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Auto Mode Medtronic MiniMed 670G Pump Settings

Spike Control is Auto Mode’s Biggest Weakness for the 670G

Now that I have been using Auto Mode for the Medtronic MiniMed 670G for the last one-and-a-half years, I can say that spike control is one of the major weaknesses of this closed loop system.

Auto Mode does a decent job of controlling BGs for low to moderate glycemic index foods. But for high glycemic index foods, the pump struggles because of inherent Auto Mode safeguards.

As a safeguard against hypoglycemia, the pump pauses basal and microbolus delivery following meal bolus delivery for close to thirty minutes. This makes it very hard for the pump to catch up with a meal related BG spike.

In the photo snapshot, as soon as I bolus for my breakfast comprising a cup of tea and a piece of toast, there are purple dots dissapear for close to thirty minutes (purple dots signify every time the pump dispenses a microbolus or basal dose).

As you can see, there is a period of close to thirty minutes (green box) where the pump does not dispense microbolus or basal dose. In cases of high glycemic index foods, the MiniMed 670G cannot catch up with the runaway BG numbers.

According to Medtronic, this period of no microbolus or basal delivery is needed to determine the BG trend after meal bolusing.

Even though the pump resumes microbolus and basal delivery, it is too late and the BG spike is inevitable.

Waiting longer than the 5-15 minutes before eating recommended by Medtronic somewhat helps. But it is still hard to recover from 30 minutes of no insulin delivery.

The reason manual mode is so good with spike control as compared to Auto Mode is because manual mode allows for a good balance between bolus and basal. The user can be able to adjust the basal does just right to assist the meal bolus counteract BG spikes.

Categories
Auto Mode Pump Settings

Tunable Settings in Auto Mode for the MiniMed 670G

Tuning Auto Mode for the Medtronic MiniMed 670G is just like tuning an engine. Changing one setting throws off the other settings
Getting Auto Mode settings just right seems to be a balancing act – more fine tuning than just dialing settings up or down

UPDATE - I have certainly found out that dialing the Carb Ratio and Active Insulin time up and down do not necessarily mean that you will get better control. That is why it is important to work with your endo or educator to tune these settings.

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When it comes to Auto Mode for the MiniMed 670G, tuning the settings to get as close to your sugar targets feels a little more complicated as compared to the manual mode. This is because the closed loop system has a feedback mechanism which will likely throw-off one setting when you change another.

In the course of your day, the system is performing a balancing act between bolus and basal to keep you as close to Auto Mode’s fixed and preset BG target of 120mg/dL by introducing a third input – the micro bolus.

When it is all said and done, the user has control of two settings only, namely Carb Ratio (CR) and Active Insulin time (AIT).