An important goal of a closed loop system for individuals with type 1 diabetes is prevention of hypoglycemia, particularly overnight. We developed a system to suspend insulin pump delivery overnight when the glucose trend predicts hypoglycemia.1,2 The predictive low-glucose suspend (PLGS) system involves a continuous glucose monitor (CGM) device communicating with an insulin pump via a laptop computer that contains the hypoglycemia prediction algorithm. In an at-home randomized trial of 81 children aged 4-14 1 and 45 adults aged 15-45 2 with type 1 diabetes, we found that the PLGS system reduced the frequency of nocturnal hypoglycemia by 25% and 36%, respectively, compared with a control arm. Median time less than 70 mg/dL was reduced by more than 50%, prolonged nocturnal hypoglycemia (≤60 mg/dl for >2 hours) was reduced more than 3-fold, and there was no meaningful increase in hyperglycemia or ketosis. While the PLGS system greatly reduced hypoglycemia overall, We developed a system to suspend insulin pump delivery overnight when the glucose trend predicts hypoglycemia. This predictive low-glucose suspend (PLGS) system substantially reduces nocturnal hypoglycemia without an increase in morning ketosis. Evaluation of hypoglycemia risk factors that could potentially influence the efficacy of the system remains critical for understanding possible problems with the system and identifying patients that may have the greatest benefit when using the system.
Methods:The at-home randomized trial consisted of 127 study participants with hemoglobin A1c (A1C) of ≤8.5% (mmol/ mol) for patients aged 4-14 years and ≤8.0% for patient aged 15-45 years. Factors assessed included age, gender, A1C, diabetes duration, daily percentage basal insulin, total daily dose of insulin (units/kg-day), bedtime BG, bedtime snack, insulin on board, continuous glucose monitor (CGM) rate of change (ROC), day of the week, time system activated, daytime exercise intensity, and daytime CGM-measured hypoglycemia.
Results:The PLGS system was effective in preventing hypoglycemia for each factor subgroup. There was no evidence that the PLGS system was more or less effective in preventing hypoglycemia in any one subgroup compared with the other subgroups based on that factor. In addition, the effect of the system on overnight hyperglycemia did not differ in subgroups.Conclusions: The PLGS system tested in this study effectively reduced hypoglycemia without a meaningful increase in hyperglycemia across a variety of factors.