediate, fast, descent, then right back up (pretty much the same N2 loading as a freediver)
DM and buddy knew what I was doing, and I had mentioned to them the possibility of shallow water blackout (low % of O2 goes to low ppO2 in the last 20 feet of water, causing unconsciousness).
I stopped the ascent at 15', got stabilised at depth, then went back on scuba.

A large part of my motivation to do this was that during OW cert I had a hard time doing even a 25' CESA. The reason for difficulty was that I was continuously exhaling. There is a huge difference between actively exhaling and simply keeping your airway open. You don't have to go to 90 or 100' to feel the difference. Just doing a 20' to surface CESA properly will teach you the difference.

Link to earlier "Emergency Ascents" thread.

 

[pete340]

Just curious as to how many regulators out there that aren't noticeable 'til the last breath.

I ran a tank dry once, noticed a change in breathability about three breaths before it went empty. This was on the surface during my Rescue class, practicing a tired diver tow into a strong current and heavy swells, so it wasn't seriously life-threatening. I signalled the instructor that I was out of air, and he called off the drill. Two lessons there: "once around the boat" can consume a lot of air when there's a strong current, and don't take unnecessary chances.

 

[Gary D.]

Most of the prior posts, where people have practiced CESA have done it from shallow depths and are questioning if it can be done deeper.

Sure it can and practicing deeper is a lot safer than shallow.

If you revert to your basic training they should have taught volume changes at various depths. Basically it is the shallower you are the bigger the volume change.

There is little room for error shallow but the deeper you do a CESA practice the more leeway you have to get it right.

This is just an example so don’t get upset about the depths or exact figures. You could most likely get away with holding a full breath of air from 600’ to 400’ without any problems. But holding that same volume of air from 15’ to the surface would most likely kill you. So why does everyone practice shallow? Try it from 100’ to 50’ instead of 30’ to the surface.

Most of your Submariners and Military divers will do more Free and Buoyant rides from 100’ to 120’ than most sport divers will ever dream of. They are easy and fun when you HAVE THE PROPER TRAINING. I don’t know if the medical community even knows how deep they can be done from and still survive.

Proper training is the key. Don’t have someone who has just survived a couple think they can teach you.

Gary D.

 

[Splitlip]

My PADI OW text says to use CESA (controlled emergency swimming ascent) at depths down to 30 feet in OOA situations (and no buddy). [You know the technique--swim up saying ahhhhh all the way.]

But a commercial diver I was talking to said he's done a CESA from 100 feet. Is that credible? What's the greatest depth you've done or know someone's done?

The answer is important because below the greatest depth (whatever it is), PADI says to drop weights and make a buoyant emergency ascent, risking DCI as the lesser of two evils. If the greatest depth is actually around 100 feet, then I don't need to take a pony along for resort diving.

OBTW, with a CESA, what's the fastest I should swim up? Slower than my smallest bubbles?

Penny for your thoughts.

I was taking AOW class late 70's. Made ascent from 60-65' as part of class. 2nd (oops edit) stage in right hand, inflator (deflator) in left, exhaling on the way up. Can't remember if we started with lungs full or not, but could "feel" the expanding gas. Flared out about 15 to 10' to slow ascent.

 

[slingshot]

String:

It really is oxygen AND carbon dioxide.
"The rhythmic discharges from the brain that produce spontaneous respiration are regulated by altenations in arterial PO2, PCO2, and H+ concentration...a rise in the PCO2 or H+ concentration or a drop in its PO2 increases the level of respiratory neuron activity in the medulla..." from Review of Medical Physiology, William F. Ganong, 16th Ed. pp. 611-612.

I've done a CESA in training from 30 feet, over about 30-40 seconds, but don't recall feeling "out of breath". Perhaps it was just the excitement of the moment?