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Thread: Fascinating lecture on Decompression by Dr. Simon Mitchell

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    RBW Member decostanza is an unknown quantity at this point decostanza's Avatar
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    Re: Fascinating lecture on Decompression by Dr. Simon Mitchell

    Thank you Dr. Mitchell for sharing this fascinating and very thought provoking information!
    Don

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    RBW Member westy is an unknown quantity at this point westy's Avatar
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    Re: Fascinating lecture on Decompression by Dr. Simon Mitchell

    Sorry, it did come across that I was trying to force onus onto manufacturers which as you say isn't their responsibility. I was not trying to do this at all, my comment simply came from the fact that some computers come out of their boxes with quite a low (30?) as the default low GF and that with this research, might we see a shift in this? (maybe, maybe not). And I certainly concur with your point that it should be the instructors teaching this to their students, rather than a lecture online!

    Quote Originally Posted by PSotis  View Original Post
    I see why you would make this remark and I don't disagree. But rather than putting it on the manufacturers. How about making note of all the training agencies that produce decompression class information and never require their instructors to explain decompression algorithms to the extent that a diver can choose for themselves.

    Even better, how about requiring all decompression instructors passing the minimum requirement of having to understand these concepts and theories so they can teach them thoroughly. Everyone knows this is not a requirement and that is truly an abomination. This is why we have so many diver's literally lost on how to choose or if they have chosen, they do so based on a myth, rather than facts. This is also why we have so many instructors teach anecdotle information instead of the facts...they simply don't know and haven't been required to learn.

    In fairness, some learn on their own and exceed these standards, but it's rare. In my experience, most students dive an algorithm and especially a conservatism based on the same verbiage they so often quote to me... "that's what instructor told me to use, but I don't understand why". The reason for this is MOST instructors have no idea and they have never been required to know and yet they call themselves decompression instructors...its a bit ironic. I sincerely don't blame them, i blame the industry and training agencies that allow it to continue.

  3. #13
    Hammerhead CCR diverklondike has a reputation beyond repute diverklondike has a reputation beyond repute diverklondike has a reputation beyond repute diverklondike has a reputation beyond repute diverklondike has a reputation beyond repute diverklondike has a reputation beyond repute diverklondike has a reputation beyond repute diverklondike has a reputation beyond repute diverklondike has a reputation beyond repute diverklondike has a reputation beyond repute diverklondike has a reputation beyond repute diverklondike's Avatar
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    Re: Fascinating lecture on Decompression by Dr. Simon Mitchell

    I know for a fact that there are mfg's that are evaluating this...

    Quote Originally Posted by westy  View Original Post
    Sorry, it did come across that I was trying to force onus onto manufacturers which as you say isn't their responsibility. I was not trying to do this at all, my comment simply came from the fact that some computers come out of their boxes with quite a low (30?) as the default low GF and that with this research, might we see a shift in this? (maybe, maybe not). And I certainly concur with your point that it should be the instructors teaching this to their students, rather than a lecture online!

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    RBW Member rjack will become famous soon enough rjack will become famous soon enough rjack will become famous soon enough rjack's Avatar
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    Re: Fascinating lecture on Decompression by Dr. Simon Mitchell

    A GF low of 30 (vs say 50) really isn't going to matter at the introductory deco level. That might add up to 1 minute at 24m instead of 21m for instance. At least for the 20-30mins of deco people are taught to start.


    Beyond those levels where it does start to matter (60-90-200+mins of deco) its on the diver to know what they are doing and why. Does AP not allow you to change the GF low in their handsets?

  5. #15
    So Cal Tech Diver aainslie has a reputation beyond repute aainslie has a reputation beyond repute aainslie has a reputation beyond repute aainslie has a reputation beyond repute aainslie has a reputation beyond repute aainslie has a reputation beyond repute aainslie has a reputation beyond repute aainslie has a reputation beyond repute aainslie has a reputation beyond repute aainslie has a reputation beyond repute aainslie has a reputation beyond repute aainslie's Avatar
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    Re: Fascinating lecture on Decompression by Dr. Simon Mitchell

    ...so the battle has been won? The helicopter pilot's dogma is gone? Thank god, glad to hear we might avoid a bunch of unnecessary DCS from overly deep stops.
    Last edited by wedivebc; 24th October 2017 at 15:47. Reason: Fixed it for you
    Andrew Ainslie

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    Re: Fascinating lecture on Decompression by Dr. Simon Mitchell

    Quote Originally Posted by aainslie  View Original Post
    ...so the battle has been won? The helicopter pilot's dogma is gone? Thank god, glad to hear we might avoid a bunch of unnecessary CDs from overly deep stops.
    CDs = DCS, sorry, can't find the edit button!
    Andrew Ainslie

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    VPM/RGBM = Mend and Bend
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    Re: Fascinating lecture on Decompression by Dr. Simon Mitchell

    Quote Originally Posted by aainslie  View Original Post
    CDs = DCS, sorry, can't find the edit button!
    Thank god. Who needs a bunch of unnecessary CDs laying around in this day and age?

  8. #18
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    Re: Fascinating lecture on Decompression by Dr. Simon Mitchell

    Best talk I've ever seem on DCS theory. I was just beginning my technical training when VPM-B was all the rage. I actually remember Deep stops being talked about quite a lot by older instructors and technical divers.

    Model VPM-B still works but it's the rate of DCS is higher, if that sounds correct.

  9. #19
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    Re: Fascinating lecture on Decompression by Dr. Simon Mitchell

    Wonderful presentation, left me a bit breathless at times!


    Correct me if I am mistaken but it seemed to me that one of the points made in relation to dynamic airway compression and gas density at depth is that dives even at a relatively shallow depth of 100ft result in ventilation effectiveness and CO2 off-gassing that is reduced by as much as 50% and are higher risk than most people realize in the event of increased work of breathing load! This seems to tie in with the conventional recreational limits as defined by agencies such as PADI and also may be to be a bit of a wake up call to many people who regard deeper recreational diving or shallower technical diving on air as relatively low risk?


    The comments re- BMCL vs OTSCL were also interesting- what rebreather does Dr Simon Mitchell currently dive?

  10. #20
    Fake Diver Jeff Pack will become famous soon enough Jeff Pack will become famous soon enough Jeff Pack will become famous soon enough Jeff Pack will become famous soon enough Jeff Pack's Avatar
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    Re: Fascinating lecture on Decompression by Dr. Simon Mitchell

    After just running VPMB+3 for 10 consecutive days of tech diving, it gave us on the average of about 20m extra time on the wrecks in Truk. PS, we've been running VPMB2 for past 6 years with no incident. Its not for everyone, but Simon has told me physical conditioning plays a large part in susceptibility to DCS.

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