Monitoring of lung edema using focused impedance spectroscopy: a feasibility study

Abstract

Currently only ionizing or invasive methods are used in clinical applications for the monitoring of extracellular lung water. Alternatively a method called focused conductivity spectroscopy (FCS) is suggested, which aims at reconstructing a pulmonary edema index (PEIX) by measuring the electrical conductivity of the region of interest (ROI) at several frequencies. In contrast to electrical impedance tomography (EIT) a minimum number of strategically placed electrodes is used. The goals of this study were the analysis of the sensitivity for the PEIX, an estimate of the optimal electrode configuration and the determination of the required frequencies. In order to calculate the solution of the FCS forward problem a realistic 3D model of a human torso was developed containing both lungs, the heart, the liver and the thorax musculature. The bioelectrical properties for each compartment were described with appropriate tissue models which relate the conductivity spectra to physiological parameters. The PEIX was defined as the interstitial volume fraction of the alveolar septa. Furthermore the model includes 48 electrodes subdivided into three layers. The optimal electrode configuration was selected by minimizing the number of electrodes, among certain subsets of these electrodes. The analysis shows that eight to ten electrodes and six frequencies are theoretically sufficient to obtain a coefficient of variation.

Bioimpedance imaging: an overview of potential clinical applications

“…With this approach, a range of frequencies (typically 9.6 kHz to 1.2 MHz) can be used to produce static images of the thorax. 8 Frequency ranges greater than this have been reported (up to 10 MHz) for imaging breast and prostate cancers 9 where most of the ion flow is within the intercellular region. For thorax imaging, EITS enables the analysis of changes in tissue impedance with respect to frequency after reconstruction for subjects where breath was held at maximum inspiration and at maximum expiration.…”

Principles of electrical impedance tomography and its clinical application

“…After a first wave of articles in the mid-1990s of the last century, the technology was not used in a published study on thoracic organs until 2005 when Mayer et al (46) published results of a feasibility study aiming to quantify a pulmonary edema index. They developed a new device and reduced measurement complexity to eight to ten "strategically placed electrodes" and to six distinct ac frequencies.…”

Design and development of a low-cost arduino-based electrical bioimpedance spectrometer

“…This device can be used to estimate human body compositions, through information on total body water, extracellular fluid and intracellular fluid, fat-free mass, and fat mass from its impedance data. [ 1 2 3 ] BIS analysis is capable of giving immense amount of helpful information on physiological conditions such as lymphedema,[ 4 ] pulmonary edema,[ 5 ] diabetic,[ 6 ] tongue cancer,[ 7 ] ischemia,[ 8 ] skin cancer,[ 9 ] and intramuscular tumors. [ 10 ] Since there is an increasing demand of BIS usage in both hospitals and homes, it is desirable to advance an improvement for a more practical BIS.…”