Non-Invasive Estimation of Plasma Sodium Concentration During Hemodialysis via Capacitively-Coupled Electrical Impedance Spectroscopy

This paper presents a compact, low-cost, and non-invasive 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 blood-mimicking 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 an

Finite-element modeling of time-dependent sodium exchange across the hollow fiber of a hemodialyzer by coupling with a blood pool model

INTRODUCTION: Hollow fiber models describe the exchange of solutes between blood and dialysate across the membrane of a single fiber of the hemodialysis filter (hemodialyzer). This work aims to develop a new approach to simulate the solute exchange in a hollow fiber in a dynamic and realistic way. Sodium was chosen as our solute of interest due to its importance in hemodialysis as an osmotic regulator. METHODS: A 2-dimensional (2D) hollow fiber model based on the finite element method (FEM) is coupled to a simple blood pool model to dynamically update the concentration of the solute entering the dialyzer. The resulting coupled model maintains the geometrical detail of the 2D fiber representation and gains a dynamic, blood-side inlet solute concentration. In vitro dialysis sessions were carried out for model validation, by implementing a combination of blood volume loss and/or sodium concentration steps. Plasmatic sodium concentration was recorded by blood gas sampling. Dialysate inlet and outlet conductivities were continuously recorded. RESULTS: Simulated plasmatic sodium concentration was compared with data from the blood gas samples. A mean error of 1.76 ± 1.03 mM was found for the complete dataset, along with a 3.87 mM maximum error. The simulated outlet dialysate sodium concentration was compared with the recorded outlet dialysate conductivity: a very high correlation was found on the whole dataset (R2 = 0.992). CONCLUSIONS: Coupling our FEM hollow fiber model to a simple blood pool model proved to be an effective approach for dynamical analysis of the properties of the hemodialyzer

The French do it better. The distributive effect of introducing French family fiscal policies in Italy.

Italy has one of the lowest fertility rates in the world. A solution, often advocated to incentivize fertility, could be to reform the Italian tax and benefit system taking inspiration from the French fiscal family treatment. This would imply to introduce the quotient system, where taxation is not on an individual basis, as in Italy, but the tax applies to the family as a whole, and to introduce the cash- benefits provided in France to families. The purpose of our paper is to assess the distributive effects of such a fiscal reform. We estimate these effects using MicroReg, a static microsimulation model able to predict the first order effects of tax and benefit system reforms. We show that a shift to the French income tax system would lead to decreased income inequality and a substantial tax reduction for households with three children, especially those who are medium- high income. The new income tax would result in a substantial disincentive to female labour supply, albeit mitigated by greater progressivity in favour of low income groups with children. Moreover, adopting French- style family benefits would further reduce inequality and increase disposable income for households with at least two children. However, those with just one child would be slightly worse off