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 peripheral nerve stimulators. The pulsed outputs (pulse width, frequency, and voltage) of three devices were measured with an oscilloscope across a 500-ohm resistance, meant to simulate subdermal tissue stimulated during electroacupuncture. For each device, at least two measured parameters were not within 25% of the manufacturer's claimed values. The measured values were compared with the American National Standard ANSI/AAMI NS15 safety standard for implantable peripheral nerve stimulators. Although for two stimulators the pulse voltage at maximum intensity was above that specified by the standard, short-term clinical use may still be safe because the standard was written for long-term stimulation. Similarly, the net unbalanced DC current, which could lead to tissue damage, electrolysis, and electrolytic degradation of the acupuncture needle, was within the limits of the standard at 30 pulses 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 safely.