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Thread: Discussion on Co2 monitoring (split from another Apoc thread)

  1. #241
    Just add ice & water plazma is a name known to all plazma is a name known to all plazma is a name known to all plazma is a name known to all plazma is a name known to all plazma is a name known to all plazma is a name known to all plazma is a name known to all plazma is a name known to all plazma is a name known to all plazma is a name known to all plazma's Avatar
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    Re: Discussion on Co2 monitoring (split from another Apoc thread)

    Quote Originally Posted by Simon Mitchell  View Original Post
    Plazma,

    The way this is dealt with in anaesthetic machines is that gas is continuously sampled from the mouthpiece via a very fine tube that has insignificant internal volume. This tube carries the sampled gas back to the analyser. The beauty of this system is that it gives you useful information about CO2 levels during inhalation (viz: the issue of scrubber breakthough) and exhalation (viz: a true end tidal CO2 with minimized contamination by expired anatomical dead space gas). The problem is that the gas must be drawn through the tube by some sort of pump, which is why it would be difficult to use underwater.

    Alex says this is unnecessary. I say that there simply has to be some dilution of CO2 in the end tidal gas by the exhaled anatomical dead space gas if you allow the opportunity for the two to mix in an exhale hose and then measure CO2 at the end of that hose. It does not follow that one of us has to be wrong. Indeed, it is possible we are both right. The key question is whether the dilution I am concerned about is of sufficient magnitude to affect the practical utility of the CO2 readings at relevant / realistic tidal volumes. It will happen if the tidal volumes are low enough, but I don't know how low they have to be for it to be an issue.

    Simon M
    Yup, a pump may be impractical. That's why I was thinking about an optical fiber. The optical fiber may also be impractical since they discarded the communication fibers.
    But it would be nice to know if you can measure via an optical fiber since it's an IR sensor.

  2. #242
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    Re: Discussion on Co2 monitoring (split from another Apoc thread)

    Quote Originally Posted by AD_ward9  View Original Post
    Happy to take your money, but I arranged one for Simon already free of charge and PM'd him on it.

    On cells: we published the data (very detailed, as usual in our verification reports).

    Alex
    Was there ever any follow through on this with Dr. Mitchell or others?
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  3. #243
    New Member Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell's Avatar
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    Re: Discussion on Co2 monitoring (split from another Apoc thread)

    Quote Originally Posted by saveourseas  View Original Post
    Was there ever any follow through on this with Dr. Mitchell or others?
    No,

    I have not yet seen the CO2 test data that Alex was going to find. In any event (and as I said in a previous post), I have doubts about its relevance to the discussion we have had here because the design of the test ventilator did not appear to mimic the anatomy of the human respiratory tree (in terms of anatomical dead space).

    I am also still happy to have a play with a mouthpiece-hose-CO2 sensor unit myself.

    Simon M

  4. #244
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    Re: Discussion on Co2 monitoring (split from another Apoc thread)

    Hi Simon,

    I offered you access to my unit in response to your question on training.

    Might be the quickest way to resolve concerns over veracity of the APOC CO2 monitor.

    PM if interested and I will ship to NZ once it arrives.

    Regards,
    Tony

  5. #245
    New Member Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell's Avatar
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    Re: Discussion on Co2 monitoring (split from another Apoc thread)

    Quote Originally Posted by Tony_Q  View Original Post
    Hi Simon,

    I offered you access to my unit in response to your question on training.

    Might be the quickest way to resolve concerns over veracity of the APOC CO2 monitor.

    PM if interested and I will ship to NZ once it arrives.

    Regards,
    Tony
    Hello Tony,

    I'm not sure that would be a smart move. The relevant bits might require a few mods to adapt them to an anaesthetic circuit. At the time the discussion was going on I got the sense from Alex that there would not be much problem with just providing the bits I need, but have not heard anything since.

    Simon M

  6. #246
    RBW Member Nemisis is an unknown quantity at this point Nemisis's Avatar
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    Re: Discussion on Co2 monitoring (split from another Apoc thread)

    Hi Simon
    Given your views on Apoc CO2 monitor,having seen the Sentinel PDF on their new CO2 monitor have you any views as to their claims

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    Re: Discussion on Co2 monitoring (split from another Apoc thread)

    Quote Originally Posted by Simon Mitchell  View Original Post
    At the time the discussion was going on I got the sense from Alex that there would not be much problem with just providing the bits I need, but have not heard anything since.
    That is really a shame. It would have been nice to have some solid answers before releasing these to the public. So the rebreather industry remains a "buyer beware" wasteland even after the "Open Revolution". Vive la résistance!
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  8. #248
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    Re: Discussion on Co2 monitoring (split from another Apoc thread)

    Quote Originally Posted by saveourseas  View Original Post
    Vive la résistance!
    ..or sticking with the French, plus que ca change, plus que c’est la meme chose
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    Re: Discussion on Co2 monitoring (split from another Apoc thread)

    Quote Originally Posted by aainslie  View Original Post
    ..or sticking with the French, plus que ca change, plus que c’est la meme chose
    "the more it changes, the more it's the same thing", usually translated as "the more things change, the more they stay the same" (Les Guêpes, January 1849)

    For those of us that can't speak french.

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