Reduction in Duration of Hypoglycemia by Automatic Suspension of Insulin Delivery: The In-Clinic ASPIRE Study

Background: The efficacy of automatic suspension of insulin delivery in induced hypoglycemia among subjects with type 1 diabetes was evaluated. Subjects and Methods: In this randomized crossover study, subjects used a sensor-augmented insulin pump system with a low glucose suspend (LGS) feature that automatically stops insulin delivery for 2 h following a sensor glucose (SG) value <= 70mg/dL. Subjects fasted overnight and exercised until their plasma glucose (measured with the YSI 2300 STAT Plus(TM) glucose and lactate analyzer [YSI Life Sciences, Yellow Springs, OH]) value reached <= 85mg/dL on different occasions separated by washout periods lasting 3-10 days. Exercise sessions were done with the LGS feature turned on (LGS-On) or with continued insulin delivery regardless of SG value (LGS-Off). The order of LGS-On and LGS-Off sessions was randomly assigned. YSI glucose data were used to compare the duration and severity of hypoglycemia from successful LGS-On and LGS-Off sessions and to estimate the risk of rebound hyperglycemia after pump suspension. Results: Fifty subjects attempted 134 sessions, 98 of which were successful. The mean +/- SD hypoglycemia duration was less during LGS-On than during LGS-Off sessions (138.5 +/- 76.68 vs. 170.7 +/- 75.91 min, P = 0.006). During LGS-On compared with LGS-Off sessions, mean nadir YSI glucose was higher (59.5 +/- 5.72 vs. 57.6 +/- 5.69 mg/dL, P = 0.015), as was mean end-observation YSI glucose (91.4 +/- 41.84 vs. 66.2 +/- 13.48 mg/dL, P < 0.001). Most (53.2%) end-observation YSI glucose values in LGS-On sessions were in the 70-180 mg/dL range, and none was >250 mg/dL. Conclusions: Automatic suspension of insulin delivery significantly reduced the duration and severity of induced hypoglycemia without causing rebound hyperglycemia.