I spent nearly an hour and a half speaking to Tandem tech support today asking various questions about Control IQ. Here’s a pretty significant take away:
In the X2 simulator goto My Pump -->Control IQ–> Control IQ. There is as setting for “Total Daily Insulin”. On the simulator this value maxes out at 100 units. I had tech support that on a real live pump that it also maxes out at 100 units. This value is important…read on…
Refer to page 261 in the manual (Page 263 in the PDF version) --> Maximum Insulin Delivery:
"When Control-IQ technology predicts that your glucose value will be above the upper limit of the target range 30 minutes in the future, but the maximum rate of insulin delivery has been reached, Control-IQ technology stops increasing the insulin delivery rate."
Once you hit a system maximum of 100 units of infused insulin in a day (or whatever you as a patient and your doctor program as the maximum per day), Control IQ will only provide basal insulin reductions & suspend basal it will not increase your basals above your personal profiles, nor presumably provide correction boluses. I confirmed that with tech support. I read that as a kill switch to shut down the A.I. algorithm to protect the user from being over-medicated.
My take away is that this was built in to the pump to shut down the algorithm from potential over delivery in case your CGM was incorrect or from insulin stacking which is a good protection, however if you average near or above 100 units a day of insulin, or just have a bad day in general in terms of diet or illness, and near that set ceiling, Control IQ will not do anything to reduce high sugars, the patient will have to manually bolus.