An article published Online First and in an upcoming edition of The Lancet reports that the use of ‘artificial pancreas’ closed-loop insulin delivery systems can improve blood sugar control in patients with type 1 diabetes. In these systems the insulin is delivered in response to changing blood sugar levels. The article is the work of Dr Roman Hovorka, Institute of Metabolic Science, University of Cambridge and Addenbrooke’s Hospital, Cambridge, and colleagues.
The incidence of Type 1 diabetes has doubled during the past ten years. It is one of the most common chronic childhood diseases. Children and adolescents need lifelong insulin treatment to achieve glucose control that is sufficient to prevent long-term complications.
The combination of continuous glucose monitoring devices and insulin pumps can form closed-loop systems. Then insulin is delivered according to real-time sensor glucose data. It is directed by a control algorithm rather than pre-programmed rates. Few closed-loop prototypes have been developed. Progress has been delayed by suboptimum accuracy and reliability of monitoring devices, slow absorption of subcutaneously administered rapid-acting insulin analogues, and inadequate control algorithms. The authors intended to investigate in this study whether closed-loop systems reduce risk of nocturnal hypoglycaemia. Also, they examined whether good glucose control in children and adolescents can be achieved, even after variable evening meal intake and differing exercise patterns.
A total of seventeen children and teenagers were studied during 54 nights in hospital. They were aged between 5 and 18 years and all had type 1 diabetes. Researchers measured how well the artificial pancreas system controlled glucose levels compared with the children’s regular continuous subcutaneous insulin infusion (CSII) pump. This pump delivers insulin at preselected rates.
Nights when the children went to bed after eating a large evening meal or having done early evening exercise were included in the study. Both of these cases are challenging to manage. A large evening meal can lead to so-called “insulin stacking” and, as a result, a potentially dangerous drop in blood glucose levels later in the night. Late afternoon or early evening exercise can increase the body’s need for glucose in the early morning. Therefore, it can increase the risk of night time hypoglycaemia.
Findings indicated that children with the artificial pancreas maintained blood glucose levels in the normal range for 60 percent of the time, compared with 40 percent for the CSII pump. The artificial pancreas halved the time that blood glucose levels fell below 3.9mmol/l, which is the level considered as mild hypoglycaemia. It also prevented blood glucose falling below 3.0mmol/l, which is defined as significant hypoglycaemia, compared with nine hypoglycaemia events in the control studies.
The authors comment: “Our results show that overnight manual closed-loop insulin delivery can improve glucose control and reduce risk of hypoglycaemia in young patients with type 1 diabetes.”
They explain: “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-h control. Overnight closed-loop delivery is appealing because it addresses the issue of nocturnal hypoglycaemia.”
They write in conclusion: “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.”
In an associated note, Dr Eric Renard, Centre Hospitalier Universitaire de Montpellier, France, reviews the various technological issues surrounding the closed-loop insulin delivery. He comments: “Starting with overnight control before addressing control at meal times and during various activities is the most rational way forward. This seems to be the track to follow towards progressive implementation of automated insulin delivery at home.”
“Manual closed-loop insulin delivery in children and adolescents with type 1 diabetes: a phase 2 randomised crossover trial”
Roman Hovorka, Janet M Allen, Daniela Elleri, Ludovic J Chassin, Julie Harris, Dongyuan Xing, Craig Kollman, Tomas Hovorka, Anne Mette F Larsen, Marianna Nodale, Alessandra De Palma, Malgorzata E Wilinska, Carlo L Acerini, David B Dunger
DOI: 10.1016/S0140-6736(09)61998-X
The Lancet
Written by Stephanie Brunner (B.A.)