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05 ElectricalStimulation

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Electrical Shock - Definition
„„
„„
Electric
Electric Shock
Shock :: unwanted
unwanted or
or unnecessary
unnecessary
physiological
physiological response
response to
to current
current
Three
Three phenomena
phenomena
①
① electrical
electrical stimulation
stimulation of
of excitable
excitable tissue
tissue
(nerve
(nerve && muscle)
muscle)
②
② resistive
resistive heating
heating of
of tissue,
tissue, and
and
③
③ electrochemical
electrochemical burns
burns and
and tissue
tissue damage
damage
Electricity Conduction Mechanism
Charge carrier
e-
Charge carrier
Charge carrier
e-
skin
ions
cell
wire(metal)
electrode(metal)
wire(metal)
Tissue
electrode(metal)
Electrolyte/Dielectric
Electrochemical Reactions
Physiological effects of Electricity
Type
(60Hz)
Current range
(mA)
Physiological
effects
Threshold
1 – 5
tingling sensation
Pain
5 – 8
intense or painful
sensation
Let-go
Paralysis
Fibrillation
8 - 20
>20
threshold of involuntary
muscle contraction
respiratory paralysis
and pain
80–1,000 ventricular and heart
fibrillation
Defibrillation 1,000 10,000
sustained
myocardial contraction
and possible tissue burns
Electrical Shock - Types
The
Thecurrent
currentdensity
densityaccompanying
accompanyingmicroshock
microshockversus
versusthat
that
accompanying
accompanyingmacroshock
macroshock
Important susceptibility parameters
Fibrillation current : lead I > lead II, III
For dog: 20µA, human : 80~600 µA
Safety limit : 10 µA
Effect
Effect of
of entry
entry point
point on
on current
current distribution
distribution
Distribution of Electric Power
Ex) 120V, 500W instruments, power-cord resistance 0.25Ω
Then the voltage drop across the neutral to ground is 0.25(500/120) = 1.04V
Macroshock Hazards
질문 : 왼쪽 그림을 보고
macroshock이 일어나는
과정을 설명하시오.
Microshock Hazards
질문 : 왼쪽 그림을 보고
microshock이 일어나는
과정을 설명하시오.
Perception Threshold
„„
D’Arsonval(galvanometer
D’Arsonval(galvanometer fame)
fame) :: showed
showed when
when
current
current was
was passed
passed through
through the
the human
human body,
body, no
no
sensation
sensation was
was perceived
perceived as
as the
the frequency
frequency was
was
increased
increased beyond
beyond 2500-5000Hz.(100W
2500-5000Hz.(100W light
light bulb
bulb
connected
connected two
two human
human subjects
subjects (arm
(arm to
to arm)
arm)
burn
burn brilliantly
brilliantly with
with 1A
1A current)
current)
„„
Medical
Medical diathermy,
diathermy, Electro-surgical
Electro-surgical Unit
Unit (Bovie)
(Bovie)
Electrosurgical Unit(ESU) - Bovie
World
WorldWar
WarIINavy
Navyship
shipspark-gap
spark-gaptransmitter
transmitterat
atHarvard
HarvardUniv.
Univ.
„ 1925 : W.T. Bovie  Harvey Cushing for neurosurgery
„ 1925 : W.T. Bovie  Harvey Cushing for neurosurgery
„
„
1950
1950::widely
widelyused
usedwith
withnonflammable
nonflammableanesthetics
anesthetics
„
„
Electrosurgical Unit(ESU) - principle
radio
radiofrequency
frequencyoscillator
oscillator::300kHz
300kHz--33MHz,
MHz,noise
noisegenerator
generator
„ voltages : 1,000 - 10,000 volts peak-to-peak
„ voltages : 1,000 - 10,000 volts peak-to-peak
„
„
breakdown
breakdownfield
fieldintensity
intensityin
inair
air::30kV/cm
30kV/cm¿
¿0.33cm
[email protected]
@10,000
10,000VV
„ mode select : cutting, coagulation
„ mode select : cutting, coagulation
„
„
return
returnelectrode
electrode::low
lowresistance
resistance
„
„
Electrical Safety - ESU
How doesn’t
doesn’t ESU
ESU produce
produce electrical
electrical shock
shock in
in patients?
patients?
„„ How
6.3A isis required
required @
@ 500kHz
500kHz to
to generate
generate action
action potential
potential
-- 6.3A
causing the
the cells
cells to
to vaporize
vaporize rather
rather than
than depolarize
depolarize
-- causing
Equivalent circuit of
a cell and tissue model
Let-go current from
arm to arm as a
function of frequency
Electrical Stimulation
Cardiac Pacemaker
Advanced Pain TherapyNeurostimulation
Deep-brain Stimulator
Cochlear Implant
Functional Electrical Stimulation
- restoring function through electrical stimulation -
Defibrillator
Energylevels
levels
„„Energy
Externaldefibrillation:
defibrillation:22--360
360JJ
--External
Capacitorcharging
chargingtime:
time:8sec
8secto
to360J/4sec
360J/4secto
to
--Capacitor
200J.
200J.
Defibrillationpulse
pulse
„„Defibrillation
Waveform:Damped
Dampedsinusoidal
sinusoidalhalfwave
halfwave(Edmark)
(Edmark)
--Waveform:
Synchronizeddelay:
delay:@@40
40ms
msfrom
fromR-wave
R-wavetrigger
trigger
--Synchronized
Defibrillationelectrodes
electrodes
„„Defibrillation
Hardpaddles:
paddles:Hard
Hardpaddles
paddles(80
(80cm
cm2)2)
--Hard
2).
Pediatricadapter
adapter(17
(17cm
cm2).
Pediatric
Scarica