Saturday, November 11, 2017

My Medtronic 670G experiences: Making this pump work

I blogged recently about starting to use the Medtronic 670G.  After my history with diabetes, I really love this pump!  I've gotten to know a lot of people other people on this pump and I've discovered a lot of people really struggle with it in the beginning.  I don't know if I adapted more quickly because I'd never been on a pump before and didn't have to unlearn previous habits, or because I never developed the control freak approach to managing my diabetes, or for some combination of several factors... but I've done pretty well on the 670G.

Here's what I've learned about making the 670G work well for you.


Learning Curve

The first and most important thing for newbies to know is that there will be a learning curve with this pump -- both for you and for the 670G.  There's some discussion about how much the pump really "learns" you, but at minimum it looks at the last 6 days of total daily dose (TDD).  It uses that information plus your current sensor glucose (SG) reading to give you a microbolus every five minutes.  Those microboluses are essentially your basal insulin, but instead of a set basal rate like pumps used to have, the amounts can change every five minutes based on what your blood sugar is doing.

Which is where the user learning curve comes in.  The 670G is completely different from any other pump, so some experienced pumpers are having trouble adapting.  With the 670G:
  • You have to report every carb.  No more guessing, and no more "free" foods.  Because the basal is controlled so tightly, food boluses have to be super accurate.  (I say this even though I guess regularly.  You can get away with it, but if you're getting frustrated you might need to try being more accurate with carb counting.)
  • Active insulin time is important.  This is only one of two settings that make a difference in auto mode, but it's a really important setting.  When AI time is too long, you'll run high all the time, start spiking a couple hours after meals (when the bolus insulin runs out but the system thinks you still have active insulin in your system), and won't be able to correct when you're high and the system thinks you still have active insulin.  If you get it too short, though, you'll find yourself running low all the time and crashing a few hours after meals.  To figure out your active insulin time, look at a correction-only bolus and see how long it takes to get back down to 150 (what auto mode corrects down to).  It's important though not to jump straight to this value -- according to this test, my AI time should have been about 2 hours or 2:15, but both were too short (I'm at 2:30 now).  It's best to change AI time in 15 minutes increments, and wait a few days between changes to let the algorithm update.  If you go too fast, you might miss your sweet spot!
  • Carb ratios may need to be more aggressive.  The only other setting you can change in auto mode is your carb ratios.  Most people find that they have to have more aggressive carb ratios in auto mode, probably because we were relying on basal rates to cover the difference.  Auto mode will ramp up microboluses as your SG climbs, and reduce or stop them when your SG is stable or dropping, so carb ratios need to be able to handle the carbs all by themselves.
  • Be patient.  Between the system's learning curve and the user's learning curve, it takes a few weeks at least for auto mode to really shine.  At first you'll likely run high, which some people have trouble with, but just remember it's temporary.  The system may increase or decrease your basal insulin, depending on what it determines you need, and it has to do so gradually.  The system also corrects very conservatively at first, but that'll improve too, as the system learns you and as you dial in your settings.

It may take some time to get things right in auto mode, but remember, it's totally worth it.  I love the 670G.  Virtually every night is stable around 120 the entire night, rather than the wild swings I used to get during the night.  And during the day is great, too -- my spikes are no longer as high and they come right back down again.  With my basal taken care of, I can see better now what large meals, high fat meals, and different kinds of carbs do to me.

With so many of the extremes taken out of the equation -- fewer spikes and almost no lows -- my A1c is for the first time a true average.  I dropped from 8.1 at the beginning of the year to 6.7 just a couple months ago, and that lower A1c was achieved without a bunch of lows misleadingly dragging it down.

Most importantly, I feel healthy and safe and confident that I'm not going to crash or spike uncontrollably at any time throughout the day.  It's a good feeling!

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