Medical Electronics Manufacturing Magazine
MEM Article Index

Medical Electronics Manufacturing Fall 1998

EMC Regulations

Manufacturers should take note of recent developments in the EMC regulatory arena to ensure that their devices make it through the approval process.

Daniel D. Hoolihan

Recent reports of medical device malfunctions caused by interference from licensed radio-frequency sources have underscored the importance of ensuring electromagnetic compatibility (EMC) in the design, production, and use of electronic medical apparatus. FDA issued a public health advisory concerning this issue in March of this year. Titled "Interference between Digital TV Transmissions and Medical Telemetry Systems," the advisory alerted personnel in healthcare facilities that a telemetry system that had been using an unused TV channel for several years had experienced severe electromagnetic interference (EMI) problems when a digital TV station started to use the channel. Both manufacturers and users of such systems will need to address this problem.

Ongoing developments in the regulatory and standards areas will also affect manufacturers of electromedical devices. In early 1998, as part of its implementation of the FDA Modernization Act of 1997, FDA released its "Guidance on the Recognition and Use of Consensus Standards." The purpose of this document was to provide Office of Device Evaluation reviewers and the device industry with information about the agency's recognition and use of national and international consensus standards, such as the International Electrotechnical Commission (IEC) standard IEC 60601-1-2, during the evaluation of premarket submissions for medical devices. FDA's draft guidance document, "Use of IEC 60601 Standards—Medical Electrical Equipment," released in late 1997, also refers to the international consensus standard IEC 60601-1-2 on EMC requirements for the product family of electrical medical devices. This standard is, however, undergoing revision, with voting on the new edition expected to occur in late 1999. After reviewing the FDA documents mentioned above, this article outlines the provisions of the current draft of the standard's second edition.

FDA Public Health Advisory

FDA's March public health advisory was based on an incident that occurred in Texas earlier in the year: EMI from digital TV signals rendered a telemetry system unusable. Medical telemetry devices have shared the TV broadcast spectrum on channels 7–13 for many years, and, in October 1997, the Federal Communications Commission (FCC) authorized their operation on much more of that spectrum. However, by the end of 1998, the transmission of digital TV signals will be initiated on previously unused channels in 10 major market areas, thereby increasing the probability of EMI problems.

Because medical telemetry devices, operated under part 15 of the FCC rules, are considered "secondary users," they must accept (that is, be immune to) whatever interference is produced by the "primary users," such as licensed television stations. To avoid problems, health-care facilities should use only otherwise unused channels for their existing telemetry equipment, and the suppliers of telemetry equipment should improve their systems to be able to run successfully with the licensed broadcast signals. Facilities using medical telemetry systems can find out which channels have been allocated to TV stations in their geographic area by accessing the FCC Web site and selecting DTV Table of Allotments.

FDA Guidance on Consensus Standards

Section 204 of the FDA Modernization Act allows FDA to recognize consensus standards that were established by international and national standards development organizations and to permit manufacturers to use conformity with such standards as a means to satisfy certain portions of the premarket review requirements. The purpose of the agency's guidance document on the implementation of these provisions was threefold: (1) to provide guidance to industry and FDA reviewers on the use of recognized consensus standards during the evaluation of premarket submissions for medical devices, (2) to publish the initial list of recognized standards that can be used in the premarket process, and (3) to explain agency policy on updating the list of recognized standards.

According to the document, FDA reviewers will now accept conformance with applicable recognized consensus standards as a reasonable assurance of the safety and/or effectiveness of many types of devices. Furthermore, if a premarket submission contains a declaration of conformity (DOC) to a recognized consensus standard, this will in most cases eliminate the need to provide actual test data for those aspects of the device addressed by the standard. The requirements for the contents of a DOC are consistent with ISO/IEC guide 22, "Information on Manufacturer's Declaration of Conformity with Standards or Other Technical Specifications." The international EMC standard, IEC 60601-1-2, which was developed with the participation of FDA staff, is one example of a consensus standard that can be referred to in a DOC, and FDA has informally told industry that the latest draft of that standard is the preferred version for proving compliance to EMC criteria.

IEC 60601-1-2 Revision

The second edition of IEC 60601-1-2: "Collateral Standard: EMC—Requirements and Tests" is being developed to address shortcomings of the first edition, such as references to outdated basic EMC standards, unclear pass/fail criteria for immunity tests, and references to tests "under consideration." The revision is being carried out by Working Group 13 of IEC, Technical Committee 62 (Electrical Equipment in Medical Practice), Subcommittee 62A (Common Aspects of Electrical Equipment Used in Medical Practice). A first draft of the new edition was circulated for comment in August 1996, and the second draft, reflecting comments received on the first draft, was released in March 1998 as IEC 62A/247/CD. Comments on that draft were due by July 15, and the working group is scheduled to review those comments at a meeting in October. It is hoped that the group's responses to the comments will be distributed internationally early next year. If all goes well, the committee draft for voting (CDV)—the final step in the international standards voting process—will be distributed in late 1999.

Compared with the first edition, the second draft of the second edition requires device manufacturers to include more extensive EMC information in associated documents (such as labeling), adds emission and immunity testing requirements, and introduces new immunity pass/fail criteria. It also provides additional guidance on interpreting the standard (contained in an annex), adds some definitions, and extends some requirements to cables.

The standard will continue to limit radio-frequency emissions from electrical medical devices, including spatially radiated interference and power line–conducted interference. It will also limit harmonic emissions from power supplies to the public low-voltage power supply network, and voltage fluctuations (flicker emissions) from the products of concern.

Immunity tests required by the draft standard address electrostatic discharge, electrical fast transients/bursts, surges, voltage dips, and magnetic fields at power line frequencies. Tests for conducted and radiated radio frequencies also are included in the immunity repertoire. The immunity test levels specified represent the general expected-use environment; thus an electrical medical device is expected to perform essentially as intended (these levels are similar to normal ambient temperature, humidity, and atmospheric pressure).

Conclusion

The second edition of IEC 60601-1-2 will offer a comprehensive method for ensuring the electromagnetic compatibility of electrical medical devices through thorough testing (both emission and immunity), improved product labeling (disclosure), and the maintenance of a suitable electromagnetic environment during the lifetime of the devices. Manufacturers of such products should keep up to date on the progress of this revision and its requirements, as well as on FDA's policy of using consensus standards to satisfy premarket review requirements. Conformance with international consensus standards may not only ensure a device's safety, it may facilitate its market entry.

Dan Hoolihan is vice president of TÜV Product Service (New Brighton, MN). He is also chairman of ANSI's Accredited Standards Committee on EMC (C63) Subcomittee 8 on Medical Device Test Methods.