EMC Design Effectiveness in Electronic Medical Prosthetic Devices

The increasing use of electronic prostheses in a society where the numbers and intensities of radiofrequency (RF) radiation sources are ever increasing requires special attention by the manufacturers of the medical devices and the practicing physicians who prescribe these devices. One such device, the artificial cardiac pacemaker, was tested extensively to assess the extent of radiofrequency electromagnetic radiation interference (EMI) possible from a variety of RF sources. Pacemaker responses were measured on twenty-one different types (manufacturers and models) of devices, exposed in “free-field” and “simulated-implant” configurations. Relative interference thresholds were vastly different with the most sensitive pacemaker being adversely affected at electric (E) field levels as low as 10 volts per meter and the least sensitive pacemaker being relatively free of interference at levels as high as several hundred volts per meter. In many cases the real time E-field level around radiofrequency radiation (RFR) emitters manifests itself as a pulsed or pseudo-pulsed (changing E-field level) signal which can adversely affect cardiac pacemakers and is potentially hazardous for other types of medical prosthetic devices. These empirical findings demonstrate the need for continuing awareness of potential RF interference situations and provide reasonable evidence that through such awareness many of the potential EMI problems can be effectively circumvented.