Monitoring Plasma Glucose Concentration from Interstitial Glucose Measurements for Patients at the Intensive Care Unit

Abstract

The glucose homeostasis is responsible for regulating the blood glucose concentration around 100 mg / dl. When this physiological mechanism is broken due to the inability of the pancreas to produce insulin, an increase of the blood glucose levels is produced and patients are diagnosed with Diabetes Mellitus. In recent years, some research has directed towards the creation of an artificial pancreas that allows automatically the regulation of glucose levels in blood. However, one of the greatest difficulties in achieving this objective, is that not all internal variables of the mathematical model associated with the controller can be measured directly by physical sensors, either because there are no sensors for all variables, because existing sensors are not commercial, or because they are not viable from the economic point of view. Therefore, it is necessary to use estimation schemes to reconstruct the unknown states by measuring the interstitial glucose , in the case of the glucose-insulin system. However, the delay between plasma glucose and interstitial glucose has a negative effect on the performance of state estimators, so the treatment of this delay is necessary either from the modeling process of the glucose-insulin system or by a modification of the estimation techniques. According to the results it can be inferred that in the scenario at which the concentration of blood glucose is assumed, the estimated values have upper and lower peaks that are unrealistic from a physiological point of view, this due to the negative effect of the delay in measurement. Otherwise, in the scenario where the interstitial glucose concentration is considered as the measured variable, including dynamics of the interstitial glucose, the estimator exhibits better performance and rapid convergence to the real states.