When the children don't get along...
Threshold’s are the BG point at which you set your Guardian to alarm. On the low side you can choose any number between 40 (yeah, like I’m that brave) and 100 mg/dl. On the high side you can choose any number between 105 and 400 mg/dl. Well one size doesn’t fit all, after all. But nothing is that simple.
The Guardian samples every five minutes. That means if you are dropping fast here is what could happen: 15 seconds after a sample your sugar passes through your low threshold. OK, now you’ve got four minutes and 45 seconds before the next sample “catches” the low. How low will you drop in that time?
Well, my example is extreme, but you understand the principal. Medtronic suggests you set your low threshold higher than you’d think to offset this phenomena. My rep/trainer asked me at point I usually treat hypo. My personal comfort zone: if it is below 70 I’m eating some sugar. She recommended I set the low threshold at 80. Makes sense. I think I might get some alarms that don’t really need to be treated, but I’m covered better if a fast-moving low hits me. Besides, I’ve got no business being much below 80 anyway.
Obviously, if you’ve been hanging out around 90 most of the day and you haven’t taken any insulin for four hours you wouldn’t take much sugar on board for a low alarm. Conversely, if you had just indulged in three bagels and a banana split and had a boat load of insulin on board....
Any way, back to the story...I look down, expecting 80. Instead I have 76. Yikes! That’s a surprise and indicates to me that I’m dropping a bit quickly. So I skip the finger stick and take on a small bit of sugar. According to the pump I’ve got zero IOB.
I go about my business. Now, if you have you Guardian set to simple “on,” then five minutes later, if you are still low (and you will be) you’ll alarm again. I’ve got both my alarms set to “Repeat” mode. This lets me customize the length of time between alarms. Kinda of like a built in snooze alarm you can program to be the same each time. I’ve got my low alarm set for 20 minutes. This is what we all do now. You are low? You eat sugar. Wait 15-20 minutes to see where you are at and go from there. If I’m still below 80 in 20 minutes after the first alarm the Guardian will alarm again.
But for some reason, I look at the screen in about 10 minutes. Yikes! I’m down to 60! What the @#$%#?? I just took on sugar, I should be going up. So I eat another half-piece of my emergency candy. Then it occurs to me to do a finger stick. Cozmonitor has me at 126.
So what to do when the children disagree? They’ve always been neck-in-neck. I know that the Guardian is supposed to be more accurate on the low end, and that it detects impending lows more quickly than a finger stick would. Still 60 vs. 126 seems like a bit of a wide spread.
I can’t trust my feelings, because I don’t have any. Impaired hypoglycemia awareness, remember? As a general rule, I say it is better to error on the side that keeps you alive. Better to correct for a low that isn’t there than to not correct for a low that is there.
From my past experience I know that a full piece of my stash candy will always pull me out of mild hypo with low or no insulin on board, as I’ve had two one-half hits I decide to ride it out a bit and see what happens. Guardian bottoms out at 53 while Cozmonitor continues to climb. At one point they have a 100 point spread between them. Damn.
Oddly, however, one hour after all this started they are with in a few points of each other again.
Not sure how to explain this....One possible theory: the Guardian was more on the ball in detecting the hypo when it started--just like it is supposed to do. But once the recovery began the finger sticks were more accurate. Perhaps the traditional blood readings responded more quickly to rising sugars while the I.F. readings responded more quickly to dropping? I do know that the Guardian system lags at very high BG.
Hmmmm.... the traditional glucose monitor folks say not to use forearm testing for fast changing BG. With rapidly shifting sands everyone agrees that finger tips are the way to go. Is I.F. like the forearm? In other words, good most of the time, but behind the 8-ball when the fur is flying? I’ll need to get due more research and get back to you folks on this. (By the way, all of my traditional checks are finger tip.)
Well, crap. While I was finishing off this post the Guardian set off a high limit alarm. She’s showing 200 while Cozmo shows mid 150’s. I give up. Some days nothing works right. I’m going to bed.