De-mystifying the motor errors
Before Diabetes Blog Week started, you may recall that I was whining a bit about insulin pump motor errors.
Well, I don’t know what caused them – and Medtronic has certainly been willing to work with me so I don’t end up in a potentially troublesome situation (i.e. like Swampy, but asking “Where’s my Insulin?”), but I’ve decided to make a few changes on my own, just in case. But first…
Every time I’ve had a problem with my Revel, I wax nostalgia about my old Medtronic 515 which worked for years without even a hiccup. What’s different about that pump and this one? Well, first of all, the older one had much less precision with insulin delivery. I don’t know the numbers off the top of my head, but the old one only gave me the choice of one digit beyond the decimal point, while the newer one gives me a choice of at least two. That’s a tenfold increase in precision right there if you’re talking bolus. But if you’re in the basal-domain, take the hourly basal and divide it by sixty minutes (or however often the pump delivers pieces of basal) and you’ve got some really tight tolerances.
Maybe those tighter tolerances mean a better ability to detect when the pump falls out of those tolerances? Though the official definition of a Motor Error is vague and circular at best, The best definition I’ve heard of a motor error is that it occurs when the piston doesn’t line up where it’s expected. It makes sense to me, so I’m sticking with it.
Getting back on track. When I wore my 515, I always used the Activity Guard. It’s the little tiny clip at the end of the pump that keeps the reservoir from accidentally falling out — or something like that. My CDE at the time (who trained me on the pump, but is not a Medtronic employee) told me it’s pretty much useless. She never used it herself (she’s also a T1 Medtronic pumper) and found it a bit laughable that I bothered with this trivial element. Still, I used it religiously.
Until one day, while spending the weekend with relatives out-of-state relatives and doing a set change in a pre-teen’s messy bedroom (understatement!), I lost it. Yes, I worried a bit, but then accepted that I probably didn’t need it anyway, so I went on with life, sans-Activity Guard.
When I upgraded to the Revel, I still went on without the Activity Guard. Could something have possibly bumped the tip of the reservoir? Possibly. Could that, in turn, have bumped the piston? Possibly. Could that have resulted in the motor error? Maybe.
And last Saturday, while everyone was admiring Reva’s diabetes body-art, I noticed that she has the activity-guard on her pump. (UPDATE 6/3/13: Thanks to Sara’s comment below, I realized that I was wrong. That’s a belt-clip, but it has the same twisty-locky-thing as the Activity Guard. But it’s still a cool piece of artwork, so I’m leaving the image intact.)
So maybe it really is worth using.
Purging the bubbles
Aside from not using the Activity Guard, I was given another piece of possibly ill-conceived advice – this about starting a new reservoir/infusion set. I was told that, after filling the reservoir and connecting the tubing, but before inserting it in the pump, that I should use the little removable plastic plunger to begin filling the tubing. This would give me an opportunity to flick some of the air bubbles into the tubing which could be purged out during the priming process.
In reality, I noticed that when I did that, it fought me. I would fill two inches of tubing, then an inch would get sucked back out. Push another two inches, another inch back. I’ve done this since my very first site change without concern.
But now I wonder. Why is it sucking back out? Am I causing too much pressure inside the assembly? Am I creating some sort of a vacuum? Is the initial “push” damaging the first section of tubing?
Again, I don’t know. But if insulin is “backing out” of the tubing, the plunger might be getting pushed back as well. Or not.
It’s a theory, and I don’t know how credible it is. But that could certainly cause the piston to move and cause a motor error. Even days after the site-change.
This one’s probably my fault
During my most recent motor error, I made a surprising – and surprisingly embarrassing – observation. At work, I had been using a portable two-way radio – a typical walkie-talkie style, that day. When I went to get lunch, I put the walkie-talkie in my jacket pocket and forgot about it.
I bolused for lunch, and halfway through I got the motor error. That’s when I realized: my pump was clipped near my hip on the left side. My jacket was hanging over the pump. Inside my left jacket pocket, not too far from the pump, was the walkie-talkie.
I wasn’t using the radio, it was just sitting there idle. But it was there.
The folks on the phone at Medtronic always ask if I’ve been near any “strong magnetic fields”. MRI’s, airport scanners, that sort of stuff. MRI’s are strong; they can pull an earring right out of your ear (or wherever you may have it). A cell phone doesn’t count. I’ve asked — repeatedly.
Still, I’m going to make a conscious effort no to keep any kind of cell phone, walkie-talkie, or transmitter of any type (CGM transmitter excepted) on the same side of my body as the pump.
It shouldn’t matter, but it just might…
If you use a pump, particularly a Medtronic, do you make any of the “mistakes” that I did? Do you think they really are mistakes?