Method and device for stable impedance plethysmography

摘要

A method and device for impedance plethysmography, with relative immunity to skin-electrode contact resistance drift. Two measurement electrodes are placed on opposite sides of a biological object such as a patient. A reference electrode is placed next to one of the measurement electrodes. Because all three skin-electrode contact resistances drift in substantially the same way over time, the difference between an impedance measured between the measurement electrodes and an impedance measured between the reference electrode and the adjacent measurement electrode is indicative of a change in the biological object's impedance, even though the skin-electrode contact resistances may drift by an amount comparable to the change in the biological object's impedance.