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RE: [IP] "Bubble-less" Cartridges

I would also consider filling 5 cartridges at a time to make. Makes it much
more convenient when changing sets.


George, your (and John Neales) bubble-minimizing procedure is very similar
to one that I have been using for a few years, which is described below:

Insert a venting needle from a previously used cartridge and insert it into
a vial of insulin at room temperature.  This will immediately equalize the
pressure between the inside and outside the vial.

After lubricating the cartridge by maneuvering the plunger several times,
and leaving the venting needle in place, insert the needle with the
cartridge into the vial.

Withdraw ~20-30 units of insulin into the cartridge.  Withdraw the cartridge
needle and remove any air from the cartridge.

Reinsert the cartridge needle into the vial and withdraw insulin to fill the
cartridge, avoiding proximity to the venting needle to avoid withdrawing the
venting air.

Withdraw the cartridge needle from the vial, attach it tightly to the
infusion set, and prime the tubing.

Note that the venting needle remains in the vial the entire time to maintain
constant and equal pressure inside and outside of the vial.  Not removing
the venting needle until the procedure is completed also makes it easier for

John Kinsley
Type 1 - 1956
MiniMed 507 - 1998

George <email @ redacted>:
>>>  I believe that a difference in pressures in the vial is what causes
bubbles to be introduced into solution when the vortex of insulin rushes
down the needle.  To help equalize these pressures, start with a standard
syringe from which you have removed the plunger.  Insert this into the vial
to allow air to either enter or exit the vial, equalizing pressures.  Remove
the syringe and set aside (carefully, keep it sterile!).  Prime the
cartridge that you are filling to lubricate it, then expel all the air that
you can.

Insert the cartridge needle and invert the vial and draw enough (10-30
units) insulin to be able to free the bubble from the plunger tip.  Expel
that bubble back into the vial and draw just a few units into the cartridge,
at this point the pressure should be going negative in the vial.  Insert
your plungerless syringe and allow air to be drawn into the vial.  Begin
drawing your insulin slowly, making sure to keep the two syringe needles
separate from each other.  You don't want to draw air off of the equalizing
syringe.  After you have filled your cartridge, remove the equalizing
syringe, then the cartridge from the vial.

Having drawn your insulin in a "pressure-free" environment, you may discover
that fewer bubbles develop out of the insulin solution even after time.  It
has worked for me for the past 6 years.  <<<
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