Biomedical Engineering Reference
In-Depth Information
power failures. This is important if hard drives are
to avoid a crash during momentary voltage drops.
Make use of available resources
such as EMC
professionals and publications and Internet web pages
on the subject of medical device EMC;
•
Assess
the electromagnetic environment of the
facility (e.g., identify radio transmitters in around
the facility) and identify areas where critical medical
devices are used (e.g., ER, ICU, CCU, NICU);
19.3.4 Security Approach
Monitoring for IEMI of high value, high risk
targets such as government installations has been
advocated by several authors [6,7,14]. This prob-
ably exceeds the capabilities of most medical facil-
ities. Physical security, on the other hand, should
be routine at all facilities. Access to power and
wired communications should be prevented. Much
has been written regarding radiated threats, but it
is much easier to inject EMI into a building when
there is easy access to its infrastructure. Parfenov
et al. have shown that signals as low as 0.4 V
injected into the power or earthing circuits of a
commercial building can cause disruption of tele-
phone equipment. A pulsed signal of several kV
can cause catastrophic destruction of equipment
[20]. Buffer zones around all buildings should be
designed and monitored. Critical equipment should
be located towards the interior of the building,
away from outer walls and always have uninter-
ruptible power supplies.
•
Manage
the electromagnetic environment, RF
transmitters and all electrical and electronic equip-
ment, including medical devices, to reduce the risk
of medical device EMI and achieve EMC;
•
Coordinate
the purchase, installation, service, and
management of all electrical and electronic equip-
ment used in the facility to achieve EMC;
•
Educate
healthcare facility staff, contractors, visi-
tors, and patients about EMC and EMI and how
they can recognize medical device EMI and help
minimize EMI risks;
•
Establish and implement written policies and
procedures
that document the intentions and
methods of the healthcare institution for reducing
the risk of medical device EMI and achieving EMC;
•
Report
EMI problems to the FDA MedWatch
program and communicate EMI/EMC experi-
ences to colleagues in open forums such as
medical/technical publications and conferences.
Figure 19.8
FDA recommendations
for
health
care
facilities [27].
a useful, non-destructive, and non-disruptive test
of radiated immunity for high value systems.
ANSI C63.18 [23] can be used for most other
systems to detect vulnerabilities. TIR 18 [24]
from the Association for the Advancement of
Medical Instrumentation is recommended by the
FDA (see Figures 19.8 and 19.9). Strong consid-
eration should be given to obtaining the services
of a consultant who specializes in EMI/TEMPEST
assessment and mitigation.
19.3.5 Testing
Nitsch [21] demonstrated that the more complex
the system, the lower the power level necessary
to cause equipment disruption. Hoad [22] exam-
ined the susceptibility of i486
®
and Pentium4
®
computers in a mode stirred reverberation chamber.
They demonstrated, unexpectedly, that more
modern systems with higher clock rates had more
immunity. They speculate that the newer systems
had better internal shielding to accommodate the
faster speeds.
Flintoft [8] demonstrated that measuring the
re-radiated spectrum can be used to predict
the susceptibility of a device at field strengths
below that which cause actual failure. “Specifi-
cally, non-linear behavior in the cross-modulation
products was observed as the incident field
strength approached that required to cause equip-
ment failure” [
−
5 dB and below]. This suggests
19.4 Summary
Intentional and unintentional EMI is a growing
threat to the integrity of health care organizations.
It has the ability to degrade or totally disrupt
healthcare delivery. It is imperative that biomed-
ical engineers understand the problem and institute
robust mitigation programs to ensure the ability to
survive in a crisis.
