I am fully aware of the procedure, and fully aware how it's performed. I have performed EBAs myself, as required by some of the facilities I've worked for. For a complete diving resume, you're welcome to Google my name - "SeaJay Bayne." Included there you'll find some of my references to diving with Duke University's Hyperbaric Facility and DAN, specifically for the US Navy.
I did so, the links don't tell me much. You make the statement on your web page: "Studied at
Duke University's Hyperbaric Facility for the
U.S. Navy." I don't know how to interpret that. What did you study? Who was the P.I.? What papers came out of it? Were you a co-author on any of them or were you an experimental subject?
My statement, which you called "ignorant," is based on the fact that taking an N2 loaded scuba diver and forcing them into a fast ascent from depth due to catastrophic unweighting - and perhaps even inflation of their BC - is going to cause at the very least a pre-DCS condition in their body. Whether or not this is diagnosed, addressed, or whether or not the diver has medical issues from such an ascent is a gamble.
Going diving causes a pre-DCS condition, each and every time.
If the diver has a bad day - and especially if he/she is unfit, has heart disease, is dehydrated, has symptoms of obesity, is in poor physical health, or is heavily N2 loaded (read: near or over their NDLs, for the layman), then serious injury could occur that includes air embolisms, anneurisms, or DCS. Many of these problems can prove fatal or permenantly injuring.
If that seems ignorant to you, I recommend expanding your education regarding the subject. Calling someone else "ignorant" doesn't change the facts.
If you look at DAN's figures (something that I try not to do because of problems that I feel are inherent to their data set) you will note that fatalities stemming from DCS are almost non-existent, from AGE are much higher and from drowning are yet and order of magnitude larger. Sure, serious injury could occur, but stress is on the word "could." I know of no cases of DCS that occurred as a result of a properly conducted (e.g., non-missle launch) emergency ascent, I know of no cases of AGE that have occurred outside of the recreational community (which says to me that it is a skill problem not a problem inherent in the procedure), but there are a sizable number of drowning or just plain dead diver on the bottom cases. This leads me to the conclusion that the recreational community has it's collective head up it's nether orifice when it comes to developing a rational approach to the teaching and conduct of emergency ascents.
Yes, I'm aware. They were just recently out of style when I first started diving in the 1980's. Recommending a procedure based on a piece of equipment that hasn't been in practice or production in 30-something years seems a bit irresponsible.
Of course. It's also not recommended for a diver to do a bounce dive - on air - to 363 feet... Or 180' in your other example.
I guess I'm going to have to spend some time in there and compare it to what are known and accepted scientific resources like
http://www.aaimedicine.org/journal-of-insurance-medicine/jim/1995/027-01-0015.pdf .
I would not call that an "accepted scientific resource." That is an actuarial article written for the insurance industry by an M.D. It is not science.
The information there is several years old, but clearly shows the trends and averages... Something like a 0.0035% fatality rate... That is, three and a half fatalities per four hundred million divers - or - one fatality per 114,000,000 divers. The largest single common denominator was "heart disease," seen in nearly 31% of the dive fatalities, and close to 2/3rds of the fatalities occurred on the bottom, during the ascent, or on the surface, immediately following the ascent.
This information is dated 1993, and takes fatalities into account from 1970-1993... 23 years of it. There may be a more current data set, but regardless of year, this set can be deemed "statistically significant." It's doubtful that you'll find radically different information in more modern data.
I have written extensively, even here on ScubaBoard, about the myriad problems of combining the data set that I help develop at the National Underwater Accident Data Center (that's the pre-1993 data) with the subsequent DAN data set. If you look at the two data sets separately you do reach some different conclusions ... but I feel that those conclusions are due to differences in data collection methods and analysis rather than reality.
My point is... If you're basing your idea that EBAs can prevent LOTS AND LOTS of "diver fatalities" as a "last resort" on the Accident forum here at Scubaboard, please have a better look at actual diver fatality data. Actual data suggests that divers with heart disease (in poor physical condition) are the leading cause of the very tiny number of them that die diving. Of these, most of them have issues with the ascent or immediately prior or after the ascent.
That is one of the conclusions that I feel is poorly supported. I've seen hundreds of autopsy reports that give the cause of death as "heart attack" with are, if the truth be know, merely supposition with no definitive evidence.
None of these issues could be solved with an emergency bouyant ascent. That is, if you're reading the accident forum here on Scubaboard and think that the solution to "all of these diver fatalities" is an emergency bouyant ascent, you're wrong. Firstly, there's NOT "all these diver fatalities," and secondly, the largest common denominator between those few fatalities is heart disease (which is usually brought on by poor fitness levels and diet) and improper ascents.
I disagree ... but, in any case, even a heart attack victim has a better chance of survival on the surface than he or she does on the bottom ... no?
Of course I "get" "last resort." I'm telling you that a few kicks to the surface, and you're bouyant anyway. It's called a controlled emergency swimming ascent. You're recommending a different procedure, where a diver drops his weight belt and/or inflates their BC, assumes this upside-down skydiver body position, and "rides" up. Both procedures are designed as a "last resort."
A few kicks will not get you to the surface, and surely will not help you to relax as you head for the surface, a flared buoyant ascent will. I don't remember recommending inflation of the BC, except in the context of using an Air Siphon technique that is way more controlled than finning your way up.
One is controlled and immediate and capable of ascent rates from zero to around 300 fpm, depending on what the diver chooses. It's also the most commonly taught method of "last resort" ascension. The other is not controlled, although it is possible to "slow" the ascent from 200 fpm to about 60 or 70 fpm if a very unusual body position is taken.
A modicum of effective training is what turns the "very unusual" into the perfectly normal. Being underwater is, at least on the face of it, "very unusual." If you were to go through my class you would have made ten to twenty flared ascents (as part of the doff and don exercises) in each pool and session. Times ten to twenty pool sessions, that renders it hardly a "very unusual" body position.
Your claim is that the latter should be utilized, and that my protests are "ignorant" because a bouyant ascent was once used successfully from 180' in WWII.
I do not remember anyone making that argument. The whole point of the submarine escape examples was simply to demonstrate that it was fairly easy to avoid the problem of AGE, which is identical for a submariner and a diver.
I am concerned with what happens if a new diver comes and reads this and chooses to believe that dropping weights at depth "as a last resort" is a good idea, rather than performing a CESA "as a last resort," especially when "last resort" decisions can be avoided.
[/quote]This particular path leads to a quagmire: since today's divers are poorly trained we should not suggest any approaches that actually require good training and real skill mastery.
I don't understand... You were told then that it wasn't recommended, which is exacty the same thing that we're all told now... Nothing's changed. I don't understand your argument in support of an EBA. Why would a diver choose it over a CESA?
Asked and answered.
Well, the scenario that we were all talking about involved a diver who had lost his buddy with no redundant source of breathing gas, and was completely out of gas... At depth. In other words, he/she had gotten themselves into a situation where there literally was no choice but to surface or drown.
Another poster had suggested dropping weights at depth, and even pointed out that in training, some were taught to also inflate their BC or "life preserver." I pointed out that an OOG diver has no gas with which to inflate their BC, and another poster pointed out the old CO2 cartridge-equipped flotation devices.
Better to surface than to drown, no? If the diver is truly out of gas then there is no way to inflate the BC (even with CO2 cartridges, they were basically useless anywhere except on the surface or very shallow). Drop the belt, it works.
Well, of course they are. When freediving to 60', you're traveling up and down, which is 120', with a stop/pause in the middle. It's also aided in one direction by your buoyancy and slowed in the other, depending on your weighting. Yes, of course an 80' EBA is going to be easier than a 60' freedive. Try a, 80' CESA and see how it compares. It's even easier.
You appear to me to be arguing from mistaken assumption rather than actual experience, and actually you've got it backwards. An 80' CESA is far more difficult than is an 80' EBA, you've just never been trained to conduct the latter nor performed the latter or you would realize that.
...
Okay, sure... Then my statement was sloppy. It can be compared to saying something like, "You know, if you jump off of a 3-story building, then don't be surprised if you end up with broken legs and/or are permenantly disabled." Or, "If you drive 150 mph down a residential street, you're gonna hurt someone." Sure, I didn't preface the jump with, "if there's no trampoline down there," or "if you're not jumping into a pool," but I was trying to make a point. Taking a scuba diver, specifically one at the end of the dive who is nitrogen-loaded (unlike an escaping submariner) and having them drop weights so as to initiate an uncontrolled, bouyant ascent is a dangerous procedure with a high likelihood of permanent injury.
Do you have any data to support this or is this entirely based on assumptions that may or may not hold up? If you have data to support this I would love to see it because it flies in the face of my personal experience.
There are other solutions to the same problem of being without any available breathing gas at depth that are less dangerous, specifically, a CESA, because it remains controllable due to not losing weights and/or not inflating a BC prior to ascent. Both a CESA and an EBA are bouyant... But the CESA is fully controllable whereas the EBA is not.
We have already dealt with this question, if you have data, or even just a line of reasoning, please present it; just saying that it is so is insufficient.
Either method allows the diver to get another breath every 1 ATA or so, depending on a variety of factors... So the procedure does not have to be rediculously fast to be successful, although I've never seen any diver OOA at depth who doesn't hurry to the surface in a CESA or EBA maneuver.
That speaks more to the folks that you have seen diving than it does to reality. In the old days almost every diver was ended OOA, with with a CESA, a gentle, controlled, slow ascent to the surface.
Very little, assuming no latent loading from previous dives.
The same could be said about the escaping submariner, which is why he's different, physiologically, than a scuba diver at the same depth. Sure, if there's no difference in the profiles, then there's no difference between the two situations... Of course, assuming other things are equal, too, like core body temperature, hydration level, physical fitness, lack of PFO, overall health and BMI. But the fact is, a diver does NOT have the same profile as an escaping submariner because of the difference in time at depth... That is, nitrogen loading... Closeness to each compartment's M value...
That's why it's a really bad idea to drop weight - or use any other method to force yourself into an uncontrolled bouyant ascent... Especially if there's another, more controlled option that creates an identical solution.
You're repeating yourself ... this has been answered.
