Subcutaneous versus intra-peritoneal insulin delivery in the artificial pancreas

Research and development for the realization of a commercial artificial pancreas (AP) device, for ambulatory patients suffering from type 1 diabetes, has overwhelmingly focused on subcutaneous (SC) insulin infusion and subcutaneous (SC) blood glucose measurement. There is a substantial time-lag associated with insulin absorption, via the SC route, which makes automatically controlled blood glucose regulation an extremely difficult problem. Technological developments are trying to reduce this SC-associated time-lag. Faster insulin absorption simplifies the control problem potentially leading to better regulation of blood glucose levels. The corresponding reduction in both hypoglycaemic and hyperglycaemic events, due to the improved control, also reduces the safety risk to the patient. This work considers the possible performance improvement that could be achieved using an alternative approach to insulin infusion - intra-peritoneum insulin infusion. The presented in silico performance comparison, between a SC-based insulin injection AP and an IP-based insulin infusion AP, uses Model Predictive Control (MPC) as the feedback control algorithm. The IP-based AP, using just feedback MPC, is shown to outperform the SC-based AP with a more complicated feedback MPC and feedforward control architecture. The possible practical implications of such a result are discussed.