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전 기 안 전 (Electrical Safety). 서울대학교병원 의공학과 김 희찬. 목 차. Clinical Engineer A Historical Perspective Safety Issue Electrical Safety Physiological effects of electricity Important susceptibility parameters Perception threshold Electricity conduction mechanism

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electrical safety

전 기 안 전(Electrical Safety)

서울대학교병원 의공학과

김 희찬

slide2
목 차
  • Clinical Engineer
  • A Historical Perspective
  • Safety Issue
  • Electrical Safety
  • Physiological effects of electricity
  • Important susceptibility parameters
  • Perception threshold
  • Electricity conduction mechanism
  • Distribution of Electrical Power
  • My Experience
  • Macroshock Hazards
  • Microshock Hazards
clinical engineer definition
Clinical Engineer-definition
  • Biomedical Engineers assist in struggle against illness and disease by providing materials and tools that can be utilized for research, diagnosis, and treatment by health care professionals.
  • Clinical Engineer have achieved this position by assuming responsibility for managing the use of medical equipment within the hospital environment
clinical engineer definition1
Clinical Engineer-definition
  • The American Hospital Association : “a person who adapts, maintains, and improves the safe use of equipment and instruments in the hospital”
  • The Association for the Advancement of Medical Instrumentation (AAMI) : “a professional who brings to health-care facilities a level of education, experience, and accomplishment which will enable him/her to responsibly, effectively, and safely manage and interface with medical devices, instruments, and systems and the user thereof during patient care”
clinical engineer definition2
Clinical Engineer-definition
  • The American College of Clinical Engineering (ACCE) : “a professional who supports and advances patient care by applying engineering and managerial skills to health-care technology”
  • The Board of Examiners for Clinical Engineering Certification : “an engineer whose professional focus is on patient-device interfacing; one who applies engineering principles in managing medical systems and devices in the patient setting”
a historical perspective
A Historical Perspective
  • Engineer’s first enter to clinical scene : late 1960s in response to concerns about electrical safety of hospital patient
  • Ralph Nader (consumer activist) : “at the very least, 1200 Americans are electrocuted annually during routine diagnostic and therapeutic procedures in hospitals” Ladies Home Journal, April 24, 1970
  • Raise the level of concern about safe use of medical device
a historical perspective cont
A Historical Perspective- cont.
  • Overnight growth of a new industry : hospital electrical safety
  • National Fire Protection Association (NFPA) : standards addressing electrical safety in hospital
  • Joint Commission on the Accreditation of Hospital : “hospital must inspect all equipment used on or near a patient for electrical safety at least every 6 months”
  • Hospital administrator’s options
    • Paying medical device manufacturer
    • Service contracting
    • In-house staff
  • New engineering discipline – clinical engineering - was born.
safety issue
Safety Issue
  • In USA, about 10,000 device-related patient injuries each year
  • Most injuries are attributable to improper use of a device as a result of inadequate training and lack of experience
  • Medical personnel rarely read user manuals until a problem occurred
  • “Everything that can go wrong eventually will go wrong” Murphy’s law
electrical safety1
Electrical Safety
  • Electric Shock : unwanted or unnecessary physiological response to current.
  • Three phenomena :
    • (1) electrical stimulation of excitable tissue (nerve & muscle)
    • (2) resistive heating of tissue, and
    • (3) electrochemical burns and tissue damage
slide10

Physiological effects of electricity

70-Kg

(1~6A)

(75~400mA)

(max. current at which the subject

can withdraw voluntarily:min. 6mA)

important susceptibility parameters
Important susceptibility parameters

Fibrillation current vs. shock duration & weight

Let-go current vs. frequency

perception threshold
Perception Threshold
  • D’Arsonval(galvanometer fame) : showed when current was passed through the human body, no sensation was perceived as the frequency was increased beyond 2500-5000Hz.(100W light bulb connected two human subjects (arm to arm) burn brilliantly with 1A current)
  • Medical diathermy, Electro-surgical Unit (Bovie)
slide13

Cross-sectional view

of skin layers

A cell model

slide14

Electricity Conduction Mechanism

Charge carrier

Charge carrier

e-

e-

skin

Charge carrier

ions

cell

wire(metal)

wire(metal)

Tissue

Electrolyte/Dielectric

electrode(metal)

electrode(metal)

Electrochemical Reactions

slide15

Important susceptibility parameters

For dog: 20A, human : 80~600 A

Safety limit : 10 A

Fibrillation current : lead I > lead II, III

Effect of entry point on current distribution

slide16

Distribution of Electric Power

Ex) 120V, 500W instruments, power-cord resistance 0.25

Then the voltage drop across the neutral to ground is 0.25(500/120) = 1.04V

my experience
My experience

- Isolation transformer 와 3-prong plug의 중요성 -

질문: 다음과 같은 회로에서 Isolation transformer를 쓰지 않는 것과 2구, 3구 플러그를 혼용해서 쓰는 것의 위험성을 설명해 보시오.

slide18

Macroshock Hazards

질문: 왼쪽 그림을 보고 macroshock이 일어나는 과정을 설명하시오.

slide19

Microshock Hazards

질문: 왼쪽 그림을 보고 microshock이 일어나는 과정을 설명하시오.