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 the 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] $_{\mathrm{Pl}}$ . Validation of the EIS was performed by estimating the conductivity of the blood-mimicking fluid (BMF). The complete method was validated using the whole bovine blood, comparing the results to those obtained with standard instruments. The system was able to estimate the [Na] $_{\mathrm{Pl}}$ with sufficient accuracy (root-mean-square error (RMSE) of 3.0 mol/ $m^{3}$ 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.

中文翻译：

---

通过电容耦合电阻光谱法对血液透析过程中血浆钠浓度的无创估计

本文提出了一种紧凑、低成本、无创的系统，用于实时估计血浆钠浓度 ([Na] $_{Pl}$ ) 在血液透析 (HD) 会话期间以最先进的精度。它基于使用电容耦合阻抗传感单元和高频测量设备进行的电阻抗谱 (EIS)，两者都是定制的。处理 EIS 数据以推断细胞内液体的电阻，与光学血红蛋白传感器一起使用以估计 [Na] $_{\mathrm{Pl}}$ . EIS 的验证是通过估计血液模拟液 (BMF) 的电导率来进行的。使用全牛血对完整方法进行了验证，并将结果与​​使用标准仪器获得的结果进行比较。该系统能够估计 [Na] $_{\mathrm{Pl}}$ 具有足够的精度（均方根误差 (RMSE) 为 3.0 mol/ $m^{3}$ 关于参考数据]以提供临床有用的信息。概念验证硬件可以转换为便宜且紧凑的电路板，以集成到高清机器中。