Probing deep lung regions using a new 6-electrode tetrapolar impedance method

Abstract

Probing deep regions of the lung using electrical impedance is very important considering the need for a low cost and simple technique, particularly for the low and medium income countries. Because of complexity and cost, Electrical Impedance Tomography is not suitable for this envisaged application. The simple Tetrapolar Impedance Measurement (TPIM) technique employing four electrodes is the age old technique for bioelectrical measurements. However, it has its limitations in respect of organ localisation and depth sensitivity using skin surface electrodes. Recently, a new 6-electrode TPIM with two current electrodes but two pairs of appropriately connected potential electrodes positioned on the front and back of the thorax, proposed by one of the authors, came with a promise. However, this work gave a qualitative proposal based on concepts of physics and lacked a quantitative evaluation. In order to evaluate the method quantitatively, the present work employed finite element method based COMSOL Multiphysics software and carried out simulation studies using this new 6-electrode TPIM and compared the results with those from 4-electrode TPIM, with electrodes applied either on the front or at the back of the thorax for the latter. Initially, it carried out a sensitivity distribution study using a simple rectangular volume conductor which showed that the 6-electrode TPIM gives better depth sensitivity throughout the lung region. Next it used a near life like thorax model developed by another of the authors earlier. Using this model, extensive studies were carried out to quantify the overall sensitivity over a target lung region, the contribution of the target lung to the total measured impedance, and several other parameters. Through these studies, the 6-electrode TPIM was established on a stronger footing for probing deep regions of the lungs.

Sensitivity study of a locally developed six electrode focused impedance method

“…Although much work has already been done on FIM by the innovating group in Dhaka and elsewhere [ 11 ], the main motivation of the present work was to design and develop the whole instrumentation locally in Nepal and evaluation of the system using a simple experimental phantom, again designed, and developed locally in Nepal. The instrumentation developed and tested gave satisfactory performance and was published earlier [ 9 ].…”

Regional Pulmonary Ventilation Assessment Method and System Based on Impedance Sensing Information from the Pentapulmonary Lobes

“…Reference [27] integrated focused impedance techniques with traditional spirometry to facilitate the straightforward evaluation of restrictive lung ventilation disorders. Additionally, reference [28] explored the depth sensitivity of impedance measurements in lung tissues using a six-electrode model, suggesting that focused impedance measurements in specific lung regions can be achieved by designing an appropriate driven measurement model.…”