A number of machines have come on the market which purport to detect acupuncture points electrically. Most depend on the theory that acupuncture points are areas of reduced skin resistance, and they usually have a neutral electrode plus a searching electrode ending in a blunt point. The weakness of nearly all these machines is that it is very easy to produce artifacts when using them. Leaving the probe a little longer in one place on the skin or pressing a little harder will produce an “acupuncture point” almost anywhere. Some more sophisticated machines have been developed in an attempt to get round this difficulty but most have been used only in a research context. Reichmanis and Becker (1976) carried out a study at Upstate Medical Center, Syracuse, New York.
The measuring electrode assembly consisted of 36 steel rods in a 6 x 6 square, connected to a DC Wheatstone bridge circuit. Using this rather elaborate apparatus the researchers were able to demonstrate local variations in conductance at a number of classic acupuncture points on the Triple Warmer and Lung channels, although not all the points were detected in every subject.
Some researchers at the University of Missouri School of Medicine used a device that did not apply a current to the skin but instead measured the electrical activity of the body itself (Brown et al., 1974). The outer surface of the skin is electrically negative with respect to subcutaneous tissue, and the experimenters used this fact to test for acupuncture points. They found 18 points on the upper arm, which included all those shown as acupuncture points on charts as well as a few not shown. These points were distributed symmetrically on the two arms and did not change in situation or electrical activity over time.
At a more practical level, the most useful machine for detecting local electrical differences in the skin seems to be a Japanese device called the Neurometer, which is used for a neo-classic form of acupuncture used in Japan called Ryodoraku. This machine puts out a brief spike of current every 0.6 of a second and measures the resistance to this. In Celestial Lancets (1980) Needham and Gwei-Djen report a convincing demonstration of many acupuncture points with the Neurometer; moreover these points could still be demonstrated on a cadaver several hours after death. My own experience is that the machine gives reproducible results provided it is used carefully. For example, I have never failed to find a pair of points at the back of the head, almost but not quite corresponding in position to G20. Constant points can also be found on the ear and probably elsewhere. Sometimes the passage of the electrical current through them produces a pricking sensation.
Other kinds of point can also be detected with the Neurometer. Areas of decreased impedance can be found on the back, though they are not as sharply demarcated as those on the ear or “G20”. There seems to be a tendency for these back areas to become more obvious when there are active TPs. However detecting these areas does not add any useful information to that obtained by simple manual palpation.
The practical use of even the best point detection machines is in my opinion small. At most they indicate sites on the skin where there is a change in resistance, but in most cases one is interested, not in the skin, but in TPs or ATAs lying at some distance beneath the skin. I find it much simpler and more effective to use my fingers to look for such areas than to spend time attempting to do so electrically.