Glycemic Control Strategy Based on an Impulsive MPC With Safety Layer Coupling for IOB Limitation

Insulin stacking is one of the major concerns in intensive insulin therapy for type 1 diabetes. Despite the development of several control strategies for constraining the insulin-on-board (IOB), the benefits and drawbacks of this type of constraint under hypo- and hyperglycemia sensitivity scenarios have not been deeply analyzed for model-based controllers. Here, a safety layer based on IOB estimation is coupled with an impulsive offset-free zone model predictive control to tackle this problem. First, the resulting glycemic behavior of applying the safety layer under different scenarios of physiological variations are discussed. And then, simple rules for adapting the safety layer are developed. The envisioned strategy takes advantage of the plant-model mismatch estimation to determine when physiological variations in a subject are inducing hypoglycemia or hyperglycemia, and thus, the IOB safety layer can be tightened or released according to the sign of the estimated mismatch. The performance of the strategy was assessed in-silico on a cohort of 10 adult patients under challenging scenarios considering parameter variations of ±30%, a circadian insulin sensitivity, and sensor noise.