Non-invasive impedance based continuous glucose monitoring system

The aim of this work is to describe the ongoing development of a non-invasive continuous glucose monitoring system based on Impedance Spectroscopy (IS). Previous work has shown the importance of taking a multi-sensor approach to aid in the compensation of various potentially perturbing parameters, such as the impact of environmental/body temperature, changes in the blood perfusion of the measured skin, underlying tissue volume and changes in the sensor / skin contact due to movements. Here we describe how this multi-sensor concept has been implemented into an integrated functional model (FM). In our recent studies, this integrated FM has been tested in an experimental clinical study in subject groups with patients with Diabetes type I/II (D) and healthy subjects (ND). The relation between changes in the blood glucose concentration and the impedance of the skin / underlying tissue has been investigated under controlled clinical conditions. The clinical study protocol allowed the use of an intravenous glucose clamp technique to control the subject's glucose concentration and enabled two hyperglycemic episodes to be achieved within a ten hour study day. Here we report on the experimental findings and discuss the developments related to this IS based measurement technique. The work indicates that further quantitative and qualitative analysis of the interaction of electromagnetic fields (EMF) with specific skin tissue layers will help in the characterisation of in-vivo biological systems (i.e. solving the inverse profile of the skin in order to determine the dielectric properties of individual layers in the skim) or in the detection and correction of movement artifacts as discontinuities in a measured time series.