Meal Disturbance Effect on Blood Glucose Control for Type 1 Diabetes Using Improved Hovorka Equations

摘要

Artificial pancreas (AP) device consists of continuous subcutaneous insulin infusion (CSII) pump, continuous glucose monitoring (CGM) sensor, CGM receiver and control algorithm which measure and regulate current blood glucose level (BGL) of Type 1 Diabetes (T1 D) patients in an automated manner. All components of the AP device are now well-established and readily available in the world market, however, its control algorithm is still at infant stage. This sometimes leads to insufficient or excessive amounts of insulin injected into their body causing hyperglycaemia or hypoglycaemia episodes, respectively. Mathematical equations of Hovorka model were widely used in the control algorithm; however, the model had shown somewhat lacking in terms of interaction and interrelation of selected parameters in its glucose-insulin dynamics. An attempt was made by previous researchers to modify certain subsystem equations in the Hovorka model involving glucose, plasma insulin, and insulin action subsystems by introducing additional parameters which, in turn, resulted in producing so-called improved Hovorka equations. This study aims to develop a computer algorithm in order to simulate the BGL of T1D patients during their meal intakes using the improved Hovorka equations via MATLAB and model predictive control (MPC). Results showed that different amounts of administered insulins(U_t) namely; 0.0003 U/min and 0.009 U/min were required to maintain the BGL within normal range (4.5 to 6 mmol/L) when the amounts of meals (D_g) taken by the patients were at 57g CHO and 86.5g CHO during lunch and dinner times, respectively. However, the BGL was above the normal range, i.e. hyperglycaemia when D_g and U_t were at 32g CHO and 0.035 U/min, respectively during breakfast time. In conclusion, this study has proven that the improved Hovorka equations can be used to simulate the meal disturbance effect on BGL for T1D patients.