Universidad Nacional de Colombia, Facultad de Minas, Grupo GITA, Medellin, Colombia.
Universidad EAN, Facultad de Ingeniería, Grupo ONTARE, Bogotá, Colombia.
Front Endocrinol (Lausanne). 2022 Feb 21;13:796521. doi: 10.3389/fendo.2022.796521. eCollection 2022.
The aim of control strategies for artificial pancreas systems is to calculate the insulin doses required by a subject with type 1 diabetes to regulate blood glucose levels by reducing hyperglycemia and avoiding the induction of hypoglycemia. Several control formulations developed for this end involve a safety constraint given by the insulin on board (IOB) estimation. This constraint has the purpose of reducing hypoglycemic episodes caused by insulin stacking. However, intrapatient variability constantly changes the patient's response to insulin, and thus, an adaptive method is required to restrict the control action according to the current situation of the subject. In this work, the control action computed by an impulsive model predictive controller is modulated with a safety layer to satisfy an adaptive IOB constraint. This constraint is established with two main steps. First, upper and lower IOB bounds are generated with an interval model that accounts for parameter uncertainty, and thus, define the possible system responses. Second, the constraint is selected according to the current value of glycemia, an estimation of the plant-model mismatch, and their corresponding first and second time derivatives to anticipate the changes of both glucose levels and physiological variations. With this strategy satisfactory results were obtained in an adult cohort where random circadian variability and sensor noise were considered. A 92% time in normoglycemia was obtained, representing an increase of time in range compared to previous MPC strategies, and a reduction of time in hypoglycemia to 0% was achieved without dangerously increasing the time in hyperglycemia.
人工胰腺系统的控制策略旨在通过减少高血糖和避免低血糖诱发来计算 1 型糖尿病患者所需的胰岛素剂量，以调节血糖水平。为此目的开发的几种控制配方涉及到由胰岛素 aboard（IOB）估计给出的安全约束。该约束的目的是减少由于胰岛素叠加引起的低血糖发作。然而，个体内变异性不断改变患者对胰岛素的反应，因此需要一种自适应方法根据患者的当前情况限制控制作用。在这项工作中，脉冲模型预测控制器计算的控制作用通过安全层进行调制，以满足自适应 IOB 约束。该约束通过两个主要步骤建立。首先，使用考虑参数不确定性的区间模型生成上下 IOB 边界，从而定义可能的系统响应。其次，根据当前血糖值、植物模型失配的估计值及其相应的一阶和二阶时间导数来选择约束，以预测血糖水平和生理变化的变化。使用这种策略，在考虑了随机昼夜节律变化和传感器噪声的成年队列中获得了令人满意的结果。获得了 92%的正常血糖时间，与之前的 MPC 策略相比，范围时间增加，并且将低血糖时间减少到 0%，而不会危险地增加高血糖时间。
