What's The Frequency?

Medical Device & Diagnostic Industry Magazine
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An MD&DI September 1999 Column

EDITOR'S PAGE

In another example of issues raised by the expanding technological base of medical devices, the advent of digital TV is crowding the airwaves.

Picture yourself in the intensive care unit, with your cardiac function and respiration transmitted via a wireless monitor to the nurses' station around the corner. Just as your caregiver is furrowing his or her brow at an unusual breath or a slight dip in systolic pressure, your vital signs on the screen are suddenly replaced by . . . a wrestling match, or maybe a rerun of Mister Ed.

Although the last image is a bit fanciful, something along these lines took place not long ago in Texas, when a local television station began testing its digital TV (DTV) system in a previously unassigned frequency band. The band was the same one being used at a nearby medical center for its telemetry system, which the DTV tests effectively shut down. Fortunately, no one was injured and the problem was quickly rectified, but the incident served as a wake-up call for FDA, the Federal Communications Commission (FCC), healthcare providers, and manufacturers of wireless telemetry equipment.

Until recently, telemetry systems have functioned according to a kind of "squatters' rights" arrangement. Conventional—that is, analog—television stations were each assigned a second channel to be employed for future DTV services. Because these channels have generally remained vacant during the slower-than-anticipated development of DTV, they are often selected for transmissions by telemetry device users. Now that DTV technology is progressing, however, the potential for interference with ongoing telemetry operations has increased as stations actively test new digital systems.

In March 1998, FCC's Office of Engineering and Technology issued a fact sheet that in essence counseled TV stations and healthcare facilities to make nice and share, under the assumption that "interference can be avoided by appropriate planning and exchange of information." The idea was that the stations would inform hospitals of their DTV plans, the telemetry device manufacturers and installers would inform users about possible interference, and the users would then inform themselves about which channels were actually vacant and either continue operating on a still-vacant channel, switch to a different vacant channel, or replace nonretunable devices with new ones.

If the above reads like a run-on sentence in need of pruning, FCC evidently came to the same conclusion regarding its policy. On July 14 of this year, following consultation with a task force organized by the American Hospital Association, FCC adopted a notice of proposed rule making that would create a separate Wireless Medical Telemetry Service to operate on a "blanket-licensed, interference-protected basis" over specified frequency bands. The proposal would also establish an FCC-designated frequency coordinator, just to make sure that nobody's transmission gets squelched.

FDA, which participated in the task force and supports the FCC action, has noted in a July 29 letter to manufacturers that "this initiative marks the first time in the U.S. that wireless medical telemetry will have primary or co-primary status for use of the airways." FDA is encouraging companies that market devices based on wireless technology to submit comments on the proposed rule to FCC before the October 16, 1999 deadline.

The fretting over frequency is another example of the unanticipated technical and regulatory repercussions that can arise from ever-more-complex devices. Citing what he called the "challenge of new technology," CDRH director David Feigal stated in a July 27 presentation that the center had 763 applications under review or pending for artificial intelligence and visual recognition programs, data interpretation, software-operated miniaturized devices, and software-driven monitoring devices with alarm function for critical care. Though not all of these are wireless, they will nevertheless require manufacturers and regulators alike to stay tuned for the next episode.

Jon Katz

[email protected]

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