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Thread: Rebreather Accident Research Project

  1. #21
    RBW Member SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ's Avatar
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    Re: Rebreather Accident Research Project

    Quote Originally Posted by aplord  View Original Post

    If your research was able to identify the most important risk/survival factors, and provide a statistical basis for this, then that in turn would provide CCR divers with something to aim for. Especially if the evidence concludes that CCR is safer than rec/OC diving if you are an old fat beer swilling git... :) Thanks again for the numbers!
    I'm afraid Al that the evidence is very unlikley to conclude that CCR is safer for old fat beer swilling gits.

    There is anecdotal evidence of an increase in heart attacks on rebreathers which may be related to CO2 and WoB issues but also may be linked to the fact that too many CCR divers are as you describe.

    CCR divers tend to be an older more affluent group than OC divers and hence possibly less fit. Learning more about these and other uncertainties is the reason I want to do this project.

    Best Wishes,

    Steve

  2. #22
    RBW Member SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ's Avatar
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    Re: Rebreather Accident Research Project

    Quote Originally Posted by JohanW  View Original Post
    Will you use a specialist panel of equipment analysts?
    No, I primarily want to focus on human factors rangeing from health to fitness to training.

    Should we come across new equipment hazards, we will of course respond but detailed FMECA type work is beyond the scope of the project.

    Best Wishes.

    Steve

  3. #23
    RBW Member SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ's Avatar
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    Re: Rebreather Accident Research Project

    Hi,

    The Rebreather Accident Research Project has a home on the internet

    Diving Network

    Going live today and in an embryo fashion but please have a look.

    I will keep RBW up to date with developments and thanks to Curt and all members who expressed an interest or offered support.

    Best Wishes,

    Steve

  4. #24
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    Re: Rebreather Accident Research Project

    Quote Originally Posted by SteveJ  View Original Post
    Hi,

    The Rebreather Accident Research Project has a home on the internet

    Diving Network

    Going live today and in an embryo fashion but please have a look.

    I will keep RBW up to date with developments and thanks to Curt and all members who expressed an interest or offered support.

    Best Wishes,

    Steve
    Excellent summary! In my literature survey, you may have one of the higher fatality rates for RB.


    How did you derive the 23/10,000 annual fatality rate, i.e., the source of the numerator and denominator?




    To refine the number, have you looked at just a more controlled subset, such as RB fatalities for BSAC members in the UK or DAN members, in the USA?


    Sincerely,


    Marv

  5. #25
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    Re: Rebreather Accident Research Project

    Quote Originally Posted by saturation  View Original Post
    Excellent summary! In my literature survey, you may have one of the higher fatality rates for Rebreather.


    How did you derive the 23/10,000 annual fatality rate, i.e., the source of the numerator and denominator?




    To refine the number, have you looked at just a more controlled subset, such as Rebreather fatalities for BSAC members in the UK or DAN members, in the USA?


    Sincerely,


    Marv
    Hi Marv,

    As I put in a previous post:

    'Attempts have been made in the past to get at the denominator and you get a wide distribution of answers.

    For ALL recreational divers (OC, tech, CCR) the mortality rate is around 1 - 2 deaths per 10,000 divers per year (DAN and BSAC figures). There have been in the order of 130 rebreather fatalities since 1997(reported in English speaking literature). Various complicated but probably inaccurate estimates of the numbers of active rebreather divers have been made ranging from a low of 3000 to a high of 10,000. Assuming 10,000 rebreather divers (in Europe, US and Australasia) in 2007 and starting from a base of a few dozens in 1997 then my estimate for mortality in rebreather divers is in the order of 23 deaths per 10,000 divers per year. Others will argue that there are far fewer active rebreather divers hence significantly increasing the comparative mortality.

    To further complicate matters, the ALL divers mortality must include a lot of holiday divers who only dive 10 times a year which is probably much less than the committed rebreather diver.'

    If you speak to Alex Deas he will try to convince you that the numerator is higher and the denominator lower and that the relative mortality is thus much higher. I'm actively seeking to refine the 23/10,000 per year average and any help is welcome.

    Steve

  6. #26
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    Re: Rebreather Accident Research Project

    HI Steve,

    Thanks for the clarification. I left a copy of my post on your website. It would be good to join forces and try to eck this out. I couldn't agree more, denominators are hard to come by. DAN USA has a compendia of fatalities, but suffers the same issue with the denominator. At last meeting, its being tracked by Petar Denoble.

    One thing I've used to make comparisons to divers is the fatality rate in automobile crashes, this helps make sense of what this ratio means to real people. In the USA, roughly driver fatalities over the whole population of licensed drivers is ~ 1.3/10,000, very similar to recreational diving. Now, licensed motorcycle fatalities is about 7.2/10,000. I think many folks who drive both cars and motorcycles will sympathize with these changes in risk, its ~5.5x greater on a motorcycle compared to a car.

    See under: OCCUPANT FATALITY RATES BY VEHICLE TYPE, 1996 AND 2006
    here: III - Motorcycle Crashes


    Now, take into perspective the risk you raise of 23/10,000.


    Quote Originally Posted by SteveJ  View Original Post
    Hi Marv,

    As I put in a previous post:

    'Attempts have been made in the past to get at the denominator and you get a wide distribution of answers.

    For ALL recreational divers (OC, tech, CCR) the mortality rate is around 1 - 2 deaths per 10,000 divers per year (DAN and BSAC figures). There have been in the order of 130 rebreather fatalities since 1997(reported in English speaking literature). Various complicated but probably inaccurate estimates of the numbers of active rebreather divers have been made ranging from a low of 3000 to a high of 10,000. Assuming 10,000 rebreather divers (in Europe, US and Australasia) in 2007 and starting from a base of a few dozens in 1997 then my estimate for mortality in rebreather divers is in the order of 23 deaths per 10,000 divers per year. Others will argue that there are far fewer active rebreather divers hence significantly increasing the comparative mortality.

    To further complicate matters, the ALL divers mortality must include a lot of holiday divers who only dive 10 times a year which is probably much less than the committed rebreather diver.'

    If you speak to Alex Deas he will try to convince you that the numerator is higher and the denominator lower and that the relative mortality is thus much higher. I'm actively seeking to refine the 23/10,000 per year average and any help is welcome.

    Steve

  7. #27
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    Re: Rebreather Accident Research Project

    Quote Originally Posted by SteveJ  View Original Post
    If you speak to Alex Deas he will try to convince you that the numerator is higher and the denominator lower and that the relative mortality is thus much higher. I'm actively seeking to refine the 23/10,000 per year average and any help is welcome.
    Scientists don't make snide remarks about "convincing" people, they simply publish their data, and are able to substantiate it to a reasonable degree. You have my data. I would like to see yours, so I can reach objective conclusions. My team are not salesmen, we are engineers and scientists. We work with facts and numbers.

    Scientific studies should be objective. You state here your result and ask for data to "prove it". You mention that your result is different from mine, so you must have a different number for either:
    1. The number of rebreather accidents (and you have a list of 162 I sent you, after your scrutiny just two were uncertain and there was also two unallocated that were very likely the rebreather in question). So an error that might be a few percent in mortality numbers in your check.
      or
    2. Sales figures. You have my sales figures, which are within 10% of the figure the manufacturers have stated publicly in almost every case.
      or
    3. You are blending the figures from different types of rebreather for your study (eCCRs, mCCRs and SCRs have very different mortality figures).
      or a combination.
    Your 23/10,000 figure gives a mortality rate per unit for a rebreather life of 7 years, of 160/10,000 (i.e. a probability of surviving of (1-23/10000)^7). This is one in 62.

    Take for example, the biggest selling sports eCCR. The sales figures should not have to be debated much because the MD stated them on oath ("few thousand", which I take to be 3,000 and you said on NBD that you understand to mean 3,000 to 6,000 - and our number for the sales was 3,300 and now is 2,700 - pretty close to the MD's statement). The accidents are known within about one or two percent after your own review of these. How come your number is out by a factor of 2 when you have such accurate source data? I think I know ...

    I suspect the reason our numbers "differ", is that our 1 in 39 mortality figure per unit sold is for a specific eCCR. Our mortality number per unit on mCCRs is about 1 in 900. Our mortality number per unit on SCRs is about 1 in 600. By blending these data sources our team assembled, of course you will end up with a figure of around 1 in 60 or 70. Which is pretty close to your 1 in 62 number. So why are you trying to denigrate me publicly with this falsehood you are circulating? So you can hide what you know to be a high eCCR accident rate, by blending it with the mCCR and SCR figures? As your conclusion seems no different from ours, if you take all rebreathers, what are you trying to prove by the statement I quote?

    Finally, the problem with your study is that it is not scientific. You need to fix the population from which you take your samples, and the samples need to be random. If you want divers' health data, you would need to offer free medicals or something. You are a GP who does diving medicals, so you should get a good cross section of divers. That is, good samples. If you ask them if you can use their data for research purposes, you will get a decent body of data, instead of appealing for those who have health problems on an internet forum.

    It would be good to have answers for the diver health questions you raise, but the data has to be scientific otherwise it is worthless. That means either comprehensive research to get at the numbers, or in this case using a random selection of the population.

    Alex

    NB: I had a look around your web site. Seems to have taken over from NBD. Could you put a link to the data please on which your figure is based? I have my data fully in the open.
    Last edited by AD_ward9; 20th January 2009 at 18:41.

  8. #28
    RBW Member SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ is a jewel in the rough SteveJ's Avatar
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    Re: Rebreather Accident Research Project

    Alex,

    Firstly my comment was not meant as snide and I am sorry you took it that way. Secondly I have not tried to denigrate you with any falsehood.

    My figure of 23/10,000 per year is indeed for all rebreathers not just eCCRs.

    In our previous discussions elsewhere, I challenged your very high mortality rate for a specific unit on two counts, both the numerator and the denominator.

    For the numerator, I sought clarification on 10 incidents for which I thought the evidence was either sketchy or not in the public domain. You gave assurance on 7 that you had independent verification but that some of it was 'confidential', one incident was allocated to a different unit and two await further clarification.

    For the denominator you state that there have been only 3000 inspos produced. MP's comment that there were a few thousand you take to mean 3000 units whilst I suggested this way not desperately strong evidence of any figure but could cover 3-6000. As long as 18 months ago you told me that you had good circumstantial evidence about the lower that accepted numbers of units in circulation but for legal reasons you were unable to show me this evidence.

    It is entirely possible that your figures are more accurate than mine but you have information that is not available to me and so cannot be included in my own estimates.

    Besides, all this seems to be missing the point that we both agree that there is a huge excess in mortality in rebreather divers and that eCCRs appear much worse than SCR and mCCRs.

    Thankyou for your comments about my cross sectional study. Sadly, my clinical practice does not allow me to see sufficient OC and rebreather divers to produce other than anecdotal evidence.

    A cross sectional study by questionnaire is an accepted scientific method although it is ranked a lot lower than prospective blinded studies etc in terms of strength of evidence. It is hard to get representative samples from sufficient numbers to achieve statistically significant results because people who respond to questionnaires are by definition, opting in.

    The results of analysis of the data may be highly valid however. If there is no significant difference between cohorts of OC and rebreather diver in terms of age, obesity, fitness, pre-existing morbidity then this must further question the safety of the equipment.

    If the rebreather population is older, less fit, more obese and more prone to hypertension then this will focus more attention on issues such as WoB and hypercapnia and the heart attack theory.

    The study is not perfect but it should answer the above questions.

    Best Wishes,

    Steve

    Quote Originally Posted by AD_ward9  View Original Post
    Scientists don't make snide remarks about "convincing" people, they simply publish their data, and are able to substantiate it to a reasonable degree. You have my data. I would like to see yours, so I can reach objective conclusions. My team are not salesmen, we are engineers and scientists. We work with facts and numbers.

    Scientific studies should be objective. You state here your result and ask for data to "prove it". You mention that your result is different from mine, so you must have a different number for either:
    1. The number of rebreather accidents (and you have a list of 162 I sent you, after your scrutiny just two were uncertain and there was also two unallocated that were very likely the rebreather in question). So an error that might be a few percent in mortality numbers in your check.
      or
    2. Sales figures. You have my sales figures, which are within 10% of the figure the manufacturers have stated publicly in almost every case.
      or
    3. You are blending the figures from different types of rebreather for your study (eCCRs, mCCRs and SCRs have very different mortality figures).
      or a combination.
    Your 23/10,000 figure gives a mortality rate per unit for a rebreather life of 7 years, of 160/10,000 (i.e. a probability of surviving of (1-23/10000)^7). This is one in 62.

    Take for example, the biggest selling sports eCCR. The sales figures should not have to be debated much because the MD stated them on oath ("few thousand", which I take to be 3,000 and you said on NBD that you understand to mean 3,000 to 6,000 - and our number for the sales was 3,300 and now is 2,700 - pretty close to the MD's statement). The accidents are known within about one or two percent after your own review of these. How come your number is out by a factor of 2 when you have such accurate source data? I think I know ...

    I suspect the reason our numbers "differ", is that our 1 in 39 mortality figure per unit sold is for a specific eCCR. Our mortality number per unit on mCCRs is about 1 in 900. Our mortality number per unit on SCRs is about 1 in 600. By blending these data sources our team assembled, of course you will end up with a figure of around 1 in 60 or 70. Which is pretty close to your 1 in 62 number. So why are you trying to denigrate me publicly with this falsehood you are circulating? So you can hide what you know to be a high eCCR accident rate, by blending it with the mCCR and SCR figures? As your conclusion seems no different from ours, if you take all rebreathers, what are you trying to prove by the statement I quote?

    Finally, the problem with your study is that it is not scientific. You need to fix the population from which you take your samples, and the samples need to be random. If you want divers' health data, you would need to offer free medicals or something. You are a GP who does diving medicals, so you should get a good cross section of divers. That is, good samples. If you ask them if you can use their data for research purposes, you will get a decent body of data, instead of appealing for those who have health problems on an internet forum.

    It would be good to have answers for the diver health questions you raise, but the data has to be scientific otherwise it is worthless. That means either comprehensive research to get at the numbers, or in this case using a random selection of the population.

    Alex

    NB: I had a look around your web site. Seems to have taken over from NBD. Could you put a link to the data please on which your figure is based? I have my data fully in the open.

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    Re: Rebreather Accident Research Project

    Quote Originally Posted by SteveJ  View Original Post
    A
    The results of analysis of the data may be highly valid however. If there is no significant difference between cohorts of OC and rebreather diver in terms of age, obesity, fitness, pre-existing morbidity then this must further question the safety of the equipment.

    If the rebreather population is older, less fit, more obese and more prone to hypertension then this will focus more attention on issues such as WoB and hypercapnia and the heart attack theory.

    The study is not perfect but it should answer the above questions.

    Best Wishes,

    Steve
    This is what I'm thinking, more health related problems than equipment related. Go ahead Steve, errors can be corrected so can the aim, to rich a result as close as possible to the true.

    Nad

  10. #30
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    Re: Rebreather Accident Research Project

    Quote Originally Posted by AD_ward9  View Original Post
    Scientists don't make snide remarks about "convincing" people, they simply publish their data, and are able to substantiate it to a reasonable degree. You have my data. I would like to see yours, so I can reach objective conclusions. My team are not salesmen, we are engineers and scientists. We work with facts and numbers.
    You sorta gave up your ability to claim scientific purity when you 1) decided to become an expert witness, and 2) decided to sell a rebreather. When we met at DEMA, you were doing a fairly good impersonation of a salesman.

    Just saying... :)

    Also, your figures ARE somewhat suspect, Alex. I remember in a previous thread commenting (along with many others) on the fact that you seem awfully willing to attribute very dodgy and complex deaths to a rebreather issue... or even worse, to a specific rebreather. A lot of them look like training, fitness or serious user error might be equally plausible hypotheses as the ones you offer.

    Steve, if you need help with the stats, let me know.
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