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

The effect of insulin feedback on closed loop glucose control.

Author information

1
Children's Hospital Boston, 300 Longwood Avenue, Boston, Massachusetts 02115, USA. garry.steil@childrens.harvard.edu

Abstract

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.

PMID:
21367930
PMCID:
PMC3085208
DOI:
10.1210/jc.2010-2578
[Indexed for MEDLINE]
Free PMC Article

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