Abstract

Objective: The aim of this study was to develop a partial closed-loop system to safely prevent nocturnal hypoglycemia by suspending insulin delivery when hypoglycemia is predicted in type 1 diabetes (T1D).

Research Design and Methods: 40 subjects with T1D (age range # to #) were studied overnight in the hospital. For the first 14 subjects, hypoglycemia (<60 mg/dL) was induced by gradually increasing the basal insulin infusion rate (without the use of pump shut-off algorithms). During the subsequent 26 patient studies, pump shut-off occurred when either 3 of 5 (N=10) or 2 of 5 (N=16) algorithms predicted hypoglycemia based on the glucose levels measured with the FreeStyle Navigator® (Abbott Diabetes Care).

Results: The standardized protocol induced hypoglycemia on 13 (93%) of the 14 nights. Using a voting scheme that required three algorithms to trigger insulin pump suspension, nocturnal hypoglycemia was prevented during 6 (60%) of 10 nights. When the voting scheme was changed to require only two algorithms to predict hypoglycemia to trigger pump suspension, hypoglycemia was prevented during 12 (75%) of 16 nights. In the latter study there were 25 predictions of hypoglycemia due to some subjects having multiple hypoglycemia events during a night, and hypoglycemia was prevented for 84% of these events.

Conclusions: Using algorithms to shut off the insulin pump when hypoglycemia is predicted, it is possible to prevent hypoglycemia on 75% of nights (84% of events) when it would otherwise be predicted to occur.