Variability in EIT Images of Lung Ventilation as a Function of Electrode Planes and Body Positions

Abstract

This study is aimed at investigating the variability in resistivity changes in the lung region as a function of air volume, electrode plane and body position. Six normal subjects (33.8 ± 4.7 years, range from 26 to 37 years) were studied using the Sheffield Electrical Impedance Tomography (EIT) portable system. Three transverse planes at the level of second intercostal space, the level of the xiphisternal joint, and midway between upper and lower locations were chosen for measurements. For each plane, sixteen electrodes were uniformly positioned around the thorax. Data were collected with the breath held at end expiration and after inspiring 0.5, 1.0, or 1.5 liters of air from end expiration, with the subject in both the supine and sitting position. The average resistivity change in five regions, two 8x8 pixel local regions in the right lung, entire right, entire left and total lung regions, were calculated. The results show the resistivity change averaged over electrode positions and subject positions was 7-9% per liter of air, with a slightly larger resistivity change of 10 % per liter air in the lower electrode plane. There was no significant difference (p>0.05) between supine and sitting. The two 8x8 regions show a larger inter individual variability (coefficient of variation, CV, is from 30% to 382%) compared to the entire left, entire right and total lung (CV is from 11% to 51%). The results for the global regions are more consistent. The large inter individual variability appears to be a problem for clinical applications of EIT, such as regional ventilation. The variability may be mitigated by choosing appropriate electrode plane, body position and region of interest for the analysis.

Global and regional lung function in cystic fibrosis measured by electrical impedance tomography

“…As recent studies state, electrode positioning in more cranial levels than 5–6th intercostal space might be relevant, especially characterizing lower lung volumes during forced expiration . Concerning electrode positioning, especially in childhood and upright position during forced expiration maneuvers, more studies should follow with linearity testing by simultaneous pneumotachography or body plethysmography, preferably combined with MRI to consider organ‐ and electrode movement during forced in‐ and expiration maneuvers.…”

“…Three dimensional EIT systems are still under development with the aim of EIT displaying the whole lung . Zhang et al analyzed variability in EIT images of lung ventilation as a function of three electrode belts, placed between the 2nd intercostal space to xiphisternal and found consistent results for global EIT. Based on this, it is unclear if global EIT data displayed the whole lung in our pediatric subjects with a body length of 112–174 cm and thorax circumference 53–70 cm.…”

Effect of Position Change From the Bed to a Wheelchair on the Regional Ventilation Distribution Assessed by Electrical Impedance Tomography in Patients With Respiratory Failure

“…The sample size was estimated based on ROI4 (ventilation in the dorsal region). The µt (SD) and µc (SD) were 4.1 (0.98) and 5.2 (1.87) based on a previous study (19), respectively, with a correlation coefficient of 0.6. The minimum sample size to obtain a study power of 90% was 29 pairs.…”

Fully printed, stretchable and wearable bioimpedance sensor on textiles for tomography

“…The rise in air volume causes the resistivity of the lungs to increase further. [66][67][68]. This makes EIT a notable technique to assess the breath functioning by monitoring the size and shape of the lungs in a real-time manner.…”

“…The lung is one of the largest organs in the human body and it has got a much higher resistivity as compared to other soft tissues. The rise in air volume causes the resistivity of the lungs to increase further [63][64][65]. This makes EIT a notable technique to assess the breath functioning by monitoring the size and shape of the lungs in a real-time manner.…”