The reservoir

reservoirOne of the handy little perks of the Medtronic insulin pump is what I call the convenient “little blue collar”  (not to be confused with the terrifying death-grip of the “big blue ‘serter“). The little blue collar is used to hold a new reservoir against a vial of insulin, and has a double-sided needle to help draw the insulin from the vial into the reservoir. Compared to the clumsy syringe needle system of filling the cartridge of other pumps (such as the Animas), it’s really quite nice. The official name of the little-blue-collar is a “transfer guard”.

When you use it right — and apparently, I’ve been doing it wrong. This is according to the latest information (here as PDF) broadcast by Medtronic (I spotted it via social-media, but surprisingly not by email. I guess a letter will arrive in the mail soon).

From the web-site linked above:

While changing an infusion set, if insulin, or any liquid, gets on the inside of the tubing connector on Paradigm infusion sets, it can temporarily block the vents that allow the pump to properly prime. We are discussing this issue with our customers because it can potentially result in too much or too little insulin being delivered, which may cause hypoglycemia or hyperglycemia.

The verbiage in the PDF version is a bit more morbid. It uses phrases like “loss of consciousness” and “death.”  Lets not go there.

But hang on a second… What? There are vents in my insulin-delivery-system? Something doesn’t sit right with me on that one. I always believed that the entire length from the reservoir to the tip of the cannula should be air-tight. If there are vents, then insulin can leak out — or air can sneak in. Not good.

Apparently, the top of the reservoir needs to stay dry – and in order for that to happen, the vial should remain upright with the reservoir upside down when disconnecting the two. Otherwise, insulin can drip through the needle and make a mess all over the place.

vial-uprightThis illustration shows the proper way to remove the reservoir and transfer-guard from the vial. (I can’t help but think that this image, with carefully-positioned fingers but dimensionless wrists and arms, was drawn by the same guy who illustrates the proper application of a condom to middle-school sex ed students. I still get nightmares from those textbooks. But I’m getting waaay off track here…)

Historically, I’ve done just the opposite. I hold the reservoir right-side-up and the vial upside down, because that’s really the only way to get the insulin in and the air-bubbles back out. Flip it over, and all the hard work of purging bubbles is for naught.

Moving on…


It seems that “pre-priming”, the topic which took center-stage in the comments section of my “De-mystifying the Motor Errors” post from last month, is not only acceptable, but it is explicitly prescribed by the manufacturer. Who knew?

One more thing:

If you notice anything unusual during the infusion set prime process such as the insulin continuing to drip from the infusion set cannula when priming has been completed, this may indicate that the connector vents are not working properly. If this occurs, do not insert the infusion set and call the HelpLine immediately for additional assistance.

Yes, I’ve seen that. I’ve seen insulin drip from the cannula after priming is complete. I just waited for it to stop, and for all the pressure to equalize, then connected it to my body.

If this is the cause of Motor Errors (and I say “if”, because I’ve seen nothing documented that links the two), then perhaps they will finally cease. But I’ve those errors both with brand-new infusion sites and days-old ones, so I doubt there’s a linkage.

Plus, a couple of other things I learned yesterday that make me pessimistic. I won’t get into them today.

But this little refresher is valuable, and I’ll be sure to follow it going forward.

Posted on June 13, 2013, in Diabetes, Insulin pump. Bookmark the permalink. 6 Comments.

  1. I never, ever, do this in the way your first illustration shows. I read all of this yesterday online, and I’m still having trouble wrapping my head around it. Next change coming in about 2 1/2 days.


    • I already had read the literature and was scripting this blog post in my mind, when a set change came due. Halfway through, I stopped and realized that I was doing it improperly – with the vial up and the reservoir down. Even when it’s in the forefront of my mind, my subconscious still has me doing it the other way, as I have done for so many years.


  2. I know Medtronic has to be cautious and forthcoming. But in about 15 years of Minimed usage I’ve not experienced any problems with this.


  3. Same here! Vial on bottom/reservoir on top goes against my very nature of filling an insulin cartridge. By the way, I’ve had NO motor errors since receiving my replacement pump, and I apparently fill the cartridge the “wrong” way every time. Sometimes I pre-prime, sometimes I don’t. Sometimes I use the “transfer guard” to take insulin out of one bottle and put it in another, and the suck all my insulin for that cartridge into it all at once. I’m sure I’m doing illegal things with it, according to the manufacturers specifications.


  4. Wow, good thing I read your blog, I’ve been doing it wrong all along. I even saw the Medtronic letter in the mail and on Facebook I think and I didn’t read the info because I haven’t had any problems with my pump so I figured the notice didn’t apply to me. Thanks for sharing! I’ve also never pre-primed-oops


  5. OK, I too have been doing this very wrong. Also, just watched some of the videos, and I can’t pay attention because the fingernails on the animated hands are really long and look dirty. I digress.

    Thank you for posting! I ignored the letter MM sent me, so.. whoops 🙂



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