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

[peterbj7]

Using modern equipment (since 1979) I have made some 6000+ dives and I have yet to run out of air. I've had out-of-air/gas drills in training of course, some of them way more demanding than anything described in this thread. And I've made some pretty extreme dives. There's no great skill in this, just a modicum of care and a desire not to drown.

 

[John C. Ratliff]

'Sorry for the departure; my wife had cataract surgery this morning, and I had to leave to get her to the doctor for a post-op checkup.

Continuing my thoughts, let me give some thoughts about out-of-air situations. When I said that we experienced out-of-air regularly, that was a bit of a stretch as I was using two regulators in my first diving years that had what is called a "restrictor orifice." These two regulators were the Healthways SCUBA regulator, and the Healthways Scuba Star regulator. The former is a double hose regulator, and the latter a single hose, tilt-valve regulator (a single hose regulator was just that, one LP hose to the second stage, and that was it). I have been collecting these old regulators, putting them back into service and diving them in the last five or so years. The restrictor orifice is a small hole through which the all the diver's air must pass, and it works on the high pressure side of the regulator. So there was a warning, via increased inhalation resistance, when the cylinder pressure got down to between 500 and 700 psig. Therefore, for those first six or so years, I had good indications when I was running low on air. These regulators would force you to the surface to get adequate air, but could not be used in overhead environments as you could not go deeper without loosing the air supply to high resistance.

Then I got an AMF Voit 40 fathom regulator, the Voit equivalent to the U.S. Divers Company Calypso regulator (original). This had a balanced first stage, so you could not tell when the air supply was getting low until you were out-of-air. Here is where I sometimes found the J-valve tripped accidentally, and no air (this regulator was not equipped with a SPG). So it was in this time frame that I had some out-of-air situations. But this was sport diving (usually <60 feet depth, no decompression diving). The surface was available too.

When I mentioned the requirement to be able to swim underwater 50 feet, that is the equivalent of of an ascent from 50 feet. But when ascending from 33 feet sea water (2 atmospheres absolute) air expands twice its initial volume. From 66 feet sea water, the expansion is three times the original lung full, and from 99 feet, 4x the original volume. You have to blow out air upon ascent. So saying that a diver is "out-of-air" assumes that the diver does not ascend. But sport divers can ascend to the surface from depth; they have dived a no-decompression profile.

On top of this, the same physics applies to the scuba tank, and as the diver ascends there will be one to several extra breaths available from the scuba tank, depending upon depth.

My feeling is that scuba training now is telling divers to get "advanced" courses in nitrox, wreck, cave, etc. diving that are using either overhead environments or decompression diving as a "normal" practice. Therefore, divers are being taught from the start that out-of-air will kill them, as evidenced by the quote above. This is a mainly economic decision based upon trying to get divers to "progress" from the basic course to the specialized courses. But here, the diving community is getting out of the strictly "sport diving" realm, and going where the professional divers go. It started with cave and wreck diving, and the inherent attractions. But the sport diving community can't or won't endorse on-board deck decompression chambers, and uses water decompression depending upon the cylinders (as many as six on one diver), or rebreathers to conduct these dives. This has strayed away from strictly sport diving, into a highly specialized set of courses that put the divers at higher risk.

SeaRat

 

[Ken Kurtis]

Therefore, divers are being taught from the start that out-of-air will kill them, as evidenced by the quote above.

We sort of had this discussion in another thread a year or so ago and I don't intend to re-hash it here but:

I would disagree most strongly with this statement. I would contend that divers are NOT being taught how dangerous running out of air is. And before you all say "WTF???" . . .

Yes, we all tell basic students "DON'T RUN OUT OF AIR!!!" And then we follow that up with, "But if you do, you've got some options like buddy breathing, octopus, independent alternate air source, or even a free ascent to the surface." But offering options IMHO, we totally dilute the "DANGER WILL ROBINSON" nature of the first statemement.

Instead, I'd rather see us teach it as "If you run out of air, you will significantly increase the chances of dying on this particular dive from drowning. You may be able to marginally improve your odds if you are able to buddy breathe, octopus breath, use an indpendent air source, or do a free ascent. 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 statsitic."

- Ken

 

[John C. Ratliff]

Ken, I had to look up that "DANGER WILL ROBINSON" quote; it's been quite some time since I watched Lost In Space. Concerning what I would say, I don't use that expression.

Could you provide the reference for that "out-of-air was the trigger for the fatality 41% of the time" statement? I looked in the 2010 Fatality Workshop and cannot find it there. I also could not find it on the DAN website. I have been reading the 2010 Fatality Workshop, and some of the information is rather confusing to me. It seems that DAN is using some common terms to the safety profession, but providing their own interpretation of them (for instance, the Table 2, Modified Root Cause Analysis is specific to DAN and diving, and not seen in professional safety. They also quote the Health and Safety Executive in the UK for other Table 2, Individual Risk per Annum. I'm not saying there are problems, just that I need time to study this information to make sense of it.

Now let me address directly your strong disagreement with my statement. If we train people to say that if you are "out-of-air" you will significantly increase your chances of dying, will this help or hinder the tendency toward panic? Would it be better to equip them to handle this situation? Yes, we can prevent out-of-air too; one method is to use a J-valve in addition to the SPG, and not use it for normal diving. Another is to have a spare air, or pony bottle. My thoughts are that we want competent divers who are comfortable in the water, and not divers who are close to panic if anything goes wrong. 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.

I see NAUI is now highly invested in specialty courses (from their website). What is your perspective on where NAUI is now; I see they have slightly modified their "Safety Through Education" to "Dive Safety Through Education."

 

[Ken Kurtis]

Could you provide the reference for that "out-of-air was the trigger for the fatality 41% of the time" statement? I looked in the 2010 Fatality Workshop and cannot find it there.

Page 79 of the proceedings, second paragrpah.

I agree that if you didn't know what you were looking for, you could skip by it. This was part of the presentation (and given in greater detail) made by Dick Vann that's summarized starting on page 73. In his presentation, he had slides (and I took copious notes) indicating that of the 947 cases they studied over ten years, they identified the trigger in 350 of those cases. And of those 350, the trigger was out-of-air in 144 of the caes (41%).

- Ken

---------- Post added February 16th, 2013 at 07:00 AM ----------

If we train people to say that if you are "out-of-air" you will significantly increase your chances of dying, will this help or hinder the tendency toward panic? Would it be better to equip them to handle this situation?

I think it will lessen the chance of panic. I'm not saying don't teach them th eoptions. I'm simply syaing we've got the emphasis on the wrong end. Panic seems to result with suddenly dealing with unknown factors and not reacting well. If you start in your head with the thought of "This is REALLY bad" i think you'll be more focused on getting a survivable solution (or avoiding the problem in the first place). However, I think the thought divers have nowadays is, "This isn't THAT bad because I have all these other options" and not understanding the gravity of the situation makes them panic if the option/solution doesn't go exactly as practiced once or twice (and probably a long time ago) in the controlled setting of a pool under the watchful eye of an instructor.

 

[boulderjohn]

While I agree with almost everything Ken says about the trigger and all, I disagree about the training problem and its solution, IIRC, while OOA was the trigger, the rapid ascent and ensuing embolism were usually the real problem. That suggests that the divers did not perform a proper emergency ascent. I have been arguing for years that we do a lousy job teaching that skill, and I have written frequently about how many principles of learning theory we violate in teaching it.

The net result of that poor teaching is, IMO, the opposite of what Ken suggests. Students get the idea that the emergency ascent is an enormously difficult task that they somehow got through in training but could never do in a real emergency. When they are then actually in such an emergency, they hold their breath because they don't believe they can make it exhaling, and they have never been taught that their regulator will give them air at shallower depths so it is OK to inhale.

 

[InTheDrink]

Isn't a large part of the problem that some agencies don't put hardly emphasis on drilling frequently? If part of the training was an S-drill at the start of every dive people would a) be less likely to panic and b) get a sense of how important this is?

 

[John C. Ratliff]

While I agree with almost everything Ken says about the trigger and all, I disagree about the training problem and its solution, IIRC, while OOA was the trigger, the rapid ascent and ensuing embolism were usually the real problem. That suggests that the divers did not perform a proper emergency ascent. I have been arguing for years that we do a lousy job teaching that skill, and I have written frequently about how many principles of learning theory we violate in teaching it.

The net result of that poor teaching is, IMO, the opposite of what Ken suggests. Students get the idea that the emergency ascent is an enormously difficult task that they somehow got through in training but could never do in a real emergency. When they are then actually in such an emergency, they hold their breath because they don't believe they can make it exhaling, and they have never been taught that their regulator will give them air at shallower depths so it is OK to inhale.

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

 

[FlyingSquid]

Technically, cause of death will be something like drowning because the phrase "Cause of Death" really means "what was the mechanism of death"? The is what's great about the DAN 4-step method of analysis with (1) trigger, (2) disabling event, (3) disabling injury, (4) cause of death. Running out of air is the trigger, which causes panic & rapid ascent (disabling event), which causes embolism (disabling injury), which cause drowning (mechanism of death).

This was great input Ken. Thank you.

Is there data of what triggered the trigger? I mean, what most often led to those OOG situation? Carelessness in checking SPG? Pushing the limits to "dry the tanks" and extend the dives? I suppose it's not equipment failure, or that would be consider the trigger. If OOG is the trigger, everything before this was calm.

 

[John C. Ratliff]

In my preliminary reading of the DAN 2010 report on fatality statistics I noted their discussion of the limitations on the data because of a lack of consistency in reporting diving fatalities in the USA. I would also like Ken to respond to this, as he has taught way more than have I, and might have insights from his students as well as the literature.

SeaRat