Today’s CGM Primer: “Don’t fool yourself into thinking a CGM is smart. It isn’t. It uses the magic of science to determine if your glucose is higher now than it was 20 minutes ago, and in some cases, how rapid that change is—but the CGM doesn’t actually know what your blood sugar is. It has no frickin’ clue what-so-ever. In this way, without your help, it’s as useless as a blind seeing-eye dog.”
---- Excerpted from Beyond Fingersticks: The Art of Control with Continuous Glucose Monitoring
A good vibration. I look down at my desk. Two glowing red blood drops greet me. It’s time to calibrate. To feed the G4 its first compass setting. To tell it what my blood sugar is so it can get on the job of tracking changes and keeping me in the loop
Excuse me, I tell my patient. I gotta…umm… do this diabetes thing. And… umm… this will look strange, but I need to take a picture of it, too.
“Oh. Are your writing an article on it?” she asks, sitting up a little straighter. “I really liked your one on VialSafe at dLife.”
Holy crap. I always forget that people I actually work with read what I actually write. For some reason, I blush. Zorro unmasked.
My beloved iBG Star now a thing of the past, I dig out my new meter case from one of my cargo pants pockets. Have you noticed none of these cases comes with a loop to carry it on a belt anymore? I’ve caved to my health plan’s evil desires and am now (under protest) using an Accu-Chek Nano. Actually, it seems like a harmless little machine, but I’m infuriated every time I use it that the test strip vial is so fucking big. It’s taller than the meter, for crying out loud, and is much, much, much larger in diameter than pretty much every other strip vial on the planet. Of course the Accu-Chek strips are big mothers. The vial is so large I’ve been unable to find any kind of small camera belt pouch that I can stuff the stupid things into without busting a zipper.
Sorry… got distracted. So Dexcom knows that test strips suck. They know that if a strip used for a first calibration runs high, then the sensor will start off running high for half a day. And they know that if a strip used for a first calibration runs low, then the sensor will start off running low for half a day. What’s a CGM manufacturer to do?
Their elegant solution is to take the average of two readings for the first calibration at the start of a sensor run. From there on out, the sensor has at least some notion of where on the map it is, and single fingersticks can be used. If you’re stuck with really crappy strips, you can still do dual sticks and average them for all calibrations going forward, but you’re not required to.
My Nano clocks the first stick at 116 mg/dL. I enter it in the receiver and repeat the fingerstick testing process. My Nano clocks the second stick at 120 mg/dL. I enter it in the receiver and that’s it: The sensor is live. On the job. Reporting its opinion on my blood sugar. My spies tell me to expect the first day to be a little rocky, like with all current state of the art CGMs, but that I should expect to be impressed on days two-through-seven.
I can’t wait. I’m also eager to hear it’s voice for real (it has a way to “sample” the various sounds, but that’s not the same as getting a real alarm when you don’t expect it). I’m also dying to know how close the two CGMs track to each other in highs, lows, excursions, and dips. I had just put a new Dex Seven sensor in before the G4 arrived. I figured I might as well wear them both simultaneously for the first week. Hmmmm…. Simultaneous CGMing. Sounds kinky.
But, alas. No kink. No excitement. At all. In fact, wouldn’t you know it? My first three hours of running the Dexcom G4 Platinum have been the most boring blood sugar I’ve seen for months (damn it).