Friday, June 1, 2007

Identifying Differences - Finally!

One of the major differences between pumps is how they count insulin on board (IOB); Minimed pumps use pharmodynamics while Animas uses pharmokinetics. Currently Diabetes Mine has some more information about this. As I understand it pharmodynamics takes the cellular level of insulin present to deliver a bolus shot; this reduces the amount of IOB in the bolus wizard calculation possibly causing more lows than a pharmokinetic system. However, a pharmokinetic system may not allow the pump wearer to fully cover all additional carbs they are eating due to how it calculates IOB. I need to do some more research on studies that determine which is a more effective way of treating diabetes.

A second major difference between the 2 pumps is how they deliver the bolus insulin. The minimed pump delivers a unit of insulin every 30 seconds, so a 3 unit bolus will take a minute and 1/2 to deliver. The Animas pump delivers a unit of insulin every second in the 2020's normal mode and a unit of insulin every four seconds in the 2020's slow mode. I have yet to find any medical significance to the speed of a bolus and how the body absorbs it but I'm hopeful that I can find an article on it soon.

Lastly, the basal rate of each pump is calculated completely differently. The Minimed pump uses a mathematical formula of (units of insulin per hour) / .05 to determine how often you will receive a basal injection. Animas simply delivers basal insulin every 3 minutes. Therefore, if you receive .6 units of insulin per hour the Minimed pump will give you insulin every 5 minutes or 12 times per hour (.05 units of insulin for each injection). For the same .6 units of insulin per hour the Animas pump will give you a shot every 3 minutes or 20 injections of insulin in that hour (.03 units of insulin for each injection).

I've identified some major differences between the two pumps. My next step will be to talk to Leigh my diabetic educator to find out what/ if any the difference is between delivering insulin in the above methods. Although Minimed has received alot of goodwill I want to make sure they are using the most effective method of insulin deliver, I do not want to chose their pump simply because they were the first to introduce a CGM meter that spoke directly to their insulin pump.

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