An Upgraded Version of a Bioimpedance Transducer for Non-Invasive Monitoring Artificial Insulin Bioavailability After Subcutaneous Administration

A new version of a bioimpedance transducer is proposed for non-invasive monitoring the insulin bioavailability after subcutaneous administration. Both the firmware and the hardware were upgraded in order to improve safety, wearability and metrological performances of the device. As far as the firmware upgrade is concerned, a new block to manage a Bluetooth low energy 5.0 channel for data transmission was implemented. As far as the hardware upgrade is concerned, a shortening of the cables connecting the measurement system to the measurand was realized to minimize the inductive effect. Moreover, a feasibility of a new block to be added in the architecture of the bioimpedance meter was realized. In particular, the new block is able to identify and calibrate the residual cable effect on impedance measurements, by means of a builder of equivalent electrical circuits. After presenting the hardware, the firmware, and the software of the upgraded device, the metrological characterization during (i) laboratory (on passive electrical components), and (ii) in-vivo (on an human subject) experiments is reported. In laboratory tests, a mean percentage deterministic error of 0.20 % and 0.19 % was obtained for impedance magnitude and phase, respectively and an improvement of one order of magnitude was achieved respect to the previous version of the transducer. Regarding the in vivo-measurements, in addition to the impedance module trend already available with the old version of the transducer, it was possible to acquire a phase diagram in accordance with literature.