Scuba fatalities - Los Angeles County - 1994-2007

[DandyDon]

Originally Posted by swamp diver
1) In what percentage of the fatalities was a blood carboxyhemoglobin level done?

I don't know. I'll ask the Coroner but may not get an answer right away.

I'll look forward to that too. I have become increasingly concerned about CO problems outside the US and away from the USCG and USDOT oversight, mostly in tropical destinations, but would wonder how often it's a problem in the US?

Quote:
2) In what percentage of the fatalities was a tank air/gas analysis done?

100% for all the ones I've done (since about 2004). Now I will tell you that what we do is simly an oxygen analysis. We don't look specifically for CO or do a full-sprectrum analysis unless the oxygen level is off or if we have some other evidence to consider the air may have been a culprit. (Other people getting sick, for instance.)

How far off before you look further, if I may? For example, if a tank happen to have 15-50 ppm CO, would that affect your O2 analysis enough to get your attention? I'm pretty sure it would not on a diver's O2 tester, but I don't know anything about your equipment altho I am sure it's much more sensitive and accurate.

Thanks so much for bring us this info and discussing it with us...!!

 

[scjoe]

The average number of deaths per year does not vary much over 6, 8 and 14 year periods. If the number of divers was increasing that would indicate an improvement in safety, but the industry has actually been flat for a number of years, so it would appear that diving safety has not changed appreciable during the periods studied. On the other hand, training standards have gotten progressively weaker over the years, and divers today are an older and less fit crowd than in the past. At the same time, safety gear has improved and older divers may be more cautious than the younger crowd of the past. Perhaps all of these changes net each other out and we end up with little change in the stats.

According to an Undercurrent article last year, back in 1988 the industry claimed to have 3.5 million active divers making at least 3 dives a year. Not very active actually, and it is now generally accepted that the number was highly inflated. Undercurrent quoted Renee Duncan of DAN as stating, "There's really no true number for certified divers because this is not a regulated industry, so it will always be a squishy figure. We've quoted the 1 to 3 million number on our diving fatality reports." According to Duncan, the industry is flat. "Everyone acknowledges that. We're not attracting as many new divers, we're a graying population, and younger people seem to be going for more extreme sports."

Undercurrent itself came up with an estimate of 1.2 million, plus or minus 15 percent.

Undercurent also reported that the industry has no definition of what an active diver is. One industry consultant was quoted as saying ,”We evolved from a 'dive once a month' to a 'one dive vacation a year' to be considered active."

Finally, Undercurrent addressed the dropout rate by stating, “ All sorts of numbers are bandied about for the actual dropout rate after the first year, ranging from as low as 40 percent to as high as 80 percent, but nothing is official.” It noted that its own dropout rate of first time subscribers was 60% after the first year and 78% over three years.

 

[drbill]

These will be interesting data to dispel the commonly held belief that diver deaths occur in the dive park at a much higher rate than the Coroner's stats indicate.

It is interesting that the number of certified divers is so undetermined. I assume some of this stems from the fact that certs are lifetime for most levels and agencies. Therefore if someone got certified back in the 60's like I did, they may not be in current databases.

You would think an accurate figure for the number of divers certified would be available. However, then you'd have to account for the deaths, etc. within that population over the time frame to know how many certified divers are still alive. Then you'd have to apply a reasonable drop out rate (as mentioned above) to determine how many of those living divers still actively dive. And on and on...

 

[ianw2]

The corollary to that, Dr. Bill, is those of us who were certified back in the early '80's and then didn't dive again for 30 years weren't tracked as "non-returning" divers (sounds so much nicer than drop-outs).

Interestingly, there doesn't seem to be a standard definition as to what constitutes a diver. Three dives in a year? Hmmm.

Hasn't anyone got a budget to do any follow up with certified divers 12 months, 24 months, 36 months, 60 months after certification? Why not? How can you determine where and what to spend on training programs and efforts?

I'm stunned that an entire industry seems to know so little about its own demographics.

 

[drbill]

Agreed... how do we keep them down under water after they've been certified, done their vacation trip and discovered sky diving or some other "extreme" sport? Too bad there is lifetime certification as renewals would help track this kind of information.

 

[Ken Kurtis]

How far off before you look further, if I may? For example, if a tank happen to have 15-50 ppm CO, would that affect your O2 analysis enough to get your attention? I'm pretty sure it would not on a diver's O2 tester, but I don't know anything about your equipment altho I am sure it's much more sensitive and accurate.

That's a good question and I don't know that I have a definitive answer. Anything significantly less than 21% is going to be suspect. But a lot of this we would do anecdotally. In other words, talk to others to find out if there were any of the symptoms of CO poisoning in either the victim pre-dive or in others. (Sort of like that incident in thre Maldives. With CO, you shouldn't get just ONE bad tank of air.)

Here's what I just lifted off a CO poisoning website:

At what level does carbon monoxide become toxic?
For healthy adults, CO becomes toxic when it reaches a level higher than 50 ppm (parts per million) with continuous exposure over an eight hour period.. When the level of CO becomes higher than that, a person will suffer from symptoms of exposure. Mild exposure over a few hours (a CO level between 70 ppm and 100 ppm) include flu-like symptoms such as headaches, sore eyes and a runny nose. Medium exposure (a CO level between 150 ppm to 300 ppm) will produce dizziness, drowsiness and vomiting. Extreme exposure (a CO level of 400 ppm and higher) will result in unconsciousness, brain damage and death.

OSHA standards call for 10PPM or less. You're right that a mild increase in CO might not affect the oxygen levels to the point where it would that it would trigger any concern.

On the one hand, I don't think it's as prevalent as some people suggest (otherwise we see a lot more problems/fatalities). But perhaps we should be a better job of routinely checking levels after a fatality.

 

[swamp diver]

That's a good question and I don't know that I have a definitive answer. Anything significantly less than 21% is going to be suspect. But a lot of this we would do anecdotally. In other words, talk to others to find out if there were any of the symptoms of CO poisoning in either the victim pre-dive or in others. (Sort of like that incident in thre Maldives. With CO, you shouldn't get just ONE bad tank of air.)

Here's what I just lifted off a CO poisoning website:

At what level does carbon monoxide become toxic?
For healthy adults, CO becomes toxic when it reaches a level higher than 50 ppm (parts per million) with continuous exposure over an eight hour period.. When the level of CO becomes higher than that, a person will suffer from symptoms of exposure. Mild exposure over a few hours (a CO level between 70 ppm and 100 ppm) include flu-like symptoms such as headaches, sore eyes and a runny nose. Medium exposure (a CO level between 150 ppm to 300 ppm) will produce dizziness, drowsiness and vomiting. Extreme exposure (a CO level of 400 ppm and higher) will result in unconsciousness, brain damage and death.

OSHA standards call for 10PPM or less. You're right that a mild increase in CO might not affect the oxygen levels to the point where it would that it would trigger any concern.

On the one hand, I don't think it's as prevalent as some people suggest (otherwise we see a lot more problems/fatalities). But perhaps we should be a better job of routinely checking levels after a fatality.

As Don pointed out earlier 50 percent of DAN fatalities are still listed as a drowning of unknown cause. The four accredited compressed breathing air laboratories in the continental USA report a CO failure rate of about 3 percent for all dive air samples sent in for "routine" analysis. There is a significant and growing body of literature which implicates low-level CO exposure to cardiovascular troubles, particularly in persons with undiagnosed coronary artery disease. If the tank air or person's blood is not checked for CO exposure one will likely record a death where CO was a factor as a drowning of unknown cause.
Carbon Monoxide tester for scuba and firefighting
Rubicon Research Repository: Item 123456789/1424

In our jurisdiction all dive fatalities have a full air/gas analysis done by an accredited compressed breathing air laboratory. Until this is routine in other jurisdictions we really don't have a good idea as to the true prevalence of CO or other air contamination in dive fatalities, but the 3 percent CO failure figure from the laboratories should be enough evidence to suggest we do make both an air analysis and blood COHb a routine part of any dive fatality investigation.

For CO or volatile hydrocarbon exposures which might be fatal at recreational dive depths the percentage oxygen will not change. We are talking about concentrations in the range of 10 to 100 ppm which is 0.001 to 0.01 percent by volume.

There is an excellent accredited compressed air breathing lab just south of you in San Diego called Analytical Chemists, Inc..

 

[DandyDon]

Edit: Swamp Diver was posting as I was, which really negates my post - but I'll leave it....

That's a good question and I don't know that I have a definitive answer. Anything significantly less than 21% is going to be suspect. But a lot of this we would do anecdotally. In other words, talk to others to find out if there were any of the symptoms of CO poisoning in either the victim pre-dive or in others. (Sort of like that incident in thre Maldives. With CO, you shouldn't get just ONE bad tank of air.)

I certainly don't want to hijack your thread, but as we've discussed on other threads recently - when a CO problem does exist, it is possible that the tanks in a batch can have a wide variety of readings, some much more harmful than others.

Here's what I just lifted off a CO poisoning website:

At what level does carbon monoxide become toxic?
For healthy adults, CO becomes toxic when it reaches a level higher than 50 ppm (parts per million) with continuous exposure over an eight hour period.. When the level of CO becomes higher than that, a person will suffer from symptoms of exposure. Mild exposure over a few hours (a CO level between 70 ppm and 100 ppm) include flu-like symptoms such as headaches, sore eyes and a runny nose. Medium exposure (a CO level between 150 ppm to 300 ppm) will produce dizziness, drowsiness and vomiting. Extreme exposure (a CO level of 400 ppm and higher) will result in unconsciousness, brain damage and death.

OSHA standards call for 10PPM or less. You're right that a mild increase in CO might not affect the oxygen levels to the point where it would that it would trigger any concern.

For recreational dive limits along, 130 ft roughly equals 5 atmospheres; for brevity and simplicity, a few examples of CO contents and rough comparisons...

• 10 ppm is the maximum allowed in Scuba air = 50 ppm effect @ 130 ft, but only affect your O2 content by 0.0001%. I don't know much at all about precision O2 testing, but I doubt that any read that close.
  
• 50 ppm = 250 ppm effect @ 130 ft, but only affect O2 content by 0.005%.
  
• 200 ppm = 1,000 ppm effect @ 130 ft effect: loss of consciousness after one hour, but only effect O2 reading by 0.02%.
  
• 400 ppm = 2,000 ppm effect @ 130 ft effect: exceeds the 1,600 ppm level that causes headache, nausea, dizziness after 20 minutes but only effect O2 reading by 0.04%.
  
• 600 ppm = 3,000 ppm effect @ 130 ft effect: very close to the 13,200 ppm level that causes headache, nausea, dizziness after 5-10 minutes, loss of consciousness after 30 minutes, but only effect O2 reading by 0.06%. Using "Anything significantly less than 21%..." even that would not be detected.
  
• I know that Nitrox is not commonly used there, or wasn't on my recent trips, but any level of Nitrox would completely negate your approach to CO appraisal, and you have some divers going below 130 ft on simple air.

Now, it may be that the tanks are actually being tested accurately for CO with never enough of a reading to be communicated to you, perhaps? Or then, it may not be; it might be an unstudied possibility, perhaps? If you are perhaps not testing for CO, then it would be I suppose.

On the one hand, I don't think it's as prevalent as some people suggest (otherwise we see a lot more problems/fatalities).

Common or not I don't know. I only know that very few standards are enforced. How many cases of "travelers flu" were really close calls of CO? Perhaps not many, but if perhaps you are not testing for CO even on fatalities - who knows about the ones who survived only ill.

But perhaps we should be a better job of routinely checking levels after a fatality.

Well, maybe you are. If you are not, I wish you would. Something around a 1,000 tank study over time might be needed to illustrated previously unknown problems, but even 100 tanks over time would be of interest.

But if even you are not testing for CO, this goes back to "who knows?" and diving air on the faith that it was prepared correctly, but if 50 ppm or higher level were slipping by, no one is going to know.

 

[bleeb]

In our jurisdiction all dive fatalities have a full air/gas analysis done by an accredited compressed breathing air laboratory. Until this is routine in other jurisdictions we really don't have a good idea as to the true prevalence of CO or other air contamination in dive fatalities, but the 3 percent CO failure figure from the laboratories should be enough evidence to suggest we do make both an air analysis and blood COHb a routine part of any dive fatality investigation.

What exactly is the jurisdiction you're talking about? (Obviously, I'm wondering if this potentially covers me. )

More on-topic, for this region (whatever it is) how many dive fatalities might we be talking about here over the last few years, and does the 3% figure from compressor testing previously mentioned correlate with the actual accident analyses? Granted a small number won't be terribly conclusive, but it would be helpful for this discussion to have a more direct measure of the frequency of CO in dive accidents, whether they're a direct cause or not. Any idea?

 

[swamp diver]

What exactly is the jurisdiction you're talking about? (Obviously, I'm wondering if this potentially covers me. )

More on-topic, for this region (whatever it is) how many dive fatalities might we be talking about here over the last few years, and does the 3% figure from compressor testing previously mentioned correlate with the actual accident analyses? Granted a small number won't be terribly conclusive, but it would be helpful for this discussion to have a more direct measure of the frequency of CO in dive accidents, whether they're a direct cause or not. Any idea?

Yes I am referring to the province of Ontario. In any fatality the equipment is secured by the provincial police and sent to the military for inspection. The tank air/gas is also analyzed for a list of contaminants which includes carbon monoxide.

If you go to the Ontario Underwater Council web site you can see the number of fatalities is usually in the ballpark of three to six per year. I can't give you an exact number for the laboratory failure rate for CO in dive air here in Canada, but it is significantly lower (< 1%) than for dive air in the US. CO test failures for scba air in the US also is much lower and parallels the Canadian rate. The differences have to do with the average ambient temperatures, differences in purifier components, and purifier monitoring. Also remember that the large US labs such as Trace Analytics and Lawrence Factor receive many samples from the tropics offshore where there are poor compressor installations, untrained operators, and poor compressor maintenance in a high ambient heat environment. One is more likely to observe CO failures from these regions which will raise the overall domestic failure rate.

There has only been one study looking at the frequency of COHb monitoring in dive fatalities. This was conducted by a DAN pathologist and he found that over a 5 year period the diver's blood was checked for CO exposure in only 15 percent of fatalities. Of the 15 percent who were checked close to 3 percent had a fatal level of COHb if I recall correctly. So we do not have good data on the true incidence of CO contamination in dive fatalities.