- advertisement -

Active insulin while pumping

Discussion in 'Parents of Children with Type 1' started by Mindy and Tim, Feb 3, 2008.

  1. Mindy and Tim

    Mindy and Tim Approved members

    Joined:
    Oct 6, 2007
    Messages:
    36
    Can someone give me a little insight into this? My son pumps since 12/07. His insulin duration time (if that is what it is called?!) is 3 hours. His sensitivity is 75. If at 2 hours I check him for whatever reason, and say he needs some correction, how much validity do you give to the active insulin?
    For clarity, here's an example: He eats lunch, doses with say 3 units, then 2 hours later tests and his BS is still a little up. His active insulin would say 1 unit. Can I assume that he will still drop another 75 points (based on his sensitivity) even though his Apidra has already peaked, or should I assume that he will only come down a little bit of that?
    Any insight?
    Mindy
    mom of Adam, 10 (11 in 2 days)
    d since 3/07
     
  2. WestinsMom

    WestinsMom Approved members

    Joined:
    Mar 27, 2007
    Messages:
    3,137
    Your setting seem really close to ours...both 10 year old boys...so that makes me feel good :) I generally don't have a problem with avoiding a requested correction. Maybe it is the apidra? It takes us about 3 hours to get back to around our starting number. I think it just takes some trial and error to see how to proceed. It's a "your diabetes may vary" kind of thing.
     
  3. Nancy in VA

    Nancy in VA Approved members

    Joined:
    Jul 16, 2007
    Messages:
    7,308
    I have generally trusted the IOB as calculated by the pump. In almost every case where I have overridden, we have ended up a little low. But, we are using Humalog and I don't know if its different than Aprida. We have our duration set at 4.5 hours. The tail is small compared with the first two hours but its still usually there
     
  4. twodoor2

    twodoor2 Approved members

    Joined:
    Oct 30, 2007
    Messages:
    6,440
    The active insulin is extremely important, and I'm not just saying this. John Walsh (re: Pumping Insulin) indicates that one of the biggest mistakes parents make when going on the pump is underestimating the active insulin period, or DIA (Duration of Insulin Action) as he calls it. We thought ours was 3 hours, but we actually were told to make it at least 4 hours, and it turns out she's probably closer to 5 hours. I don't know how long Apidra takes to act, so I can only speak from the perspective of using Novolog which as an average time of 4 hours.

    The DIA helps to guesstimate the IOB (Insulin on Board) which helps to prevent stacking if you're giving more than one correction in within the same DIA.

    Therefore, in your example, if he has 1 unit left, he is still coming down, and if you give a correction, some pumps will actually subtract this amount from the correction dose to prevent stacking of too much insulin. I don't know how your pump does it, but my pump, the Minimed 552, will subtract the IOB value, or the 1 unit in your case from the calculated baseline correction dosage. This helps to avoid hypoglycemia. I have found that the correction dosage is much more accurate when the DIA is over. This is because people have variation in how the IOB is used up, and the pumps use standard charts to make these calculations. However, it is better than giving two full correction doses during the DIA period!!

    With 1 unit left and an ISF of 75, I would probably wait until the DIA was over to give another correction if that's what's needed.

    I hope I made sense and that answered your question :)
     
    Last edited: Feb 3, 2008
  5. Mama Belle

    Mama Belle Approved members

    Joined:
    Jan 23, 2007
    Messages:
    4,540
    This is definitely a YDMV situation. Most of the time we are able to trust the pump with the IOB calculation and the suggested correction is perfect. Other times when there are maybe extenuating circumstances (growth, sports, illness, set issues, etc.) the correction bolus either isn't enough or is too much. But under normal conditions, we have had lots of luck with corrections based upon IOB.
     
  6. nebby3

    nebby3 Approved members

    Joined:
    Jun 5, 2007
    Messages:
    923
    The tricky part is the carbs on board. Your pump may tell you there is 1u on board but was that to cover a meal? If so, there are probably carbs on board to balance out at least some of it too.
     
  7. Boo

    Boo Approved members

    Joined:
    Jan 6, 2006
    Messages:
    1,958
    Is his active insulin time (DIA, whatever...) set at 3 hours because that's what the pump trainer TOLD you to set it at, or is it set at 3 hours because through trial and error you have found this to be about how long the particular insulin (apidra) works in his system? There can be a big difference, and I think sometimes people just go with what it recommended and don't make changes. You need to find what works for HIM, and how long the apridra generally takes to work IN HIM after a normal meal (not really high fat/protein).

    Once you are sure that your Insulin on Board time is set accurately, then, as nebby 3 says, you also have to consider the previous bolus. Was it given to cover carbs, or just as a correction (with no food)? If it was to cover a meal or snack, what are the chances that the food is already digested? High protein/high fat meals will take significantly longer. If an extended bolus wasn't used, then chances are that the BG may keep going up after the 3 hour timeframe (at least that is the case with my son).

    YDMV, and you really need to experiment and find out what works best for your son.
     
  8. BrendaK

    BrendaK Neonatal Diabetes Registry

    Joined:
    Oct 29, 2005
    Messages:
    3,835
    This is a really good point. Some of the food from the meal could still be digesting, so he may NOT drop the 75 points. You really have to pay attention to what kinds of foods he's eating. Simple sugars/starches are in and out of the system in no time. But other foods with more fat and protein and fiber take longer to digest -- and that all plays into effect with IOB. I wish I knew how to calculate CARBS on board, too!
     
  9. twodoor2

    twodoor2 Approved members

    Joined:
    Oct 30, 2007
    Messages:
    6,440
    Again, I'm citing John Walsh's book "Pumping Insulin" but he does complain about this with pumps. The one way to deal with this is to set the low target range higher (at least on the MM pumps) so it will do a negative correction if the blood glucose range is lower than you want it to be by the next dose. Then it will subtract some of the food bolus. However, I hear what you are saying, that would be a nice feature to add to the pumps.

    When I look at IOB, I look at it this way, if her ISF if 150, and I have 1 unit on board, the maximum her blood glucose will drop is 150 points, or that's what it shoud do in theory. If the 1 unit is covering food, or part correction and food, then it will drop less than or equal to what the ISF dictates, but it should not drop more than that (unless you overdosed or your ISF is incorrect).

    That's how I look at it, but others may look at it differently.

    I find IOB very helpful, especially at night time. If she has 1 hour of DIA left, and I see a small amount of IOB left, and her blood glucose is in a good range, I usually don't worry about a low occurring.

    For example, if she has a bg of 150 and there is .15 IOB left, then the max she can drop is .15*150, or about 22 points. It's usually never the full 22 points though because some of that .15 was used to cover food, as well. This should work in theory if she is someone who remains steady after the IOB leaves her system, and her basal dosage is correct. However, YDMV, so I'm just citing how we use it the IOB.
     
    Last edited: Feb 3, 2008
  10. Mindy and Tim

    Mindy and Tim Approved members

    Joined:
    Oct 6, 2007
    Messages:
    36
    I didn't think about the carbs on board. That would definitely be something to consider, esp if it was a high fat/protein meal. Our trainer had told us to use the 3 hours, because that is what Apidra says is its active time. Our pump does make the negative correction, and I've found that if he's only got a couple tenths of a unit left of IOB, and I go ahead and add that back on to the bolus, then he's fine. I guess to really test it, I'd have to wait right about 3 hrs after his dose and test him to see if he's back to where he started (although this would have to be done with a really well calculated meal I would think)
    Mindy
    mom of Adam, 10 (11 tomorrow)
    d since 3/07
     
  11. Mom2rh

    Mom2rh Approved members

    Joined:
    Mar 15, 2006
    Messages:
    2,334
    Actually, how I tested this, and over time shortened my son's insulin duration to 2 1/2 hours (I think) was by checking his BG when he still had IOB (with only half an hour left) and then testing in half an hour to see if it went any lower. Both times I did this, his BG was virtually unchanged leading me to believe the insulin was "done" at the earlier time. We have had no problems from lowering this...even with grazing type days where he eats all day.
     
  12. twodoor2

    twodoor2 Approved members

    Joined:
    Oct 30, 2007
    Messages:
    6,440
    I love talking about DIA, it's one of my favorite diabetes subjects, and I think a very underrrated one. However, it is so important and I believe is a prime reason for so much unexplained hypoglycemia (John Walsh, who I keep citing, believes this as well). Love his books!!

    I guess YDMV, but in our case, we were under the impression that our daughter had a DIA of 3 hours because her BG didn't seem to go down after that time. However, little did we know, but it really did drop more after that. At first I was perplexed as to why she would go hypoglycemic at dinner time, with all other variables being the same (exercise, stress, health). I had thought all the IOB was completely out of her system by the time I gave her the luch dose.

    At first I thought her basal was incorrect, but it did keep her steady all night. The true culprit was the DIA, now that we have it set to 4 hours, we no longer have problems of hypoglycemia associated with dinnertime. The hypoglycemia would occur on and off, but mostly when I had to give a correction at lunchtime. That extra tail end of insulin was not being accounted for, and gave her mild hypoglycemia because it was added to her dose if she had a correction at lunch. The breakfast IOB truly did not wear off by the time she had lunch, so the additional insulin was being added to her lunchtime correction dose. Fast forward, low at dinnertime.

    At first I thought the ISF was wrong, but it wasn't.

    It can be very diffucult to ascertain if it's the ISF or the DIA. However, if your ISF is working for much of the day, it's probably the DIA. Try that first, and see if it helps. At least that is my experience, others may beg to differ.

    With the pump, it calculates the IOB amount if you correct more than once during the DIA period, and it subtracts the IOB that is derived by the DIA chart for the period of time you select on the pump. This essentially avoids what I was doing. If your DIA is not set correctly, you will not subtract this "tail-end" of the insulin, and it will be added to the correction dose.

    The problem with DIA and insulin pumps is that there are standard charts to calculate IOB based on percentages that insulin is used up within a specific DIA timeframe (the DIA chart). These charts are based on statistics provided by testing a group of control subjects by the insulin manufacturer. However, there are always people that use up the insulin a bit differently than the standard test control group. That is why the most accurate correction dose is the one calculated when all IOB is completely gone. However, most people use the IOB calculations derived from the pumps without issue.

    It is a curvelinear chart. This is the 4 hour IOB chart that I use to do the calculations that I corroborate with the pump.
    The first column is the hours after the dose in HH:MM format, and the second column are the percentages in decimal form.

    0:00 1.00
    0:30 0.95
    1:00 0.85
    1:30 0.60
    2:00 0.40
    2:30 0.25
    2:40 0.20
    3:15 0.15
    3:30 0.10
    3:40 0.07
    4:00 0.05
    4:01 0.00

    The pump companies do not divulge these charts. I obtained mine from taking all the calculations from the pump from all my daughter's doses and figuring out what percentages they actually use.

    It's really fascinating, but it's something to take note of.
     
    Last edited: Feb 5, 2008
  13. BrendaK

    BrendaK Neonatal Diabetes Registry

    Joined:
    Oct 29, 2005
    Messages:
    3,835
    Wow, you went to a lot of work to get that chart! I find it really fascinating. Carson's on the Cozmo and they do not calculate in a "curvilinear" method -- it's strictly linear, which drives me NUTS!! If he has his IOB set at 4 hours, it will still have 50% left on board at the 2 hour mark. According to your chart (which looks much more accurate), it's 40% left at 2 hours and only 25% at 2 1/2 hours.

    Does anyone know why Cozmo figures IOB the linear way? It just doesn't make sense to me.
     
  14. twodoor2

    twodoor2 Approved members

    Joined:
    Oct 30, 2007
    Messages:
    6,440
    John Walsh notes the linear chart in his book, "Pumping Insulin," for the Cozmo. Can you tell I'm a big fan of John Walsh:p He should give me some of his royalties!!

    That's one of the reasons I chose the MM, due to the curvelinear approach - it seems more accurate.

    However, he does mention that choosing a shorter DIA for the Cozmo does help. I assume it provides smaller percentages. I would have to play with a Cozmo to see that. Same deal with the Omnipod, linear DIA chart. I do wish the pump companies would give more information on how they calculate IOB, but part of that is a trade secret I presume.

    The Animas also uses a curvelinear chart like the MM Paradigm pumps.
     
    Last edited: Feb 5, 2008
  15. jules12

    jules12 Approved members

    Joined:
    May 26, 2007
    Messages:
    2,333
    WOW - that is a lot of information to take in....I like John Walsh's book but a lot of the examples always seemed for someone on a lot more insulin than us - the "standard" just doesn't seem to apply yet. Thanks to everyone who has provided your examples - we are still major honeymooning with and ISF of 400 and DIA of 4 hours. However, I love learning more about it all!
     
  16. Momof4gr8kids

    Momof4gr8kids Approved members

    Joined:
    Sep 3, 2006
    Messages:
    4,143
    It depends on the food that is still active.....
     
  17. twodoor2

    twodoor2 Approved members

    Joined:
    Oct 30, 2007
    Messages:
    6,440
    Actually he applies his methodology to children as well since they take proportionately equal amounts of insulin when compared to adults (honeymooning is not being taken into account here). For example, if a 50 pound child takes 10 units of insulin a day, a 150 pound adult may take 30 units of insulin a day. It still remains in the body just as long as the adult vs the child because the amount of insulin is proportional to the body weight. This is a very generalized example, and YDMV, but that's what he's indicated in his literature.
     
  18. TimO

    TimO Approved members

    Joined:
    Jul 27, 2006
    Messages:
    222
    Active insulin

    I'm curious as to active insulin time based on age & when diagnosed. My 6 y/o son has had an active insulin setting of 3 hours since we went on the pump 3 years ago. I know parents who have their kids on 4 and even 2 hours active. For those of you who've got a kid around the same age w/D & pumping for a few years, what is the active insulin time on your pump? Just curious.
     
  19. twodoor2

    twodoor2 Approved members

    Joined:
    Oct 30, 2007
    Messages:
    6,440
    We use 4, but I might go to 5. I'm still playing with her pump settings.

    Have you recently tested your son's DIA? It can change. Three hours is very short, insulin usually tends to take longer to leave the body. John Walsh indicates that the insulin manufacturers are very competitive and always claiming a very short action, but in fact, they usually take much longer to leave the body. In other words, "short acting insulins are not that short."

    For the MM Paradigm pumps, Walsh recommends a longer DIA (at least 4 hours) for safely calculating dosages. This is due to the curvelinear DIA that the Paradigm uses.
     
  20. momtojess

    momtojess Approved members

    Joined:
    Aug 15, 2007
    Messages:
    2,682
    Jess is 6, has been pumping for 5 yrs.. Her active insulin has always been set at 3 hrs and we have never had a problem. YDMV
     

Share This Page

- advertisement -

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice