Biomedical Engineering Reference
In-Depth Information
that dielectric breakdown or single-fault conditions may result in any part of the device under
test becoming electri
fi
ed at very high voltage, threatening anyone who came close to it.
Testing for Other Risks
You will probably be able to get by just by being able to pass the tests outlined above as
long as evaluation of the prototype is conducted on a very limited number of patients while
under the supervision of a physician. As long as the instrument is built solidly enough to
inspire con
dence, we have seldom encountered situations where an engineering evalua-
tion prototype would be required to pass the battery of tests speci
fi
ed by the standards to
ensure compliance with the mechanical and labeling requirements demanded for prere-
lease or commercial products. However, there are other very realistic risks in a clinical
environment, and you should make sure that you will not cause undue interference or harm
through mechanisms other than leakage currents.
For an evaluation prototype, you should at least test for and verify that the following
conditions are met:
fi
• The equipment has been designed to minimize the risk of
fire and explosion. Safety
standards typically limit temperature rises allowed for components as well as de
fi
fi
ning
enclosure requirements for containing
fires within the instrument. Whenever possible,
select materials to be compliant with UL-94V (
Flammability of Plastic Materials for
Parts in Devices and Appliances
). In addition, if the device is supposed to operate in
areas where
fi
flammable anesthetics or oxygen-enriched atmospheres are used (e.g.,
operating rooms, hospital rooms), special requirements must be met to ensure that
these explosive atmospheres are not ignited.
• If intentional sources of ionizing radiation are present, the equipment must be evalu-
ated by the Center for Devices and Radiological Health (CDRH). If components are
used that may generate ionizing radiation which is not used for a diagnostic or ther-
apeutic purpose (e.g., from CRTs), you must ensure that the exposure at a distance of
5 cm from any accessible part of the equipment, averaged over a 10-cm
2
area, is less
than 0.5 milliroentgen per hour. Devices that make use of ultraviolet radiation and
lasers should also be investigated to ensure safety. In addition, devices that make
use of ultrasound and RF emissions are also regulated in speci
fl
fi
c substandards of the
IEC-601-2 series.
• The equipment must not emit electromagnetic interference (EMI), which may cause
other equipment to malfunction. The device should also be designed to be immune to
electromagnetic interference, power line “glitches,” and electrostatic discharge. We
deal with these issues in Chapter 4.
• Applied parts designed to come in contact with the biological tissues, cells, or body
fl
fluids of a patient must be assessed as to their biocompatibility. Diligent prudence
should be applied in the selection of materials, making sure to test for biological
e
ects, including cytotoxicity, sensitization, irritation, intracutaneous reactivity, and
so on.
• The medical device and all peripheral equipment should be
ff
fitted with the means neces-
sary to disconnect them from a patient immediately and completely should an emer-
gency arise. In addition, connectors used on patient connections are identi
fi
ed clearly and
uniquely and must be of a type that cannot be plugged into the power line accidentally
or form an electrical path to any point when they are not connected to the equipment.
fi
mem-
bers who support your evaluations as to the potential dangers posed by an instrument,
In addition to establishing reasonable safety, take the time to educate clinical staff
ff
Search WWH ::
Custom Search