Safe tuning and improvement of the postprandial response in closed-loop blood glucose controllers.

LEÓN-VARGAS, FABIAN; FABRICIO GARELLI; HERNÁN DE BATTISTA; JOSEP VEHÍ

Viena

Conferencia; 7th International Conference on Advanced Technologies & Treatments for Diabetes; 2014

Kenes

This work presents a performance evaluation of a novel safetylayer for Type 1 diabetes closed-loop glucose controllers, the socalledSAFE loop [1], and shows that it can be employed to safelyre-tune such controllers. Traditional therapies are prone to showpoor glucose regulation especially in the postprandial periodowing to both physiological and technological limitations.Regarding this problem, a single control loop for glucoseregulation has to be tuned to: 1) minimize the postprandial excursion,and 2) avoid late hypoglycemia. Due to the intrinsiclimitations of the problem, a trade-off between postprandial peakand late hypoglycemia risk is implicit. The SAFE outer loopmonitors the estimated amount of insulin on board, and accordingto a unique constraint which can be adjusted with clinicalcriteria, modifies the control action if the constraint is close to beviolated. Here, a very challenging test scenario for the SAFElayer is implemented including mixed meals, diurnal and day-todaytime-varying metabolic changes, inherent drawbacks insensor and actuator, and other realistic conditions.The results show a significant reduction of hypoglycemiaevents when SAFE is added, regardless the closed-loop glucosecontroller. The SAFE approach becomes not only a safety??net??, but it also allows re-tuning the inner controller so that avery good postprandial response can be obtained (close to thegiven by an aggressive controller) while maintaining safety(even better than a relaxed controller).[1] Revert et al. Safety Auxiliary Feedback Element for theArtificial Pancreas in Type 1 Diabetes. IEEE-TBE, 60(8):2113:22, 2013.