A novel method to obtain proximal plethysmographic information from distal measurements using the impedance plethysmogram

We present a novel method to detect proximal volume changes based on the impedance plethysmogram (IPG) measured from limb to limb with two electrode pairs symmetrically placed at distal areas of the upper or the lower limbs. Since the measurement is sensitive to changes along the whole current path, this method allows us to detect changes in arteries that are more proximal to the torso than the measurement sites. Our results show that the Pulse Arrival Time (PAT) measured from the R peak of the ECG to the hand-to-hand IPG is close to the PAT to the elbow whereas the PAT measured from the R peak of the ECG to the foot-to-foot IPG is close to the PAT to the knee. This opens new avenues for noninvasive cardiovascular measurements based only on electrodes in contact with hands or feet.