Design of a high signal to noise ratio electrical impedance plethysmograph

We have developed a high signal to noise ratio automatically resetting electrical impedance plethysmograph for noninvasive determination of blood pressure in pigeons. Pigeons are finding increased use as an economical and appropriate animal model for the study of human atherosclerosis. The impedance plethysmograph obtains the pulsatile arterial volume change as an impedance pulse. Nyboer's equation may then be used to extract the arterial volume change from the impedance pulse. The designed impedance plethysmograph has a sensitivity of 430 mV/m$\Omega$ and a noise level of 0.12 m$\Omega$ peak-to-peak, significantly better than systems reported earlier. Refinements to further enhance the performance are also presented.