OBJECTIVE: Officially licensed hybrid closed-loop systems are not currently available worldwide; therefore, open-source systems have become increasingly popular. Our aim was to assess the safety, feasibility, and efficacy of an open-source hybrid closed-loop system (AndroidAPS) versus SmartGuard® technology for day-and-night glucose control in children under extreme sports conditions. RESEARCH DESIGN AND METHODS: Twenty-two children (16 girls, 6-15 years of age, median HbA1c 56 ± 9 mmol/mol) were enrolled in this pivotal winter sports camp study. The participants were divided into two groups using either the AndroidAPS or SmartGuard technology. Physical exertion was represented by all-day alpine skiing. The primary endpoints were mean glucose level, time below the threshold of 3.9 mmol/L, and time within the target range of 3.9 to 10 mmol/L. RESULTS: The children using the AndroidAPS had significantly lower mean glycemia levels (7.2 ± 2.7 vs. 7.7 ± 2.8 mmol/L; 129.6 ± 49 vs. 138.6 ± 50 mg/dL, P < 0.042) than the children using the SmartGuard. The proportion of time below the target (median 5.0% ± 2.5% vs. 3.0% ± 2.3%, P = 0.6) and in the target zone (63% ± 9.5% vs. 63% ± 18%, P = 0.5) did not significantly differ. The AndroidAPS group experienced more frequent malfunctions of the cannula set (median 0.8 ± 0.4 vs. 0.2 ± 0.4, P = 0.02), which could have affected the results. No significant difference was found in the amount of carbohydrates consumed for the prevention and treatment of hypoglycemia [median 40 ± 23 vs. 25 ± 29 g/(patient ·3 days)]. No episodes of severe hypoglycemia or other serious adverse events were noted. CONCLUSIONS: This pilot study showed that the AndroidAPS system was a safe and feasible alternative to the SmartGuard Technology.

3rd Department of Internal Medicine 1st Faculty of Medicine Charles University Prague Prague Czech Republic

Department of Pediatrics University Hospital Motol and 2nd Faculty of Medicine Charles University Prague Prague Czech Republic

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