RFID Systems May Disrupt the Function of Medical Devices

24 June 2008—The use of radio-frequency identification (RFID) systems in hospitals may not be entirely safe, new research suggests. According to a study published this week in the Journal of the American Medical Association , RFID tags and the devices they communicate with can disrupt the performance of medical equipment, including pacemakers and dialysis machines, potentially endangering the patients who depend on those devices.

Erik Jan van Lieshout and Remko van der Togt, along with their colleagues at the University of Amsterdam’s Academic Medical Center, tested whether the presence of RFID transponders and the readers they transmit to could interfere with the function of 41 different electronic medical devices. The team examined both an active RFID system, in which the tags have batteries that allow them to transmit continuously, and a passive system, whose tags are powered only when in the range of a transmitter’s electromagnetic field. In 123 tests, they found 34 incidences of interference.

Of those, the researchers categorized 22 cases as hazardous, meaning that the interference caused an equipment fault that could have direct physical impact on a patient. For example, in two such incidences, a mechanical ventilator and a syringe pump switched off when the RFID system was transmitting near them. The passive RFID tag they used, which had a higher energy output and operated at a frequency of 868 megahertz, induced three times as many disruptions as the active system, which operated at 125 kilohertz.

None of the tests involved patients—just equipment—and no real-life cases have yet been reported of RFID transponders causing a device to malfunction, according to the Dutch research.

The health-care market for RFID systems, according to IDTechEx, a consultancy that focuses on RFID, is about US $121 million, and the tags are increasingly becoming integrated into the hospital environment. They are used, for instance, to track the location of surgical sponges so they are not inadvertently left inside patients. RFID tags are also embedded in bracelets given to newborn babies to prevent kidnapping.

For van Lieshout, who works in his hospital’s intensive care unit, the question of RFID interference arose after he had conducted some similar experiments on the use of cellphones in hospitals. Noticing the growing presence of RFID transponders in the ICU, van Lieshout decided to consult the medical literature and ask his colleagues for guidance on whether the tags’ transmissions could affect the health of his patients. ”They told me, ’Oh yeah, it’s pretty safe.’ But I wanted to know, ’Well, how safe?’ And no one knew,” van Lieshout recalls.

He and his colleagues set out to gain a qualitative sense of their safety: rather than exhaustively testing all the configurations of each available RFID tag and reader, they chose two systems already used in retail and drug-supply chains. They placed a transmitting reader and tag near each medical device and observed the distances at which an electromagnetic field caused disturbances in the devices’ performance. They found that the median distance at which interference occurred was 30 centimeters, with a range extending to 600 cm for several of the devices. ”For a critical-care physician, it was astonishing to find out,” says van Lieshout.

Donald Berwick, president of the Cambridge, Mass.–based Institute for Healthcare Improvement, notes in an editorial accompanying the study that the impact of hospital electronics on patient care has been largely positive but poorly understood. ”Health care is full of tightly coupled, hard-to-see systems, and the naive introduction of a change as apparently isolated as RFID tags…might cause remote and dire consequences far away in space and time,” he writes. Berwick suggests that hospitals look into routinely checking for electromagnetic interference and that regulatory agencies consider updating safety standards for electronic medical equipment.

Setting meaningful standards for testing every existing RFID system with all electronic medical equipment might be a near-impossible task, however. ”RFID means a lot of different things—a lot of different frequency bands, and a lot of ways to use it,” says Ralph Herkert, a senior researcher at Georgia Tech Research Institute’s Medical Device Test Center. As Herkert explains it, tags can operate with readers from different manufacturers at the same carrier frequency, but each signal may be modulated at a different rate. In some cases, the interference might be due to the modulation rather than the carrier frequency or the energy output.

For years, hospital staff has questioned whether the transmitters in cellphones are dangerously disruptive to medical equipment, and bans have been both imposed and then lifted in hospitals across the developed world. This latest batch of evidence—the first to document the influence of RFID technology on medical devices—is unlikely to revive the contentious debate about the hazards of using transmitting technologies in hospitals, says Marlin Mickle, an electrical engineering professor at the University of Pittsburgh and executive director of its RFID Center of Excellence. ”Cellphones are uncontrolled because visitors with cellphones wander all over the place. But RFID readers are installed by the hospital staff,” Mickle says. ”They just have to be smart about where they put them.”

The question remains of how often those interactions between life-saving devices and RFID transponders would arise in the day-to-day operations of a hospital. ”I’m not hoping there will be a frenetic ban on RFID in health care,” van Lieshout says. ”We just have to know what we’re dealing with.”

Mickle compares the study’s relevance to the warnings that accompany implanted devices and pharmaceutical drugs. ”When companies advertise drugs on television, they also tell you all the things that could go wrong,” Mickle says. ”Many electronic devices have those same kinds of warnings. It doesn’t mean we can’t use them.”