Fatalities statistics: what kills people the most in scuba diving?

[FlyingSquid]

Many people graduating from scuba class don't have the confidence that they used to have in the water. This so-called "out-of-air" is only true if someone believes that there is no air available at all, and they will die without either the buddy's octopus or an alternative air source. This leads to panic, and to increased efforts which use the oxygen faster.

I second that what John is saying should not be taken lightly. You make the most to avoid being in an OOA situation. But if it comes and you are unable to keep your calm, things get worse quicker. His point is that there used to be much more training and emphasis on building the psychological and physical skills to deal with those situations.

 

[InTheDrink]

John, I think this is what I'm trying to communicate. Let me give an example.

Very near my home, we have a competition pool, with a competition diving area 18 feet deep. It is a 50 meter pool on the long end and 25 yards wide so competitions can be on either a national or regional basis; in other words, it's a big pool. On Sundays between 11:00 AM and 1:00 PM (when there are no competitions going on) they allow kayak and scuba diving in the pool. On those occasions I take my old, antique regulators (double hose and single hose) into the pool to try them out. I watch the kayakers practice their rolls from underneath and then many times I'll do ditch and recovery drills. I'll also watch the other divers, most of which are trying to perfect their frog kicks and doing their buoyancy control. On some of those ditch and recovery drills, I'll take my scuba off in the deep end, then rather than swim to the surface 18 feet above me, I'll swim across the pool, simulating an ascent from 75 feet or so exhaling all the way. It is easy! I'll take a breath, submerge and swim the 75 feet back to the scuba unit, turn the air back on, clear the mouthpiece and begin breathing again. It's a good drill, and at 67 I can still do it easily.

Swimming 75 feet underwater is like doing a snorkel dive to about 37 feet, which is well within almost everyone's capability. This is why it boggles my mind that an otherwise competent diver will freak out having to do an emergency swimming ascent from 40-60 feet!

In the 1980s I was Finswimming Director for the Underwater Society of America. Finswimming is a competition using fins, and one of the events is the 50 meter apnea swim. The current world record for 50 meters immersion apnea (breathholding underwater) is 14.64 seconds. 50 meters is 164 feet. I can swim 50 meters underwater right now, at age 67. That to me means I can make an emergency swimming ascent from the entire range of sport diving (to 120 feet; sport diving is not specialty diving). Swimming from depth, I will have many lungs full to exhale too. So what's the big deal?

SeaRat

Ascent drills are great and the fact you can swim 50m on a breath hold is great altho I'd say that's not the norm.

One thing that is ignored is that in many failure modes OOA will occur such that you won't have a big deep breath of air to enjoy first. Your first indication that you have no gas may be on your inhale. This gives you fewer options IMO. And why having either a buddy or alternative gas source a better option. And an alternative gas source seems to me more reliable.

Personally I struggle to understand why an independent alternative gas source isn't standard. I can see few downsides.

 

[FlyingSquid]

Wrong statistical conclusions

But statistics from DAN show that in cases studied with complete information, out-of-air was the trigger for the fatality 41% of the time. So please don't ever run out of air so that you don't risk becoming another statistic."

Ken, while I agree with most of your arguments, your conclusion above simply doesn't follow. The fact that 41% of the fatalities come from OOA says nothing about the percentage of OOA cases that lead to fatalities. Likewise, if 95% of the rich people you know were hard workers it doesn't mean that working hard will make you rich.

Without more data, it's possible to think of a scenario where (say) 99% of OOA situations are solved by buddy breathing or emergency ascent, and the 1% that doesn't will contribute to the 41% of recognised fatalities. And maybe the other 59% could be because of problem X, which happens to be rare but kills 50% of the time.

I think that telling them "So please don't ever run out of air so that you don't risk becoming another statistic" is telling them that they are out of options if "out-of-air" when in fact there are still options to stay alive and healthy.

Consistent with my answer above: yes, John, maybe. But to be able to tell how likely those "other options" are to save you we would need numbers that are nowhere in the DAN data and we're just speculating about.

We only have from 100 deaths, how many were OOA situations.

The missing data here is the opposite path: from 100 OOA situations, how many die? Those who don't die, how do they solve it? Etc.

 

[Ken Kurtis]

Numerous quick points about various comments. But the first one I want to say is "Thank you" for the dicussion, To me, THIS is what ScubaBoard should be all about and THIS is the type of discussion that makes us all better instructors.

Isn't a large part of the problem that some agencies don't put hardly emphasis on drilling frequently?

I think frequent/regular drilling after class is completed would certainly help. However, it's probably not realistic to expect that people who don't dive regularly/often (however you want to define that) will jump in a pool and practice skills. What I have personally taught, and what is in our (Reef Seekers) standard dive briefing, is a suggestion that everybody practice - on the surface prior to descent on the first dive - out-of-air responses and then do it again if they switch buddies at some point in the day. My thought is that by at least putting in your head the thought of "You could run out of air so don't do that but you need to know what to do about it if you do" heightens your air-monitoring awareness as well as gives you some recent practice with a person you may have to rely on should the need arise.

---------- Post added February 16th, 2013 at 05:52 PM ----------

Is there data of what triggered the trigger?

Short answer: No.

My GUESS/SPECULATION is that it's failure to monitor the pressure gauge. I have yet to see a case where equipment failure caused a diver to run out of air. (Not saying it hasn't happened, simply that I am unaware of it. If anyone knows of any and wish to post a counter to this, please give some details.)

---------- Post added February 16th, 2013 at 05:57 PM ----------

I noted their discussion of the limitations on the data because of a lack of consistency in reporting diving fatalities in the USA.

Yes, absolutely. Different jurisdictions may have different standrds for the M.E./Coroner. In LA, the Coroner RARELY says heart attack with a diving death unless there was someone there who saw the victim clutch his/her chest, etc. but they'll note that underlying heart disease may have been a contributing factor. In other jurisdictions, they may just go with "drowning" because it's easy, they don't suspect foul play, and they'd like to close out the case. There are plenty of diving court cases where the M.E./Coroner, who is under time pressure to come to a conclusion, has that medical opinion disagreed with by either plaintiff or defense experts who have a lot more time to study the nuances of the case.

So yes, one jurisdiction's heart attack may be another's drowning and that skews the results.

---------- Post added February 16th, 2013 at 06:13 PM ----------

Ken, while I agree with most of your arguments, your conclusion above simply doesn't follow.

Let me state it another way.

We would assume that there is a correlation between how often something occurs in the general population and how often something occurs, in this case, in accidents. For instance, if 10% of the population is left-handed, we would expect that 10% of the dead divers would be left-handed, because there's a reasonable assumption that being left-or right-handed shouldn't factor in here.

However, if we discovered that 40% of the dive fatalities involved left-handers, we might think something is amiss. So we would first see if the % of left-handers in the dive population is the same as the % of left-handers in the general population. Assuming that we discovered that only 10% of the dive population was left-handed, we might draw an inference that there's some connection about being left-handed that increases your chances of becoming a fatality statistic.

I am confident that the 41% as the number of triggers from out-of-air is relatively accurate. Perhaps a study of more fatalities spread over more time (the DAN numbers are based on 10 years of fatality stats) would yield a more accurate number. It may be 30% or it might be 50%. But it's not 10% and it's not 90%. I believe that 41% is fairly close and certainly gives a framework for discussion.

So now my question would be: How often does a dive end up with the diver running of out of air? If you would like to argue that 41% of the dives made result in a diver running out of air, then maybe there's no correlation. But that is not at all my experience in supervising literally thousands of dives a year. I would estimate that the % of dives that end in an out-of-air scenario is certainly less than 1% of the total dives made (and most likely a faction of 1%).

If you will accept my 1% number, then the question becomes: How can somethjing that happens 1% of the time in the general population account for 41% of the triggers in a fatality? I believe the inference you can draw is that there is some connection between running out of air and dying that indicates that running out of air is far more dangerous and less likely to be survivable than we teach.

Happy to be shown the folly of my ways (and I don't mean that as a macho/ego challenge, just saying feel free to point out what I'm missing).

---------- Post added February 16th, 2013 at 06:16 PM ----------

The missing data here is the opposite path: from 100 OOA situations, how many die? Those who don't die, how do they solve it? Etc.

You've hit the nail on the head here. We know the numerator (how many people die from out of air) but we don't know the denominator (how many people run out of air but survive). And we proably never will know that number because people don't think of that as an "accident" when there's no injury. But yes, THAT would be what we need to know: How did you survive running out of air and what did you do that worked to survive the OOA? (Perhaps a good topic for a spearate thread discussion.

 

[InTheDrink]

Obviously I believe I'm right. But good OOG drills will keep ppl close. It just happened to have save my life so I may be even more biased.

Basic training from the agencies I'm familiar with just don't cut the mustard.

I think that new divers die from OOG more experienced divers die from other things, like getting lost.

My concern has always been with newer divers because they don't know what they're getting into. This is why I believe that getting a defensive attitude into divers is good.

 

[John C. Ratliff]

My GUESS/SPECULATION is that it's failure to monitor the pressure gauge. I have yet to see a case where equipment failure caused a diver to run out of air. (Not saying it hasn't happened, simply that I am unaware of it. If anyone knows of any and wish to post a counter to this, please give some details.)

Ken, let me give you two examples.

In 1975, I was diving on the Warm Mineral Springs Underwater Archeological Project with Sonny Cockrell and Larry Murphy and crew. From time to time we would get some notable divers to come and dive with us. Dimitri Rebikoff and Dr. Silvia Earle were two examples. I say that not to drop names--they don't know me--but to mention that this project was pretty high profile. In the process, the Florida Secretary of State, Ron Jones decided he wanted to see this site himself, and because there was Florida funding got to dive with the team. He was using our twin 80 AL tanks with a Cyclone regulator, when it malfunctioned and he had no air. He calmly went over to his buddy diver, got his octopus (Larry Murphy insisted everyone dive with an octopus--my first experience with them, by the way) and completed the dive for about 10-15 more minutes breathing off his buddy's system. Cyclone regulators were notorious for this kind of failure. It helped that he was an ex-Navy SEAL too. We were mostly diving the 45-50 foot level, which was where a lot of the survey work was being done because there was a ledge there that Larry's team had found a 10,000 year old atlatl embedded in the mud. But Ron's incident happened at 90 feet depth; I know because I still have the incident report that I sent to NAUI Headquarters in my dive log book. I'll scan it and post it here too later this evening.

If you'll look at Sonny Cockrell's report (linked above) you'll see that he talks about all the diving that they did without an accident. This was because there was meticulous planning for diving. We had oxygen decompression, provided by a bank of oxygen cylinders (300 cubic foot cylinders, stationed on land) with lines running into the water and separate lines for each diver, and a regulator second stage on each line. We had planning (see the Dive Master's Log I put together) which detailed emergency services nearby, including ambulance, nearest decompression chamber, nearest diving doctor, and helicopter rescue. I was able to put most of that together so that they had it. I was at the time a USAF Reserve Pararescueman, attached to the 304th Aerospace Rescue and Recovery Squadron (ARRSq) in Portland, Oregon. So I knew how to get ahold of the 301st ARRSq in Miami, and there 24 hour number. Later I switched them to Detachment 14, 38th ARRSq at McDill AFB, Tampa, Florida because it was closer. These are the types of things I see missing in the specialty diving programs as currently taught.

The second incident happened to me in the 1980s, when I was diving on the Edmonds Underwater Park with my friend Bruce Higgins. I was diving twin 45s, and had my Trieste II double hose regulator on the scuba. It had an MR-12 octopus second stage. I had modified this regulator a lot, and one of the modifications was to put a baffle plate into the mouthpiece. I was swimming toward shore toward the end of the dive when I exhaled and tried to inhale--and got nothing. I immediately switched to my MR-12 second stage, and completed the underwater exit about ten minutes later. I knew the tanks were not empty, as my SPG read something like 700 psig. What had happened is that this baffle plate (from a Healthways double hose regulator) had come loose inside the mouthpiece, and had became lodged against the inhalation non-return valve in the mouthpiece. No air could get through due to the suction between the silicone mushroom valve and the baffle plate. The baffle plate is a circular plate meant to be in the center of the mouthpiece, which had holes drilled around its periphery to allow water to be expelled while directing incoming air down the mouthpiece. It was necessary as I had increased the venturi effect of the nozzle, and did not want blow-by through to the exhalation hose. But simply switching to the octopus solved the problem for that dive.

SeaRat

 

[FlyingSquid]

However, if we discovered that 40% of the dive fatalities involved left-handers, we might think something is amiss. So we would first see if the % of left-handers in the dive population is the same as the % of left-handers in the general population. Assuming that we discovered that only 10% of the dive population was left-handed, we might draw an inference that there's some connection about being left-handed that increases your chances of becoming a fatality statistic.

Ken, I wished all posts were as well-thought and civilized as yours.

Let me briefly tell you that the two examples are not quite the same.

First, I agree with your left-handed example. With those numbers, sure there was something about left-handed that would ask for investigation. (Although it wouldn't be obvious the problem is really left-handedness. It could be. But it could also be, for example, that some other condition that causes, or comes with, or is caused by left-handedness would be the proximal responsible for the fatalities. Meaning that not only because left-handedness precedes and is correlated with fatality it is the direct cause. Correlation does not imply causation)

In those cases, ignoring ambidexterity, people are either left-handed or right-handed. So we can quickly see that the 90% of right-handed people correspond to only 60% of the deaths. So no need to do much math, clearly there seems to be something directly or indirectly related to left-handedness that constitutes a risk factor.

Now...

If you will accept my 1% number, then the question becomes: How can something that happens 1% of the time in the general population account for 41% of the triggers in a fatality? I believe the inference you can draw is that there is some connection between running out of air and dying that indicates that running out of air is far more dangerous and less likely to be survivable than we teach.
Happy to be shown the folly of my ways (and I don't mean that as a macho/ego challenge, just saying feel free to point out what I'm missing).

Now... here is different. Because there could be any number of possible causes other than OOG, and because it doesn't sum up to 100%. Above you have left and right handed dives mapping into left and right handed deaths. Here you have OOG dives mapping into OOG deaths, cause B dives mapping to cause B gas, etc, then a lot, say 95% or more dives that simply have no death representation.

But forget this point, it's not the most important.

Here is the main point, which I have previously said:

If I accept your 1%, this means that 1% x 200million/10 = 200 thousand dives a year have OOG problems. Of those, 41% x 350/10 = 14 deaths. So, given your own numbers, the risk of dying of OOG causes once you had an OOG problem is 14 / 200 thousand = only 0,007%. So, by your own numbers, OOG problems are manageable in 99,993% of the cases.

Wait a second, so maybe OOG is rarer, say it happens once every 100 thousand dives. Then only 7% of those die, and it's manageable in 93% of the cases. Now, if the frequency is 1 every million dives, then you can only save yourself 30% of the time. You see, without knowing the frequency with which OOG situations happen, we cannot access how fatal it is once it happened. We can only calculate it based on total dives, that is, given that you dive, what is the chance of fatality due to OOG? Only 140 in 200 million, or 1 in 1.43 million.

In that sense, your fictitious handedness problem is the same. Say you have only 1000 fatalities for 200 million dives, roughly DAN numbers. So 40 are "due to left-handedness". And 10% of dives, so 20 million, are left-handed dives. So the fatality rate in left-handed dives is 40 in 20 million or 1 in 500 thousand. And the fatality rate in right-handed dives is 60 in 180 million or 1 in 3 million.

Left-handedness is 6x as dangerous as right-handedness but both are extremely safe.

I don't like saying this because it may foster recklessness, but if DAN numbers are right, then the kind of scuba diving most people do (likely shallow rec) is extremely safe.

 

[Ken Kurtis]

I don't like saying this because it may foster recklessness, but if DAN numbers are right, then the kind of scuba diving most people do (likely shallow rec) is extremely safe.

I happen to agree with you on that. 80-90 fatalities a year from a pool of 20,000,000 dives is extremely safe . . . except for those 80-90 people who died.

I think you're getting a little too hung up on the minutae of the numbers and not really looking at the problem. So try this one:

We know that in this 10-year period that DAN studied 947 people died. Of those, we have complete information on 350. Of those - and assuming they represent the diving population as a whole - 144 of them (41%) ran out of air and died. Had they NOT run out of air, they would not have died (on that dive). So if we could figure out a way to eliminate out-of-air situations, we could reduce the number of deaths annually by 41%.

So here's the question for you: Is it eaiser/bebter/more-efficient to REALLY teach people not to run out of air in the first place (eliminating the problem) or is it easier to teach them four or five options to deal with solving the problem and hope they're executed correctly? (And this is an either/or choice. "BOTH" is not one of the choices.)

IMHO, I'd rather put a LOT of effort into eradictaing the problem than I would in teaching people how to fix it once they create it. And I've chosen my words very carefully here. Out-of-air IS a problem divers CREATE. It isn't (as I stated previously, I sort of reject the equipment failure scenario) thrust upon them by an outside force. If you have a hole in a bucket (problem), don't you patch the hole instead of continually finding new ways (spoon, cup, bottle) to replace the water you lose to the hole????

- Ken

 

[FlyingSquid]

So here's the question for you: Is it easier/better/more-efficient to REALLY teach people not to run out of air in the first place (eliminating the problem) or is it easier to teach them four or five options to deal with solving the problem and hope they're executed correctly? (And this is an either/or choice. "BOTH" is not one of the choices.)

IMHO, I'd rather put a LOT of effort into eradicating the problem than I would in teaching people how to fix it once they create it. And I've chosen my words very carefully here. Out-of-air IS a problem divers CREATE. It isn't (as I stated previously, I sort of reject the equipment failure scenario) thrust upon them by an outside force.

Ken,

Fair, I get your point, and sure better if those 15 people a year wouldn't die.

My take: more efficient means less redundant means exposure to failure. I really don't see why it should be an either/or. Emphasis on both: minimize the chance for OOG, but if for whatever crazy reason you're OOG (knock on wood), you know what to do. With both, you are more likely to take this 41% to near zero.

I want to highlight a point again, though. If resources are limit and there is a choice between either educating people to prevent or to solve the problem, we need to know where the weakness is. With the fixed and low risk of 1 OOG death per 1.43 million, it's either one of this:

A=OOG happens a lot but people get out of it as if it was a walk in the park.
B=OOG is very rare, but when it happens, people are screwed.

Your example of 1% seems to suggest it's A. Your emphasis on preventing the OOG scenario in the first place assumes it's B.

So either we find the numbers for a more informed choice, or we bet on one or the other, or we just cover both.

I'd cover both because I see no reason not to. Does it make sense?

Great discussion.

 

[John C. Ratliff]

Guys, I added a lot to post #55 above. Please go back and read it.

Ken,

One thing you might now take into account is that not everyone thinks of out-of-air as an emergency. I had one of those dives years ago on a subtidal clam bed survey with the Oregon Department of Fish and Wildlife. We were conducting multiple dives, and I dove a tank that had less air than I thought. So when I got to the bottom to photograph the diver dredging for clams for our survey, I ran out of air. I buddy breathed with him for about five minutes, until I got the photos I wanted, then surfaced from about 44 feet. I did not consider it an emergency, nor did anyone else; I simply put a small note to see many years later in my dive log.

SeaRat