The Dexcom G7 and Tandem pump overlap: what you need to know
By Integrated Diabetes Services
Users of Dexcom G7 sensors have known for some time that it is possible to start “warming up” a new sensor while the old one is still working, thus eliminating any gap in data when transitioning from sensor to sensor.
Tandem, makers of the t:Slim and Mobi pumps, recently issued a formal statement that this practice can potentially lead to an accidental correction bolus by the system’s Control-IQ algorithm.
Not to worry.
The chances of this happening are less than winning the lottery. We have learned that a series of highly specific and unlikely conditions must occur in order for the system to deliver an undesired correction bolus:
- The user must insert a new G7 sensor while wearing the existing (old) sensor
- The user must connect the sensor to the pump prior to connecting it to the Dexcom app
- The last reading from the old sensor must have been received by the pump less than five minutes ago
- The first reading from the new sensor must be at least 50 seconds older than the final reading from the old sensor
- The reading from the new sensor must be valid (i.e., not during warmup, and not affected by compression)
- Conditions must be met for the reading from the new sensor to elicit a correction bolus:
- Predicted glucose value must be >180 mg/dL
- Not enough IOB to cover the predicted value
- No bolus was given within the last hour
- Not in sleep mode
As you can see, the chance of all this happening simultaneously is slim to none.
Nonetheless, Tandem is working diligently to update its pump software in order to bring the risk down to zero.
Watch for updates from Tandem in the weeks ahead.
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