Prevention of Nocturnal Hypoglycemia Using Predictive Alarm Algorithms and Insulin Pump Suspension

  1. Francis J. Doyle III, PhD5
  1. 1Department of Pediatric Endocrinology, Stanford University, Stanford, CA
  2. 2Department of Pediatrics, University of Colorado, Aurora, CO
  3. 3Aeronautics and Astronautics, Stanford University, Stanford, CA
  4. 4Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, NY
  5. 5Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, CA


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.


    • Received December 17, 2009.
    • Accepted February 6, 2010.