In the last year, the European Union has gotten much of the attention with regard to the regulation of electromagnetic compatibility (EMC) and medical electronics. This fact reflects the reality that, although there has been plenty of activity in the United States as well, the Europeans are leading the pack in EMC regulations.

Accordingly, we start this review of medical EMC regulations with a look at where the European Union is today, and where it is going. Then we'll outline the FDA approach, including its influence in the European Union. We'll conclude by examining some emerging EMC concerns that are under scrutiny by FDA and industry leaders in the United States.

Today, most medical EMC regulations originate within the International Electrotechnical Commission (IEC). As its name implies, the IEC is a standards body comprising representatives from around the world. The standards it produces may be adopted by any organization, a practice led by the European Union. Increasingly, other countries are following suit.

As is generally the case with all IEC EMC standards, the commission's standard for medical EMC, IEC 60601-1-2, cites various basic standards for both emissions and immunity.¹ Naturally, there are a number of categories, depending on the criticality of the function; but for any particular category, the path and the requirements are well defined. For the European Union, EMC in medical electronics is covered in EN 60601-1-2, which adopts IEC 60601-1-2 essentially intact.

IEC 60601-1-2 is in the process of a major revision to the current requirements, which were adopted in 1993. The second draft edition of the standard is now being revised, following the second round of comments. It is expected to be voted on late in 1999 and become effective in 2001. Table I gives a comparison of the existing and the expected revised requirements.

Note that the limits for ESD, RFI, and EFT have increased, and some new tests are added, including injected RF, magnetic fields, voltage dips and dropouts, harmonics, and flicker. These changes are likely to show up in standards for nonmedical electronics as well. Perhaps even more important, much more comprehensive pass/fail immunity criteria have been established. Specifically, the following degradations shall not be allowed:

These criteria shall apply to each function, parameter, and channel. We expect these IEC requirements to be adopted within roughly the same time frame by the European Union.

FDA has adopted a considerably different approach to EMC, relying on its submission reviewers to evaluate specific devices and to levy appropriate EMC requirements (along with a plethora of other requirements).

FDA does not have mandatory EMC requirements. While compliance with IEC 60601-1-2 is recommended, such compliance is neither necessary nor necessarily sufficient to satisfy the reviewer. The FDA reviewers guide takes precedence whenever a conflict arises with the IEC standard.²

The manufacturers are expected to propose requirements to the reviewer in their submissions, citing similarity to previous equipment, or other rationale.

FDA's approach has the advantage that the manufacturer is not encumbered by a set of inappropriate requirements. But it also raises manufacturer concerns about reviewer consistency.

There are numerous reviewers guides for specific types of medical products, such as wheelchairs and pacemakers, but the most widely read is the guide intended for respiratory devices. It has often been applied to other devices as well. The most recent reviewers guide for respiratory devices, dated 1995, is summarized in Table II. Note that FDA has cited some IEC basic standards, some MIL-STD 461D requirements, and a few of their own. FDA recognizes IEC 60601-1-2. Note that compliance with this standard will meet most of the requirements in the reviewers guide; however, existing guidance documents take precedence. For additional information, visit http://www.fda.gov/cdrh/modact/genappst.html.

FDA has been influential in the development of the proposed revision of IEC 60601-1-2. In addition to the added tests and increased test limits, the new standard includes the detailed pass/fail criteria cited earlier, absent in the current version. Adoption of the revised IEC standard should greatly reduce differences with the reviewers guides used by FDA, but the extent of agreement between them will not likely be known for several years.

As with most of the electronics industry, medical EMC requirements need to be reviewed not only for adequacy for existing device types, but also for emerging technologies. Thus, as the existing EMC standards are being revised, new situations that need to be addressed are constantly being identified.

In the United States, FDA is charged with keeping tabs on reported problems, hopefully to head off problems before they become serious. Depending on the nature and urgency of the problem, FDA will either tackle the problem directly, or involve a committee of the American National Standards Institute (ANSI) or the Association for the Advancement of Medical Instrumentation (AAMI). These committees generally comprise representatives from manufacturers, clinicians, and other industry leaders, as well as from FDA. Some of the current issues being explored are described below.

Pacemakers and Defibrillators. Reports of cellular phone interference with pacemakers have spurred investigations (see the related article on page 36). In testing carried out by both FDA and the University of Oklahoma, it has been determined that some pacemakers exhibited anomalies in the immediate proximity of digital cellular phones (specifically MIRS). Most pacemaker models ceased reacting to the cell phone at distances of 9 cm or more, but some were unaffected at any distance. This issue is being addressed by the AAMI Pacemaker EMC Task Group, which has developed a draft document covering the higher frequency ranges typically encountered in handheld devices, including cellular phones and walkie-talkies (450 MHz to 3 GHz). While anomalies have been reported, none of the effects were serious.

Electronic Article Surveillance. Similar scrutiny is being given to the lower frequencies used for surveillance devices and metal detectors, such as those commonly found in drugstores and airport security, not to mention employee and pet identification devices. These devices commonly employ low-frequency magnetic fields for detection.

There have been reported interactions with implanted devices, and alerts have been issued to clinicians. Reported anomalies with pacemakers and defibrillators have been minor, with the effects being transitory, and no serious problems have occurred. Reports of nerve stimulators administering shocks are being investigated. An advisory group to FDA, the Technical Electronic Product Radiation Safety Standards Committee (TEPRSSC) has recommended further study of these issues.

Investigations involve the electronics industry (both medical electronics manufacturers and security companies) and clinicians. This issue was scheduled to be the subject of a session at an AAMI conference in June 1999.

Telemetry and DTV. Digital TV interference to hospital telemetry was reported at two hospitals in Dallas last year, prompting FDA to publish an alert to television stations and clinicians last spring. Although no serious effects were reported in these incidents, it is clear that the problem will need to be resolved quickly.

Generally, the telemetry frequencies occupy unused TV channels and private land-mobile frequencies, but having secondary FCC status, they must not interfere with primary usage. This means that the telemetry must use frequencies not presently in use in each locale. Digital TV uses more channels than analog TV, and all of the available band. The TV spectrum will be particularly crowded until analog TV is phased out (scheduled for 2006). Thus, it is harder to sneak in secondary usage for telemetry, and new channels coming on-line are likely to collide with existing telemetry. In the case in Dallas, the pilot run of a digital channel conflicted with some of the telemetry channels used in local hospitals. This situation would be expected to be common in large urban areas.

FDA and the FCC have both prepared position papers on the subject.^3,4 The immediate efforts are informative in nature, making sure that affected parties are communicating. The FCC will make frequency usage available so that local TV stations can work with nearby healthcare facilities to resolve problems. An investigation reveals that approximately half of telemetry systems use land-mobile bands, which will not be affected by DTV. But because the other half use the TV bands, it will be necessary for local TV stations and the hospitals to identify and resolve frequency conflicts. Manufacturers will be asked to identify technology that will ameliorate the problem. FDA and the FCC are working with an American Hospital Association task group to explore long-term spectrum needs so as to avoid future problems. This group, which includes users and manufacturers, is asking for FCC primary status for their telemetry and for new spectrum allocation. Further information should be available soon, following the task group meeting that was scheduled for May 1999.

RFI and Hospital Equipment. The continuing concern about radio interference with electronic equipment in the hospital environment has resulted in a number of hospitals banning the use of cellular telephones in certain parts of the hospital. Newer equipment has been tested to some EMC standards, but there is much existing equipment that has had little or no testing. An ANSI working group, C63 SC8 WG1, has generated an ad hoc RFI test suitable for use in a hospital setting. This test procedure has been thoroughly tested by the Winchester Engineering and Analytical Center (WEAC), and good repeatability is reported.

The test uses a handheld radio or a wireless phone operated in proximity to the tested equipment in order to determine the distance at which the equipment exhibits anomalous behavior, using 450-MHz, 900-MHz, and TDMA phones, and any other portable transmitters used in the hospital. Equipment users will be instructed to maintain this minimum distance and to be alert for situations where a violation of this distance may occur. The procedure is defined in ANSI C63.18-1997, but revisions are in process.

Cellular Phones and Hearing Aids. Another ANSI working group, C63 SC8 WG3, is developing a test method to evaluate compatibility of cellular phones with hearing aids. A draft method, C63.19, is now under review by the working group. Many hearing-aid wearers cannot use certain types of phones (TDMA and GSM) because they cause interference at close distances (2 cm). An early concern that the phones might cause a hearing aid to emit dangerously high audio levels does not seem to be justified. The University of Oklahoma's Center for Wireless EMC has been making numerous measurements in connection with this study.

RF to Patient-Connected Devices. Yet another ANSI working group (C63 SC8 WG2) is investigating the validity of standards for RFI immunity and patient-connected devices. Preliminary results of FDA testing indicate that RFI effects on patient-connected electronics may be more severe when tested on a patient than when using a simple dummy load, particularly at body resonant frequencies (in the low hundreds of megahertz). This discovery raises questions as to the validity of existing standards. The WG2 has initiated testing to assess the magnitude of this effect. Underwriters Laboratories has been performing the tests based on a protocol developed by the working group.

Clearly, this has been a very active year for developments in EMC and medical electronics. As existing standards are revised, we expect that the U.S. and European Union standards will be brought into closer alignment in the near future.

At the same time, we see that as new technologies are introduced and become widespread, interference is likewise evolving. Continuous vigilance will still be needed to keep on top of these issues. In particular, we see that nonmedical electronics are becoming an increasing factor for medical devices (see sidebar). We expect that the manufacturers of these nonmedical products are going to become increasingly involved in medical EMC, like it or not.

The authors wish to thank Jeff Silberberg and Don Witters of FDA for their comments.