Adjustment of Open-Loop Settings to Improve Closed-Loop Results in Type 1 Diabetes: A Multicenter Randomized Trial

J Clin Endocrinol Metab. 2015 Oct;100(10):3878-86. doi: 10.1210/jc.2015-2081. Epub 2015 Jul 23.


Context: Closed-loop control (CLC) relies on an individual's open-loop insulin pump settings to initialize the system. Optimizing open-loop settings before using CLC usually requires significant time and effort.

Objective: The objective was to investigate the effects of a one-time algorithmic adjustment of basal rate and insulin to carbohydrate ratio open-loop settings on the performance of CLC.

Design: This study reports a multicenter, outpatient, randomized, crossover clinical trial.

Patients: Thirty-seven adults with type 1 diabetes were enrolled at three clinical sites.

Interventions: Each subject's insulin pump settings were subject to a one-time algorithmic adjustment based on 1 week of open-loop (i.e., home care) data collection. Subjects then underwent two 27-hour periods of CLC in random order with either unchanged (control) or algorithmic adjusted basal rate and carbohydrate ratio settings (adjusted) used to initialize the zone-model predictive control artificial pancreas controller. Subject's followed their usual meal-plan and had an unannounced exercise session.

Main outcomes and measures: Time in the glucose range was 80-140 mg/dL, compared between both arms.

Results: Thirty-two subjects completed the protocol. Median time in CLC was 25.3 hours. The median time in the 80-140 mg/dl range was similar in both groups (39.7% control, 44.2% adjusted). Subjects in both arms of CLC showed minimal time spent less than 70 mg/dl (median 1.34% and 1.37%, respectively). There were no significant differences more than 140 mg/dL.

Conclusions: A one-time algorithmic adjustment of open-loop settings did not alter glucose control in a relatively short duration outpatient closed-loop study. The CLC system proved very robust and adaptable, with minimal (<2%) time spent in the hypoglycemic range in either arm.

Trial registration: NCT01929798.

Publication types

  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Blood Glucose / drug effects*
  • Blood Glucose Self-Monitoring
  • Cross-Over Studies
  • Diabetes Mellitus, Type 1 / blood
  • Diabetes Mellitus, Type 1 / drug therapy*
  • Female
  • Humans
  • Hypoglycemic Agents / administration & dosage*
  • Hypoglycemic Agents / therapeutic use
  • Insulin / administration & dosage*
  • Insulin / therapeutic use
  • Insulin Infusion Systems*
  • Male
  • Middle Aged
  • Treatment Outcome
  • Young Adult


  • Blood Glucose
  • Hypoglycemic Agents
  • Insulin

Associated data