Re: [IP] insulin duration MM512
Herein lies the problems...
1. Pump companies have to be cautious about making insulin recommendations that
might result in a low. I spoke to John Walsh on the phone personally about his
unused insulin rule, and he said it was meant to be a "compromise" that
calculated some unused insulin, but was lax enough to not cause a low later on.
If a pump company makes a recommendation that leads to a low resulting in an
accident, etc., they have to worry about liability. So, the solution is to
overestimate unused insulin rather than underestimate it.
2. MM's choice, from a scientific standpoint, is actually the most accurate
method. Despite what people think, the fact is there IS insulin active in your
body for as much as 8 hours in very minute quantities. What is left out of the
picture, however, from a practical standpoint, is that it isn't JUST insulin
concentrations that affect BGLs! So, while there may continue to be insulin in
the bloodstream, carbs from sources such as fat-delay, glucagon production, and
protein conversion ALSO enters the bloodstream. The result is that these extra
amounts of carbs overcome the minute remaining insulin such that it APPEARS that
it isn't working.
Realize that numerous people have said something to the likings of, "Unless I
take a really large bolus, I find that my Humalog is gone in 3 hours." That
FIRST part is actually quite significant. It isn't that the Humalog lasts longer
if you take more...only that the amount that continues to last is enough that it
becomes significant in affecting BGLs. If MM calculates that, at 6 hours
post-bolus, 95% of the insulin is used up...then for a rather small bolus, the
amount of insulin it calculates will be very small, almost negligible. For a
larger bolus, this unused insulin will calculate to be more significant. MM's
calculation is quite accurate in both accounts...again, ignoring the other "real
In the case of a larger bolus, there is now MORE unused insulin than
protein/glucagon/fat-delayed carbs in the body, and so it appears to affect the
BGL. Using the John Walsh/Cozmo method, it will not account for this.
So, neither method is perfect. In my own software, I have a "dual-action" mode
of unused insulin calculation that works better than the John Walsh/Cozmo
method. (I can't say how it compares to MM's.) Anyhow, you can configure not
only the duration...but the percentage of the total that is gone at any given
point. So, I might say that 90% of the insulin is used up in the first 2 hours,
but the remaining 10% continues in the blood over the next 1.5 hours, etc.
Anyhow, I think debates about which method is "better" is rather moot. Both
have their advantages and disadvantages. MM's is truly more accurate from a
purely blood/insulin concentration standpoint, and for larger boluses, will
likely be more accurate. Cozmo's can be tailored, but will be less accurate for
large boluses, and certain points along the "action curve" of the insulin.
> The way I look at this is that the Cozmo users will base it on their OWN
>research, not on
> what someone else says, so MM's argument doesn't particularly wash with me.
>All of the
> "medical research" in the world still is not as good as a persons own
> particularly if they are diabetic. As my Endo says to me "you are your own
>and we all know, YMMV! ;>)
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