The effect of insulin feedback on closed loop glucose control

J Clin Endocrinol Metab. 2011 May;96(5):1402-8. doi: 10.1210/jc.2010-2578. Epub 2011 Mar 2.


Context: Initial studies of closed-loop proportional integral derivative control in individuals with type 1 diabetes showed good overnight performance, but with breakfast meal being the hardest to control and requiring supplemental carbohydrate to prevent hypoglycemia.

Objective: The aim of this study was to assess the ability of insulin feedback to improve the breakfast-meal profile.

Design and setting: We performed a single center study with closed-loop control over approximately 30 h at an inpatient clinical research facility.

Patients: Eight adult subjects with previously diagnosed type 1 diabetes participated.

Intervention: Subjects received closed-loop insulin delivery with supplemental carbohydrate as needed.

Main outcome measures: Outcome measures were plasma insulin concentration, model-predicted plasma insulin concentration, 2-h postprandial and 3- to 4-h glucose rate-of-change following breakfast after 1 d of closed-loop control, and the need for supplemental carbohydrate in response to nadir hypoglycemia.

Results: Plasma insulin levels during closed loop were well correlated with model predictions (R = 0.86). Fasting glucose after 1 d of closed loop was not different from nighttime target (118 ± 9 vs. 110 mg/dl; P = 0.38). Two-hour postbreakfast glucose was 132 ± 16 mg/dl with stable values 3-4 h after the meal (0.03792 ± 0.0884 mg/dl · min, not different from 0; P = 0.68) and at target (97 ± 6 mg/dl, not different from 90; P = 0.28). Three subjects required supplemental carbohydrates after breakfast on d 2 of closed loop.

Conclusions/interpretation: Insulin feedback can be implemented using a model estimate of concentration. Proportional integral derivative control with insulin feedback can achieve a desired breakfast response but still requires supplemental carbohydrate to be delivered in some instances. Studies assessing more optimal control configurations and safeguards need to be conducted.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Algorithms
  • Biosensing Techniques
  • Blood Glucose / metabolism*
  • Calibration
  • Diabetes Mellitus, Type 1 / drug therapy*
  • Dietary Carbohydrates / therapeutic use
  • Feedback, Physiological / physiology*
  • Female
  • Humans
  • Hypoglycemia / drug therapy
  • Hypoglycemic Agents / administration & dosage
  • Hypoglycemic Agents / therapeutic use*
  • Insulin / administration & dosage
  • Insulin / blood
  • Insulin / therapeutic use*
  • Male
  • Middle Aged
  • Models, Biological
  • Postprandial Period / physiology
  • Treatment Outcome
  • Young Adult


  • Blood Glucose
  • Dietary Carbohydrates
  • Hypoglycemic Agents
  • Insulin