I have been using the new Medtronic Enlite sensors for a little over 5 weeks now (since January 7, 2014). I wanted to share some of the problems and happy moments I have had.
Was it worth the switch?
Yes! I did have a lot of problems with the older Medtronic Sof-Serter sensors and I have similar problems with the Enlite sensors but they are so much more comfortable and less aggressive on my skin and tissue, it was still worth it. It means less scar tissue and more space to use for future sensors and infusion sets!
I used my abdominal area a lot for injections before getting my insulin pump. My abdominal tissue is already so much better after 4 years of not doing injections 4 to 5 times a day. Some day maybe you might not even know I'm diabetic from the way my belly looks! ;)
A year ago I was not wearing my CGM (Continuous Glucose Monitor) all the time. When I first tried wearing it I was having so many alarms, errors and inaccuracies I wouldn't wear it for weeks at a time. When I did wear it, if I had a false low alarm at night (the CGM would indicate I was low, but when I checked my meter BG it would be normal or sometimes even high), I would turn off the low alarm completely. It prevented me from being woken up every 20 minutes by the alarms, but it also meant that I when I was unaware of real lows I completely slept through them--a great danger to my health. Then I would be dealing with rebound highs the entire next day.
June 2013, I was recovering from ankle tendon surgery and I was able to go for hikes at the park near my house for the first time in years. The extra exercise was making my bloodsugars plummet. I figured I needed to wear the CGM if I was going to know what was going on, and where to make changes (not to mention the insistence of my endocrinologist to wear it as well). The Sof-Serter sensor is approved for use for 2 to 3 days. My insurance only covered 10 for 60 days. If I tried to get them more frequently I had to pay $400+, but I wouldn't know if it was covered or not covered until I got a bill 2 months later. I found I could wear the Sof-Serter longer if I: 1) exercised consistently, 2) ate well (no high fat food, no snacking) and 3) didn't expose the sensor to too much moisture (water, sweat, etc). Basically you have to be "a good diabetic" to use a CGM effectively. My average time with 1 sensor was around 8 days. Every 3 days, my pump required me to reset the sensor (in essence, you make the pump think you've connected a new sensor), which somehow takes less than 10 minutes instead of the normal 3 hours. Most of the time, however, this happens at the most inconvenient time: I just tested a few minutes ago (too long ago to be accurate enough) or I had just eaten a meal.
Shortfalls of the CGM in general
Which leads me to general problems I think all CGM have by design (please let me know if I am wrong: I've only ever used the Medtronic system).
- Blood glucose and interstitial glucose will never match. The CGM is excellent because instead of several readings throughout the day as with just doing meter blood glucose readings (once before each meal/snack and bedtime, and ideally two hours after each meal) it shows what is going on in between.
- You should NOT calibrate when there is a large difference between CGM and meter readings. There is always going to be a time difference between rises/drops in blood glucose and rises/drops in interstitial glucose and when it comes to calibrating your CGM (which is required a minimum of every 12 hours with the Medtronic system) it is only going to calibrate well when blood and sensor readings are as close as possible. If somehow the "planets align" multiple times in a day, you should not calibrate more than 4 times in a day.
- Something I learned from the Medtronic training in January: a bad calibration can take a minimum of 5 good readings to get the sensor working properly again. There are times when a sensor just won't work. I hate getting that "BAD CAL" Alert on my pump. When I know I can't calibrate because there is too big a discrepancy between my meter reading and my CGM reading, I try waiting. Sometimes I will turn off the sensor and reconnect as a new sensor. I could wait an hour, put in a reading, but if it is off, I get another "BAD CAL" Alert. If it's really unhappy I could get "BAD SENSOR" or even "CHANGE SENSOR."
This is actually what happened today. Even though I had the sensor in for only 4 days (What a waste!) and the trainer said you can call the Medtronic hotline and they will troubleshoot with you, I decided to pull it out (see photo below) and realized the sensor was not cleanly inserted.
You may notice there is also a significant amount of blood. Probably not a good idea to hit a blood vessel with the sensor. This happened almost every time with the old Sof-Serter sensors but it is the first time this has happened for me with the Enlite sensor. Probably wasn't good that the electrode got bent too!
Enlite sensor problems
This is the scariest thing about these sensors. On Sunday, I was ready to insert a new sensor. I prepped my skin, loaded the insertion device, removed the pedestal and adhesive, placed on my abdomen, pressed the button and let go and...nothing. The interior part of the device did not move, click or do anything. I tried 3 times. I pulled the adhesive portion forward and tried to find a release mechanism or some way to pull the sensor out so I could load a new sensor--no luck. I hit the insertion device lightly against the counter, then harder. Though it is a very durable device, it did not help to release the sensor. Pushed the button and released in the air several times. Smacked it with my hand, jiggled the sensor with my fingers, pushed the mechanism in more while pressing and releasing the button repeatedly. I called the 1-800 number for Medtronic and after 10 minutes on hold, I gave up, went out to lunch.
2 hours later I came home, dialed the Medtronic help line again and decided to try pressing the insertion device button (without putting it against my skin: at this point the sensor was not sterile anymore!) and released, and out popped the sensor! I spoke to the Medtronic rep within a few minutes and explained what had happened. They had me use another sensor to test the insertion device and it worked immediately. They also said they would replace the sensors I had wasted and the insertion device, but only if I returned the insertion device I had. Since there didn't seem to be a permanent problem with the insertion device, I decided I would keep the one I had. The rep said I could always change my mind if I had more problems. I am going to test the insertion device a few times before loading a sensor from now on.
Accuracy
Despite improvements in my own diligence to be a "good diabetic" (which really helps everything), I still have fair to major discrepancies between my blood glucose and CGM readings. Sometimes this is advantageous, such as with "false lows." I have noticed that even if my meter glucose reading is not low, the CGM indicating a low could mean I will eventually drop. Particularly at night, when I am motivated to not get woken up again, I am now in the habit that if it tells me I'm low, but my BG is low normal or low, I will take eat or drink 15-25 g of carbs. So far this has prevented the extreme rebound highs I was tending to have in the past.
Good things
- Stays in consistently for the full 6 days. As long as I don't have more issues like bending the electrode or hitting a blood vessel, the adhesive on these sensors is quite impressive at continuing to stick through quite a bit of abuse. There have been a few times clothing or pump tubing has got caught around the transmitter half of the CGM and I am sure that I've pulled the sensor out, but when I look the adhesive around the electrode continues to hang onto my skin. The "O"-shaped tape they include in the Enlite box also sticks much better than the IV-3000 adhesive ever did. However, I do wonder why they include extra pieces of these. It is very difficult to remove this tape: you have to remove the tab from over the transmitter, disconnect the transmitter (which resets the sensor!), cut the "O" tape from around the adhesive under the transmitter, carefully remove the "O" tape from on and around the sensor without pulling it out and then place a new piece perfectly over top. Not a simple procedure. I would not want to try it in a public restroom and I doubt I'd have the equipment (i.e. scissors) to use on a vacation, or day trip.
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| Look at that adhesive pulling up my skin (after 6 days) |
- CGMing has given me a great sense of relief. The more I wear my CGM, the more I enjoy interpreting the data. Data collection is a diabetic's best friend. I've already been able to adjust my overnight basal rates to nearly eliminate overnight lows which has improved my sleep quality tremendously. Now I just have to figure out how to adjust my temporary basal rate for exercise. Overall I'm very happy.
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