Regional Pulmonary Time-Constant Maps based on EIT-Measurements

Abstract

This article introduces a promising approach of assessing a patient’s lung status non-invasively by analyzing regional time constants from electrical impedance tomography (EIT) sequences. The main idea of this approach depends on the fact that the lung can be modeled using gas-flow resistivity Rrs and lung compliance Crs, which describes the elasticity of the lung tissue. Thus, global lung mechanics may be approximated by a first order system in which the global time constant τrs = Rrs x Crs is a very important parameter. Based on EIT images, a noninvasive method that provides images of impedance distribution in the thorax allowing to quantify regional ventilation, we extend the concept of a first order mechanical lung model to regional time constant maps. We expect monitoring of regional time constants to be an important tool to assess lung status and to evaluate protective ventilation schemes.