Triggers of Dive Accidents

[Ken Kurtis]

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 am again struck by the information as to the triggers of dive accidents and how they don't really seem to correlate very well with a lot of Open Water training.

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

 

[dumpsterDiver]

My conclusion is that we need to train them to use a pony bottle as part of the most basic certification course. Is there another, more simple and direct conclusion?

 

[TSandM]

Wow, beautifully thought-provoking post, Ken! Of course, revoking someone's cert card probably isn't feasible, since how would their certifying agency ever learn of their error, unless it occurred on a dive boat where the crew could report it?

But I think we should spend far LESS time on tables and decompression in training, and put in some gas management stuff -- how do you plan so that you DON'T run out of gas? People are told to be back on the boat with 500 psi, but not how to accomplish that. And instructors should watch students for gauge checks, and really chastise them for not checking. Imagine if the instructor told every student, "When you surface, I'm going to ask you how much gas you have, and before you look at your gauge, you have to tell me. If you can't do that, you don't pass the class."

I remember being in the middle of a class a few years ago, and the instructor was doing dives with two groups of students, so he was diving, coming up and going back down. At the beginning of the third dive, the captain asked him, "Are you OK on deco?" And Joe smiled at him, and at us, and said, "He's asking the wrong question. He should be asking me if I'm okay on GAS." That stuck with me. I'll bet, if you polled new OW grads as to what the biggest danger to them in their dives is, you'd have a lot more of them say DCS than would say running out of gas. We're emphasizing the wrong thing. We're asking the wrong question.

 

[zaberman1]

Ken, allow me to begin by saying you bring up an excellent point. I have put in a request to review the raw data and statistical models DAN is using because I find them to be very interesting. I think the conclusions you draw from the evidence are accurate but I can't say I agree with all of your recommendations.

Recommendation 1: Don't teach students contingency scenario's (ie ooa)

I don't think you are accurately deriving the conclusion from instructors teaching these skills. There are unforeseen events, like mouthpiece falling out, that causes a diver to believe they are out of air. Without proper training and reinforcement, I assume the fatality/incident statistics would be much higher. Second, I don't see how contingency planning necessarily entails divers actually running out of air. Applying the same logic, we shouldn't teach divers about emergency deco or any other profession contingency scenarios. Perhaps they had bad instruction or are just bad divers. Keep in mind: the incidence of fatalities is small, shouldn't it be higher if your analysis is correct?

Recommendation 2: Penalize people for running out of air.

People respond to incentives. This statement is kind of tautological because it means that people respond to things that motivate them to action, it would be kind of foolish if people responded to things that motivated them to inaction. Translation: People aren't that stupid.

This analysis is important and heavily lacking. I think a conclusion you might be able to draw is the way instructors teach running out of air does not allow divers to properly see the consequences of doing so. Therefore, when they are 30 ft and catching lobsters faster than a soccer mom pops zanies, they don't effectively calculate their risks. Adding the penalty would be VERY VERY useful. If a diver hits a certain psi/bar during training, they have to repeat that dive. If they do it again, they have to repeat the entire training program. If its on a charter, they should not be able to dive again on that charter. These are reasonable penalties. Additionally, I think we should TELL DIVERS ABOUT THIS EVIDENCE. Its crucial that they are taught the risks grimly so they understand the risks!

 

[scubaren]

While your point is well taken there are occasions where equipment failure may necessitate the need for air sharing. I think it is important for divers to know how to help each other in the event of equipment failure.

 

[Ken Kurtis]

I don't want my reply to come off as sounding nasty because that's not the intent. But . . .

My conclusion is that we need to train them to use a pony bottle as part of the most basic certification course. Is there another, more simple and direct conclusion?

How does having a pony bottle prevent them from running out of air in their main tank?

And if they run out in their main, and switch to the pony (I'm assuming 13cf or so), what's to stop them from thinking of the pony as a dive time extender and then running THAT one down to zero?

I believe what your solution says (unintended consequence) is that it's OK to run out of air. Because the reason you'd use a pony bottle is if you run out of air. If you don't run out of air, you're likely not to need the pony.

Also don't lose sight of the fact that running out of air is nothing new. Divers have been doing it since the sport got started. Why do you think they invented J valves????

- Ken

 

[Jax]

Wow, beautifully thought-provoking post, Ken! Of course, revoking someone's cert card probably isn't feasible, since how would their certifying agency ever learn of their error, unless it occurred on a dive boat where the crew could report it?

But I think we should spend far LESS time on tables and decompression in training, and put in some gas management stuff -- how do you plan so that you DON'T run out of gas? People are told to be back on the boat with 500 psi, but not how to accomplish that. And instructors should watch students for gauge checks, and really chastise them for not checking. Imagine if the instructor told every student, "When you surface, I'm going to ask you how much gas you have, and before you look at your gauge, you have to tell me. If you can't do that, you don't pass the class."

I remember being in the middle of a class a few years ago, and the instructor was doing dives with two groups of students, so he was diving, coming up and going back down. At the beginning of the third dive, the captain asked him, "Are you OK on deco?" And Joe smiled at him, and at us, and said, "He's asking the wrong question. He should be asking me if I'm okay on GAS." That stuck with me. I'll bet, if you polled new OW grads as to what the biggest danger to them in their dives is, you'd have a lot more of them say DCS than would say running out of gas. We're emphasizing the wrong thing. We're asking the wrong question.

Thanks!

<out of thanks>

 

[Jax]

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.
- Ken

Wouldn't that promote panic when the diver realizes s/he is somehow short on air?

 

[Ken Kurtis]

Keep in mind: the incidence of fatalities is small, shouldn't it be higher if your analysis is correct?

But don't lose sight that, in the DAN study, 41% of the fatalities were caused by out-of-air. I think that's a phenomenally high incidence, especially when compared to how often it's presumed to occur on a total dive basis.

And even if my conclusions or recommendations are wrong, what I'd really hope we'd start doing as an industry is just to start THINKING about this issue. Because something's definitely out of whack between what wwe teach and how divers dive (and die).

- Ken

 

[zaberman1]

But don't lose sight that, in the DAN study, 41% of the fatalities were caused by out-of-air. I think that's a phenomenally high incidence, especially when compared to how often it's presumed to occur on a total dive basis.

And even if my conclusions or recommendations are wrong, what I'd really hope we'd start doing as an industry is just to start THINKING about this issue. Because something's definitely out of whack between what wwe teach and how divers dive (and die).

- Ken

I agree (See Recommendation 2).

That being said 41% of diver related deaths is a small number, not enough to draw a meaningful conclusion about not teaching divers ooa skills.

The industry must change and instructors should be more conscious about reminding students that their air is limited and they CAN DIE if they don't monitor it.