The MiniMed 670G in AutoMode. The blue shield means it is all-systems-go and in AutoMode.

The MiniMed 670G in AutoMode. The blue shield means it is all-systems-go and in AutoMode.

There is a lot to like about the Auto Mode feature for the Medtronic MiniMed 670G. This feature is analogous to self-driving technology where a car employing this technology drives along fine until the camera hits a blind spot. The same happens for Auto Mode, it works fine until an unexpected situation arises and the Auto Mode algorithm cannot handle this sudden change.

The closed-loop hybrid system is ground-breaking technology that as a research scientist I really appreciate. Yes it is a work in progress. But its current intricacies and potential to give people with Diabetes better control of their glucose numbers and more freedom to pursue other important things in their lives is really laudable.

This is what I Like about Auto Mode

  1. No more basal entries. By the time I was transitioning to the 670G, I had about eight entries in my basal pattern on the Minimed 530G. And it seemed as if I was fasting every two weeks to tune my basals. So for me getting on Auto Mode was what sold me on the 670G. And it hasn’t disappointed. But I think having that many basal entries from my 530G also gave the Auto Mode algorithm a lot of data points to work with and that made my transition to auto mode a little more easier.
  2. The Temp Target feature works beautifully when I have needed to do some strenuous work or exercise as long as I set it an hour before the activity.

    Auto Mode Temp Target for the MiniMed 670G

  3. No more of those night lows. Auto Mode seems to work beautifully when one is at rest and fasting since there are no curve-balls for the Auto Mode algorithm. I would say that 95% of the time I wake up at the targeted 120 mg/dL or below.
  4. Auto Mode allows me to snack without having to bolus every time so long as the snack is low in carbs and not high in the glycemic index. The micro bolus does a good job correcting for small changes in glucose readings.
  5. The Guardian sensors are a great improvement over the Enlite sensors I used with the 530G. Maybe not at par with the Dexcom G5 but so far have not had any sensor failures and have been happy with its accuracy and transmitter range.  (see note below on my experience with the Dexcom G5)

This is what I do not like about Auto Mode

  1. Alarms galore. I have learnt not to insert a sensor during the day and not at night and calibrate right before going to bed. Especially if Auto Mode is not happy with BG readings. A lot of people have noted how much work it is to stay in Auto Mode and for good reason. For example, although not a daily occurrence, Auto Mode requested for 3 BG calibrations last night in a span of eight hours.
  2. The algorithm is not able to compensate easily for complex events such as stress events, dawn phenomenon or sickness. So not as adaptive. But I think this is a great beginning for Medtronic. I think if the algorithm becomes more adaptive, allowing user entry to prompt the system to become more aggressive for complex events would be a great next step. For example, my Monday and Friday mornings are normally busy with a series of appointments in addition to dropping my daughter at school. This past Monday, my sugar crept to 206 mg/dL by around 11 am. By 1PM Auto Mode had caught up and reading was 150mg/dL. But that was 2 hours of my post-meal BGs being above 180 mg/dL.
  3. The “BG required to Enter Auto Mode” loop. I think it  is a glitch in the system but this seems to happen when the pump requests the first calibration on inserting a new sensor. The system keeps asking for a BG entry even after you have entered one. Hopefully Medtronic resolves the issue soon but the following seem to resolve the glitch:
    1. Waiting for about an hour before entering a new BG. It could just be that the sensor is not stable enough to give consistent reading and might need more quiet time to stabilize. Might be prudent to change the sensor during the day.
    2. Entering the BG under the Options ->Utilities-> Sensor Settings -> Calibrate Sensor instead of using Enter BG  in the main screen. Not sure why this matters but it seems to get the pump out this loop.
    3. UPDATE 11/13/18- See my latest article on this issue. Changing BG meters seems to be the best solution to this loop.

I have read in a lot of forums of how people with tight control (shooting for HbA1c lower than 6.0) were not able to replicate their numbers with Auto Mode due to the conservative nature of the Auto Mode algorithm. In my case, my endocrinologist  has set my blood glucose target closer to a HbA1c of 7.0 since I am more susceptible to severe hypoglycemic events and Auto Mode seems to work well to achieve this target.

Couple Notes

  • Not sure how Medtronic fits blood glucose data during calibration but seems a little complicated as compared to the Dexcom 5 which seems to average readings on the screen and the requested calibration BG meter number. I must say I prefer the Dexcom G5 insertion process though over the Guardian sensor.
  • At this time you can treat lows or highs based on Dexcom G5 readings (no need to confirm with a BG meter reading) since it is that accurate and FDA approved to do so. The fact that you can’t do same for the Guardian sensor is interesting since FDA thinks it is accurate enough to treat highs or lows in Auto Mode.
  • For those interested in reading more about the PID closed loop algorithm such as the one used in the Medtronic 670G, follow this link.
  • See ADA recommended BG targets here.
  • It would be great for Auto Mode to be able to mark out sensor reading outliers and in that way reduce the need for BG meter readings to confirm or ignore sensor reading outliers.