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[IPk] Getting too much insulin as the insulin warms
I was looking at the Disetronic website the other day, and I came across
the above page about avoiding getting air bubbles in the insulin cartridge.
One point I've never seen before is the importance of raising your insulin
to normal pump temperature before loading it into the cartridge. If you
take it out of the fridge, refill your pump and connect up, then over the
next few hours the insulin will rise to normal pump temperature, and in the
process it will expand, possibly pushing a few extra units of insulin into
you. At least, that's what the Dresden team seem to claim.
If you wear your pump on your belt, then going outside for a few hours will
cause the whole pump to cool - say to 10:C. When you come back into the
office, the whole pump will rise to 30:C. This cooling and warming could
effect the amount of insulin you get - in ways we may not realise.
Out of curiousity, has anyone been trained to take account of this, or is
it all a load of rubbish?
Text from Disetronic article:
How to avoid air bubbles in the insulin cartridge
Many people know that water contains oxygen-this allows even fish to
breathe. Some people also know that warm water has less oxygen than cold
water. In the illustration in the margin you can see that the lower the
temperature, the more oxygen is dissolved, and the other way around. It
follows that oxygen escapes when water is warmed. The same happens with
insulin-pump insulin is an aqueous solution. Many patients have already
observed the occurrence of one or several air bubbles in insulin they were
using directly from the fridge, although there had been no bubbles in the
cartridge before they started using it. The reason for this is that oxygen
escapes as the insulin warms in the pump. As soon as the oxygen bubble
reaches the tubing of the infusion set, it is pushed towards the cannula.
After the bubble arrives at the cannula, no more insulin can be delivered
and blood sugar increases.
If the insulin in the cartridge has reached the correct "operating
temperature" of 300C before being inserted into the pump, the formation of
air bubbles can generally be avoided. Therefore, please note the following:
- Keep the pre-filled cartridge, or the insulin vial for filling the
cartridge, at room temperature for several hours or days before using it in
- Leave the insulin in your breast or trouser pocket for 1 - 2 hours before
using it so that it can reach body temperature.
- Should you once forget to "warm" the insulin as described above, keep the
cartridge or the insulin vial in your hand for at least 15 minutes in order
to bring it quickly to the correct temperature.
The insulin pump team at the University of Dresden recommends that its
patients store the cartridge at room temperature for 24 hours and then wear
it for another 30 minutes on the body before using it in the pump. And
- When you reinsert the infusion set after not having worn the pump for a
while, make sure that the insulin has the same temperature as it did before
the removal of the pump. This way you can avoid a delivery of 1 - 2 units
of insulin, which the Dresden group's experience shows may happen due to
thermal expansion of the solution and of the rubber plunger in the glass
cartridge. The reaction to the effect of temperature in the plastic
cartridge is less distinct.
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