Daily Archives: May 5, 2015
Say, come on Eileen
These things they are real and I know
How you feel
Now I must say more than ever
Things round here have changed
I say, too-ra-loo-ra, too-ra-loo-rye-aye
–Dexy’s Midnight Runners
Initially, I thought switching CGMs would be effortlessly simple – like performing the same familiar dance to the same cheesy 80s song, just in a different discothèque.
But now I must say, more than ever expected, things have changed with my venture into a new Continuous Glucose Monitoring venue. Even the little things, which I thought were insignificant and irrelevant, turn out to be real and to really matter.
The obvious changes are procedural. The not-so apparent changes have to do with the feelings the different device evokes. Since I’m not such a touchy-feely type of guy, I never gave much thought to this aspect of things. Needless to say, the change in my mental-state over the past week or so has really caught me by surprise.
(Missed Part 1 of this series? You can find it here.)
May 2014 prediction: Not considered.
Warning: this section deals with a common, yet still off-label use of CGMs. If you are the type who prefers to operate “by the book”, or if you are tasked with enforcing the book, you may wish to skip this section.
The Enlite “lasts” for six days. It can be re-started, but the Minilink transmitter holds enough charge for seven. So by the seventh day, I would find that I need to carefully unwrap the layers of adhesive, charge the transmitter for about 20 minutes, then re-connect, go through the menu sequence, and wait a two-hour warm-up period. In my overall experience, the sensor would last about ten days, though once I had a sensor last nearly two weeks.
I’m still wearing my first “seven-day” Dexcom sensor, completing day twelve as of this writing. It seems the back of the sensor-pod is now lifting from the adhesive, and I did need to call in reinforcements for the adhesive on the sides on Day 9. But it seems to be going strong with no sign of slowing down.
What does this have to do with feelings? Well, as nervous as I may be about knocking the monstrous bulge off of my body, it’s comforting to know that I’ll always have spares. With the Enlite, I felt it was pretty much an unwritten requirement to extend the life of my sensors beyond the on-label duration. It would ensure that I wouldn’t run out of sensors in case one didn’t work quite right and I needed to insert a new one prematurely. It made me nervous not to have an ample stash.
My Dexcom supplier only ships one month’s worth (actually, 28 days worth) of sensors out at a time. Stupid, if you ask me, because they called me to tell me it was time to re-order just three days after I received my initial shipment. (I declined the re-order at that time, because I needed to “feel-out” the system during my 30-day return period). But knowing I can double (at least) the length of just about every sensor I use makes me comfortable that I’ll never run out and I can survive any sort of shipment delays.
Verdict: Unexpected source of peace and comfort.
HYPOCRISY / INTIMATION
I miss my predictive alerts. I miss them dearly. It’s shifted my whole method of CGMing from one of being proactive to being reactive. No longer do I adjust a basal, take a correction, or enjoy a nosh because of an impending low or high BG. I generally always wait until the alert comes, and then I curse myself for not catching it sooner.
In my attempt to “catch it sooner”, my low threshold is a bit higher than it was on my Medtronic. Only by a little — my low threshold is 85 mg/dL instead of 80, but when the brilliant color display shows 84 mg/dL in “rage-red”, it angers me. 84 mg/dL is pretty damn good, especially if it comes with a flatline. But because it’s close enough to a low to warrant notification, the Dexcom congratulates me with a blood-curdling Everything Is Horrible visual. Surprisingly, it affects me and my self-perception of success and failure. I’m contemplating lowering my threshold – allowing me even closer to danger – so that I don’t get scolded for walking the tightrope so well.
Yet, with the absence of Predictive Alerts comes a dramatic decrease in alerts overall (and more restful nights as well). It’s a really nice feeling to wake up after my first night with the Dexcom to realize it hasn’t woken me up once all night. I’ll go hours during the day without an alert as well, which makes me happy and was unheard of with the Medtronic. Yet, I think I spent more time “in-range” with the Enlite system. So which is better? That’s what I need to figure out…
Verdict: Perhaps I ask for too much.
ACCURACY / MECHANICS-revisited
May 2014 [before algorithm upgrade] prediction on accuracy: “Never used it [G4] myself, but anecdotes and MARD statistics (whatever that is) say it’s better.”
It may seem unexpected to see me couple accuracy and mechanics into the same discussion. Trust me, there’s good reason for this.
It may also seem unexpected to read these words that I am about to type from my fingertips: So far, I find the accuracy of the Dexcom G4 and the Medtronic Enlite to be about the same.
You read that right: I find the accuracy of the Dexcom G4 and the Medtronic Enlite to be about the same.
When both systems are working at their best, they both work well. Or well enough to be useful, anyway. I haven’t compared them side-by-side.
On Day One of a sensor, I actually find the accuracy of the Enlite to be better. This goes double for the 24-hours after a sensor-restart. I feel like the Medtronic can perform well with one good calibration. If you calibrate to tell the unit what interstitial measurement means a BG of 100, it doesn’t need another calibration to tell it what 200 looks like. I really loved this about restarting sensors, because it picked up with the same level of accuracy at which it left off.
Dexcom, on the other hand, seems to require many calibrations, especially at first (heck, it requires two calibrations within five minutes just to get started!) I’m not sure what it does with them, but I know it takes four or five calibrations to get it trending accurately. Again, this is based on VERY limited expereince. I do also find that the Dex tends to “drift” more than Enlite, requiring a correction-calibration to get it on track.
So why do so many folks (myself included, I admit) have such trouble with the Medtronic? Well, it is my personal (and unvalidated and unsubstantiated) belief that the Enlite sensor is just fine. They put the same care and effort into perfecting that little subcutaneous wire as Porsche did in designing their flat-six engine. The engine is a work of art and engineering precision. But if you take it out of the Porsche 911 and drop it in a Volkswagen Beetle, it won’t quite work right.
What I think happened with Enlite is that they took some beautiful sensor technology and housed it in a haphazardly-designed shell. The shell would not keep the sensor firmly implanted beneath the skin by itself, so the work-around became, quite literally, tape. Any DIYer can tell you that duct-tape fixes everything. But fitting a Porsche engine in a VW requires more than just tape — it needs careful positioning and manipulation — this is where I think many Enlite users (or former Enlite users) have encountered trouble.
Actually, it’s unfair and incorrect for me to say that the shell was a haphazard design. I do think they put some honest effort into the design of the Enlite shell (evidenced by the comfort-improvements over the Sofsensor). But the improvements were geared too much towards the wearer’s needs, and the sensor’s needs got neglected. It is crucial for the Enlite introducer-needle to fully go into the skin, which is something that can’t be controlled, seen, or maintained with the spring-loaded inserter, and then for the sensor to remain beneath the skin. With very little adhesive underneath the sensor, this is accomplished by applying extra tape over the top to keep the sensor firmly in place.
The problem is that you have a(n older-design) transmitter hanging off the side, and together the sensor and transmitter take up a lot of surface-area on the skin. But there is not enough flat area on the skin to accommodate that surface area, so to the contraption tends to rock. The rocking motion pulls the sensor (which is off to the side, not in the center) in and out, which can result in erroneous readings.
Try taping a quarter flat and firmly against a softball. It’s essentially the same challenge. Unless you find a flat part of the softball or you find something to stuff underneath one side of the quarter, it can’t be done.
(Sidebar: I’ve been told by a Dexcom rep that the 90-degree sensor wire is actually detrimental, and that the angled-insertion used for the Sofsensor and the Dexcom helps to better anchor it in the skin. I can neither confirm nor deny this, nor can my engineering mind make any sense of it. Maybe it’s true, maybe it’s not).
Fortunately for me, my body is not too curvy, especially in a certain location on my upper-butt, so I’ve come close to getting it right (after a l-o-n-g learning curve). When a good site is chosen and the taping is effective, Enlite is as good as, or perhaps even better than, Dexcom in terms of accuracy. But combining a workable site (along with proper rotation) with a proper taping technique is arduous, and knowing that a bump to, or roll over of, the transmitter could easily lift out the transmitter is discouraging. If MedT could design a sensor/shell/transmitter that is physically balanced; with sensor wire in the center, and a low-profile transmitter surrounding it (use the QuickSet as a model); they’d have a real indisputable winner in my book.
Verdict: Dexcom accuracy is very good; but I had very high expectations and it didn’t “wow” me.
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Still to come: talk about data reporting, landfill-contribution, trustworthiness, and some other stuff I didn’t get to…