Acupuncture points and skin impedance.

OVERLAPPING OF MERIDIAN AND VEIN A superficial vein named the median vein located on the midline of the anterior forearm is a common site for phlebotomy. It is rather parallel to the invisible PC4 and pericardial meridian (figure 1), although individual mappings of the vein are not uniform. The veins have thin elastic walls and blood flowing inside; electrically they are very conductive. Mechanically, a skin portion with superficial veins is more compressible than skin without veins. Rezaei et al used a 15 mmHg blood pressure cuff to stabilise the impedance probe on the forearm; the skin on the top of the median vein would form a closer electrode–skin interface than the adjacent skin, so a greater efficiency of current flow is allowed through the interface as well as a lower reading of skin impedance. These electrical and mechanical considerations may explain the skin impedance of PC4 and pericardial meridian being significantly different from that of the surrounding area.