There are no CESA's (required) in any courses after open water. At least for all the major worldwide agencies.
Am I too afraid of lung barotrauma? Remedies/Techniques?
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You do not need a full breath to start a CESA. In fact, if you look at the US Navy video I posted, you will see that they are taught to exhale before starting the ascent so they don't have too much air in the lungs when they start. Not only do you not need a full breath, you don't want a full breath. That can be done from 300 feet. Look at how much air is being exhaled in those videos.
Now, those are videos of buoyant ascents, so they are ascending faster than you would on a CESA, when you are supposed to ascend at a "normal" ascent rate, even dumping air from the BCD as you become buoyant.. That rate of ascent is really the only difference between a CESA and a buoyant ascent. What does "normal" mean? When PADI first used that language, decades ago, pretty much everyone was ascending at 60 FPM as the "normal" rate. When I took my instructor exam, the examiner said it was perfectly fine to allow students to ascend faster than that, which is likely what would happen in a real OOA event.
PADI training as to when you should use a buoyant ascent rather than a CESA is vague--it really comes to your judgment as to what you need to do to get to the surface. A lot of people will use 30 feet or 60 feet as a hard line below which they will use a buoyant ascent. The reason for using the CESA rather than the buoyant ascent is to minimize the dangers of a fast ascent, but reaching the surface is always the primary goal, and if you are not sure you can do that at a "normal" rate, then go buoyant at any depth.
In an earlier post, someone mentioned that you have a minute (really more) of O2 in the body, implying that you have a minute to get to the surface. That is only true if there is no O2 exchange going on in the lungs. The fact that air is gushing out of the lungs as you ascend means that you have air (and therefore O2) in the lungs, so a normal O2 echange is happening. You have plenty of O2 (and therefore time) to make it to the surface from any depth.
That was said by my swimming coach way back when, explaining the "15 metre rule". I've no idea if it included air in the lungs or not. But even if it did, at 130' you'll have 5 times more of it so you'll certainly much more than a minute of O2.
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Understood. Do you agree that if you have enough air in your tank for a complete breath but it feels like there might not be much (or any ) more, you should begin with a normal (breathing) ascent and take it from there?
Yes.
Years ago I was at about 150 feet breathing from an AL 80 stage bottle before switching to my doubles. I wanted to get everything I could out of the stage, so I waited until I was well into the red on the SPG before starting the process of switching. I don't remember why, but I had trouble getting my primary regulator unclipped. I felt that first harder-to-inhale breath. I could have put my alternate in my mouth while trying to get the primary free, but I continued to breathe from the stage. I didn't count the breaths, but I remember being surprised by how much I was able to breathe after that first harder draw. I have no doubt that if I had needed to ascend and only had that nearly empty AL 80, I could have made it to the surface without a CESA.
In the PADI hierarchy of emergency ascent steps, the first choice is a normal ascent, the second choice is your buddy's alternate air, the third is the CESA, and the fourth is the buoyant ascent. I was taught to teach that the "normal ascent" first option was for when you see by your gauge that things are bad, but I read somewhere years ago that the original theory behind that hierarchy was that when you first feel that harder pull, you can (and should) still do a normal ascent. Back then, that was very much preferable to what was then the second choice--single regulator buddy breathing, which was considered too likely to lead to two drownings. (The alternate regulator was not an option then.) I have no credible source for this, but it makes sense to me. If I were a single tank diver, felt a hard pull, realized I was almost OOA, I would much rather begin a normal ascent than start buddy breathing. In the modern era, I would prefer to use an alternate air source.
As was explained to me by an emergency room physician and diver named Lynne Flaherty, you have a minute to a minute and a half of O2 in your tissues, with no oxygen exchange in the lungs adding to it. If you are doing a breath hold dive, there is continual oxygen exchange with whatever you inhaled before the dive, which is why you can hold our breath for more than a minute or two. As you noted, at 130 feet, you are starting with 5 times as much oxygen as you would have on a breath hold dive.
tmassey
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And tissues with much higher then the 0.21 (nominally) PO2 they would have on the surface. You’ve clearly got more time than you might think. The biggest takeaway is to not panic and drown. I’m intrigued by the mention of freediving techniques to address the CO2 breathing response.
And a hat-tip to @TSandM. She is still missed.
Yes she is.
Getting back off-topic, apparently, armed with that "one minute" knowledge the freestyle swimmers tried going the full minute dolphin kick underwater: it's the fastest way to swim and freestyle is technically "any recognized style". They found out the hard way that the one minute rule does not hold when swimming at the record-level pace. And after a couple of emabarrasing near-drowning incidents, freestyle added the rule: no more than 15 metres underwater after the splash or turn.
I donated my reg to an OOA diver at 140 feet. When I couldn’t get the reg back I had to make an emergency assent with him. After picking up his reg I got 3 full breaths before reaching the surface. If you have to make an emergency assent keep the reg in your mouth.
...and that is why I would personally choose to do a normal ascent, a CESA, or a buoyant ascent rather then try buddy breathing in a real OOA emergency. The only exception on an NDL dive would be if the other diver was someone with whom I had practiced buddy breathing, and since I don't practice buddy breathing, that is not a likely scenario. (I can imagine a tech scenario where I would have to do it because none of the other options were available; in a recent fatality in a cave, it is possible that the two sidemount divers shared their last functioning regulator, but we will never know.)
With the near ubiquity of alternate air sources, it is hard to imagine the need for buddy breathing in an NDL dive. In the only case I know of in the last decade, a woman in Florida was given a rental regulator set with only a primary second stage. As luck would have it, she ended up sharing air with an OOA diver, and they both drowned. I am pretty sure the resulting lawsuit made it unlikely that any dive operator is going to hand out a rental unit like that ever again.
This can be tied to CESA, BTW. A few years ago a prolific SB poster, an instructor, insisted on several occasions that agencies should stop teaching CESA ("blow and go," as he put it) altogether, and they should return to teaching buddy breathing instead. On two occasions, I asked him if he advocated that an OOA diver with no alternative air source available should swim around looking for a diver with no alternate second stage so they could buddy breathe rather than head for the surface. He didn't answer me either time, so I don't know what he told his students.
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