title: Evaluation of a portable ambulatory prototype for automated overnight closed-loop insulin delivery in young people with type 1 diabetes.
abstract: OBJECTIVE
  To evaluate an ambulatory, portable prototype, overnight automated closed-loop (CL) system and to explore optimal time of CL initiation.
  
  
  METHODS
  We performed a randomized crossover study and compared automated overnight glucose control started at the time of an evening-meal or at bedtime. Eight young people with type 1 diabetes (T1D) on insulin pump therapy [M = 4; age = 14.3 (1.7) yr; HbA1c = 8.2 (1.3)%; mean (SD)] were studied on two occasions at clinical research facility. A standardized self-selected evening meal [70 (11)g CHO] and snack [22 (4)g CHO] accompanied by prandial insulin boluses were given at 18:00 and 21:00 hours, respectively. In random order, automated CL was started at 18:00 or 21:00 hours and ran until 8:00 hours the next day. Basal insulin delivery was automatically adjusted by a model predictive control algorithm based on real-time continuous glucose monitor readings.
  
  
  RESULTS
  Overnight plasma glucose levels (between 21:00 and 08:00 hours) were within the target range (71-145 mg/dL) for 82 (59, 98)% of time when CL started at 18:00 hours and 64 (48, 70)% when CL started at 21:00 hours [median (IQR), p = 0.036]. Time spent above 180 mg/dL [8 (0, 17) vs. 13 (3, 26)%, p = 0.310] or below 70 mg/dL [0 (0,7) vs. 0 (0, 8)%, p = 1.000] did not differ between the two occasions. Mean overnight glucose [121 (14) vs. 137 (13) mg/dL, p = 0.731) was also similar. Overnight insulin infusion rates were comparable [0.8 (0.5, 1.3) vs. 0.8 (0.6, 1.4) U/h, p = 0.263]. No interruptions to CL delivery were observed.
  
  
  CONCLUSIONS
  Automated CL delivery can be applied reliably and safely to control glucose levels overnight in young people with T1D. Tighter glucose levels may be achieved with an earlier time of CL initiation.
authors: Metabolic Research Laboratories, Institute of Metabolic Science, Cambridge, UK.
authors: Daniela
authors: D
authors: Elleri
authors: Janet M
authors: JM
authors: Allen
authors: Martina
authors: M
authors: Biagioni
authors: Kavita
authors: K
authors: Kumareswaran
authors: Lalantha
authors: L
authors: Leelarathna
authors: Karen
authors: K
authors: Caldwell
authors: Marianna
authors: M
authors: Nodale
authors: Malgorzata E
authors: ME
authors: Wilinska
authors: Carlo L
authors: CL
authors: Acerini
authors: David B
authors: DB
authors: Dunger
authors: Roman
authors: R
authors: Hovorka
mesh_terms: D000293:Adolescent; D017668:Age of Onset; D001331:Automation; D001786:Blood Glucose / Q000032:analysis; D015190:Blood Glucose Self-Monitoring / Q000295:instrumentation / Q000379:methods; D002648:Child; D002940:Circadian Rhythm; D018592:Cross-Over Studies; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000188:drug therapy* / Q000453:epidemiology / Q000628:therapy; D004864:Equipment and Supplies; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage; D007328:Insulin / Q000008:administration & dosage*; D007332:Insulin Infusion Systems; D008297:Male; D018670:Monitoring, Ambulatory / Q000295:instrumentation / Q000379:methods
chemical_list: D001786:Blood Glucose; D007004:Hypoglycemic Agents; D007328:Insulin