The Corpus Callosum

RFIDs and Medical Devices: Fail!

Radio Frequency IDentification tags ( href="http://en.wikipedia.org/wiki/Radio_frequency_identification">RFIDs)
are little devices that communicate with other devices, sending an
identification signal.  You’ve probably seen them on various
items purched in stores.  They commonly are used for inventory
control and theft prevention.  They are increasingly used in a
wide variety of applications.

Now, they have been found to interfere with medical devices.
 This includes critical items such as mechanical ventilators
and external pacemakers.

The study was published in JAMA ($ for full access):

href="http://jama.ama-assn.org/cgi/content/short/299/24/2884">Electromagnetic
Interference From Radio Frequency Identification Inducing Potentially
Hazardous Incidents in Critical Care Medical Equipment

Remko van der Togt, MSc; Erik Jan van Lieshout, MD;
Reinout Hensbroek, MSc; E. Beinat, PhD; J. M. Binnekade, PhD; P. J. M.
Bakker, MD, PhD

JAMA. 2008;299(24):2884-2890.

Context  Health care applications of
autoidentification technologies, such as radio frequency identification
(RFID), have been proposed to improve patient safety and also the
tracking and tracing of medical equipment. However, electromagnetic
interference (EMI) by RFID on medical devices has never been reported.

Objective  To assess and classify
incidents of EMI by RFID on critical care equipment.

Design and Setting  Without a patient
being connected, EMI by 2 RFID systems (active 125 kHz and passive 868
MHz) was assessed under controlled conditions during May 2006, in the
proximity of 41 medical devices (in 17 categories, 22 different
manufacturers) at the Academic Medical Centre, University of Amsterdam,
Amsterdam, the Netherlands. Assessment took place according to an
international test protocol. Incidents of EMI were classified according
to a critical care adverse events scale as hazardous, significant, or
light.

Results  In 123 EMI tests (3 per medical
device), RFID induced 34 EMI incidents: 22 were classified as
hazardous, 2 as significant, and 10 as light. The passive 868-MHz RFID
signal induced a higher number of incidents (26 incidents in 41 EMI
tests; 63%) compared with the active 125-kHz RFID signal (8 incidents
in 41 EMI tests; 20%); difference 44% (95% confidence interval,
27%-53%; P < .001). The passive 868-MHz RFID signal induced EMI
in 26 medical devices, including 8 that were also affected by the
active 125-kHz RFID signal (26 in 41 devices; 63%). The median distance
between the RFID reader and the medical device in all EMI incidents was
30 cm (range, 0.1-600 cm).

Conclusions  In a controlled nonclinical
setting, RFID induced potentially hazardous incidents in medical
devices. Implementation of RFID in the critical care environment should
require on-site EMI tests and updates of international standards.

Note that the “passive” devices are not really passive.  They
still
emit radio waves, despite being called passive.  They are
called passive because they don’t have an
internal battery; rather, they are powered by a capacitor that is
connected to a coil.

A little more detail about the study can be seen openly in a USA Today
article, href="http://www.usatoday.com/tech/wireless/2008-06-24-hospital-devices_N.htm">here.

Out of 123 tests for electromagnetic interference
between RFIDs and medical devices, 34 instances of interference
occurred. In those cases, the midpoint between reader and device was
less than a foot. Among the hazardous incidences, a mechanical
ventilator switched off, a syringe pump stopped, and an external
pacemaker malfunctioned.

The language is a little muddled in that section.  They meant median
distance
, not midpoint.  The
median distance was 20cm (8 inches) The range is also important to
note: up to 600cm (20 feet).  

I once read about a patient who died, when a housekeeper unplugged a
ventilator in order to use a floor buffer.  That was bad.
 But imagine being able to have the same effect, just by
walking by with a package or other item.  

It would not be difficult to set up detectors in hospitals, to warn if
potentially hazardous RFIDs are brought in.  Better yet, it
would be possible to shield devices so that this cannot happen, or can
happen only from a specified direction.  Or, critical devices
could be designed so they won’t shut off without a specific
intervention from a human.  

The galling thing is, it has been known for years that UHF RFIDs
operate in the ISM (Industrial, Scientific, Medical) part of the
spectrum, specifically the passive 868-MHz RFIDs.  So it seems
that the potential for this kind of thing should have been obvious.
 

Comments

  1. #1 Barry Leiba
    June 25, 2008

    Note that the “passive” devices are not really passive. They still emit radio waves, despite being called passive. They are called passive because they don’t have an internal battery; rather, they are powered by a capacitor that is connected to a coil.

    Right… they’re passive because they have to be activated by the reader. It’s important to note, here, that the tests done in the study were done with a live reader — the IDs were being read at the time.

    Passive tags are not a danger in the absence of a reader: there’s no EM to activate them. So the point is that if, say, medicine bottles are tagged, the presence of a bottle in someone’s room is not a worry. But if someone was planning to install a reader at the patient’s bed, say, to warn that the wrong drug was just brought within range… that could be a problem.

  2. #2 Daniel Newby
    June 25, 2008

    I am not surprised. A lot of medical equipment is poorly shielded: its circuitry incorrectly picks up radio-frequency radiation and treats it as a real signal, causing misoperation. You would think that life-critical equipment would be shielded to hell and gone, but this feature is often sorely lacking.

    “The galling thing is, it has been known for years that UHF RFIDs operate in the ISM (Industrial, Scientific, Medical) part of the spectrum, specifically the passive 868-MHz RFIDs.”

    Spectral overlap is not the major problem. The medical device circuitry erroneously picks up signals over a wide range of frequencies. The RFID equipment might jam wireless telemetry systems that operate in the ISM band, but the central monitor would simply signal an alarm due to loss of contact.

    Anyway, I question the utility of RFID in a hospital, since RFID cannot positively track the exact location of an item. E.g., giving the prescription computer a list of all the ampoules in a room is not nearly as useful as have a nurse barcode scan them one at a time as they are dosed.