'Institute of Electrical and Electronics Engineers (IEEE)'
Abstract
This paper presents a compact, low-cost, and noninvasive system for real-time estimation of plasma sodium
concentration ([Na]Pl) during a hemodialysis (HD) session with
state-of-the-art accuracy. It is based on electrical impedance
spectroscopy (EIS) performed with a capacitively-coupled
impedance sensing cell and a high-frequency measurement
device, both custom-built. The EIS data are processed to infer the
resistance of the liquid inside the cell, which is used together with
an optical hemoglobin sensor to estimate the [Na]Pl. Validation of
the EIS was performed by estimating the conductivity of bloodmimicking fluid (BMF). The complete method was validated
using whole bovine blood, comparing the results to those
obtained with standard instruments. The system was able to
estimate the [Na]Pl with sufficient accuracy (RMS error of 3.0
mol/m3 with respect to reference data) to provide clinically useful
information. The proof-of-concept hardware can be converted to
a cheap and compact circuit board for integration into an HD
machine
