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Published on: June 11, 2012
Adjustment of Open-Loop Settings to Improve Closed-Loop Results in Type 1 Diabetes: A Multicenter Randomized Trial
Eyal Dassau1, Sue A Brown1, Ananda Basu1
1Department of Chemical Engineering (E.D., R.G., J.B.L., H.C.Z., F.J.D.), University of California Santa Barbara, Santa Barbara, CA 93106; William Sansum Diabetes Center (E.D., J.E.P., R.G., J.B.L., K.C., W.C.B., P.K.B., H.C.Z., F.J.D.), Santa Barbara, CA 93105; Center for Diabetes Technology (S.A.B., S.P., D.L., M.M.-M., C.A.W., B.K.), University of Virginia, Charlottesville, VA 22904; Endocrine Research Unit (A.B., Y.C.K., L.H., A.M., V.D., S.K.M.-S.), Mayo Clinic, Rochester, MN 55905; and Department of Information Engineering (M.S., D.M., C.C.), University of Padova, 35131 Padua, Italy.
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.
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