Tiny bubbles, big problem

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1

So I have mixed feelings about Eric’s pump at the moment. He’s been on it since Monday, and every night since Tuesday we’ve had difficulties. That night, I checked him at midnight to find him in the 400s–figured maybe the basal ratio was too low and gave a correction, only to find him in the upper 300s 2 1/2 hours later with .3 ketones, not good. OK, so something was wrong with the infusion set, perhaps? We changed the site and infusion set, and I looked at it and realized it had lots of bubbles, some of them more than half a centimeter in length. Yikes, no wonder he was high–he hadn’t been getting insulin! I thought, gee, I must have nicked the tubing with the safety pin I used to close the pump pocket, but a new infusion set will solve that problem, and it seemed to… his numbers were terrific all day… until the following night. Midnight came, I checked again, and once more, he was in the 400s, this time with .4 ketones. DAMN. Once again, we changed the infusion set and the site, and for good measure drew up a new cartridge, primed the pump, and within an hour and a half, he was down to 249. Well, OK, I thought, and sent an email off to our diabetes educator saying, in essence, “WTF???” She said she’d never ever heard this particular problem before and was stumped, but I found chats and FAQs that indicated this wasn’t such an unheard of problem. So tonight, after dinner, as Eric sat in my lap watching his movie, I took the tubing out of the pump pocket and gave it a good hard look. Yep: more bubbles. They hadn’t reached the cannula yet but by bedtime they surely would have. So at bathtime, we took his pump off and did a complete reworking: changed the infusion set, the site, the cartridge, even the battery! and started him fresh before he went to sleep. Unfortunately, having had his pump off for over 90 minutes he was over 300, so we gave him a bolus that approximated the insulin he should have gotten from it during the time it was off, and now I’m waiting on the midnight check now to see where his BG is at. I also picked up some Lantus at the pharmacy because if we have the same problem tonight, I’m going to tell the folks at the clinic that I want to do Lantus for his basal until we can find out from Medtronic what is going on with this pump. Occasional bubbles are one thing, but every freaking night? Never during the day? Something is up.

I’m going to put in the effort to make this thing work because the daytime numbers are the best we’ve EVER seen, but oh, these nights are stressing me out!

2

Now it’s happening during the day, too. We’ve got a call in to Medtronic and are contemplating going back to injected insulin over the long weekend, just so we can get some badly-needed rest. sigh

3

Hi, Elizabeth. I’ve been using Paradigm pumps for several years and haven’t ever experienced the bubble problem. The pump itself shouldn’t be the problem – all it does is push a small cylinder against the bottom of the reservoir to push the insulin through the tubing. The air will enter when the insulin flows past some opening that allows the air to get “siphoned” into the tubing. Other than holes in the tube caused by a pet (which you said in an earlier post isn’t a problem), the only other defects I can think of that’ll allow air to get into the tubing is if the seal is bad where the tubing joins the cap that attaches to the reservoir, or if the tubing has holes in it, or if the connection between the tubing and reservoir isn’t tight. So my recommendations are (1) review how you’re attaching the tubing to the reservoir to make sure it’s a good connection (it can be a little tricky), (2) make sure you’re using the activity guard to prevent the reservoir from getting loose overnight and (3) consider getting a different lot number of infusion sets and reservoirs in case either of those is defective. I’ve never had a bad lot of either of those and can only think of 1 time I detected a defect in any individual piece, so I don’t think it’s likely to be the cause. I suspect the tube-reservoir connection. I hope this helps!

4

Elizabeth, do you load the pump with cold insulin that you keep in the fridge until then? This is definitely capable of causing this problem. What happens is that cod insulin holds air bubbles invisibly in suspension. Once the insulin warms up the bubbles are able to separate out, wherever they happen to be at the time, INCLUDING in the hose.
So, given that you load the pump cartridge directly from a refrigerated insulin vial (if not just ignore this idea) you need to pre-warm the vial before loading the cartridge by warming it in your hand until it doesn’t feel cold anymore . Then load then be cartridge with insulin and warm it for a few minutes in your hand. Just fold your hand around it and make sure it gets to feel about room temperature.
I faced this problem some 15 years ago when using my first insulin pump, and it’s surprising how simple the answer is. I realized at the time that soda pop acts this way to, if it’s cold it doesn’t explode into bubbles nearly as easily as it does when it’s warm. Same thing, just the nature of fluids.
Guess there’s some good effect of growing up in a home full of inventor/engineers.

5

Here is a link to a video that will show you how to rid yourself of bubbles. I had a problem with this when I started pumping so now I always leaved my open bottle of insulin at room temperature. Now bubbles only happen to me if I run my reservoir until it is empty. I find that once my reservoir gets below 15 units, I will get some bubbles in the tubing.

6

Thanks guys - but the problem appears to be a defect in the reservoir. I went through my standard practices (now VERY well known!) for setting up the pump with a Medtronic rep and he felt that from my description, it wasn’t anything I was doing wrong. We did a high pressure test on the pump and it passed, and the only thing we found that could possibly explain it was that the reservoir that I’d used until the last episode of bubbles appeared to have an incomplete seal between the insulin chamber and the area where the plunger attaches - which would explain why the bubbles don’t show up for 8 hours or more, because the leakage of air into the chamber is so very slow. They’re sending me new reservoirs (mine are all from the same lot number) and we’ll put ERic back on his pump as of Wednesday.