Closed-loop control of blood glucose levels in critically ill patients

A closed-loop control system was constructed for automatic intravenous infusion of insulin to control blood sugar levels (BSL) in critically ill patients. We describe the development of the system. A total of nine subjects were recruited to clinically test the control system. In the patients who underwent closed-loop control of BSL, the controller managed to control only one patient's glycaemia without any manual intervention. The average BSL attained during closed-loop control approached the target range of 6-10 mmol/l, and had less deviation than when BSL had been maintained manually. We conclude that closed-loop BSL control using a sliding scale algorithm is feasible. The main deficiency in the current system is unreliability of the subcutaneous glucose sensor when used in this setting. This deficiency mandates high vigilance during use of the system as it is being developed.