title: Feasibility of overnight closed-loop control based on hourly blood glucose measurements.
abstract: BACKGROUND
  Safe and effective closed-loop control (artificial pancreas) is the ultimate goal of insulin delivery. In this study, we examined the performance of a closed-loop control algorithm used for the overnight time period to safely achieve a narrow target range of blood glucose (BG) concentrations prior to breakfast. The primary goal was to compare the quality of algorithm control during repeated overnight experiments.
  
  
  METHODS
  Twenty-three subjects with type 1 diabetes performed 2 overnight experiments on each of three visits at the study site, resulting in 138 overnight experiments. On the first evening, the subject's insulin therapy was applied; on the second, the insulin was delivered by an algorithm based on subcutaneous continuous glucose measurements (including meal control) until midnight. Overnight closed-loop control was applied between midnight and 6 a.m. based on hourly venous BG measurements during the first and second nights.
  
  
  RESULTS
  The number of BG values within the target range (90-150 mg/dl) increased from 52.9% (219 out of 414 measurements) during the first nights to 72.2% (299 out of 414 measurements) during the second nights (p < .001, χ²-test). The occurrence of hypoglycemia interventions was reduced from 14 oral glucose interventions, the latest occurring at 2:36 a.m. during the first nights, to 1 intervention occurring at 1:02 a.m. during the second nights (p < .001, χ²-test).
  
  
  CONCLUSIONS
  Overnight controller performance improved when optimized initial control was given; this was suggested by the better metabolic control during the second night. Adequate controller run-in time seems to be important for achieving good overnight control. In addition, the findings demonstrate that hourly BG data are sufficient for the closed-loop control algorithm tested to achieve appropriate glycemic control.
authors.affiliation: Roche Diabetes Care, Roche Diagnostics, Mannheim, Germany.
authors.forename: Caroline
authors.initials: C
authors.lastname: Patte
authors.forename: Stefan
authors.initials: S
authors.lastname: Pleus
authors.forename: Paul
authors.initials: P
authors.lastname: Galley
authors.forename: Stefan
authors.initials: S
authors.lastname: Weinert
authors.forename: Cornelia
authors.initials: C
authors.lastname: Haug
authors.forename: Guido
authors.initials: G
authors.lastname: Freckmann
mesh_terms: D000328:Adult; D001069:Appetite Regulation / Q000502:physiology; D001786:Blood Glucose / Q000032:analysis*; D015190:Blood Glucose Self-Monitoring / Q000295:instrumentation / Q000379:methods; D002940:Circadian Rhythm / Q000502:physiology; D003922:Diabetes Mellitus, Type 1 / Q000097:blood* / Q000188:drug therapy*; D004334:Drug Administration Schedule; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage; D007328:Insulin / Q000008:administration & dosage*; D007332:Insulin Infusion Systems; D008297:Male; D062407:Meals / Q000502:physiology; D008875:Middle Aged; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D007004:Hypoglycemic Agents; D007328:Insulin