March 20, 1998
Director, Clinical/Biomedical Engineering
Nursing Home Director
Purpose of this Advisory
FDA has recently become aware of incidents involving digital television (DTV) transmissions interfering with medical telemetry systems that use TV channels. The purpose of this Advisory is to alert you to the potential for this problem and provide recommendations for your facility. In one case the telemetry system was operating on a TV channel which had been unused for many years but had been recently re-assigned by the Federal Communications Commission (FCC) to a TV station in the vicinity of the hospital for DTV. The new TV signal interfered with the hospital's telemetry system and rendered it unusable. A second hospital in the same city was also affected.
Many medical telemetry devices are operated under 47 CFR Part 15 of the FCC regulations. These devices are secondary users of the radio-frequency (RF) spectrum. Licensed users such as television stations are the primary users. As a secondary user, your telemetry devices may be subject to interference from the primary user at any time, but must not cause interference with the primary user. If your telemetry devices are operating on frequencies licensed to a primary user, you need to be aware of the potential for interference and take any steps necessary to avoid device malfunctions due to interference.
Medical telemetry devices have shared the TV broadcast spectrum on channels 7-13 for many years. Last October FCC authorized the operation of medical telemetry devices on much more of the TV broadcasting spectrum. However, at this time most medical telemetry systems are still believed to operate on the original channels 7-13.
In the next six months, 10 major market areas for DTV will begin transmitting signals on previously unused channels. Although most of these first DTV stations will operate outside the channel 7-13 band, some will be broadcasting within that band. Many more DTV stations will be on line by 2003 and could begin transmitting at any time. The latest information on which channels have been allocated to TV stations is listed by geographic location in an FCC table of allotments. This table can be found on the FCC website, then selecting DTV Table of Allotments (view in either WordPerfect version or Acrobat version to see table headings). Facilities using medical telemetry systems should consult this table to determine the channel allotments for TV stations in their area.
To address potential interference problems for medical telemetry systems, FDA recommends that you work with the manufacturer of your telemetry systems to:
- determine the channel/frequencies your telemetry systems use; and
- consult the FCC table of allotments for DTV channels that will be coming on line in your area.
If your telemetry systems are transmitting on channels that are scheduled to be used by a local station, you should work with the manufacturer of your telemetry systems to:
- consult with the local television stations to determine when they plan to begin broadcasting on those channels; and
- change your telemetry channels to unused channels prior to the expected broadcast date to avoid interference.
If you find that your telemetry systems are transmitting on channels that will remain unused, you should not have a problem due to DTV transmissions. However, you should periodically check the FCC allotments to assure that those channels remain available.
Reporting Adverse Events to FDA
The Safe Medical Devices Act of 1990 (SMDA) requires hospitals and other user facilities to report deaths and serious illnesses and injuries associated with the use of medical devices. Thus, if interference with a medical device results in a death or serious injury, it must be reported. We request that you follow the procedures established by your facility for such mandatory reporting.
If a telemetry system fails to function due to electromagnetic interference or any other reason, it is a device malfunction. Such malfunctions should be reported to the manufacturer or can be reported directly to MedWatch, the FDA's voluntary reporting program. Submit these reports to MedWatch: by telephone at 1-800-FDA-1088, by FAX at 1-800-FDA-0178, or by mail to MedWatch, Food and Drug Administration, HF-2, 5600 Fishers Lane, Rockville, MD 20857.
Getting More Information
FDA Medical Device Public Health Notifications are available on the Internet. You can also be notified through email each time a new Public Health Notification is added to our web page. To subscribe, visit: http://service.govdelivery.com/service/subscribe.html?code=USFDA_39.
D. Bruce Burlington, M.D.
Center for Devices and Radiological Health
Food and Drug Administration