A parametric model for the changes in the complex valued conductivity of a lung during tidal breathing

TL;DR

This paper develops a parametric model based on homogenization theory to describe how the complex conductivity of a lung changes during tidal breathing, aiding lung imaging and clinical monitoring.

Contribution

It introduces a novel parametric model linking lung conductivity changes to alveolar air-filling using homogenization theory, validated with numerical and clinical EIT data.

Findings

The model predicts a linear relationship between real and imaginary conductivity changes.

The loss cotangent remains approximately constant during tidal breathing.

Numerical and clinical data support the model's accuracy and potential clinical utility.

Abstract

Classical homogenization theory based on the Hashin-Shtrikman coated ellipsoids is used to model the changes in the complex valued conductivity (or admittivity) of a lung during tidal breathing. Here, the lung is modeled as a two-phase composite material where the alveolar air-filling corresponds to the inclusion phase. The theory predicts a linear relationship between the real and the imaginary parts of the change in the complex valued conductivity of a lung during tidal breathing, and where the loss cotangent of the change is approximately the same as of the effective background conductivity and hence easy to estimate. The theory is illustrated with numerical examples, as well as by using reconstructed Electrical Impedance Tomography (EIT) images based on clinical data from an ongoing study within the EU-funded CRADL project. The theory may be potentially useful for improving the imaging algorithms and clinical evaluations in connection with lung EIT for respiratory management and monitoring in neonatal intensive care units.