Abstract
A field-theory model of blood-pulse measurement by four-electrode impedance plethysmography was developed and tested empirically. The model relates current distribution in the upper arm to the configuration of the drive electrodes. It predicts observed impedance change as a function of sense-electrode configuration and the increase in segmental volume associated with each blood pulse. The model was simulated on a digital computer for a number of critical cases. Corresponding measurements were taken on human subjects with an improved instrumentation system, which virtually eliminated the artifact caused by the skin-electrode interface. These measurements substantiated the major predictions of the model. It was concluded that precise impedance measurements were closely related to changes in segmental volume, and that any change in conductivity caused by the incoming arterial blood probably played a minor role. Insight was gained into the optimum placement of drive and sense electrodes at this measurement location.
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Weltman, G., Freedy, A. & Ukkestad, D. A field-theory model of blood-pulse measurement by impedance plethysmography. Ann Biomed Eng 1, 69–86 (1972). https://doi.org/10.1007/BF02363419
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DOI: https://doi.org/10.1007/BF02363419