New RFID Study Finds No Interference With Medical Devices

By Beth Bacheldor

July 11, 2008—A new study on the effects of passive ultrahigh-frequency (UHF) RFID systems on medical equipment did not discover any problems with electromagnetic interference (EMI). The clinical study was conducted in March of this year at Community North Hospital in Indianapolis, by researchers at Indiana University Purdue University Indianapolis (IUPUI) and by RFID consulting and systems integration firm BlueBean. BlueBean, based in Carmel, Ind., initiated the study because there had been a scarcity of research on EMI and radio frequency identification, and the company hoped to have definitive answers for customers as it builds out an RFID practice for the health-care market.

The study, entitled "RFID Usage in the Patient-Care Environment," can be downloaded here, and also at BlueBean's Web site. Its publication comes just two weeks after a prior study was published in the Journal of the American Medical Association (JAMA) that found incidents of EMI by RFID on critical-care equipment in a non-clinical setting (see Researchers Warn RFID May Disrupt Medical Equipment). That study was conducted by researchers at the University of Amsterdam's Academic Medical Center in the Netherlands as part of a government research project.

Gregg Maggioli

Both studies examined whether electromagnetic radiation from RFID systems would disrupt infusion pumps, EKG monitors and other medical equipment. The Dutch group employed an active 124 kHz battery-powered tag and reader, as well as a passive 868 MHz tag and interrogator, to study RFID's effect on 41 medical devices. The IUPUI-BlueBean group studied RFID's effects on 25 medical devices and used only passive UHF (902-928 MHz) RFID tags and readers, which included one system (host computer, transceiver, antenna and tag) containing a near-field antenna operating in a "dense reader mode" and a near-field tag, and another system consisting of a far-field antenna operating in a "high-throughput" mode and a far-field tag. Researchers from both studies carried out their tests operating the RFID devices continuously at full power (2 to 4 watts).

The Dutch study was performed in a one-bed patient room with no patients present. The IUPUI-BlueBean study was conducted in a patient care room in a hospital, but was staged to best replicate the setting in which both antennas and clinical devices would be utilized. "Our layout was a real-life scenario, and we put the antenna where you'd expect to put an antenna, and the equipment where you'd expect the equipment to be," says Barbara Christe, associate professor and program director of IUPUI's biomedical engineering technology department, and the study's lead researcher. "Their test, while physically housed in a patient room, used a scenario where devices and systems were physically placed where you'd not expect them to be."

For the most part, Christe's group utilized patient simulators, though in some cases, test subjects were involved. The non-invasive blood pressure devices, for instance, were triggered to measure the blood pressure of a human subject during testing, but the EKG monitors were tested while connected to patient simulators.

Another critical difference is that while the Dutch study tested scenarios in which RFID systems were placed quite close (within centimeters) to the medical devices, none of the devices tested in the IUPUI-BlueBean study were ever closer than 1 foot (30.5 centimeters) to the RFID antennas during the test—a scenario that's much more consistent with real-world RFID system implementations, Christe says. The IUPUI study began each test at a distance of 6 feet, device performance was assessed and recorded, and the device was then moved closer to the antenna through 4-, 2- and 1-foot intervals, with the team verifying device performance at each interval.