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EM Field Theory Applied: EM Field Theory Applied:

Defibrillators Defibrillators

Vince BaierCorey ProvencherAdam SpirerKory Williams

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HistoryHistoryFirst Demonstration; 1899, Prevost andFirst Demonstration; 1899, Prevost and BatelliBatelli , Physiologists from, Physiologists fromSwitzerland.Switzerland.Small charges cause ventricular fibrillationSmall charges cause ventricular fibrillationLarge charges reverse the syndrome.Large charges reverse the syndrome.Claude Beck, 1947, Western Reserve UniversityClaude Beck, 1947, Western Reserve University

Heart too good to dieHeart too good to die 14 Year Old Boy saved from congenital heart disease by14 Year Old Boy saved from congenital heart disease bydefibrillation with procaine amide heart medicine.defibrillation with procaine amide heart medicine.AC Current 110AC Current 110 --240 V240 V 300300 --1000 V1000 V ; Damage to Cells; Bulky; Damage to Cells; Bulky

TransformersTransformersDr V.Dr V. EskinEskin and A.and A. KlimovKlimov in Frunze , USSR 1950in Frunze , USSR 1950 s; Closed Chests; Closed ChestMethod; AC >1000VMethod; AC >1000V

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HistoryHistoryBernardBernard LownLown ; 1959 DC Capacitors to achieve ~1000V (Approx.; 1959 DC Capacitors to achieve ~1000V (Approx.100100 --200 Joules)200 Joules)Charge through an inductance to produce heavily dampedCharge through an inductance to produce heavily dampedsinusoidal wave;sinusoidal wave; LownLown WaveformWaveform19801980 s BTE Lower Energy, Weight Reductions BTE Lower Energy, Weight Reduction

Modern Machines: BTE with Automatic measurement of Modern Machines: BTE with Automatic measurement of transthoracictransthoracic impedanceimpedanceFrankFrank PantridgePantridge , Belfast, Belfast ; Portable Machines; Portable MachinesStephenStephen HeilmanHeilman ,, AloisAlois Langer, Morton Mower,Langer, Morton Mower, MichelMichel MirowskiMirowski ,,andand Mir Mir ImranImran ; ICD; ICDFebruary 1980 atFebruary 1980 at Johns Hopkins HospitalJohns Hopkins Hospital by Dr. Levi Watkins,by Dr. Levi Watkins, Jr Jr

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TypesTypes

External ManualExternal ManualDefibrillator Defibrillator

Internal ManualInternal ManualDefibrillator Defibrillator

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TypesTypesAutomated ExternalAutomated External

Defibrillator (AED)Defibrillator (AED)

ImplantableImplantable Cardioverter Cardioverter --Defibrillator Defibrillator

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CapacitorsCapacitorsStores electric chargeStores electric charge

when voltage appliedwhen voltage applied(finite charge time)(finite charge time)Discharges currentDischarges current

rapidly to load (morerapidly to load (moreso than a battery)so than a battery)

C =C = s / ds / d

Charge Q=CVCharge Q=CVEnergy E=(1/2)CVEnergy E=(1/2)CV 22

Discharge time t=RCDischarge time t=RC

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CircuitryCircuitryCapacitor stores energy for Capacitor stores energy for defibrillationdefibrillation

Cap charged to ~1000VCap charged to ~1000VDelivers 100Delivers 100 --200 J to patient200 J to patientDischarge time ~5Discharge time ~5 --10ms10ms

Inductor used to create a finiteInductor used to create a finite

damped sine wave from DCdamped sine wave from DC((LownLown waveform)waveform)MonophasicMonophasic vs. biphasicvs. biphasicwaveformswaveforms

Body modeled as impedanceBody modeled as impedanceBody contactsBody contacts 25 lbs.25 lbs.pressure required to avoidpressure required to avoidstatic dischargestatic discharge

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ApplicationApplicationExternal Units:External Units:

GelGelLower ResistanceLower ResistanceWet vs. Dry GelWet vs. Dry Gel

Apply Paddles; 25lbsApply Paddles; 25lbsAutomatic vs. ManualAutomatic vs. ManualElectrodesElectrodes

Safer, Better EKGSafer, Better EKG

ReadingsReadings

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ApplicationApplicationInternal Units:Internal Units:

Only for those who are atOnly for those who are at

severe risk;severe risk;Ventricular fibrillation (unproductiveVentricular fibrillation (unproductiveheartbeat), ventricular tachycardiaheartbeat), ventricular tachycardia(abnormally fast heartbeat), long QT(abnormally fast heartbeat), long QTsyndrome (an inherited heart disease)syndrome (an inherited heart disease)

Placement:Placement:Lead Wire from Cephalic vein to heartLead Wire from Cephalic vein to heart

chamber chamber Electrode implanted lower chamber Electrode implanted lower chamber heart muscle (LV or LA)heart muscle (LV or LA)

Tech. SpecsTech. SpecsLiLi--Ion BatteryIon BatteryWandWand Programming over RFProgramming over RFElectrodes; Platinum, SiliconeElectrodes; Platinum, Silicone

TreatmentTreatmentPacing RegimenPacing Regimen CardioversionCardioversion DefibrillationDefibrillation

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ReferencesReferencesAmerican Red Cross: Saving a Life is as Easy as AAmerican Red Cross: Saving a Life is as Easy as A --EE --DDFDA Heart Health Online: Automated External Defibrillator (AED)FDA Heart Health Online: Automated External Defibrillator (AED)Resuscitation Council (UK)Resuscitation Council (UK)History of defibrillationHistory of defibrillationHow an internal defibrillator is implantedHow an internal defibrillator is implanted from Children's Hospital Heartfrom Children's Hospital HeartCenter, Seattle.Center, Seattle.http://www.arpansa.gov.au/uvrg/rginfo_p15.htmlhttp://www.arpansa.gov.au/uvrg/rginfo_p15.htmlhttp://www.arpansa.gov.au/uvrg/rginfo_p15.htmlhttp://www.arpansa.gov.au/uvrg/rginfo_p15.htmlhttp://www.medical.philips.com/main/products/resuscitation/biphahttp://www.medical.philips.com/main/products/resuscitation/bipha sic_technosic_technology/understanding_electricity.htmllogy/understanding_electricity.html