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

Abstract

Artificial pancreas (AP) device consists of continuous subcutaneous insulin infusion (CSII)pump, continuous glucose monitoring (CGM) sensor, CGM receiver amd control algorithm which measure and regulate current blood glucose level (BGL) of type 1 diabetes (T1D) patients in automated manner. All components of the AP device are now well-established and readily avaialble in the 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 workers to modify certain subsytem 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 oder to simulate the BGL of T1D patient during their meal intakes using the improved Hovorka equations via MATLAB and model based predictive control (MPC). Resuls showed that different amounts of administered insulin (Ut) 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 (DG) taken by the patient 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 DG and Ut 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.