Development of Bioelectric Impedance Measurement System Using Multi-Frequency Applying Method

Abstract

Abstract In order to measure the segmental impedance of the body, a bioelectrical impedance measurement system (BIMS) using multi-fre-quency applying method and two-electrode method was implemented in this study. The BIMS was composed of constant current source ,automatic gain control, and multi-frequency generation units. Three experiments were performed using the BIMS and a commercialimpedance analyzer (CIA). First, in order to evaluate the performance of the BIMS, four RC circuits connected with a resistor a nd capac-itor in serial and/or parallel were composed. Bioelectrical impedance (BI) was measured by applying multi-frequencies -5, 10, 50, 100,150, 200, 300, 400, and 500 KHz – to each circuit. BI values measured by the BIMS were in good agreement with those obtained bythe CIA for four RC circuits. Second, after measuring BI at each frequency by applying multi-frequency to the left and right forearmand the popliteal region of the body, BI values measured by the BIMS were compared to those acquired by the CIA. Third, when thedistance between electrodes was changed to 1, 3, 5, 7, 9, 11, 13, and 15 cm, BI by the BIMS was also compared to BI from the CIA.In addition, BI of extracellular fluid (ECF) was measured at each frequency ranging from 10 to 500 KHz. BI of intracellular fluid (ICF)was calculated by subtracting BI of ECF measured at 500 kHZ from BI measured at seven frequencies ranging from 50 to 500 KHz.BI of ICF and ECF decreased as the frequency increased. BI of ICF sharply decreased at frequencies above 300 KHz.Keywords: Bioelectrical impedance, Impedance analyzer, Multi-frequency impedance meter, Extracellular fluid, Intracellularfluid