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First day of MM CGMS help!!

Discussion in 'Parents of Children with Type 1' started by dqmomof3, Jan 28, 2009.

  1. Tigerlilly's mom

    Tigerlilly's mom Approved members

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    I would also shut it off, so that it isn't alarming at her all day....I will tell you that false alarms during the school day really annoyed Tyler and he is a pretty easy going, go with the flow kind of kid....

    When I was speaking with CDE this week about our sensor issues, she said to make sure there are NO arrows on the sensor when calibrating.

    Despite your difficulties so far...it's still pretty cool to see the graphs with trends etc, isn't it?:cwds:
     
  2. dqmomof3

    dqmomof3 Approved members

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    I love the graphs! I wouldn't even call them difficulties, really...it's just a learning process, which is made much easier by all the support I'm receiving on here. Thanks to all of you!
     
  3. Darryl

    Darryl Approved members

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    First thing to know, the CGM arrows should never be trusted. They are based on a flawed
    algorithm. You will see this at times when BG is actually heading up but there are one or
    two arrows pointing down. The flaw in the algorithm is that the arrows are based on the
    last 10 to 20 minutes of data, not the most recent two data points. Trust me on this, you
    will soon find that the arrows sometimes tell the opposite of what is really going on. The
    determination of the rate of "up or down" should be made only by manual examination
    of the current data point vs. the last one or two data points, and never by trusting the
    "arrows".

    What you describe sounds like a perfectly good calibration opportunity, for four reasons:

    1) BG was flat for the past 2 hours
    2) She just woke up, and presumably has not yet eaten
    3) The sensor is more than 12 hours old, and therefore will likely be very accurate
    4) You are very close to target range of 100, which is an excellent place to cal.

    We would always cal under the circumstances you describe.

    Unless you have a definite reason to believe that BG is changing quickly (large swings on
    the CGM, just ate, or or just bolused), then you should always cal. If you see that BG changes
    rapidly in the 15 mintes that follow (before the cal takes effect), you could always assume
    retroactively that maybe the cal was not good and do another one.
     
  4. dqmomof3

    dqmomof3 Approved members

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    Well, we did decide to calibrate, because about five minutes after I posted, Jayden woke up and did her fingerstick bg, which was 119. Sensor said 116, no arrows at that point. I told her to use it! I figured worst case, we could recalibrate later.
     
  5. Darryl

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    That's great... the 3-point difference you saw is typical of what you can expect to see
    from here on out, just as you will see differences of 20 or 30 points sometimes, but it
    will usually be somewhere in that range.
     
  6. dqmomof3

    dqmomof3 Approved members

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    ISIG...how do you get this to show up on the pump? When I get to the screen where all the settings are, the ISIG line is blank - there is no number there. Will that show up after I have done additional calibrations?
     
  7. Darryl

    Darryl Approved members

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    You should be able to see the ISIG by pressing the ESC button a few times. There should always be a # there (such as 10.63).
    It should only show as a blank like ("--.--") when there is a lost signal. That's true on the Guardian, so I assume it's the same for yours.

    Once you get your first good cal, you should make a note of the ISIG vs. the BG. The ratio (say, 14.0 for a BG of 100) should remain
    relatively constant for the life of the sensor, maybe vary 20% at most. By comparing the ISIG to the BG value at each cal, you can get
    a heads-up if something has gone wrong with the sensor. For example, if the sensor is usualy 14.0/100 and you see an ISIG of 6.0 for
    a BG of 100, I'd test a few extra times after that cal to be sure things are lining up... and possibly look into whether the sensor may
    have partially pulled out or be near the end of its life.
     
  8. dqmomof3

    dqmomof3 Approved members

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    Thanks - found it. The ISIG is 24.4, bg is 136. Do those sound reasonable?
     
  9. Darryl

    Darryl Approved members

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    That would be 17.9 for a BG of 100... yes, that sounds good!

    Keep track of how that tracks your cal's over the next 7 days. We find our ratios to be pretty consistent over the 7-day period, which is nice because it gives us a good indication of when a calibration is "suspicious". I actually trust the CGM more than BG readings, because BG readings can be affected by things like the fingers not being clean, or the wrong test strip code. When we see an ISIG that is way off-ratio, we proceed in this order:

    1) Re-check the test strip code setting. If OK, then:

    2) Check the sensor for any sign of loosening, bleeding, site inflamation, etc. (those are all very rare), or if there is pressure on the sensor (i.e., sleeping in a position that compresses the area where the sensor is). If none of those are a problem, then:

    3) Repeat the BG. The BG is wrong at least as often as the CGM is wrong, and the last thing you want to do is mess up a good CGM cal by entering a bad BG reading!

    4) If the BG and sensor are still in disagreement after the 2nd BG check, re-cal the sensor, but do a few extra checks in the hours that follow to see if things are back on track.
     
  10. cwdAdmin

    cwdAdmin Administrator Staff Member

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    Reminders

    Good conversation about cgms. Just a gentle reminder to consider contacting the manufacturer if you have product questions. And to note the manufacturer's suggested usage and expiration dates.

    Be safe! :cwds:
     
  11. Darryl

    Darryl Approved members

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    No offense taken to the reminder, however if the pump and CGM companies provided this
    kind of practical info, we would not need to be here exchanging this advice!

    The FDA approval for the Minimed sensor is 3 days, and the device has not been tested by
    the FDA for longer usage. This was not made clear in the earlier posts.

    So, it should be stated here that common use of the sensor for 7 days, and in some cases
    up to 30 days, speak only to the useful life of a sensor and not to possible safety concerns
    with extended use.
     

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