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EMI and medical devices.ppt - EMI and medical devices

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EMI and medical devices.ppt - EMI and medical devices Powered By Docstoc
					EMI and medical devices

    The problem: the EMI environment; why?
    Device types emitting EMI
    Devices affected
    Stakeholders
    Historical development and issues
    Solutions
    Standards
    The problem
   EMI—causes potential malfunctions of
    medical devices
   --near misses

   In USA, most medical devices are exempt
    from FCC emission requirements
    The problem..continued
   1979-93: 100 reports FDA
   Now FDA re-evaluating 400,000
    malfunctions (1984-94) to see if EMI
    involved– expect 1000 to be related
EMI environment

   Changes with time

   Expensive to monitor

   Can behave differently in a lab
    Why problems can be
    common
   Physiological & biological signals are
    typically very low (mV or microV)
   Use high gain amplifiers
   Leads, cables, body, act as antennas
   Coupling signals and rectification signals
    at electrode interfaces
   Home devices
    Typical devices that emit EMI

   Local high power AM/FM & TV transmitters
   Paging systems
   Cellular phone base stations & repeaters
   Two way radios
   Amateur or CB radio
   Wireless communication devices
   Microwave ovens
   Static discharge (people)
    Others (medical)
   Electrosurgical generators
   Diathermy machines
   Ultrasound therapy machines
   Interferential therapy machines
   Electrical drills
    Devices frequently affected
   Patient monitors
   Infusion devices
   Pacemakers and implantable defibrillators
   Infusion pumps
   Ventilators
   Pulse oximeters
   Apnea monitors
   Hearing aids
   Incubators and radiant warmers
    Who are the stakeholders?
   Users
   Manufacturers
   Voluntary standards organisations (ex.
    AAMI, )
   Regulators (ex. FDA, Medical Device
    Bureau in Canada)
   Test laboratories and researchers
    Historical perspectives (30
    years)
   In the 1970s: Main sources AM/FM, elevators,
    microwave ovens
   Examples: EEG signals to confirm brain
    death; EMG and evoked potential signals;
    pacemakers
   Solutions: Separation, Isolation, or Faraday
    cage? Education? Better cover (Titanium),
    bipolar leads, stronger signals
Continued….
   Apnea monitors (the NB experience)
   Infusion pumps and wheel chairs out of
    control
   Incubators shut off or re-programmed
   Dialysis re-programmed

   Today: More sources than ever but
    more EMC protection
    Solutions
   Policy for safe zones (ex. Moncton H. in 1979
    (ban equipment in ICU, etc)
   Policy for home care devices in 1980
   Policy for use of insulation (gloves) to
    manipulate sensitive equipment
   Policy to manage equipment and EMI sources
   Document all malfunctions & investigate
   Use low power devices, better EMC
   Move patient or move the source!
    Other issues

   Lack of appropriate standards
   Proliferation of medical equipment
   Potential interaction between devices
   Awareness level of users/manufacturers
   Intermittent sources of emission
    Types of incidents
   True positives—replication of incident at a
    site and /or a lab—increases degree of
    confidence on nature of incident
   False positives– attributed to EMI but
    probably is NOT– perhaps a software problem
    or other malfunction
   False negatives– not attributed to EMI but is
    likely from EMI—often happens if reporter
    NOT familiar with EMI—sometimes confirmed
    by alert from manufacturer
    Types of malfunctions
   Operation out of specifications
   Operator intervention needed
   Fault—needing repair
   Operation out of control
   Silent malfunction-- Not functioning at all
   Discrepancy between clinical reality and
    readout
   Impossibility of reading signals
   Note: Some devices are unreasonably
    susceptible
    Standards
   MDS-201-0004 (1979) voluntary –inadequate
    and not harmonized IEC
   IEC.601-1-2 Collateral to IEC.601-1 (general
    safety of medical equipment)—determined
    that tests in BW significant for labelling of
    medical devices
   Recommendation: testing at 3V/m (pulse
    modulation or 80 % sine wave modulation at
    0.5 Hz, over 26 MHz to 1 GHz, with standard
    placement of cables
   Quasi-static field: 2000V/m at 0.5 Hz
    Sources of information
   http://www.fda.gov/cdrh/ost/reports/fy98/ELE
    CTRO_MAG.HTM

    http://www.fda.gov/cdrh/emc/persp.html

    http://www.fda.gov/cdrh/ost/ostannrpfy98.pdf

   http://www.fda.gov/cdrh/ost/emi.html

				
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