HYPOGLYCEMIA PREVENTION IN CLOSED-LOOP GLYCEMIC CONTROL VIA CONSTRAINTS IN THE GLUCOSE SLOPE

NICOLÁS ROSALES; HERNAN DE BATTISTA; FABRICIO GARELLI; FABIAN LEON VARGAS

Viena

Conferencia; 11th International Conference on Advanced Technologies & Treatments for Diabetes; 2018

Within the development of closed-loop glucose controllers for type 1 diabetes mellitus, one of the major risks is the insulin induced hypoglycemia that can be produced due to controller overreaction. Here a supervisory methodology is proposed for the prevention of hypoglycemia, which differs from previous work (Revert et al., IEEE TBME 2013) by considering a limitation on the controlled variable or output of the system.The GSAFE (Glucose-based safety auxiliary feedback element) is a security layer based on the Sliding Mode Reference Conditioning technique. By means of a reduced-order glucose estimator, the GSAFE modifies the reference of the main controller to regulate the slope with which the glucose decreases, thereby limiting the insulin delivered by the controller. The proposed technique can be applied to any control algorithm, both PID and MPC.The algorithm was tested in a platform based on the UVa/Padova T1D Simulator (3-meals scenario with varying insulin sensitivity) with the controller given in Palerm CMPB 2011. Different configurations of the main controller and GSAFE were tested. Preliminary results show that the amount of hypoglycemic events and time spent in hypoglycemia were considerably reduced when applying the GSAFE, even for aggressive controller configurations. In particular, low glucose values were avoided in the late postpandrial period.The promising results provided by the novel GSAFE auxiliary layer in simulations lead to consider it in the next clinical trials in Argentina, in order to prevent hypoglycemic events. After the successful first trials carried out this year, the GSAFE could be implemented as a layer over the closed-loop controller developed by the group to modulate the input of the controller so that the insulin infusion decreases until a given glycemic rate of change is not exceeded.