Electrostimulators for acupuncture: Safety issues

Three representative electrostimulators were evaluated to determine whether they meet the manufacturers' labeled nominal output parameters and how the measured parameters compare with a safety standard written for implanted p eripheral nerve stimulators. The pulsed outputs (pulse width, frequency, an d voltage) of three devices were measured with an oscilloscope across a 500 -ohm resistance, meant to simulate subdermal tissue stimulated during elect roacupuncture. For each device, at least two measured parameters were not w ithin 25% of the manufacturer's claimed values. The measured values were co mpared with the American National Standard ANSI/AAMI NS15 safety standard f or implantable peripheral nerve stimulators. Although for two stimulators t he pulse voltage at maximum intensity was above that specified by the stand ard, short-term clinical use may still be safe because the standard was wri tten for long-term stimulation. Similarly, the net unbalanced DC current, w hich could lead to tissue damage, electrolysis, and electrolytic degradatio n of the acupuncture needle, was within the limits of the standard at 30 pu lses per second, but not at higher frequencies. The primary conclusions are (1) that the outputs of electrostimulators must be calibrated and (2) that practitioners must be adequately trained to use these electrostimulators s afely.