Stress Testing of an Artificial Pancreas System With Pizza and Exercise Leads to Improvements in the System’s Fuzzy Logic Controller

TLDR

The Dose Safety artificial pancreas system uses fuzzy logic to calculate insulin doses and has successfully managed glycemic excursions under controlled conditions. This study aimed to determine whether stress testing with high‑carbohydrate/high‑fat pizza meals and exercise would expose deficiencies in the fuzzy‑logic controller and enable dosing matrix improvements. Ten type‑1 diabetes subjects completed 30 studies (17 meals, 13 exercise) using two controller versions; after 13 studies with v2.0, interim data guided a matrix revision that produced v2.1, which was validated against v2.0 CGM datasets before being used in the remaining 17 studies. Compared to v2.0, the revised v2.1 controller lowered mean blood glucose during pizza tests (205 mg/dL vs 232 mg/dL, P = .04) and during exercise tests (146 mg/dL vs 201 mg/dL, P = .004), reduced time >180 mg/dL (19.3 % vs 46.7 %, P = .001), and increased time 70–180 mg/dL (80.0 % vs 53.3 %, P = .002), demonstrating improved performance after stress‑testing‑driven adjustments.

Abstract

Background: Under controlled conditions, the Dose Safety artificial pancreas (AP) system controller, which utilizes “fuzzy logic” (FL) methodology to calculate and deliver appropriate insulin dosages based on changes in blood glucose, successfully managed glycemic excursions. The aim of this study was to show whether stressing the system with pizza (high carbohydrate/high fat) meals and exercise would reveal deficits in the performance of the Dose Safety FL controller (FLC) and lead to improvements in the dosing matrix. Methods: Ten subjects with type 1 diabetes (T1D) were enrolled and participated in 30 studies (17 meal, 13 exercise) using 2 versions of the FLC. After conducting 13 studies with the first version (FLC v2.0), interim results were evaluated and the FLC insulin-dosing matrix was modified to create a new controller version (FLC v2.1) that was validated through regression testing using v2.0 CGM datasets prior to its use in clinical studies. The subsequent 17 studies were performed using FLC v2.1. Results: Use of FLC v2.1 vs FLC v2.0 in the pizza meal tests showed improvements in mean blood glucose (205 mg/dL vs 232 mg/dL, P = .04). FLC v2.1 versus FLC v2.0 in exercise tests showed improvements in mean blood glucose (146 mg/dL vs 201 mg/dL, P = .004), percentage time spent >180 mg/dL (19.3% vs 46.7%, P = .001), and percentage time spent 70-180 mg/dL (80.0% vs 53.3%, P = .002). Conclusion: Stress testing the AP system revealed deficits in the FLC performance, which led to adjustments to the dosing matrix followed by improved FLC performance when retested.