Figure 1.

Schematic rendering the electrode positions with respect to the anatomy of the human thorax. Distances printed along the green horizontal and vertical axes are in cm. In order to meet the demands (i) and (ii) in subsection relative differential measurement, the electrodes are distributed along the central vertical axis of the sternum. Furthermore, the electrodes spread out to the left and the right side of the thorax below the inframammary fold to enable application on female patients without disturbance from the mammae. The positions on the thoracic skin are defined using the green 2D coordinate system (x,z), of which the origin (x=0 and z=0) coincides with the position of the top end of the sternal bone, near the incisura jugularis. The measuring electrodes are numbered e₀to e₆, and, for each value of k (with k∈{1…6}), the input voltage ${\Phi }_{\mathrm{meas}}^{\left(k\right)}$ from eq.(2) is measured between the two electrodes e_kand e_k−1. The positions of the seven electrodes e₀to e₆are (in (x,z)-coordinates and in mm): (0,0),(0,−60),(−30,−90),(−30,−120),(0,−157),(35,−187), and (−92,−197), respectively. During the tests of the HCP on human volunteers, a self-adhesive “compound electrode sticker” of comfortable and flexible material, containing all measuring electrodes, has been used.