Artificial Pancreas: Evaluating the ARG Algorithm Without Meal Announcement.

BACKGROUND

Either under standard basal-bolus treatment or hybrid closed-loop control, subjects with type 1 diabetes are required to count carbohydrates (CHOs). However, CHO counting is not only burdensome but also prone to errors. Recently, an artificial pancreas algorithm that does not require premeal insulin boluses-the so-called automatic regulation of glucose (ARG)-was introduced. In its first pilot clinical study, although the exact CHO counting was not required, subjects still needed to announce the meal time and classify the meal size.

METHOD

An automatic switching signal generator (SSG) is proposed in this work to remove the manual mealtime announcement from the control strategy. The SSG is based on a Kalman filter and works with continuous glucose monitoring readings only.

RESULTS

The ARG algorithm with unannounced meals (ARG) was tested under the effect of different types of mixed meals and intrapatient variability, and contrasted with the ARG algorithm with announced meals (ARG). Simulations reveal that, for slow-absorbing meals, the time in the euglycemic range, [70-180] mg/dL, increases using the unannounced strategy (ARG: 78.1 [68.6-80.2]% (median [IQR]) and ARG: 87.8 [84.5-90.6]%), while similar results were found with fast-absorbing meals (ARG: 87.4 [86.0-88.9]% and ARG: 87.6 [86.1-88.8]%). On the other hand, when intrapatient variability is considered, time in euglycemia is also comparable (ARG: 81.4 [75.4-83.5]% and ARG: 80.9 [77.0-85.1]%).

CONCLUSION

results indicate that it is feasible to perform an in vivo evaluation of the ARG algorithm with unannounced meals.