engleski

Some new aspects of electrical impedance and pulse plethysmography

It is shown that three element equivalent circuit can be presented as two element circuit, if is applied only in lower or higher frequency range. This is valid particularly for the plethysmography, which is applied in higher frequency range so that series connection of resistance Rs and capacitance Cs has satisfactory fitting. The dependence of Rs and Cs on applied current is depicted for pulse plethysmography. It is shown that current sensation depends mostly on current and not current density and that pulse plethysmography with pulse duration below 10ms and duty-cycle lower than 1:50 allow very high current pulses (>80mA) without any sensation. The high current pulses enable, however a much better S/N (signal to noise) ratio of the measured signals, than continuos sinusoidal current.

impedance plethysmography; pulse plethysmography; equivalent circuit; signal to noise ratio

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