Low/Rebound with MySentry?

Last night my DS's MySentry was reading low and going down quickly. I only know this because he had a low earlier in the night so i kept rolling over looking at the screen through the night. When it was at 78 I figured I'd let the alarm wake me, being that most nights when it's low my son is actually higher. Anyway, the alarm never went off and i rolled over to see 52 with double arrows pointing down. I jumped up and ran to DS's room to check him. His bg was 149. I rechecked and it was 160. Just as i was cleaning up the mess the alarm went off saying he was 49!!! Hello!! So I'm guessing he was at one point that low and his liver kicked in some glucagon. Rebound right? My question is why was the alarm so late? Isn't the reason we pay so much for the alarm/MySentry to avoid this? I was starting to trust the alarms, but now I'm not sure what to think. Do i need to adjust something? His nighttime numbers shouldn't be lower than 100 and his alarm is set at that. I'm at a loss

 

My guess would be he rolled on the sensor causing it to read low until he rolled over. That was always the reason for those low readings the year+ we used the Medtronic system. I learned to recognize what those fast quick drops looked like on the graph. We kept ours set at 80 and I rarely even saw a blood BG in the 60s at night while she was on it.

 

So the issue is that you saw a 52 on the Mysentry but an alarm did not go off. Your alarm is set at 100 right? So, did it go off for the 78 and then you cleared it? I believe that it would not have re-alarmed again if you were still in the 20 minutes or so (whatever time period you have the low repeat set for) after you cleared the first alarm. What is your "low repeat" set for?

If it makes you feel any better in my experience 9 times out of 10 a number below 60 at night on the MM CGM with double arrows down will be a false low from putting pressure on the sensor. It seems more likely to me he was actually around 150 the whole time. However, I am not sure how long you have been using the MM CGM. You will get more comfortable with figuring out false lows from the shape of the graph with time. It is crucial to note though that I think it is still important to test with EVERY low alarm.

 

It's technology, it's imperfect. The 149 and the 160 are well within the meter margin for error, they do not indicate a climb. Most likely he was never actually low. If it were a rebound, and they are pretty rare, you'd be seeing super high numbers now in the 300 range.

 

Yep, I agree with the others that it was likely a false low caused by him laying on the sensor. If you post the graph, I could tell you for sure.........

 

And, I'm going to suggest that "maybe" the alarm went off and mom either did not hear it or slept through it. It was not clear to me that she was awake or asleep waiting to hear it. I know that I have slept through my clock radio alarm in the past, would panic when it was the "time to check the BG" alarm.

 

I also think he was likely never that low. Do you have good accuracy with the sensor normally? We didnt which was a shame because I loved he Mysentry.

 

Thanks for all the responses everyone! The sensor so far is okay, not necessarily right on the mark, but i love the trends and being able see a ballpark number. I understand that it's not perfect, it just stinks that $15, 000 worth of equipment can't be more precise.:cwds: On that point though, I wouldn't go back to the world with no cgm. We do get a lot of sensor errors and weak signals, but when it is working i love it. The MySentry has been great, especially since my DS tends to go low a lot at night. The other night did scare me though. I didn't realize that the sensor could give false lows if pressure is applied. DS wears his on his bum cause he has no real estate anywhere else, so that would make a lot of sense.
I don't think i missed an alarm, I was lightly sleeping and the MySentry is very loud. I'm just going to chalk this one up to a learning experience. Another question though, what do you mean when you say you can tell I'm the graph? Enlighten me please

 

$15,000? You paid $15,000 for the MySentry unit?

 

No! That was for everything! Pump, cgms, MySentry and supplies. Luckily my deductible was paid so i didn't pay all of that. It's just crazy what technology costs isn't it?

 

If you post the graph I or someone else on here can tell you if it was a false low or not. The shape of the graph for a false low is pretty distinctive.

Yep! Pressure on a sensor reduces the ISIG which then gives you a false low.

 

Also another indicator is a rebound is between 7 to 8 times the starting #. So if he was 50, he would have shot up to about 350.

 

our experience with rebound highs have been that the resulting number is over 300 and results in a more difficult to correct, high, too...the few rebound highs we've had were actually why we invested in the CGM. After our endo suggested that the highs were caused by not enough insulin and suggested increasing insulin I felt uncomfortable and instead of sleep for a few nights I did hourly night checks to show that he was dropping at that time (I treated the impending lows and he didn't rebound, but they were quick fast drops resulting in his insulin needing to be at .025 for hours at night). We confirmed it with a"blind" CGM at the same time, which helped the endo get quick approval of the CGM, too.
So, my guess is that either your child wasn't that low and the CGM wasn't perfectly accurate, or even his BG could have just climbed because of hormones, food (slower digesting fat/protein), etc.

 

Can't figure out how to post the stupid graph. Maybe this site needs a little updating?

 

If you can't upload the graph, here's what you look for with a false low: VERY sudden drop. Think 10-20 points every five minutes. And then when you see BG go back up on the graph it will go back up almost as sharply as it dropped, but will then stop almost on a dime almost exactly where it was before the drop started. With a rebound, BG will just keep going up and end up well beyond where it started the drop.

 

Thanks for the help! Seems like a false low with that info. We'll be seeing our diabetologist on Monday so I'll see what her thoughts are as well.

 

If you like him above 100 at night as mentioned in later post, why not address the 78 and dropping BG? If he were truly 78 and dropping, given the CGM delay, wouldn't the actual BG likely have been 60s or lower?

 

I get what you're saying David, but usually it's higher when i check it. Don't worry though, I'm not gonna let that happen again

 

The Medtronic CGM tracks differently than G4. G4 tends to overpredict lows; Medtronic can be either above or below BG with the same calibration.

 

When you post a message, there is a box below the editing area labeled "Additional Options" in which you will find a button "Manage Attachments." You should be able to use that to upload images to include in your message or reply.