Effect of Electrode Belt and Body Positions on Regional Pulmonary Ventilation- and Perfusion-Related Impedance Changes Measured by Electric Impedance Tomography.

Elin Ericsson,Folke Sjöberg,Erik Tesselaar

doi:10.1371/journal.pone.0155913

Abstract

Ventilator-induced or ventilator-associated lung injury (VILI/VALI) is common and there is an increasing demand for a tool that can optimize ventilator settings. Electrical impedance tomography (EIT) can detect changes in impedance caused by pulmonary ventilation and perfusion, but the effect of changes in the position of the body and in the placing of the electrode belt on the impedance signal have not to our knowledge been thoroughly evaluated. We therefore studied ventilation-related and perfusion-related changes in impedance during spontaneous breathing in 10 healthy subjects in five different body positions and with the electrode belt placed at three different thoracic positions using a 32-electrode EIT system. We found differences between regions of interest that could be attributed to changes in the position of the body, and differences in impedance amplitudes when the position of the electrode belt was changed. Ventilation-related changes in impedance could therefore be related to changes in the position of both the body and the electrode belt. Perfusion-related changes in impedance were probably related to the interference of major vessels. While these findings give us some insight into the sources of variation in impedance signals as a result of changes in the positions of both the body and the electrode belt, further studies on the origin of the perfusion-related impedance signal are needed to improve EIT further as a tool for the monitoring of pulmonary ventilation and perfusion.

Highlights

Ventilator-induced or ventilator-associated lung injuries (VILI/VALI) contribute to increased morbidity and mortality, and the choice of optimal ventilator settings for each individualPLOS ONE | DOI:10.1371/journal.pone.0155913 June 2, 2016Regional Pulmonary Ventilation and Perfusion Assessed by Electrical Impedance Tomography (EIT) patient to avoid associated complications is a constant challenge in critical care
We hypothesized that if we studied changes in impedance related to ventilation and perfusion using an EIT-system with 32 electrodes, with the electrodes at three different thoracic levels and the body in five different positions, we could provide insights into how regional differences in ventilation and perfusion are reflected in the impedance signals
When the subject was supine, ΔZV was larger in the anterior regions of interest (ROI) than in the posterior ROI at all electrode belt positions, but the difference was significant only at i2

Summary

Introduction

Ventilator-induced or ventilator-associated lung injuries (VILI/VALI) contribute to increased morbidity and mortality, and the choice of optimal ventilator settings for each individual. Regional Pulmonary Ventilation and Perfusion Assessed by EIT patient to avoid associated complications is a constant challenge in critical care. There is a demand for a bedside technique that can help physicians to optimize the settings [1,2,3]. During the past 30 years, Electrical Impedance Tomography (EIT) has been developed as a non-invasive, radiation free, bedside monitoring technique for assessing regional distribution of pulmonary ventilation and perfusion [4,5,6,7,8]. The impedance of the lungs changes continuously as a result of both ventilation and perfusion. While ventilation-related changes in impedance are caused by regional differences in air volume, the exact mechanisms behind the perfusion-related changes in impedance remain less clear [10]

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