Practical constraint definition in safety schemes for artificial pancreas systems

Introduction: Artificial pancreas systems usually define an insulin-on-board constraint ((IOB) over bar) for safety schemes to limit the insulin infusion and avoid hypoglycemia during the closed-loop performance. Several methods have been proposed with impractical considerations requiring information from the prandial events or complex procedures for regular ambulatory use. Methods: This paper presents a simple method that consists of two novel rules that allow finding an (IOB) over bar based only on common clinical parameters that do not require patient intervention during system operation. The method robustness was extensively evaluated using a control system coupled to a safety layer under several demanding scenarios implemented on the FDA-approved simulator for preclinical studies. Results: The method maintains a safe performance, even in the face of interpatient variability, hybrid and fully automatic implementations of an artificial pancreas system, and uncertain settings. Both proposed rules work as effectively or even better and without the patient intervention than other methods that have already been clinically validated. Conclusion: This method can be used to define a constant (IOB) over bar that ensures performance and safety of the control system, even under scenarios with incorrect clinical data. Unlike other methods, this method only requires reliable information that is easily obtained from the patient, such as their total daily dose of insulin or body mass.