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Re: [IP] air bubbles

Well John, I take that as some sort of challenge :-)
But I do think you have hit it on the head this time.   What you said about
much more air in solution under pressure is surely true, and this would
potentiall lead to many more bubbles coming out once the pressure was
released.  However, the issue of time is the important one here.  Air goes
into solution by simple diffusion, and diffusion is very very slow in
unstirred liquids.  So if you just pressurized the bottle for a few seconds
and them immediately withdrew the insulin, there would actually be very
little extra gas going into solution.  Even if you injected the air upside
down through the insulin, the time is so short that even those extra little
bubbles and mixing would not be enough to get any significant extra gas
into solution.  However, if you left the bottle  for several days with
pressure in it, though that would be very bad.  You are right that the best
way to store the insulin between syringe fillings is with  negative
pressure in the bottle.  That's much more important that what you actually
do during the short time it takes to fill.

-->But Wayne will no doubt come up some calculations to demonstate that the
-->whole thing is insignificant...

> > ...that you should bubble the air through the
> > solution. It's very simple, put the needle into the bottle when it's
> > standing upright, as on a table. Push the air in the air space at the
> > top, then flip the whole thing over and draw out your insulin.
> Thanks Ted,

,<<<<<<<<Some of us are top-fillers, and some bottom-fillers so-to-speak... but
the surface area between the gas and fluid is still sufficient, however
you do it, to allow pressurised air to dissolve in the insulin even if
you top-fill and turn the bottle over (which provides an even greater
surface area in the process). If it's a full bottle, and a full
cartridge, you might end up with the air in there at 6 times atmospheric
pressure... And as the air from the dead space in the syringe passes
through the incoming insulin, that partly dissolves as well.
     If bubbles are a problem, and you think it through logically, it still
makes sense to NOT pressurise the air in the bottle before you withdraw
the insulin. In fact, it makes sense to keep the whole bottle
permanently at negative pressure.
- --

Wayne Mitzner
Department of Environmental Health Sciences
The Johns Hopkins University
615 N. Wolfe St.,  Baltimore, MD 21205
Tel. 410 614 5446,   Fax 410 955 0299

Insulin-Pumpers website http://www.insulin-pumpers.org/