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[IPk] Re: air bubbles

thanks to all those who have responded. 
A few observations.
(1) I almost always wear the pump upside down. 
Believe it or not, this doesn't prevent the air 
bubbles entering the tube. They don't always rise to 
the top.
(2) I should have explained my method.
I always use insulin at room temp.
I fill the reservoir from a bottle, not a cartridge, 
because I have problems seeing when I've got to the 
end of the cartridge and getting air in that way. But 
if you do use a cartridge, you actually don't need to 
stick an extra needle in. As you pull back the 
plunger, the rubber end of the cartridge drops down 
into the cartridge (as it would when you use it in a 
I push the first bit of insulin in and out a few 
times, which gets rid of the big air bubble you tend 
to get (see below).
I try and let the cartridge rest for a few hours 
before I load the pump. I usually prefill a reservoir 
a day or so before I need it, at a time when I can do 
it slowly at home, so I can minimise the length of 
time spent refilling the pump when it runs out.

I also fill the reservoir too full (as I only use it 
half full) and push the extra bit out through the 
tubing, to get rid of the air at the top.

>>If you keep the pump so the cartridge is always 
pointing down, the bubbles

Jeremy, I didn't quite follow your method, but then I 
don't use a Disetronic pump. I think it was roughly 
what I do anyway, but it doesn't help with the small 
lurking bubbles, only the big ones.
>can't get into the tubing.

>When I refill the cartridge, I take great care not 
to let the Humalog foam
>or spray at all. To achieve this, I stick the needle 
from my previous
>cartridge into the bottle, at the same time as I 
draw the insulin out
>through another needle into the new cartridge. This 
keeps everything at
>exactly the same pressure.

Aha - that presumably prevents the problem of 
creating too much pressure with a vacuum. 
>If, for whatever reason, it does start to foam, I 
chuck the whole cartridge
>out, and start again.
>I always store my current bottle (or the next bottle 
I will use) at room
>temperature, and suck air out of the bottle using 
the old cartridge and
>needle, so it's at negative pressure. This will 
reduce the amount of air
>dissolved in the insulin. Otherwise, this dissolved 
air has a tendency to
>come out of solution once it comes into contact with 
the inside wall of the
>cartridge. A bit like pouring Coke into a dry glass.

Now that makes sense too.

>Ultimately though, there will always be the air from 
the dead-space between
>the plunger and the tip of the needle. I just draw 
the insulin in nice and
>slowly, so this air stays up at the top. 

I avoid that by drawing the first couple of units in 
and out of the bottle a few times. You can hear when 
there is no air coming back out. But I guess that 
dissolves more air in the insulin....

I can usually get most of it to
>coalesce into one lump with a few sharp flicks.
That's the bit I can't do! It never goes into a lump 
no matter how hard I flick it!
>If you wiggle the plunger from side to side with the 
cartridge almost full,
>air can leak in past the pair of rubber seals. This 
a special risk of this
>when loading the cartridge into the pump.

I don't think I ever wiggle the plunger around!

>Loading your cartridge direct from a 3ml penfill 
cartridge is also reputed
>to be very convenient (and unorthodox). 

Oh? A 3ml cartridge? I didn't know they existed?
That might be an idea worth pursuing. As I said, you 
don't actually need to stick another needle in.

Anyway, thanks for all the suggestions.

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