Triggers of Dive Accidents

[Garth]

Due to reality, there will always be OOA diver deaths. You can address lack of training and improper training but you can't cure the DUMB mistake (no cure for stupid). People are people. There will never be a zero unemployment rate, no heart attacks and auto accidents. The best we can ever hope for is that as instructors, we do the best job possible instructing our students on how to handle the DUMB mistake which MAY prevent a statistic. Without the training, the fatality rate may be even higher.

Is this a Darwin quote?

 

[spoolin01]

Ken, thanks for the thoughtful responses. While I have more than enough time in the water to be confident of my judgement in the realm in which I swim, I'm not a bold diver when it comes to depth or NDL, so I realm and I enjoy the expertise of others on the topic.

Yes to that part of the sentence.



No to this part.

I should have clarified I meant that to appreciate the implications, you have to drill beyond the broad categorical bin, as your example shows.

So from my perspective you've got (1) mask floods, leading to (2) inability to clear mask, leading to (3) panic, leading to (3) rapid ascent, during which (4) breath was held, causing (5) embolism, which resulted in (6) drowning (listed by the Coroner as the official cause of death).
Now you can nitpick and drill down and talk about standards violations or lax instructional oversight, or bad judgement or whatever, and while those would be contributing factors, when you try to understand JUST the mechanics of the accident, it all starts with the mask flooding and then the inability to react to that and solve that problem. If the kid had cleared his mask, we wouldn't be using this as an example.

All the more tragic to see a young life lost for want of such a pedestrian skill. This must really vex instructors in particular and drives home why training and standards are such heated topics.

I wouldn't agree with that either. Although the AGE is immediately life-threatening and has to be dealt with, so does DCS if they both happen at the same time. While DCS likely won't kill you, it can certainly cause permanent neurological problems if left untreated or ignored.

You won't be dead, just crippled.

I wasn't clear here either, only meaning that once the coroner determines AGE as the cause of death, the fact that you might have died or been damaged from DCS doesn't make it into the record, I assume. All this was simply in thinking about the tally you initially brought up, and how to make it granular enough to reveal the risks in context.

DAN actually has some stats on this dealing with divers suffering from severe neurological problems (and it underscores the value of oxygen in the field prior to treatment):

If they received emergency oxygen prior to chamber treatment, 67% had full resolution.
If they received NO oxygen prior to chamber treatment, only 56% had full resolution.

You have to take some satisfaction in that, still grim...

For those with mild symtoms:
If they received emergency oxygen prior to chamber treatment, 73% had full resolution.
If they received NO oxygen prior to chamber treatment, only 49% had full resolution.

How quickly you get to a chamber makes a difference too. Of the divers who had residual pain following treatment:

4% were treated w/in 4 hours of surfacing
19% were treated 4-12 hours after surfacing
77% waited 12 hours or more hours to seek treatment

The take home message: The longer you wait to get treated, the more likely it is that it won't fully resolve.

Is it a stretch to expect a corollary for underwater and surface avoidance and remediation protocols as well? I'm thinking of the advice to substitute O2 on the boat for off-gassing below. That one surprised me.

The Catalina Hyperbaric Chamber gets a treament roughly every other week, so about 26 a year. However, there have been times when there have been treatments four days in a row. (There was one time when they dealt with four AT ONCE.) There have also been times where months have gone by without a treatment.

That is a very reassuring stat!

Old saying but appropriate: There are old divers, and there are bold divers, but there are no old bold divers.

I believe SB challenges the validity of this old saw!

 

[Peter Guy]

Ken and Diver0001 -- I, for one, did not take Ken's original post as a "proposal" for a change in training as opposed to a thought experiment as to "What would we (instructors) need to change IF we didn't teach OOA procedures -- that we 'make stupid hurt.'" And I, for one, merely took it as a thought (what if) experiment. [Ken, if you meant it to be, in fact, considered in reality, hmmmm.]

And Rob, I really liked this discussion of diving instruction:

it's more than learning 19 disjointed skills

because it elequently states my own belief. And the essence of how brilliant someone may be is how much they agree with me!

 

[Ken Kurtis]

If you feel like I'm unfairly singling you out, I apologize in advance but . . .

First of all, 41% of all diving accidents being caused by "out of air" strikes me as "reasonable", so to speak.

I realize that you put the word "reasonable" in quotes so it's not exactly what you mean but the underlying thought seems to be is that this is sort of to be expected and there's not much we can do about it.

How have we devloped a culture of diving where we consider this either sort of OK or beyond our ability to mitigate/fix????

Like saying that most climbing accidents are caused by falling: is it not the nature of the business?

The direct answer for diving, I think is: No.

I also don't think that's the exact anaolgy. I think the analogy would be to say "most climbers die from falling" and "most divers die from drowning". The questions are why?

Now if it turned out that climbers were falling because they were taking their shoes off at some point and losing their footing, I'm sure there would be a hue and cry among climbers that would be "Don't ever take your shoes off!!!"

Similarly, we have divers running out of air and drowning. Saying that there are other options to deal with the problem still doesn't attack the root of the problem: WHY are people running out of air, and what can we do about it???

- Ken

 

[spoolin01]

Spoolin,
As Lamont posted, look at the large population that dived from the 60's, 70's, and 80's..all doing 60 ft per min or faster ascent speeds with NO safety stop. If your paranoia was justified, there would be a huge incidence of bonal necrosis, or other related damage. Not only do we not see this problem in that population, most that I run into are in far better physical health than their non-diving peers. I just spoke to Living Dive Legend Frank Hammett 2 weeks ago....He began diving around 1954......he used to suck 72 cu ft tanks dry on the 145 foot deep hole in the wall, free ascend, grab another tank, and do this all over again..he did this for years...even in the 90's and later Frank did not do safety stops. Today, Frank is around 82, in very good health, and showing no signs that your fears of long term bubble damage are as insidious as you suggest.

If you can't shake this "Fear of Bubbles", then perhaps you would be better off just freediving ( which, by the way can still cause a tiny bit of bubbling).
Also, it appears that because you are a freediver, you have an inability to imagine how a new scuba diver can have a problem getting to the surface, and staying there safely, when OOA or low on air....
The skill sets are very different. As a freediver, you also KNOW you can keep your Heart Rate slow, and make it easily to the surface for the 15 feet in question...the new scuba divers will be nervous, heart racing, and have no experience free ascending....they also have far less propulsive efficiency. This list could go on and on. Many will be too negative on their stop, as they have not yet learned proper trim and bouyancy....as evidenced by the way many, many of these swim head up and feet down...
You fail repeatedly to grasp Ken's points about the need to do something to lower the death rate...and the big number of deaths are drowning and OOA related, not bubble/hypersaturation related.

DanV

DanV - I appreciate that you continue to indulge this discussion civilly (mostly). I'm trying to do the same, though Lamont is tempting me :mooner:. I pounced on your original comment to the new diver mostly for its vehement certitude, in light of my take on the situation he brought up. I hope at least we can agree that in weighing risks and responses, one protocol does not fit all divers, even new ones. You've defended your thinking, I just don't agree that the anecdotes and observations you cite have more than passing bearing on the issue of the health consequences of chronic absorbed gas exposure from NDL diving. Some life-long smokers/drinkers/etc. live to a ripe old age, and many don't show extreme overt signs either, until autopsy. What you do with the information is another thing, but the fact of physical change from chronic exposure to those substances is proven. Apparently there is evidence of tissue damage in recreational divers, and the dimensions of the syndrome are only partly explored. You may have made up your mind about that, my point was that a dead-ended absolutism forecloses them from that opportunity themselves. I'm not talking about the dictates of limited bandwidth during formal instruction, this is not that.

 

[Ken Kurtis]

Than you for the well-written dissent. Just to be clear, I take no offense to it at all. However . . .

With all due respect to Ken, this idea strikes me as complete insanity. I know it was intended to generate thought but to draw a parallel, to stop teaching emergency procedures . . .

I've put this in red a couple of times so let me try once more:

I'M NOT SUGGESTING WE STOP TEACHING OOA OPTIONS.

What I AM saying is that IF we didn't teach OOA options, would we put a better/greater emphasis on not running out of air. And would that make a difference?

I'm also asking if the fact that we teach OOA options unwittingly gives a singal to new divers that it's no big deal to run out of air because there are ways to "fix" that?

And I'm also suggesting that the data from DAN, showing 41% of 350 fatalities having OOA as the trigger should be a wake-up call that something might be amiss. If the number was 1% I don't think I'd be on my soapbox.

is akin to teaching sky diving without showing someone how to deploy their backup.

I would suggest the anaolgy is "Don't worry about packing your main properly or even deploying your main because you can always deploy your reserve."

Likewise if we stop teaching emergency procedures in scuba diving more accidents will happen.

I don't know that I agree with that as a blanket statement, but I see where you're coming from. But what I'm saying is, Are you giving people OOA options to rely on that aren't really as reliable (for whatever reasons) as we think. Because wouldn't that be like, to use your skydiving analogy, saying you've got a reserve but when you go to deploy it, you realize it's made out of fabric with holes in it and doesn't work.

What Ken fails to mention . . . (is) the total number of incidents of OOA that were solved adequately by the divers as a result of following their training.

Correct. Because we don't know. It's certainly the biggest flaw in trying to compare successful vs. unsuccessful OOA incidents. (As a sidenote, I'm pushing DAN to do a study of their database for calendar year 2010 that might help us get that info to extrapolate.)

I'm certainly not saying that 100% of the people who run out of air die. I'm also not saying that 0.1% of the people who run out of air die. We simply don't know. It seems to me that OOA as a percentage of the fatalities (41%) is a phenomenally higher percentage that OOA as a percentage of the total dives. But my gut tells me that OOA is fatal as often as it is not. And IF THAT'S CORRECT wouldn't a 50% failure rate tell us something about the proposed solutions???

In other words, to put it in blunt terms, his idea of "making stupid painful" . . .

Not even remotely close to what I'm saying.

A more helpful question, in my opinion, would have been to ask *in addition* to what we are doing now, what *else* can we do to make this number go lower?

I would say "in addition to or instead of". There's still an underlying assumption in your statement that what we do now works, and while it should, the data seems (to me at least) to suggest differently.

- Ken

 

[Freezerbrn]

Ken- "Saying that there are other options to deal with the problem still doesn't attack the root of the problem: WHY are people running out of air, and what can we do about it???"

From what I can relate to as a diver with less the 20 dives is that, there is a lot of multi-tasking with unfamiliar equipment, in an unnatural environment (for humans) in a position (horizontal) that human beings don't spend much time in. 1.Looking at gauges with lots of changing numbers, 2. Buoyancy control (inflate deflate), 3.Location/Navigation, 4. Buddy location, 5. The reason we are there looking at the sea life. For some (me included) it's a lot to take in and keep track of. I'm sure with time all of this becomes 2nd nature.

To clarify the unfamiliar equipment statement, I don't mean to imply a lack of knowing how it works, just using a piece of gear that you don't have much practice with. I know that during class I used a lot of gas inflating and deflating my BC learning how to be neutrally buoyant which in turn altered the amount of gas for me to breath, thus altering how fast I'm burning thru it.

Gas management training during OW. A long block of training on gas management and learning how to use/read your computer.

my .02

 

[Ken Kurtis]

I'm going above my pay grade here but I'll give this a shot. Others more medically inclined, please feel free to weigh in. I may also try to get Karl Huggins from the Catalina Chamber to respond but he's manning a polling place today so it would be tomorrow at the earliest.

My initial disclaimer is that I think I'm phrasing all this correectly but I won't promise it 100% spot-on.

Do you have any research that suggests more emboli are created with aveoli bursting compared to ascending and emboli created solely by the bubbles already in your bloodstream expanding?

By definition, an embolus in your bloodtream released from the your lungs (alveoli) is pretty big. HUGE in comparison to nitrogen bubbles. And the reasons these can be so dangerous is that they're big enough to stop blood flow all together.

Bends is different. Excess nitrogen absorbed by the body diffuses back into the bloodtsream, is carried to the lungs, diffuses back into a gaseous state, and is exhaled. When it's coming out of solution faster than the process can handle (bends) then nirtrogen bubbles form in the bloodtsream. But they're little, teeny-tiny bubbles. (Think of the difference between a basketball - embolus - and a BB - bends.) These bends bubbles are small enough to travel freely through the body but they get lodged in the tiny, lttile, narrow capillaries which is what causes the joint pain. If they lodge against nerves, that's what causes neurological deficit.

I'm skeptical about this. Sorry. Thank you for explaining it better though.

No problem.

As we know there are bubbles in our body from a recreational dive. To say you can go as fast as you like as long as your lungs dont go above 100% you wont have an embolism is something I don't agree with (or well depending on time depth deco obligation etc). It would be like looking at only the lung injury component.

Yes, I thought I made it clear I was ONLY talking about the AGE/lung-injury component. (I'm not advoctaing you ascend really fast. I'm only saying that, strictly from an AGE perspective, you can do so without embolising.) I think I even pointed out in the post that because ascent rate is part of decompression, a rapid ascent can cause a bends hit in an otherwise OK profile.

Bends and embolsim are two very different things. I think you're either combining them into one or confusing the two. They're apples and oranges. In it's simplest form, embolism is a result of a breath-holding ascent while on scuba. Bends is result of depth & time on scuba, absorbing more nitrogen than your body can safely outgas and coming back to surface pressure.

Most emboli don't cause immediate death....

Where did you hear that from??? Although you're technically correct . . . You don't embolise and immediately die . . . embolisms manifest themsevles relatively quickly (usually within minutes of surfacing) and are ALWAYS consdered life-threatening. They require on-site emergency first-aid oxygen, frequently CPR and life support, and immediate treatment in a qulaified hyperbaric chmaber.

While there are instances of bends going untreated and eventually resolving with no apparent after-effects (skin bends is an example that may not require chamber treatment), I don't know of any verified embolsim case where the person didn't get treated and survived. Conversely, there are many cases of embolism where the diver died, whether they got treatment or not.

- Ken

 

[Ken Kurtis]

the issue that Ken really wants to discuss: WHAT, if anything, SHOULD BE CHANGED?

Nicely stated Pete. Thanks.

Maybe another way to think of it is: If OOA options DIDN'T exist, and you couldn't invent them, would you do anything differently in training to try to ensure that divers didn't run out of air on a dive?

- Ken

 

[rongoodman]

The key word in AGE is "arterial". Bubbles resulting from off-gassing inerts are found in the venous circulation, and are removed in the lungs. (If the mass of bubbles is more than the lungs can handle, a form of DCS called the "chokes" can occur.) Bubbles on the arterial side, whether from a tear in the lung tissue or a PFO, are a much more serious problem, and will continue to forced through smaller and smaller arteries and arterioles until they get stuck, blocking further blood flow to the area, which might well be in the brain or coronary arteries.