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‘Artificial pancreas’ cuts children's nocturnal hypos

Closed-loop insulin system improves control of glucose in type 1 diabetes even after exercise

OnMedica staff

Friday, 05 February 2010

Closed-loop systems that directly link blood glucose measurements to insulin delivery could reduce the risk of nocturnal hypoglycaemia in children and adolescents with type 1 diabetes, research published today in The Lancet Online First concludes.

An "artificial pancreas" is designed to improve blood sugar control; it combines a continuous blood glucose monitoring device with an insulin pump to form a closed-loop system. Real-time glucose sensor data are analysed with a control algorithm that calculates the correct amount of insulin to be delivered.

The authors of this small study, from the University of Cambridge and Addenbrooke’s Hospital in Cambridge, conducted three randomised crossover studies of 19 children aged 5-18 years who had had type 1 diabetes for an average of 6.4 years. The children were allocated randomly to the closed-loop system or to the standard continuous subcutaneous insulin infusion pump.

Large evening meals and/or evening exercise are particularly likely to lead to hypoglycaemia in the early hours of the morning for people with diabetes. The children were monitored overnight in various situations: after slowly and rapidly absorbed evening meals and after taking early-evening exercise.

Two of the children dropped out at the start of the study, so 17 children were monitored during 54 nights in hospital – 33 closed-loop and 21 continuous infusion nights. The researchers compared nocturnal blood glucose control achieved using the closed-loop system with control achieved using patients’ standard insulin pump settings.

When children were using the "artificial pancreas", they maintained blood glucose levels in the normal range for 60% of the time, compared with 40% of the time using the standard infusion pump. They also suffered half as many occasions on which their blood glucose level fell below 3.9mmol/l compared with the standard pump.

No children suffered significant hypoglycaemia – a blood glucose level below 3.0mmol/l – while using the closed-loop system, whereas nine such events occurred among children using the standard pump.

The researchers are cautiously optimistic about the implications of their findings: “Closed-loop systems could transform management of type 1 diabetes, but their introduction is likely to be gradual, starting from straightforward applications such as shutting off of the pump at low glucose concentrations or overnight closed-loop delivery, proceeding to more complex applications providing 24-hour control. Overnight closed-loop delivery is appealing because it addresses the issue of nocturnal hypoglycaemia.”

The authors say their results would have been even better with more reliable glucose sensing, and they conclude: “Advancements in glucose-sensing technologies could further improve performance of closed-loop systems. Fully automated closed-loop delivery will need wireless data transmission to replace manual control of the pump by nurses. These technological steps are important but routine and should not affect closed-loop performance.”

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