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RE: [IP] Bubbles in the Cartridge
As Ted pointed out, bubbles are often caused by filling the reservoir /
cartridge with insulin that has not yet come to room temperature. As others
have mentioned, it is also important to fill the reservoir / cartridge
slowly and ensure you do not purge air from the reservoir back into the
insulin vial by "squirting it" through the insulin remaining in the bottle.
But what about the times when you absolutely *must* refill (you've run out
of insulin, for example) and don't have time to warm the insulin first?
Here's a trick which someone taught me some time ago. I have tried it
several times, it works o.k. "in a pinch". It might be worth storing this in
your bag of "useful pump tricks":
1) Take the bottle of cold insulin and shake it vigorously for approximately
10 seconds. You will notice a lot of bubbles in the bottle at this point.
That's good, because it means the bubbles are not trapped in the insulin any
2) Let the bottle warm for a couple minutes, until the bubbles start to
settle down and mostly disappear.
3) Insert the needle into the bottle and withdraw a *full* reservoir /
cartridge of air from the bottle. This is usually 3.0 ml. for the MiniMed,
or 3.15 ml. for the Disetronic. This will create a bit of a vacuum in the
bottle. Remember from science class that a vacuum is the absence of air (or
a definition close to this). And you thought that little tid bit of
information would never be useful again? Ha ;-)
4) Now fill the reservoir / cartridge to the desired amount.
You'll notice with this technique that the plunger must be "pulled out",
since there is now no air pressure in the bottle forcing the plunger out.
One of the problems with first injecting air into the insulin vial (as many
of us have been taught) is that it will introduce air into the solution,
which is then forced into the reservoir / cartridge when you fill it. This
situation is worsened if you inject this air into the liquid in the vial.
The trade off with this technique is that the plunger can be difficult to
withdraw, since you are working against the vacuum in the bottle. However,
you will generally end up with fewer bubbles. I don't use this trick often,
but when I need to fill a cartridge "on the run" it has saved me the
aggravation of hunting down all those little bubbles after the fact.
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