Background and Aims

We are developing a blood glucose control technology based on intravenous (IV) blood sampling and delivery of insulin. A wearable device photometrically measures glucose in IV blood samples and delivers insulin via the same IV path. This removes the time lag between the interstitial and blood compartments associated to subcutaneous technologies and ensures faster insulin action. In turn, this facilitates blood glucose control without prior meal or activity information.

As the performance of the automated glucose measurement is a critical component of automated insulin delivery (AID) systems, we evaluate the effect of measurement delay and error on the time-in-range and time-below-range for type 1 diabetes in-silico subjects.

Methods

Glucose profiles for in-silico type 1 diabetes subjects are simulated using the UVa/Padova T1DMS model (33 subjects) and the NudgeBG model (1000 subjects, including the effect of unmeasured sources of variation such as stress and exercise). The simulated time for each subject is two days, involving four unannounced meals/day (20-70 grams of carbohydrates/meal). The control interval is 15 minutes.

Time in the narrow glycemic range (70-140 mg/dl) and time below range (<70 mg/dl) are computed for measurement delays up to 20 minutes and measurement errors up to 35%.

Results

UVa/Padova T1DMS model:

NudgeBG model:

Conclusions

As the measurement delay increases, the time-in-range decreases. Because IV sampling eliminates the lag between venous and interstitial compartments, it reduces the overall delay, leading to higher performance. The time-in-range is less sensitive to the measurement error, but the high accuracy of the photometric method ensures lower hypoglycemia risks.