Triggers of Dive Accidents

[Diver0001]

In another thread, there was talk of the DAN Fatalities Workshop held in April. I was there for all three days. (Phenomenally interesting and a really good and frank exchange of information and ideas. Much of it - materials, PowerPoint presentations, videos, and more - is available online at DAN's website.)

In a separate thread on the workshop, the following comment was made:



I think Peter raises a very valid and critically relevant point and I wanted to make this a thread of its own, rather than just bury it in the other thread.

Dick Vann, VP of DAN Research, presented some info (can't recall if it was a pre-workshop paper or at the workshop itself) where he and Petar Denoble looked at 900+ case studies of fatalities over a 10-year period. In a little less than half of those (350-ish), they were able to identify the triggering event that caused the accident and led to the fatality.

Inn 41% oof those cases, the trigger was . . . OUT OF AIR.

This got me to thinking.

If you're looking at something statistically, you'd assume there's a direct correlation to how often something occurs in the population vs. how often it occurs in whatever you're measuring. In other words, if 10% of divers are left-handed, you'd assume that 10% of the people who get bent are also left-handed. If the number is significantly higher (or lower) than 10%, then you'd wonder if left-handedness plays some factor in the bends.

In this instance, we see that 41% of the fatalities start because someone ran out of air. I do not for a minute believe that 41% of the total dives made end up in people running out of air. In fact, I'd guess that the rate of people running out of air is something on the order of 0.1% (or even smaller).

Since we do not know the total number of people who run out of air in the study period, we can't really come up with a rate of out-of-air fatalities. For all we know, every person that ran out of air died. For all we know, only 10% of the people that ran out of air died.

But what we do know, is that of those who died, running of out of air factors in significantly. And the next thought is that if we could prevent people from running out of air, we could eliminate 41% of the annual fatalities (which would mean about 37 fewer deaths each year).

So then the question becomes: Why do people run out of air? The answer I've come up with is one that I think is controversial but true: Because we tell them it's OK to run out of air.

Now, before you decided I'm totally crazy, let me explain that outrageous statement above. Because I'm absolutely certain that if I polled evetry instructor reading this and asked, "Have you ever told your students that it's OK to run out of air" the answer would unanimously be "No!!!" And if I polled every certified diver who's reading this and asked, "Have you ever been told it's OK to run out of air" the answer would be a resounding "No!!!"

So how could I possibly think this? Here's why:

In basic classes, I'm sure we all teach "Don't run out of air, don't run out of air, don't run out of air." But we follow that up with: "But if you do, there are some options." (And we go into combinations of octo, buddy-breathing, pony, free ascent, etc.) We present these options as not only resonable, not only as easy to learn (after, we teach it in a BASIC class) but we also imply, if not state directly, that they have a high incidence of success. We've just inadvertently told them "Don't run out of air but if you do, it's OK because here's how you can solve that probem."

I think we need to stop doing that.

Would it be better simply NOT to teach OOA options? And to simply say, "If you run out of air, there's an excellent chance you're going to die, so don't do it." (Or maybe teach OOA options as an advanced skill.) Shouldn't we be putting the Fear of God in them about running out of air? Because we're certainly not doing it now.

The other issue with OOA is that there's no penalty for running out of air, other than killing yourself. And how many people REALLY think that whatever they're doing is going to result in their death? Right now, people run out of air and can keep diving. Assuming they don't kill themselves, there's no penalty for it other than a little embarassment in front of other divers.

Maybe we need to change that school of thought. At Reef Seekers (my dive company) we've had a very simple rule on our charters: Run out of air, and you're done diving for the day. Period. No exceptions. Our thought is that you got lucky once, and we don't want to tempt fate twice. In 30 years, we've had exactly one person run out of air (and they lived).

At the DAN workshop, I was asked what I thought the penalty ought to be. I said I thought it was simple: Run out of air, and we revoke your certification card. Want it back? Then you're required to do some remedial training that emphasizes not running out of air. Run out of air twice? Find another sport.

Running out of air, based on the stats, seems phenomenally dangerous. It's certainly not something any of us would recommend yet it's something that, as an industry, we tolerate. Yet it's also something that clearly kills people. And that in turn, has got to have an effect on our insurance rates. Think about it: If we could eliminate 37% of the fatalities tomorrow, wouldn't that also result in fewer lawsuits which should also result in lower insurance rates?

That's about it in a very long nutshell. Thoughts???

- Ken

I'm sorry to do this but I'd like to get back to the first post in this thread for a minute and add my own perspective. Unfortunately the early mention of a pony got a lot of people chasing the ball instead of thinking about the game.

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 is akin to teaching sky diving without showing someone how to deploy their backup. To pick another example, you can see it as removing the airbag from the steering-wheel of your car and replacing it with a long metal spike the shoots you through the chest if you ever make a mistake. Neither one of those things is going to lead to fewer deaths. Likewise if we stop teaching emergency procedures in scuba diving more accidents will happen.

What Ken fails to mention here although he does touch on it briefly--and I don't think it's a deliberate omission--is that while OOA is the trigger for a lot of accidents and fatalities, he totally ignores the total number of incidents of OOA that were solved adequately by the divers as a result of following their training. I seem to remember reading another article (from DAN?) about this many years ago wherein they interviewed divers who had had potentially dangerous incidents such as OOA and survived. The vast majority of the people who responded said that they solved their problems by following their training. How many of *those* people would have died if we hadn't taught them what to do? My guess: more than we would have saved by just "putting the fear of God" into them.

In other words, to put it in blunt terms, his idea of "making stupid painful" will simply result in many many more accidents than we have now. That was the first thought that came to mind when I read his post and now I've explained why I think that.

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?

The obvious no-brainer to my way of thinking is to spend a *lot* more time talking to new divers about how to plan their dives such that they get back to their safety stop at the end of the dive with a proper reserve. Part of that is clearly teaching them the conceptual basics of gas-management and to connect that to judging conditions, planning navigation, their timing, routes through a dive site, ascent strategies etc. and to put it all together in once cohesive whole.

Just teaching one of these (gas management but not navigation for example) or to focus on grinding formulas for things like rock-bottom instead of understanding how all these building blocks fit together in a coherent "dive plan" isn't the answer. Likewise, just giving them (as the OW book does) a check list of things to consider, while a start, also falls vastly short of the goal of teaching them how to make a workable dive plan.

The one thing that OW students generally don't get in the course and the main reason, in my opinion, why they often feel insecure about diving independently after the course is simply that they don't know how to plan the dive. The second and equally important reason is that we don't teach them in OW how to navigate their way out of a bathtub.

And not knowing how to plan the dive coherently (including--especially--navigation) is, to my way of thinking, very likely the trigger BEHIND the trigger. Sure, running of of air may be the trigger for the actual accident but what was the trigger for running out of air? There aren't many scenarios, namely 3: gear problems, bad (or no) planning or they got lost.

In other words, instructors, get serious about teaching planning to your students. Since I've done this (I spend about 1/2 of the theory time in mod 3,4 and 5 talking dive planning in a holistic way) I've noticed a direct and immediate improvement in the confidence and competence of my students. Learning diving is more than obsessing about being horizontal and neutral, it's more than learning 19 disjointed skills and reading a book that only tells you 1/2 of what you need to know. It's about putting it together making it make sense, being able to find a coherence in your approach to a given dive. And teaching diving is helping your students get to that point.

To me, saying "stupid should be painful" (explicitly or not) is just giving up and not taking responsibility. I think we can do better than that.

R..

 

[The Chairman]

I don't believe that instruction is all that bad, but I do see time constraints causing classes to be RUSHED. I make it a point to teach Buddy skills along with gas planning.

ooA + ooB = C

Out of Air + Out of Buddy = CATASTROPHE.

Other than that, I see a lot of needless finger pointing in this thread. I guess it has to do with this being such an emotional issue for us. We will always have an atavistic reaction to not being able to breathe, but let's tone the personal attacks down a bit. Calling people crazy or suggesting that they don't know a thing about diving needlessly polarizes the issue that Ken really wants to discuss: WHAT, if anything, SHOULD BE CHANGED?

So please, we don't need to make value statements about others (self aggrandizing, etc) in this thread. Let's stick to what we know and what we think we know as it applies to standards, procedures and theory. Anyone who thinks that they understand it all already is clearly self deceived. I have already learned a number of things and I would hate to see the relevance and candor be diminished if this degrades into meaningless personal attacks.

 

[Scott L]

In fairness to the agencies, further training is highly, highly encouraged nearly 100% of the time I am sure...

 

[The Chairman]

In fairness to the agencies, further training is highly, highly encouraged nearly 100% of the time I am sure...

While many will decry the pecuniary interests of this, I completely agree with you. People often choose based on cost only. That's fine, but it's impossible to make a living that way.

I think the greater issue is the transition from training as a loss leader to being a profit maker. It's been a tough sell to the consumer and is part of the reason why our industry has been hit so hard.

 

[boulderjohn]

What Ken fails to mention here although he does touch on it briefly--and I don't think it's a deliberate omission--is that while OOA is the trigger for a lot of accidents and fatalities, he totally ignores the total number of incidents of OOA that were solved adequately by the divers as a result of following their training.

Now that I think about it...

I have no direct knowledge of anyone who died of an OOA emergency--I only know what I read.

I have only been in the vicinity of one genuine, unplanned OOA emergency (early in dive after accidentally switching to a used tank and not checking air), and that diver calmly took her buddy's alternate.

I personally know four people who have told me that they went OOA relatively early in their diving careers while either diving solo (I know), being too far from a buddy (I know), and even having a buddy who refused to donate (Wow!). All four were at depths of at least 75 feet, with one over 100 feet a the time. All four did a CESA, reached the surface just fine, and had no complications.

 

[danvolker]

While many will decry the pecuniary interests of this, I completely agree with you. People often choose based on cost only. That's fine, but it's impossible to make a living that way.

I think the greater issue is the transition from training as a loss leader to being a profit maker. It's been a tough sell to the consumer and is part of the reason why our industry has been hit so hard.

Maybe they should change the names of the intitial courses....

1. Basic Open Water to become " Learners Permit"/ Dependant Student Certification/ or / something like " Pool Diver".....this being based on actual abilities of the bottom one third of the classes.
2. Advanced Open Water to become : " Advanced Pool diver" / Less Dependant Student Diver" / or named by number of dives since AOW cert-- going from one to one hundred...when they get to 100, they are an actual sport diver....eg.. "Student Dives 66" or a 66'er

Regards,
DanV

 

[MXGratefulDiver]

It's a loooong ways from 500/400/300/200... psi to being 'out' of air, esp at 15', which is what the last few exchanges have been about.

You might be surprised. SPGs are notoriously inaccurate ... I own 11 of them and can tell you ... because I've done this exercise ... that I can put them all on the same tank and measure a 300 psi variance on the low end of the scale (i.e. high reading 500 psi, low reading 200 psi). This inherent inaccuracy is one reason for the 500 psi rule of thumb in the first place.

I'm truly dumbfounded by the persistence with which making it to 15' with air, but choosing to breathe some or even most of that air down to get some more off-gassing time, is characterized as some crazily dangerous act. C'mon, who dies at 15'?

Again, you might be surprised. Stress does interesting things to people's thought process ... particularly when they find themselves in a situation they're not sufficiently practiced to deal with. I know of cases of divers who make it to the surface OOA and end up drowning, because it never occurs to them to drop their weights ... or that they have an option of manually inflating their BCDs. One of those cases was a former member of ScubaBoard, in fact.

So long as you'll permit me to define 'out' in the way that balances risk to my satisfaction, we're in agreement! If you have some particular insight into that other evil - I'm all eyes, it can only help me re-assess my current take on the balance.

You can define anything in whatever way you please. My insights are based on working with new divers regularly, helping them remediate what I consider inadequate training for diving in local conditions ... and it's given me an insight into how new divers tend to deal with certain situations. That experience has led me to conclude that, given the choice between skipping a safety stop and risking an OOA ... even at shallow depths ... the safest option is to make a controlled ascent to the surface as expeditiously as possible.

Of course, as in all things scuba, it always boils down to the specific situation ... but for new divers, rules of thumb are intended to give them a decision path that they can follow when stressed, and to do so in a way that provides the highest probability for a happy outcome.

... Bob (Grateful Diver)

 

[Garth]

I don't mean this cruelly, but I think I do understand your question and if I do, I'm a bit concerned. (And please free to post a follow-up for anything I've gotten wrong about what I think your understanding is.)

Let's make sure we understand that AGE stands for "Arterial Gas Embolism," also referred to many times simply as "Embolism." It's an air bubble (or bubbles) in your blood. It can kill you.

Where does the air bubble come from?

Very simply, it comes from when your lungs burst and release air bubbles directly into your bloodstream. This happens when your lung (think of a balloon) over-pressurizes and breaks. The air bubbles enter the bloodstream and go to your heart or brain, can stop blood flow, and end up killing you.

How do your lungs get so big they burst?

Hopefully you remember Boyle's Law relating to pressure and volume.

If you decide to hold your breath all the way up and never let out a bubble, the air in your balloon lung will expand (to 200% volume), and your balloon lung will burst, releasing all of that air into your

If you hold your breath all the way up, because of the expanding air (not because of the speed of the ascent) your balloon lung will burst, the air will go into your bloodstream, and you will embolise.

That's how holding your breath AND ASCENDING will cause embolism. However . . .

If during this same ascent, you are continually exhaling, and never allowing the air in your balloon lung to exceed 100% of capacity, your balloon lung with NOT burst, you will NOT embolise, and you will live to dive another day.

In fact, you can do a rapid ascent and not get embolised. As long as the volume of air you exhale exceeds the expanding volume of air in your balloon lung, and you never allow the balloon lung to get beyond 100% of capacity
(DISCLIAMER: I AM NOT ADVOCATING YOU DO RAPID ASCENTS)
you can go as fast as you like. As long as you never let your balloon lung capacity exceed 100%, you will not embolise.


The gas exchange actually takes places in the alveoli inside the lungs. The alveoli looks more like a head of broccoli. You could, in theory burst some alveoli during a breath-holding ascent even though your lungs arer not at full capacity.

Does this help out and have it make more sense to you????? Or have I totally confused you?

- Ken

I cut out some of the factoids in your post. Yes I understand what you mean. 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?
I'm skeptical about this. Sorry.
Thank you for explaining it better though.
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.
Most emboli don't cause immediate death....

 

[blinkswiler]

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.

 

[Garth]

Maybe the type of emboli you are describing would cause death immediately but there would be so many other issues along with the AGE.