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The exposure to electromagnetic environment, as well as the frequency, location, orientation, and design of a device, all influence whether and how a device might be affected by EMI. In practice, it is impossible to stop electromagnetic energy completely at its source, and society has become dependent on the convenience of instant communication. Some medical devices themselves emit electromagnetic energy, and simultaneous use of such devices can also cause EMI problems. Studies of EMI susceptibility of medical devices consistently report that wireless telecom devices can cause a high percentage of medical devices to malfunction. However, a relatively small number of EMI incidents have been reported to regulatory agencies in both Canada and the United States. Some underreporting can be attributed to a lack of awareness of EMI as the cause of the malfunction. Participants of the Round Table on EMC convened by Health Canada in September 1994 unanimously agreed that cell phones should not be totally banned in hospitals, but that policies governing their use should be established. The results of this study confirm that the very-low field intensities generated by wireless LAN systems do not interfere with medical devices in hospitals. These wireless systems are acceptable for use in hospitals, especially in view of the benefits of obtaining real-time access to patients' medical information. Nevertheless, each new wireless system should be tested on potentially susceptible devices by the hospital before being put into general use. One of the conclusions of the Canadian Task Force on EMC in Health Care was that "the potential for EMI is minimized by using RF sources having the lowest possible transmission power." The task force recommended replacing high-power sources with lower-power ones. Furthermore, these recent studies confirm that EMI from nearby digital cellular phones could affect the operation of some implanted cardiac pacemakers. The greatest risk of interference occurs when the antenna of the phone is close to the pacemaker. The chances that EMI from digital cellular phones would produce a life-threatening situation are minimal. |