Parametric EIT vs. intra-thoracic impedance for monitoring pulmonary edema using a two dimensional theoretical model of the thorax

Detection of pulmonary edema using an implantable cardiac resynchronisation device is possible with the bio-impedance technique. In this study, the ability of the parametric electrical impedance tomography (pEIT) scheme and the intra-thoracic impedance technique to monitor lung fluid status in patients with implantable pacemaker was compared using simulation in a theoretical model of the thorax. Applying pEIT scheme and the intra-thoracic impedance technique in a computerised two dimensional model of the thorax demonstrates that the pEIT converges to the exact values of lung conductivity with sensitivity of 1,400% change/S/m. The intra-thoracic impedance has lower sensitivity of 550% change/S/m for edema in both lungs and in case of unilateral left lung edema, and very low sensitivity of 26% change/S/m when unilateral right lung edema is present. When additive white Gaussian noise is added, the pEIT method requires an SNR greater than 70 dB. The simulation results suggest that the pEIT may be applicable for monitoring lung fluid status in patients with implantable pacemaker with greater sensitivity than the intra-thoracic technique.