I found something a little disturbing last week with the 670G automode feature.
After using automode for a few weeks, I happened to notice the correction boluses for high blood glucose were really REALLY SMALL. One afternoon, I ate a large lunch, and didn’t estimate the carbs very well. Around 3PM, by blood-sugar had climbed to over 300 mg/dL. I had issued a few correction boluses when my high-alarm went off, and it didn’t seem to be doing anything. Then I noticed the bolus calculator inside auto-mode gives you a ridiculously low correction bolus, and to compound matters, backs off the microbolusing after you issue a bolus while in auto-mode. According to my insulin sensitivity I needed about 14U to correct my high blood sugar; Automode said I needed 1.3U (That’s about 10%) This was at 3PM, and only had a few units of active insulin remaining in my system, and no infusion set issues.
So, watch out for this. This really tripped me up because I was expecting auto-mode to calculate high-blood-glucose correction boluses using my insulin-sensitivity; IT DOES NOT. The bolus menus in auto-mode and manual-mode (which correctly calculates a correction bolus) look very similar, and the pump does not warn you about how little insulin you will be getting.
The effect is that it takes auto-mode about 12 hours to come down from a high blood glucose value, compared to about 2.5 hours to be back to normal while in manual mode.
The take-away for me, is if you need to do a correction bolus, get out of auto-mode first, because it won’t give you enough insulin to correct your high in a reasonable amount of time.