engleski

Electrode - tissue Interface Properties in Pulse Plethysmography Measurement

Electrode-tissue interface can be represented by series connection of a resistor and a capacitor for very short current pulses (5 microsec). As duration of current pulses rises, the interface can be presented by three element equivalent circuit consisting of a series connection of resistor and parallel connection of resistor and capacitor. The resistor in series is the inner resistance of the tissue and the parallel connection of capacitor and resistor is the equivalent circuit of tissue (skin) and electrode interface. The series resistor and capacitor in both equivalent presentations are shown to be dependent of the current pulse duration and the current pulse amplitude, but not dependant of the current pulse repetition frequency. The parallel resistor have noticeable influence on three element circuit only when longer current pulses are applied (more than 22 microsec). The value of parallel resistor is shown to be independent for pulse duration interval of [0.5 microsec. - 22 microsec.]. The behavior of presented three element circuit is very similar to behavior of real situation in polse plethysmography measurements.

blood pressure measurements; current pulse plethysmography; electrode-tissue interface

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