CGMS Progress

Yes, it’s true.  I’ve taken another stab (pun intended) at the ole’ CGMS thing, and this time I’m seeing progress.  The CGMS enigma is one step closer to being solved!  I know you’ve all been anxiously awaiting my explanation since the teaser in my last post, so here it is.

As you may recall, I’ve been having trouble with glucose sensors ever since my pregnancy.  (If you don’t recall, you can read about it here.)  For some reason, in spite of the fact that the sensors are inserted with a vicious looking but totally straight needle, they come out looking like this:

What the...?

It’s been very puzzling.  It seemed that my post-baby “flesh” was to blame.  (Pregnancy does not do one’s abdomen any favours.)  But it still didn’t make much sense.  Why should a different type or density of flesh make that much of a difference?

The other odd thing was that my sensors weren’t being pushed all the way in by the inserter.  They’d go about half way and then need a (very unpleasant) push the rest of the way.  Again, it made sense that this would be related to my “mommy middle”.

So I tried different methods of stretching and pulling my skin as tight in one direction or another as possible, but nothing was helping.  I might as well have been throwing $50 bills in the garbage every time I inserted a sensor that did absolutely nothing for me. 

But a couple of weeks ago, I noticed during an insert that my sensor seemed unreasonably loose in the inserter.  Why this didn’t come to my attention sooner I really do not know.  (I blame mommy-brain.)  While I’m not a physicist, it did occur to me that, if the sensor was too loose in the serter, it would be hitting my skin with not enough force to allow it to insert all the way.  Aha!  As well, if it was wobbling and bobbling on its way to my abdomen, and then hitting my skin at a 45 degree angle, it would most likely be catching at the first point of contact and then nosediving into me, thus creating the lovely hook shape you see above.

Aha again!  It finally all made sense.

But…how to fix this?

I figured that the first step would be to see if a properly inserted sensor would, in fact, work any better than the badly inserted ones I’d been dealing with.  So a couple of weeks ago, I made the rather miserable decision to manually insert a sensor.  If you’ve never manually inserted a sensor, you might not understand why this would be a miserable decision, but please believe me when I say that it is.  The introducer needle on the sensor is significantly thicker than the one on an infusion set.  (Keep reading and you’ll see pictures of this nasty needle.)  It doesn’t really poke your skin – it tears it.  I’ve heard it.  It’s gross.   

Anyway, that sensor worked better than any I’ve used post-pregnancy…way better!  I got 5 days of reasonably reliable use out of it.  It caught lows, it caught highs….it tracked impeccably.  I was ecstatic!

But obviously manual insertion was not the answer I was looking for.  The thought of doing that every week makes my stomach turn!  (But let’s be clear – I’ll do it, if it means the sensors will work.)  So I had a discussion with my CDE (who is also a certified Medtronic pump trainer) and almost accidentally we came to an interesting conclusion:  I have not been pushing my sensors far enough into the inserter.  (This is proof that I’m clearly not as smart as I sometimes think I am.) 

We were fiddling around with her sample sensor and sample serter (try saying that 5 times fast), when I realized that the sensor was much further into her serter than mine usually are.  Our first thought was to blame the serter, but on comparison with my own it turned out that mine just took a bit more “oomph” to get it to go in that far – an “oomph” that I guess I’d just never tried.  (This realization turned me into a very sheepish pumper.) 

Here’s what I mean.  This is what the sensor/serter set-up looks like prior to pushing them together:

1, 2, 3...push!

This is a sensor that is properly pushed into the serter:

The right way

And this is how I, the sheepish pumper, have been doing it:

The wrong way

You might be surprised at the difference it makes.  So now I know.

Yeah….so….problem solved?  Not quite.

The next sensor I inserted was pushed well into the serter.  I aimed for a slightly shallower angle than the serter would normally provide since my not-exactly-buff mommy middle actually doesn’t have a lot of fat on it.  I lined it up, squeezed my eyes shut (because that’s the best way to do it) and pressed the button to insert.  Since my expectation was a perfect insertion, the halfway-in halfway-out sensor protruding from me was less than encouraging.  It still required the usual heave-ho to get it all the way in, but this time it didn’t show any indication of having done the familiar nose-dive.  I was hopeful. 

Unfortunately my hopes were dashed during the first 24 hours already when that sensor didn’t even pretend to be accurate.  Over the next few days I tried more calibrations (at as optimal times as possible), lots of hydration, and a few restarts, but when it missed a 2.8 mmol (50.4 mg/dl) reading, I quit trying and took out the sensor….

….which I then realized had inserted at approximately a 15 degree angle.  This was significantly shallower than my intended angle of insertion!

So I’m coming to the conclusion that the accuracy of my sensors is all about the angle.  An 80 degree insertion doesn’t work, but neither does a 15 degree insertion. 

Tomorrow’s next step: Insert a sensor at the usual 45 degree angle, after pushing it fully into the serter.  In other words – just do it the way it was meant to be done already!

I’ve got my fingers crossed.


4 responses to this post.

  1. Posted by Sylvie on February 22, 2011 at 7:41 pm

    Beth, I really think you need MORE fat!!! Now that’s not something you hear every day 😀 I am glad you are seeing some progress in your search for answers. Have you ever tried anywhere else but your stomach? I really do love my thigh location (although I realize you may have reservations about that…. Thanks for the update.


    • Nope. Never tried anywhere other than my abdomen for sensors. I know when I use my thigh for infusion sets I have to go really shallow, so I’m a bit worried that the longer sensor needle, at a greater angle, would go too deep in my leg and be miserably uncomfortable. Plus, I have to admit that I shy away a bit from the thought of having a transmitter lump on my outer thigh. Oh vanity. 😛


  2. ug it sounds like you’re not having much luck! i hope it gets better (and easier.)


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