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[IPk] Animas Vibe - IOB update (+ basal Q)



 An update on the Q raised earlier about the accuracy of the IOB on the Vibe. I
use Apidra and have the DIA set at 4 hr. I have been checking my pump and I
consistently see IOB indicated more than 4 hours after a bolus. The amounts are
small and the extra time is fairly short, but they are there. In a typical
example, yesterday I took a 1.95U correction bolus; by 4h and 16 mins, IOB was
shown as 0.12 U.

 I am actually not sure that this is necessarily an error in the algorithm. I
have tried (so far unsuccessfully) to Google the actual definition of DIA.
However, any bolus will have a long tail of activity, and if I remember
correctly, the action times quoted by the insulin manufacturers are a measure of
the time by which something like 95% of the insulin has disappeared from
circulation. Perhaps Animas' IOB algorithm takes this into account, in which
case there may well be some IOB still shown after the end of the DIA period.
Also, in the real world the DIA will not be fixed but will depend on bolus size
(bigger = longer). For a discussion of IOB see link below:

http://diatribe.us/issues/22/thinking-like-a-pancreas

 A different and unrelated observation: With the new pump I have had to cut my
basals quite significantly, particularly overnight (where I have had to drop the
rates by around 40%). This is odd as x U/hr should be the same regardless of
which pump is delivering it and my basals have hardly changed over the years. I
know the Animas delivers basals a bit more evenly than the Medtronic but I
cannot believe that this would make the difference The only explanation that I
can think of is that it has something to do with insulin absorption at the
infusion set. I am using what are essentially identical infusion sets, so the
only other explanation I can think of is that it is somehow related to clogging
of the set. I have never been able to keep a site working properly for more than
2 days and according to John Pickup, Apidra is particularly prone to denaturing
and blocking up the cannula. With the Animas, bolus delivery is RAPID (a 10 U
bolus goes in in less than 10 secs). I wonder if this is somehow "flushing" out
the cannula and keeping it clear.

Anyone else noticed this?

Joel
.
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