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 0.33cm@ @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
