Wrist pulse monitoring by electrical impedance using a 3D model of the arm

The paper presents the results of a study on the feasibility of monitoring the pulse at the wrist level using electrical impedance measurement method. The four electrode method, previously used, was strongly confirmed as inefficient due the limiting factor of motion induced impedance changes. The motion changes in the measured boundary voltages are orders of magnitude larger obscuring the variations due to pulse. The research results reported address the overwhelming core issue of motion art-fact signal in the measured voltages. The problem is analyzed on an extended to 3D the traditional 2D model of the wrist anatomy. For a 2D cross section electrical model of the hand at wrist level, the pulsating artery is shown to be well approximated by a generic unit area conductivity change. Using a 3D model of the wrist the determination of the optimal electrode placement around the wrist circumference is addressed. The new extended to 3D measurement approach introduced in the present paper is more encouraging for the practical application of impedance measurement for pulse monitoring. Further research is outlined to reliably separate motion artifacts from pulse extraction to obtain an admissible range of precision for normal use of the hand.