{CGM} Our First Night

by Leighann on May 2, 2012

(For several reasons, which I will reveal soon, we decided against purchasing and continuing use of the Revel and mySentry. I do feel that our experience provides valuable information, so I will continue to share our experience. These posts are not and have never been an endorsement of these products.)

I’m not a trained medical professional and none of this constitutes medical advice. Please consult your care team for questions about the use of a continuous glucose monitor.

We’ve been using the Medtronic continuous glucose monitor (CGM) and the mySentry for a month now and I want to start telling you more about our experience.

Let me first say that there are some definite pluses and a few minuses to the CGM system. But this is true of any diabetes-related technology, isn’t it? Even her insulin pump, which I don’t think we would part with at this point, has it’s own set of trouble-shooting and hassles. But for the most part, we are pro-pump and would not go back to injections.

Last time I described our experience trying to insert her first sensor. I didn’t expect it to actually go smoothly, but I also didn’t think it would be quite that difficult.

The trainer had come over in the evening, after a few hiccups where we had to reschedule our training session. When she was done explaining the system, entering all of the settings, and talking me through doing an insertion on Q, she packed up her things to go with the instruction that it would be asking for a METER BG NOW in about two hours after the system warmed up.

We were told that calibration works best when blood sugars aren’t too high or too low and that we should typically calibrate “before, before, before.” In other words, calibrate the CGM two to four times a day when blood sugars are stable (no up or down arrows indicating a rise or fall in blood sugar levels) and when they aren’t low or high. This is probably most easily done before breakfast, before lunch, before dinner, and before bed.

Well wouldn’t you know that between the pizza (we made one quickly during the training so that we could pay attention), the nerves (adrenaline can raise blood sugars), and a pump site change that afternoon (which occasionally gives us high blood sugars later at night, but which we have managed to mostly tame), when the CGM alarmed requesting a METER BG NOW her blood sugar was quite high.

I calibrated it because that’s what I thought I had to do right then.

And I think because of it, it wasn’t accurate that night.

CGM mySentry Low Alert

The damn mySentry woke me up every two hours I think telling me that she was high and then predicting lows as her blood sugar came back down. The reality was that the bedtime bolus I gave her brought her right back down into range. She was not really high or really low all night even though the CGM thought she was.

As I calibrated it a few more times the next day trying to make it more accurate (in other words more closely in range with what her meter said) Q said to me, “Hey, I thought getting a CGM meant less finger pokes.”

She had a point there and I was not living up to my promise.

I was so tired and upset by the next morning and I really questioned our decision to try out a CGM.

I was ready to throw in the towel.

But I remembered that there is always a learning curve with all new d-technology. I went to Facebook and asked some experienced Medtronic CGM users a bunch of questions.

Turns out that I didn’t need to tell the CGM what her blood sugar was right when it was done warming up. In reality I could have waited a while until she was back in range, it just wouldn’t display blood sugars until it was actually calibrated.

Several parents told me that they get the best results when they calibrate when blood sugars are between 70 and 200, some said 70 to 150. What I learned was that if her blood sugar is above 200 to just wait it out before calibrating.

(There’s also a bunch of technical details about interstitial signal (ISIG). The ISIG number is the difference between what the CGM thinks the blood sugar is versus the number you enter to calibrate it. I’m still not 100% up on ISIG. If you want a much better explanation about ISIG, read this post on the Children With Diabetes website.)

I’m learning that blood sugars are never perfectly between 70 and 150 when you need to calibrate. Given that her target range is 80-180 during the day and 100-200 over night, there’s a decent chance that her blood sugar isn’t technically low enough to calibrate even though her blood sugar is within her acceptable range.

I am also choosing not to do a calibration before lunch at school because that would mean one more thing for school staff to have to deal with. If I calibrate before breakfast at about 7:00 am, I have until 7:00 pm before it asks me for another METER BG NOW.

I know I’ve told you about the scary insertion and that I absolutely hated the CGM and mySentry that first night and the next day. But trust me, there are a bunch of positives, which I will get to in the coming weeks.

I would love to hear from other parents or PWD’s when you calibrate and if you only calibrate when blood sugars are in a certain range.

Further Reading

Medtronic Diabetes Advocate Forum: The Event (I talk about perceived pain versus real pain.)

{CGM} Taking One For the Team

All posts about continuous glucose monitors

Medtronic Disclosure

In full disclosure, Medtronic provided us with the necessary devices and supplies for this two-month trial at no cost to our family. A prescription was needed from our doctor. Medtronic provided in-home training to us, as they do for all of their customers. They did not ask me to write about the products or trial and I am free to write whatever opinions I have about the experience. I am not being paid by Medtronic.

All images are copyright D-Mom Blog and D-Mom Media and may not be copied or reproduced without express written permission.

{ 1 comment… read it below or add one }

1 Jennifer A May 3, 2012 at 1:13 pm

Our son has been on the MM CGM for almost 3 years now and we have calibrated at anything and everything in between. I NEVER calibrate below 70 and in general not below 100, but life is crazy and sometimes he is high so we calibrate and start bringing him down right then. You only need about 15 minutes for calibration and generally we don’t start seeing him drop until 30-45 minutes after his bolus. I try to keep in mind that the pump is what is keeping him safe and alive and the CGM is simply a tool for helping us make decisions for him. There are days where it is wonky and I try really hard to not use all my energy troubleshooting. I did that at one point and went nuts! When I took the pressure for “perfection” off of the sensor, I could handle the things it threw my way with much more ease and understanding. We also have the mySentry and on nights like you described, I silence it. Usually we can attribute the alarms to a specific cause so I don’t worry about it too much. And honestly, it took us a good 3-4 months to really get a smooth routine for insertions, taping everything down, and calibrations. Now I barely have to think about it, even when it is not “behaving itself” Hopefully you will get some good data during your trial to help her out!


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