Note: This post is my reading notes from the book Medical Device Accidents. It is a good source of knowledge for me and the book is easy to read.

  • Leslie A. Geddes
  • CRC Press
  • 1998
  • ENGR. R856.6 G43 1998

Product Liability and Medical Technology

Background

  • By 1938 in the U.S., it became recognized by the lawmakers that the public needed protection against unscrupulous vendors of a variety of medical products.
  • In 1938, FDA was given the authority for seizure, injunction, or criminal prosecution with respect to adulterated or misbranded devices.

Medical Technology

  • ~100,000 cardiac pacemakers are implanted manually.
  • Interference of a pacemaker, causing arrhythmia in the ECG of a patient, was due to an electronic device measure his urine.

Product Liability

  • Three aspects: manufacturing, design, and misrepresentation.
  • A hazardous situation arises from product defect, misuse, negligence, and design defect.

Medical Device Reports

  • In 1990, SMDA passed by congress. Effective on May 28, 1992. Amended in 1995.
  • Mandated the reporting of incidents associated with the medical devices to FDA in the form of MDR.

Chemical Hazards

  • A separate topic. Information can be found in the Materials Safety Data Sheet (MSDS), the Drug Insert (DI), and the Physician’s Desk Reference (PDR).

The Incident Report

  • Report the basic facts about an incident
  • Does not assign culpability to anyone

Electromagnetic Interference and Electrostatic Discharge

  • Frequency ranges from kHz—GHz.
  • Affects MD depending on intensity, frequency, and type of modulation.
  • Affecting an electronic device via many paths
    • Battery operated device: easy access if target is not shielded
    • Cable or fluid-fill catheter connects the patient, then the catheter-patient path is a antenna.
    • Power-line operated: enter via power line.
    • Battery operated but battery charged by a charger, then EMI can enter via the power line.

Sources of EMI

  • Radio broadcasting
  • TV
  • Public safety and land transportation (frequencies allocated to police, fire, and emergency services, taxis, buses, trucks, railroads, etc.)
  • Cellular telephones and paging services
  • Amateur radio and citizens bands
  • Industrial, scientific, and medical
  • Radar

Testing EMI

  • Using a patient simulator (can be as simple as a resistor)
  • Various patient models (for EMI testing) has been designed by AAMI and/or others

Examples of Device Malfunction due to EMI

  • Silbert et al. Testing of EEG of a four-year-old boy affected by cellphone signals (even no phone rings)
  • Knutson and Bulkeley. Pacemaker ECG telemetry system made by SpaceLabs Inc. shows “long periods of flat line” due to TV signals
  • Apnea (temporary breath breaks) monitor produces less accurate results due to perspiration at place of contact on skin, since the device is impedance-based. This can cause problems if patient stops breathing but the heart continues to pump blood with inadequate oxygen.
  • Silberg 1993. A variety of mishaps with ventilators.
    • Ventilator keys lockup due to interference from a guard’s walkie-talkie.
    • “Extreme events” including the simultaneous use of multiple equipment lead to power line disturbances, causing a ventilator in cessation of ventilation, inoperative monitoring, display or error messages, or display of unintelligible messages.
    • Ventilator stopped cycling and alarmed while used during a flight.
    • Etc.
  • Power-vehicle mishaps
  • Cellular and mobile telephone-generated EMI
  • Infant radiant warmer
  • Paging system generated EMI

Cardiac Pacemakers and EMI

  • Wajsczuk et al. 1969. A demand pacemaker was inhibited when electrosurgical unit was activated
  • Wise 1971. Both the cutting and coagulating current inhibited a demand pacemaker.
  • Greene and Meredith 1972. Newer demand pacemakers revert to fixed rate pacing when interference is present.
  • Bellott et al. 1984. Reprogramming of DDD pacemakers by electrosurgical current possible. Experiments on 140 cases from 5 manufactures.
  • Abandoned pacemaker lead causes arrhythmias.
  • Pacemaker malfunction due to
    • Cellphones
    • MRI (magnetic resonance images)
    • Microwave-oven
    • Low-frequency EMI
    • Arc welding machines

Electrostatic Discharge (ESD)

  • Example: Electrostatic charge released on to an infusion pump case, causing the pump to fail.

Electrosurgery

  • Chapter skipped on first reading. Most accidents related to burns and/or unintended cuts.

Anesthesia

  • 20 million anesthetic procedures performed annually (~ year 1998)
  • 5000 cases of brain damage associated
  • Pulse-ox is a great improvement in assessment of adequacy of respiratory function

Some Background (Skipped)

  • Anesthesia machine
    • In-circuit type and out-of-circuit type
    • Circuit refers to patient breathing cycle
  • Auxiliary equipment
    • Ventilator
    • Humidifier
    • Warming blanket, warming cabinet
    • Defibrillator
  • Related monitoring equipment
    • Anesthesia-machine monitoring
    • Patient monitoring
    • Alarms

Mishaps with Anesthesia Machine

  • Failure in absorbing exhaled carbon-dioxide
  • Valve malfunction
  • Leaks & disconnections

Pulse Oximeter

  • Theory on page 136–137
  • By itself not much hazards, but in the environment it is used there is high oxygen concentration and fire is possible (Comment: it is like a hazard to anesthesia machine rather than pulse-ox)

Fire Hazards

  • By defibrillator
  • By endotracheal tube
  • By laser

Four More Skipped Chapters

  • Catheter Accidents
  • Direct-Current Injuries
  • Transcutaneous Electrical Nerve Stimulation
  • Tissue Injury

Experiences That May Help Technical Experts

  • Chapter about author’s legal & investigation experience
    • Medical device investigation
    • Patent infringement and invalidation

Where to find information

  • Medical device accidents
    • Attorneys and expert witness always want to know if the accident under investigation is common or rare.
    • Medical Device Reports (MDRs) from FDA.
    • Gendron (1988). Unexplained Patient Burns. Quest Publishing.
    • Shepherd (1992). Shepherd’s System for Medical Device Investigation and Reporting. Quest Publishing.
    • Large data base on medical device accidents maintained by Emergency Care Research Institute (ECRI).
    • Journal Health Devices by ECRI.
    • On anesthesia, Closed Claims Data Base maintained by American Society of Anesthesiologists (ASA).
    • Database maintained by Wood Library of Museum of Anesthesiology.
  • Medical device standards
    • FDA
    • AAMI/ANSI
    • American Society for Testing Materials (ASTM)
    • National Fire Protection Association
    • The Underwriters Laboratory
    • The Electronic Industries Association (EIA)
    • Canadian Standards Association (CSA, FDA analog in Canada)
    • International Electrotechnical Commission (EIC, FDA analog in Europe)
    • Global Engineering Documents
  • Legal documents
    • Lexis-Nexis data base
    • WestDoc data base by West Publishing Co.