The detection of pleural effusion using a parametric EIT technique

The bioimpedance technique provides a safe, low-cost and non-invasive alternative for routine monitoring of lung fluid levels in patients. In this study we have investigated the feasibility of bioimpedance measurements to monitor pleural effusion (PE) patients. The measurement system (eight-electrode thoracic belt, opposite sequential current injections, 3 mA, 20 kHz) employed a parametric reconstruction algorithm to assess the left and right lung resistivity values. Bioimpedance measurements were taken before and after the removal of pleural fluids, while the patient was sitting at rest during tidal respiration in order to minimize movements of the thoracic cavity. The mean resistivity difference between the lung on the side with PE and the lung on the other side was -48 Omega cm. A high correlation was found between the mean lung resistivity value before the removal of the fluids and the volume of pleural fluids removed, with a sensitivity of -0.17 Omega cm ml(-1) (linear regression, R=0.53). The present study further supports the feasibility and applicability of the bioimpedance technique, and specifically the approach of parametric left and right lung resistivity reconstruction, in monitoring lung patients.