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MM pump, corrections, and IOB

Discussion in 'Parents of Children with Type 1' started by dqmomof3, Jun 12, 2008.

  1. dqmomof3

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    For all of you expert MM users out there :D...

    When you do a correction only, no food bolus, but just a correction for a high bg, does MM take into account the IOB when it gives you the suggested bolus for a correction?

    I am noticing that anytime we have to do a correction, during any time of the day, if I correct her with what the pump says, we are hypo within about 45 minutes. Clearly I'm overcorrecting, but I don't know if the ISF is off or if the IOB is not being counted.

    Thanks.
     
  2. Abby-Dabby-Doo

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    If you are using the Wizard the pump will take all IOB into consideration. I would assume your ISF is wrong.
    Are you correcting too early and your duration is off? The reason why I ask- Abby will faithfully drop 90 points from the 2 hour check to 2 1/2 hours. I've bounced between setting the duration at 3 hours or 4 hours. After several lows, no room for errors with carbs, I chose the later 4 hours.
     
  3. Mindy

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    It sounds more like ISF, but how long do you have the duration set for the insulin? It does take into account IOB when doing a correction only, but bases it off the duration.
     
  4. Lee

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    I would adjust your ISF...
     
  5. dqmomof3

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    Our duration of active insulin is set for six hours. Longer than anyone I know on the pump, LOL!
     
  6. Mindy

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    Oh wow! ha I'd change the ISF then. Austin's duration is set to 4 hours, but he took a pump break recently, and I learned that first night after a correction that I goofed on, that it only lasts 3 hours in him. I will probably not change the duration when he goes back on the pump at the end of the summer, though, as it has worked well.
     
  7. twodoor2

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    Your ISF sounds way off, what is it? What is her weight in lbs? What is her ICR at specific times of day?

    MM will ALWAYS factor in the IOB when doing a correction, unless of course, if it's zero at the time of the correction. The formula for a correction is

    [(CBG - TBG high target)/ISF] - IOB

    Where CBG is the Current BG

    and TBG is the Target BG, and it uses the high end of the target range.
     
    Last edited: Jun 12, 2008
  8. dqmomof3

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    Here's an example of what we are dealing with for corrections. At 3am, Jayden's blood sugar was 320. She had not had food or drink or bolus since 8pm, so all IOB should have been accounted for and gone.

    The pump suggested a correction of 3.8 units. I decided that was nuts, so I corrected with one unit. She woke up at 9am at a beautiful 104. I shudder to think of the consequences had I corrected her 3.8 units!!!

    Can I just say that having a child athlete with diabetes puts a whole new twist on this crazy disease?? She had gymnastics last night (two hours) and then ran around for about another hour afterward. I'm sure that makes her ISF lower. I would never have done a full correction in the middle of the night anyway, but normally I would have done half of what the pump says (as directed by endo) and that still would have been way too much.

    And of course, she heads to gymnastics camp in five days, where she will be exercising 8+ hours every day for three days, and four hours on the other two days. I have no idea what to expect!
     
  9. dqmomof3

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    Marsha - her ISF is 50. Her ICR for times of the day is: 1:20 for breakfast, 1:17 for lunch and dinner. We've had recent discussion about changing her breakfast ratio to 1:25, to avoid the hypo right before lunch. I am supposed to make that change tomorrow. She weighs 54 pounds. Target bg range is 90-120. TDD is about 20 units, which I know looks like honeymooning, but she isn't. She has no measurable circulating C-peptide. It's just the extreme amount of exercise she does that lowers her TDD - that and she doesn't eat all that much!
     
  10. twodoor2

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    Based on those calculations, and I think her target range is 120 since we had many prior conversations on that, is her ISF 50?? That seems kind of low for someone her weight since you mentioned she was very small and thin. I would use 50 for a teenager or adult.

    BTW, another hint. You may want to set the high end of her target range higher at night, like 170, just to be on the safe side. Exercise will cause substantial drops at night.

    ETA: I just read your last email before I finished this one, I see that you confirmed it is indeed 50.
     
  11. twodoor2

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    Elizabeth also weighs 54 pounds (she's a very large 5 year old) and the average BCR for that weight is around 8. Therefore, I suspect your ISF is not only off, but EXTREMELY off. Let's put it this way, Elizabeth has very similar carb ratios, and her ISF goes from 140, 170, 200, 250 (breakfast, lunch, dinner, sleeptime). The ISF can be estimated by taking the ICR * BCR. The BCR is the number of mg/dl points that 1 gram of carb will raise you. It is dependent on weight, not age, so yours sounds extremely off.
     
  12. dqmomof3

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    When I figured out her BCR about a month ago, it was 8 as well. A 4g glucose tab raised her bg by 32 points.

    If her ISF is really this far off, though, shouldn't I be seeing a lot more bad numbers? We have days and days of numbers that are almost all in range. We do very few corrections, though - just don't need to very often.
     
  13. twodoor2

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    Based on the math, if 1 unit worked perfectly and she woke up at 104, then you should use an ISF of 200 at night.

    BTW, you mentioned that you had once tested her BCR and it was also 8 in the pm you just sent me. Based on her carb ratios, set all her ISF's to be ICR*BCR.

    So for example if her ICR is 17, then 17 * 8 is 136. I would make it 150 to err on the side of caution until you get those well tested.

    I would use multiple ISF's. Once I started doing that, her corrections went down to less than 8% of the TDD a day. On most days, they're 0 to 5% of the TDD.
     
  14. twodoor2

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    If you do very few corrections, it's probably because she's very active, and you don't need as many. However, if your ISF is off for any part of the day, it could majorly cause a domino effect and you're chasing lows, followed by highs, or vice versa. If you have a correct ISF, even if you only correct once, everything should fall nicely into place (assuming you have correct basals and ICR's that is.:p).

    Hope that helps.
     
  15. saxmaniac

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    Well 320-104 for 1u would be ISF of 216. 1/4 of what you have now! Like anything else I'm quick to reduce it (higher numbers) and slower to increase it (lower numbers).

    Our ISF is based on observation. No formula or should-be's, just how much does he go down, and it's upwards of 275 at night. During the day it's 120 or 150.

    Of course your ISF can vary with exercise. If this drop happens even on night of normal activity then change the ISF. Otherwise I'd look into a temp basal after exercise.
     
  16. dqmomof3

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    LOL - is there any such thing as a night of normal activity? There is just not one of those around here. We do have two different basal patterns, one for gymnastics nights and one for non-gymnastics nights.

    I think at the very least I should double her ISF in the pump, from 50 to 100. That has got to help!
     
  17. twodoor2

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    I think it should be at least 150.
     

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