The electric resistivity of human tissues (100 Hz-10 MHz): a meta-analysis of review studies

The electric resistivity of various human tissues has been reported in many studies, but on comparison large differences appear between these studies. The aim of this study was to investigate systematically the resistivities of human tissues as published in review studies (100 Hz-10 MHz). A data set of 103 resistivities for 21 different human tissues was compiled from six review studies. For each kind of tissue the mean and its 95% conf idence interval were calculated. Moreover, an analysis of covariance showed that the calculated means were not statistically different for most tissue s, namely skeletal(171 Omega cm) and cardiac (175 Omega cm) muscle, kidney (211 Omega cm), liver (342 Omega cm),lung (157 Omega cm) and spleen (405 Om ega cm), with bone (>17 583 Omega cm), fat (3850 Omega cm) and, most likely , the stratum corneum of the skin having higher resistivities. The insignificance of differences between various tissue means could imply an equality of their resistivities, or, alternatively, could be the result of the large confidence intervals which obscured real existing differences. In either case, however, the large 95% confidence intervals reflected larg e uncertainties in our knowledge of resistivities of human tissues. Applica tions based on these resistivities in bioimpedance methods, EEG and EKG, sh ould be developed and evaluated with these uncertainties in mind.