Body impedance spectroscopy based on a step response

Among the techniques of body composition evaluation, the bioimpedance is calling the attention of the searchers, due to its simplicity, portability, low cost and a good acceptance by many patients. Both the single-frequency bioimpedance analysers (SFBIA) and the multi-frequency bioimpedance analysers (MFBIA) make use of sinusoidal currents between 300-800 μA. However, whether the SFBIA used to work with a frequency of 50 KHz the MFBIA operate with frequencies between 1-1300 KHz. The advantage of a technique based on a step response is the possibility of measuring the total body water (TBW) with only one excitation, that will scan all frequency´s components, as long as in low frequencies the current flows through the extra-cellular liquid (ECL) and in high frequencies through the intra-cellular liquid (ICL). A theoretical model is introduced, that considering the electrode/tissue interface, allow us to extract the modelling elements of body impedance. The primary results point to an utilization of these new methodology and technology