Fully Closed-Loop Insulin Delivery with High-Carbohydrate and High-Fat Meals Using the Tandem Freedom System.

BACKGROUND: To evaluate a new fully closed-loop (FCL) system in people with type 1 diabetes (T1D) with high-carbohydrate and high-fat unannounced meals. METHODS: After a 1-week Control-IQ run-in period at home with mealtime insulin boluses, ten adults with T1D used the Tandem Freedom FCL System in the hotel setting for 72 hours without meal announcement or mealtime insulin boluses. Participants consumed high-carbohydrate and high-fat meals during their stay. Exercise challenges occurred each day. A Wilcoxon signed-rank test for nonparametric data compared outcomes between periods. RESULTS: Mean participant age was 38.6 years, duration of diabetes 15.9 years, total daily insulin 0.71 units/kg/d, and HbA1c 7.3%. There were no diabetic ketoacidosis (DKA) or severe hypoglycemia events. During the hotel study, FCL was active 97.3% of the time, and median meal size was 70.8 g carbohydrate and 53.2 g fat for breakfast, 53.8 g carbohydrate and 40.0 g fat for lunch, and 96.1 g carbohydrate and 53.1 g fat for dinner. Median time in range (TIR) 70 to 180 mg/dL was 61.0% [58.9, 73.0] without any meal announcement or mealtime insulin boluses during the 72-hour FCL period, compared to 56.3% [50.9, 64.0] with their home pump with mealtime insulin boluses during the at-home run-in week (+9.0%, P = .23). Overnight TIR was 95.9% [83.8, 100.0] for FCL versus 69.6% [57.6, 77.8] for the run-in period (+26.1%, P = .01). Time <70 mg/dL was low at 0.4% during FCL. CONCLUSIONS: FCL insulin delivery with the Tandem Freedom System was safe and effective in adults with T1D with high-carbohydrate, high-fat meals.