Endocrine Abstracts

Devices for continuous glucose monitoring (CGM) measure interstitial glucose as a marker of changes in blood glucose. Although still lacking the accuracy of blood glucose meters, the CGM devices currently available have improved glucose control. The established technique of continuous subcutaneous insulin infusion (CSII) uses a portable electromechanical pump to mimic non-diabetic insulin delivery, infusing insulin at pre-selected rates. Essentially, a slow basal rate is achieved throughout 24 h, with subject-activated boosts at mealtimes.

CGM devices and insulin pumps can be combined to form closed loop systems. Insulin is then delivered according to real-time glucose sensor data, as directed by a control algorithm, rather than at pre-programmed rates. Only a few closed loop system prototypes have been tested clinically, and progress has been hindered by the suboptimal accuracy and reliability of CGM devices, the relatively slow absorption of subcutaneously administered ‘rapid’ acting insulin analogues, and the lack of adequate control algorithms. We believe that these problems can be overcome with commercially available CGM and pump delivery systems in combination with advanced control algorithms, such as those based on the model predictive control.

Fully closed loop systems may require ultra-fast insulin analogues, dual hormone approaches or novel methods to accelerate insulin absorption such as dermal delivery. Clinical infrastructure to support the use of closed loop systems will build on existing support for continuous glucose monitors and insulin pumps. This includes the training of healthcare professionals and users, and the establishment of reimbursement strategies together with health economics assessments. Larger outcome trials involving closed loop systems are required in the future.