The Joy of Tegaderm
Under any normal circumstances, that might be unsettling news indeed, but I’m thrilled for the head’s up.
What? Oh, not my life, I’m talking about the sensor’s life. The sensor in my right thigh has two hours left to live. This morning when I opened my eyes, the sensor icon on myAssistant was red. Small white numbers and letters nestled into the corner of the icon gave me the countdown to its demise.
Or is it 74 hours, not two?
Here’s the problem: Med-T sensors are FDA approved for three-day wear. They do just fine for longer, and in practice, everyone I know wears them for longer periods of time. For me and Goldilocks, three days seems too short, nine days seems too long, but six days is just right. But of course, being approved for three-day wear, all the gear is set up to recognize this. The work-arounds are super-simple, but today I encountered a minor hitch.
I couldn’t fucking remember when I put the damn sensor in.
Was it three days ago? Or six?
They say short-term memory is the first thing to go. So I guess I must be on my way.
This is also partly the fault of the newest love of my life: Tegaderm Film. For background, since day one I’ve been using Smith & Nephew IV 3000 dressings to cover my sensor/transmitter sites. This super thin semi-permeable film (designed to hold IV sites secure in hospital settings) helps to keep the transmitter secure, and protects the whole assembly for getting accidently yanked off my carcass when changing clothes.
Oh, and I didn’t think of it the other day, but we have to give points to Dexcom on this front: their sensor/transmitter sites do not need to be covered. Dex sensors are built into a little plastic foundation that has sticky tape underneath the whole affair, and the transmitter snaps into it. Med-T sensors only have sticky tape around the small hub and the seashell transmitter “flaps” loose in the breeze. Metaphorically speaking. Totally off topic, but pictures I see out of Europe suggest that the next generation of CGM stuff from Med-T addresses this. The across-the-pond seashells seem to have some sort of ribbon of tape to help secure them. Anyway, I don’t find the over-dressing to be a problem and I kinda like the extra security that comes from knowing my life support system is well-attached to my body.
But back to Tegaderm, when my box of goodies came from Med-T there were some IV-3000s, but there was also a box of Tegaderm. What the hell, I’ll give it a test drive, I thought. Well that’s a lie. I actually thought something more along the lines of: Shit! Why can’t they just leave fucking well enough alone?! For a guy who loves change, I’m slow to embrace it.
Anyway. The IV 3000 is soft, with a waxy feel to it, with a diamond pattern stamped into its surface. I imagine if you plucked a fairy’s wings off, you’d find them similar.
Tegaderm is a horse of a different color. Made by a tiny mom-and-pop company called 3M, it’s designed to cover wounds and protect skin. It’s more robust than the IV 3000. It’s thicker, shiny, and window-pane clear. I worried it wouldn’t breath well, and would give me some skin trouble.
Well, so far, so good. No skin trouble and the Tegaderm holds up great. So great, in fact, that it added to my trouble this morning.
After a few days in the shower, IV 3000s start to get a little…ummm…nasty. Water gets under them, leaving them fogged and wrinkled. Lint sticks to them. The movement of my jeans as I walk tends to curl up the edges of the film. Sometimes I need to replace the IV 3000 mid-sensor run, or slap a new one of top of one that is half-falling off.
Not so the Tegaderm. After nearly a week on my body it looks like I just put it on.
Which is when I realized that I use the sorry state of my film dressing as an analog sensor change alert. If I get a “time for new sensor” warning from the system and the dressing looks good, I can reboot for another three days. If I get a “time for new sensor” warning from the system and the dressing looks pretty nasty, I need to change the sensor.
So my day started out with me sitting on the corner of my bed with a calendar muttering to myself and counting backwards, forwards, and backwards again. I finally decided that the sensor, which has been running like a champ these last several days, was due for retirement. I shut off the sensor from the pump, and then pealed the Tegaderm off, it came off smoothly and painlessly. Then I depressed the little leavers on the edges of the sensor hub to release the seashell, and pulled it free. I slid the seashell into the charger to top up its tank, then pulled the sensor tape free and de-inserted the sensor. The area where the sensor had pierced my skin for a week was pale red, about the size of a pimple. No sign of undue irritation or infection. All looks good.
I finished my morning routine (turn on coffee pot, take Victoza, take thyroid med, brush teeth, trim beard, shave legs and stomach) then jumped into the shower. I don’t generally use alcohol or IV prep on CGM sites, so I like the put them into shower-fresh skin when I can. I also find that shower-fresh skin is softer, making it easier to slide the guide needle in. As I wasn’t paying attention last night, I didn’t pre-insert this sensor.
Still slightly damp, I open the vacuum-packed sterile bag the sensor comes in, scribble today’s date on the label, and set it aside as my new analog sensor age alert. I slip the silicone needle guard off the sensor’s guide needle, then remove the forward protective film. Med-T sensors, like Band-Aids, have two pieces of slick film that protect the sticky pad until you need to sticky it to your skin. The forward one is clear plastic, the rear is a fan-fold white paper affair. Next, I pull the paper one half off. It’s designed to pull out once the front half of the sticky pad is anchored against your skin, but I’ve had them rip on me in the past and then it’s damn near impossible to reveal all the sticky pad to the skin, and the sensor hub is loose for a week. An ounce of prevention…
With my right hand, I pinch up some skin on my left thigh. Holding the sensor in my left hand, I angle it more shallowly than the 45 degrees or so recommend: I’m lean enough that going in that deeply would slam the needle right into my muscle. Been there. Done that. Not recommend unless you get a job at a secret CIA prison and need a new torture technique.
My skin is thick and the needle is on the large side. It takes some elbow grease to break the surface, but then the guide needle slides smoothly in, Excalibur from the rock in reverse. I push the sensor firmly in, assuring the sticky pad is flush to my skin, and in good contact. In some folks, especially those with a little more fat, the needle likes to create a tough in the skin, pushing it down before breaking the skin. That can cause the sticky pad to stick to the edges of the trough and that exposes the top of the sensor to the air, which will screw up readings and or cause the sensor to fail. If you’re “fluffy” pinch a narrow mound of flesh.
I gently release my pinch, sensor still held in my left hand. With my right, I reach over the pull off the fan-fold paper. Next, I rest the middle and index fingers of my right hand on the base of the sensor, and using the thumb and index finger of my left hand, pull out the guide needle. The stiff needle out of my leg, I can safely rub the sensor site—sealing the sticky tape to my skin and forcing interstitial fluid around the sensor.
The next step is to make coffee. Well, I didn’t pre-insert, so the sensor isn’t “wet” enough to fire up. I need to give it about five minutes.
Coffee in hand, I pull the seashell out of its charger, which just gave me a solid green light—fully charged. I slip the seashell over the sensor’s hub and snap it into place. From deep inside the pale white shell an eerie green light flashes. The sensor is ready. Wet enough to start the warm up process.
From the pump I turn on the sensor, “linking” the sensor to the pump. It’ll be about two and a half hours before it’s ready for its first three day run. I’ve alternated my sensor changes and my infusion set changes to avoid possible infusion set issues on the same days that I have no CGM coverage. Still… Even though it’s only a little over two hours that I’ll have no CGM data, I feel oddly naked without the real-time info and my fingertips.
Oh. Wait. I really am naked.
I was so wound up in figuring out the sensor this morning I forgot to get dressed.
Yes, short-term memory really is the first thing to go…