insulin pump calculations

Question 1

what is the first thing you need to remember

Answer 1

pumps do NOT automatically adjust the dose for the need, even if they are linked to a sensor for tissue glucose.

Question 2

how to correct for a meal

Answer 2

You need the insulin to carb conversion ratio (ICR).

eg. 10 That would mean dividing the weight of carbs by 10 to get the number of units

E.g. 30g would require division by 10, so 3U of insulin to be delivered by the pump.

Question 3

how to correct for a high BG

Answer 3

Subtract normal (5.5 in UK units i.e. 5.5mmol/L) from the high value

lets say it is 13.8mmol/L
This gives 8.3mmol/L.

The UK Insulin Sensitivity Factor (ISF) is a variable per person, but the equivalent of the example in the booklet for UK calculations is 2.8,
so divide 8.3 by 2.8 to give 2.96U

Question 4

To correct the total bolus if a meal is coming but the BG is too high at the moment

Answer 4

A meal of 76g carb and an ICR of 10 means 7.6U normally

Say the person has a BG of 11mmol/L (ISF is 2.8. Assume normal glucose is 5.5mmol/L.

So the correct bolus would be
(11-5.5)/2.8 = 5.6/2.8 = 2U
So the total dose this time is 7.6 + 2 = 9.6 units

Question 5

To correct for a meal when the BG is low (hypo)

Answer 5

Say the meal has 80g of carbs and the person has an ICR of 10

That’s 8 units normally
ISF is 2.8. Assume normal glucose is 5.5mmol/L.

But their BG is too low at the moment… it is 4.2
(4.2-5.5)/2.8 = -1.3/2.8 = -0.46
So subtract 0.46 from the normal dose to give

8 -0.46 = say 8 -0.5 = 7.5U (adjusted down from 8)
This then covers for the meal but allows for the low BG