Researchers have assessed in a phase II study whether a closed-loop insulin delivery system could control overnight blood glucose in young people with type 1 diabetes. With this system, continuous information from a subcutaneously inserted needle-type glucose sensor is used to modulate subcutaneous insulin delivery from a portable pump according to a model predictive controller.

The study involved 19 patients aged 5 to 18 years with diabetes of 6.4 years duration, who took part in the following three randomised crossover studies:

• Standard continuous subcutaneous insulin infusion and closed-loop delivery (n=13; APCam01)

• Closed-loop delivery after rapidly and slowly absorbed meals (n=7; APCam02)

• Closed-loop delivery and standard treatment after exercise (n=10; APCam03)

During closed-loop nights, glucose measurements were fed every 15 minutes into a control algorithm calculating rate of insulin infusion, and a nurse adjusted the insulin pump. During control nights, patients' standard pump settings were applied. The primary outcomes were time for which plasma glucose concentration was 3.91 to 8.00mmol/L or 3.90mmol/L or lower.

According to the per protocol analysis of 17 patients studied for 33 closed-loop and 21 continuous infusion nights, primary outcomes did not differ significantly between treatment groups:

• APCam01 (12 analysed; target range, median 52% closed loop vs. 39% standard treatment, p=0.06; ≤3.90 mmol/L, 1% vs. 2%, p=0.13)

• APCam02 (6 analysed; target range, rapidly 53% vs. slowly absorbed meal 55%, p=0.97; ≤3.90 mmol/L, 0% vs. 0%, p=0.16])

• APCam03 (9 analysed; target range 78% closed loop vs. 43% control, p=0.0245, not significant at corrected level; ≤3.90 mmol/L, 10% vs. 6%, p=0.27)

A secondary analysis of pooled data documented increased time in the target range (60% vs 40%; p=0.0022) and reduced time for which glucose concentrations were 3.90 mmol/L or lower (2.1% vs 4.1%, p=0.0304) with closed-loop delivery. In addition, no events with plasma glucose concentration <3.0 mmol/L were recorded during closed-loop delivery, compared with 9 events during standard treatment.

The researchers conclude from these preliminary findings that “closed-loop systems could reduce risk of nocturnal hypoglycaemia in children and adolescents with type 1 diabetes.”