Bioelectrical Impedance Analysis - Historical Background

Historical Background

Electrical properties of tissues have been described since 1871. These properties were further described for a wider range of frequencies on larger range of tissues, including those that were damaged or undergoing change after death. Thomasset conducted the original studies using electrical impedance measurements as an index of total body water (TBW), using two subcutaneously inserted needles. Hoffer et al. and Nyboer first introduced the four-surface electrode BIA technique. A disadvantage of surface electrodes is that a high current (800 μA) and high voltage must be utilized to decrease the instability of injected current related to cutaneous impedance (10 000 Ω/cm2). By the 1970s the foundations of BIA were established, including those that underpinned the relationships between the impedance and the body water content of the body. A variety of single frequency BIA analyzers then became commercially available, and by the 1990s, the market included several multi-frequency analyzers. The use of BIA as a bedside method has increased because the equipment is portable and safe, the procedure is simple and noninvasive, and the results are reproducible and rapidly obtained. More recently, segmental BIA has been developed to overcome inconsistencies between resistance (R) and body mass of the trunk.