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Fatality on Rosalie Moller wreck

Discussion in 'Accidents and Incidents' started by vjongene, Sep 28, 2020.

  1. vjongene

    vjongene Barracuda

    # of Dives: 1,000 - 2,499
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    Thanks for the analysis, which I think is right on the nose. Yes, there were two working DMs in the water. One was acting as a private guide to a pair of divers, while the other was with a different group (there were 13 guests in the water). As a rule the DMs were very attuned to what was going on, but unfortunately the viz on the Rosalie M. makes it impossible to track everyone. Btw, there was an inquest after the accident, and every single diver on the boat praised the work that the DMs did. This included finding and retrieving a dead body. Both DMs were in tears.
     
  2. ginti

    ginti DIR Practitioner

    # of Dives: 100 - 199
    Location: Lyon, France
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    Not necessarily true.

    This summer I did a cave1 course; 6 days, 12 dives during the first 5 days, all in relatively easy environments (big caves with plenty of room to move and to practice exercises). Last day, since I and my friends did sufficiently well during the training, we got a prize: experience dive, which is basically a "real" cave dive, in a more challenging environment. I was pushing a bit my limits with this course, so, even if it was the last day, I didn't have a great feeling, mainly due to the new environmental challenges (small passages, a lot of corners, etc.). Luckily, this was not sufficient to stop me: it has been the best dive of my life, by far.

    The point is that, even after a week, if the conditions get particularly challenging, one can easily feel bad. It's up to the diver to understand when it is too much or not.

    @vjongene can confirm if this dive was actually more challenging or not...
     
  3. divezonescuba

    divezonescuba ScubaBoard Supporter ScubaBoard Supporter

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    My impression was that all of the reputable dive shops were highly respectful of CDWS. I heard more than once that, if this, that, or the other happened that it could result in loss of the diveshops CDWS permit.

    One CDWS dive guide who discovered an accident caused by another diveshop was prevented from working for two days while CDWS conducted an investigation. The dive guide responsible for the accident left town, presumedly to avoid losing his CDWS certification and livelihood.

    Up until last year, there was actually a list of dive shops and instructors on the CDWS website that had been “black listed” for what ever reason.
     
  4. poseident

    poseident Nassau Grouper

    # of Dives: 1,000 - 2,499
    Location: Charlotte, NC
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    Thanks for confirming regarding the air supply and the conduct of the DMs. Tragic circumstances indeed. Thanks as well for the testimonial about the difference new environments can have. Well put.
     
  5. poseident

    poseident Nassau Grouper

    # of Dives: 1,000 - 2,499
    Location: Charlotte, NC
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    Is there any chance there was a "Imperial versus Metric" issue with the borrowed computer?
     
    Jack Hammer, ginti and Hiszpan like this.
  6. KenGordon

    KenGordon Rebreather Pilot

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    People make mistakes. If she dropped a weight over a 50m bottom and went after it then she made a mistake. She might have had no idea how deep she was going, focusing on the target, and run out of gas.

    None of the other parameters were bound to kill her. People regularly go to 60m on air and her ppO2 was high but not likely to immediately get her. Not knowing how fast she was using gas at the end of the dive seems likely to end badly though.
     
    lowwall, chillyinCanada and leadduck like this.
  7. ms76

    ms76 Angel Fish

    # of Dives: 100 - 199
    Location: Austria
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    Maybe the unfamiliar computer was set to 21% and/or a high conservatism mode showing a deco obligation which she thought she could never fulfill without the lead. Very sad
     
  8. Dr Simon Mitchell

    Dr Simon Mitchell ScubaBoard Supporter Staff Member ScubaBoard Supporter

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    Hello ginti,

    Delving into this area is slightly tangential to the topic of the thread, but I have posted a fully labelled version of the graph below.

    MVV graph.JPG

    This comes from a paper written by David Doolette and I for Comprehensive Physiology [1]. For those who are physiologically minded / trained I have also uploaded the paper (pdf available below), but it might be heavy going if you are not already trained in the field.

    Basically, the graph shows how the maximum voluntary ventilation (MVV) (the amount of gas you can move in and out of your lungs per minute if you breathe as hard as you can) is affected as you breathe air at increasing depth. The mechanism for this effect is complicated (see the paper) but it is primarily mediated by increasing gas density. On the face of it, the effect is fairly dramatic. For example, if you descend to 30m (~100') your MVV falls from 200 L/min to 100 L/min, i.e., halved! These measurements were made using low resistance lab equipment in a dry chamber, so the effect is almost certainly greater in real diving when immersed and breathing through a regulator or rebreather.

    I said "on the face of it" deliberately because, for example, even if your MVV is limited to 100L/min at say 100', that should still be enough ventilation capacity to keep your CO2 normal even during moderate exercise. Thus, in most settings it is unlikely that limited ability to move gas in and out of the lungs is truly responsible for CO2 retention in diving (remember that CO2 elimination is directly proportional to breathing - breathe more and you get rid of more CO2, breathe less and the opposite applies). There are almost certainly exceptions to this though - if you combine very dense gas with poor equipment choices there may truly be situations where you simply can't breathe enough to eliminate the CO2 you are producing. That is a very dangerous and likely fatal scenario - one famous example has previously been published [2]. Although such events are probably rare, I still believe instructors like Miyaru are absolutely correct to use the dramatic effect of gas density on MVV to reinforce to students how important gas density is in a tangible way. The biggest problem with gas density (see next paragraph) is harder to explain and illustrate.

    Another more common cause of CO2 retention in diving is the effect that harder work of breathing has on breathing control. We are programmed to increase our breathing if CO2 levels begin to rise, thus eliminating the excess CO2 from the body. That process is operating in everyone as they read this post - just not in the part of the brain that you are conscious of. However, in some people (sometimes referred to as "CO2 retainers") the response is suppressed if the work involved in increasing breathing is abnormally high. Work of breathing is increased in multiple ways during diving (eg equipment resistance, dense gas) and so in "CO2 retainers", if body CO2 levels rise during diving, they may not respond as efficiently with increased breathing to get rid of it, and the deeper you are and the denser your gas, the more true this is likely to be.

    Thus, to summarise, CO2 levels may rise dangerously in diving for two reasons: because we literally can't breathe enough to eliminate the CO2 we are producing (probably very rare), or because increased work of breathing has a suppressing effect on the brain's normal response to rising CO2 and we subconsciously choose not to increase breathing. Both of these mechanisms can happen on open circuit or rebreathers. A third mechanism that can lead to CO2 buildup relevant only to rebreather diving is failure of a CO2 scrubber so that the diver is actually inhaling CO2.

    Simon M

    1. DOOLETTE DJ, MITCHELL SJ. Hyperbaric conditions. Comprehensive Physiol 1, 163-201, 2011

    2. MITCHELL SJ, CRONJE F, MEINTJES WAJ, BRITZ HC. Fatal respiratory failure during a technical rebreather dive at extreme pressure. Aviat Space Environ Med 78, 81-86, 2007
     

    Attached Files:

  9. scubadada

    scubadada Diver Staff Member ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Philadelphia and Boynton Beach
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    So, it seems she ran out of gas while attempting to recover her errant weight pocket. Her RMV was pretty high during the dive, probably 0.65 or 0.7 cu ft/min. Who knows what it might have gone up to while she was diving down to 165 ft for the weights? Narcosis may also have played a role, not only due to the depth, but she may have been hypercarbic due to her exertion and an increased work of breathing with a gas density of about 7.8 g/L.

    Even though her pO2 may have reached about 1.7, in the presence of hypercarbia, the exposure was very short. Had she experienced a seizure, I would think she would lose her mouthpiece before being able to breathe her cylinder down to empty. Though there is no evidence, it is still possible that she had a medical event, MI, arrhythmia..., seems like she might lose her mouthpiece in this case also.

    1) Call a dive for any reason if you are uncomfortable making it
    2) Develop good control of your buoyancy in all equipment combinations you use
    3) Make sure you are familiar with and comfortable with your equipment, especially for more challenging dives
    4) Try to be prepared for untoward events that might occur during your dives, to help you in making correct decisions in an emergency

    All of this is very sad. The excellent accident report by @vjongene has allowed us to have a better discussion of the event that we are often able to have.
     
    laikabear, Lostdiver71 and poseident like this.
  10. Dan

    Dan ScubaBoard Supporter ScubaBoard Supporter

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    Location: Lake Jackson, Texas
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    Really?
     

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