My memory is bad but I think that must be at least 3 or 4 rebreather deaths in Los Angeles in the last 10-12 years. If I remember correctly we have 3-6 scuba deaths a year here. So over 12 years maybe 50-60 deaths. I'm doing all of this out of memory but if I'm close that means maybe 5% or more of scuba deaths in Los Angeles are on rebreathers. Maybe there is a whole lot of rebreather diving that I don't see but I don't think rebreather dives make up 5% of our total local dives. I know nothing about rebreathers so I am not saying anything about their safety. And I know the sample size of scuba deaths is relatively small. But the statistics of this I find interesting. Do you have the exact numbers of total scuba deaths and those being on rebreathers over a certain period? Any idea of what percentage of local diving is done on rebreathers?
Allow me to answer your question in my own drawn-out convoluted way, as I think it will provide the best overview. But I'm going to start by challenging the underlying premise.
First of all (even though I know this wasn't your intent), when we focus on the equipment a diver was using (open-circuit vs rebreather), we ARE implying that somehow the equipment used factored into the accident/death. I have no specific knowledge or even guess one way or the other in this case but in general, I don't believe that to be true. Out-and-out equipment failure is extremely rare. Improperly used equipment or even improperly maintained/equipment may be a slightly different case, but not by much.
The most common cause of diver fatalities is diver error. I did a non-peer-reviewed study some years ago (which I've referenced frequently) of over 300 fatalities nationally (DAN database) over a 3-year period and found that, based on coroner reports, diver error factored in 69% of the time. Medical issues accounted for another 25% (and some other studies put the medical number at closer to 40%). In the cases I looked at, there was not one single incident where equipment failure or malfunction seemed to play a factor.
In another study done by DAN in 2010, they looked at accident triggers over a 10-year period in close to 1,000 cases and came up with what should be a sobering statistic (which I've also harped on before) and found that in 47% of the cases where a trigger could be established, out-of-air was the cause. That's also diver error.
So if I'm going to make a mistake (and I'm not implying that Patric did), whether I do it on open-circuit or on a breather or a surface supplied or whatever is moot. If I end up having a heart attack (and I'm not implying that Patric did), whether I have it on open-circuit or on a breather or a surface supplied or whatever is also moot. In the same vein, because people dive different boats at various times, if I make my mistake or have my heart attack on Boat A rather than Boat B, it doesn't mean Boat A had anything to do directly with my demise.
What I will suggest - and perhaps this goes more to the heart of your question - is that as you go deeper, stay down, longer, do deco diving, dive with gear that's more complicated, etc., etc., you may find that your margin or error has shrunk and that mistakes from which you could recover on an "easy" dive become less survivable. An example would be running out of air with no one else around. Do that at 10 feet and you'll likely survive a free ascent. Do that at 110 feet or 210 feet, and that's a whole different issue.
So I'd generally agree with you that if rebreathers make up 5% of the fatalities yet make up far less than that as the % of dives done, it's an area worth examining. But I don't think the conclusion is simply that rebreathers are necessarily more dangerous. It could also be postulated that people who are not well-trained or not physically as fit as they should be now have better access to them, or have a false sense of their skill level due to not having had recreational accidents (and again, I'm NOT implying this has anything to do with Patric), and then they start doing things (deeper, longer, techie, whatever) where the margin or error shrinks and what wasn't a problem recreationally now becomes life-threatening.
That all being said, let's look at some numbers.
You are correct that we average about 5 fatalities a year in LA County (which si the jurisdiction of the LA County Coroner/Department of Medical Examiner.) Overall in SoCal (Point Conception to the Mexican border - add in SB, Ventura, Orange, & SD counties), it's probably closer to 12-15/year. So far in 2015 (LA County), I think we're at 4, and that includes the two recent ones in December.
In the last five years, here are the numbers:
2010 - 7
2011 - 7
2012 - 10 (worst year on record - and we went the first half of the year with 0)
2013 - 4
2014 - 3
Since 1994, we've recorded (again these are only LA County stats from the "Why Divers Die" seminar we give each year at the Scuba Show) 98 fatalities. broken down in 5-year increments:
1995-1999 - 16
2000-2004 - 22
2005-2009 - 24
2010-2014 - 31 (but this also includes the year with 10, 5 higher than "average" - underscores your point of a small sample size and the numbers being easily skewed)
Of these 98 (this does NOT includes 2015), 3 of the deaths were on rebreathers and 2 of those were in 2006 within a month of each other. So the other way to look at this would be to say that of 44 fatalties from 2007-2014, only 1 was on a rebreather (although that's still 2.2%).
Of those 2 in 2006, I tested the gear for the Coroner. I did not test the gear for rebreather fatality #3.
In the first case, the diver wanted to save money on replacing 9V batteries that ran the unit so he turned off the controlling devices after the first dive. He forgot to turn them back on so on his second dive, the CO2 scrubbers would not have been working and he essentially fell asleep underwater and drowned. Diver error.
In the second case, the diver seemingly exhausted his diluent supply, which may have triggered a panicked ascent. he also did not switch over to a pony bottle he had with him, that had a separate regulator and 1900psi. Diver error.
As to your last question, I have no idea of what percentage of local diving is done on rebreathers. And if there's a way to determine that number, you'd also have to decide if you want it to be % of divers who use a breather of % of dives on which a rebreather is used. I'm sure the two numbers would be different.
Hope that helps give you some clarity of your question.
- Ken
