The Detection of Pulmonary Edema by Means of Electrical Impedance

The detection, localization, and quantification of pulmonary edema by electrical impedance were investigated using band, circumferential, and longitudinal electrode arrays in a series of four studies utilizing 35 dogs. Pulmonary edema was induced with alloxan, sucrose, and saline lavage. The ability of the various electrode arrays to distinguish between pulmonary edema and pleural effusion was also investigated. The largest absolute changes in impedance were detected by the band electrodes, although larger percent changes in impedance were measured using the circumferential arrays. The circumferential arrays indicated the possibility of differentiating between pleural effusion and pulmonary edema. The longitudinal array had essentially the same characteristics as the band array, although it permitted localization of either edema or effusion to one hemithorax. The impedance method provides a reliable quantitative index of pulmonary edema in carefully controlled experiments in dogs. (Author)