Performance evaluation of electrode design and material for a large animal electrical impedance tomography belt

Electrical impedance tomography (EIT) produces lung ventilation images via a thoracic electrode belt. Robust electrode design and material, providing low electrode skin contact impedance (SCI), is needed in veterinary medicine. The aim of this study was to compare three EIT electrode designs and materials.

Simulations of cylindrical, rectangular and spiked electrode designs were used to evaluate electrode SCI as a function of electrode size, where skin contact was uneven. Gold-plated washers (E_GW ), zinc-plated rivets (E_ZR ) and zinc-galvanised spikes (E_ZS ) were assigned randomly on two interconnected EIT belts. Gel was applied to the cranial or caudal belt and placed on 17 standing cattle. SCI was recorded at baseline and 3, 5, 7, 9 and 11 minutes later.

Simulations that involved electrodes with a greater skin contact area had lower and more uniform SCI. In cattle, SCI decreased with all electrodes over time (p < 0.01). Without gel, no difference was found between E_GW and E_ZS , while SCI was higher for E_ZR (p < 0.03). With gel, SCI was lower in E_GW and E_ZR (p < 0.026), with the SCI in E_GW being the lowest (p < 0.01).

Low numbers of animals and static electrode position may affect SCI.

Electrode design is important for EIT measurement, with larger electrode designs able to compensate for the use of less conductive materials. Gel is not necessary to achieve acceptable SCI in large animals.