EM Field Theory Applied: EM Field Theory Applied: Defibrillators Defibrillators Vince Baier Corey Provencher Adam Spirer Kory Williams
History History � � First Demonstration; 1899, Prevost and Batelli Batelli, Physiologists from , Physiologists from First Demonstration; 1899, Prevost and Switzerland. Switzerland. � � Small charges cause ventricular fibrillation Small charges cause ventricular fibrillation � � Large charges reverse the syndrome. Large charges reverse the syndrome. � � Claude Beck, 1947, Western Reserve University Claude Beck, 1947, Western Reserve University ‘Heart too good to die Heart too good to die” ” ‘ � � 14 Year Old Boy saved from congenital heart disease by 14 Year Old Boy saved from congenital heart disease by defibrillation with procaine amide heart medicine. defibrillation with procaine amide heart medicine. � � AC Current 110- -240 V 240 V → → 300 300- -1000 V 1000 V; Damage to Cells; Bulky ; Damage to Cells; Bulky AC Current 110 Transformers Transformers � � Dr V. Dr V. Eskin Eskin and A. and A. Klimov Klimov in Frunze , USSR 1950 in Frunze , USSR 1950’ ’s; Closed Chest s; Closed Chest Method; AC >1000V Method; AC >1000V
History History � � Bernard Lown Lown; 1959 DC Capacitors to achieve ~1000V (Approx. ; 1959 DC Capacitors to achieve ~1000V (Approx. Bernard 100- -200 Joules) 200 Joules) 100 � � Charge through an inductance to produce heavily damped Charge through an inductance to produce heavily damped sinusoidal wave; Lown Lown Waveform Waveform sinusoidal wave; � � 1980’ ’s BTE Lower Energy, Weight Reduction s BTE Lower Energy, Weight Reduction 1980 � � Modern Machines: BTE with Automatic measurement of Modern Machines: BTE with Automatic measurement of transthoracic impedance transthoracic impedance � � Frank Pantridge Pantridge, Belfast , Belfast; Portable Machines ; Portable Machines Frank � � Stephen Heilman Heilman, , Alois Alois Langer, Morton Mower, Langer, Morton Mower, Michel Michel Mirowski Mirowski, , Stephen and Mir Mir Imran Imran; ICD ; ICD and � � February 1980 at Johns Hopkins Hospital Johns Hopkins Hospital by Dr. Levi Watkins, by Dr. Levi Watkins, Jr Jr February 1980 at
Types Types � External Manual � External Manual Defibrillator Defibrillator � Internal Manual � Internal Manual Defibrillator Defibrillator
Types Types � Automated External � Automated External Defibrillator (AED) Defibrillator (AED) � Implantable � Implantable Cardioverter Cardioverter- - Defibrillator Defibrillator
Capacitors Capacitors � Stores electric charge � Stores electric charge when voltage applied when voltage applied (finite charge time) (finite charge time) � Discharges current � Discharges current rapidly to load (more rapidly to load (more so than a battery) so than a battery) C = ε ε s / d s / d C = Charge Q=CV Charge Q=CV Energy E=(1/2)CV Energy E=(1/2)CV 2 2 Discharge time t=RC Discharge time t=RC
Circuitry Circuitry � � Capacitor stores energy for Capacitor stores energy for defibrillation defibrillation � Cap charged to ~1000V � Cap charged to ~1000V � Delivers 100- -200 J to patient 200 J to patient � Delivers 100 � Discharge time ~5- -10ms 10ms � Discharge time ~5 � � Inductor used to create a finite Inductor used to create a finite damped sine wave from DC damped sine wave from DC (Lown Lown waveform) waveform) ( � Monophasic vs. biphasic vs. biphasic � Monophasic waveforms waveforms � � Body modeled as impedance Body modeled as impedance � � Body contacts – – 25 lbs. 25 lbs. Body contacts pressure required to avoid pressure required to avoid static discharge static discharge
Application Application � External Units: � External Units: � Gel Gel � � Lower Resistance � Lower Resistance � Wet vs. Dry Gel � Wet vs. Dry Gel � Apply Paddles; 25lbs Apply Paddles; 25lbs � � Automatic vs. Manual � Automatic vs. Manual � Electrodes Electrodes � � Safer, Better EKG � Safer, Better EKG Readings Readings
Application Application � Internal Units: � Internal Units: � Only for those who are at � Only for those who are at severe risk; severe risk; � � Ventricular fibrillation (unproductive Ventricular fibrillation (unproductive heartbeat), ventricular tachycardia heartbeat), ventricular tachycardia (abnormally fast heartbeat), long QT (abnormally fast heartbeat), long QT syndrome (an inherited heart disease) syndrome (an inherited heart disease) Placement: � � Placement: � � Lead Wire from Cephalic vein to heart Lead 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. Specs � Tech. Specs � � Li- Li -Ion Battery Ion Battery � � “ “Wand Wand” ” Programming over RF Programming over RF � � Electrodes; Platinum, Silicone Electrodes; Platinum, Silicone � � Treatment Treatment � � Pacing Regimen → → Cardioversion Cardioversion → → Pacing Regimen Defibrillation Defibrillation
References References � � American Red Cross: Saving a Life is as Easy as A- -E E- -D D American Red Cross: Saving a Life is as Easy as A � � FDA Heart Health Online: Automated External Defibrillator (AED) FDA Heart Health Online: Automated External Defibrillator (AED) � � Resuscitation Council (UK) Resuscitation Council (UK) � � History of defibrillation History of defibrillation � � How an internal defibrillator is implanted from Children's Hospital Heart from Children's Hospital Heart How an internal defibrillator is implanted Center, Seattle. Center, Seattle. � � http://www.arpansa.gov.au/uvrg/rginfo_p15.html http://www.arpansa.gov.au/uvrg/rginfo_p15.html � � http://www.arpansa.gov.au/uvrg/rginfo_p15.html http://www.arpansa.gov.au/uvrg/rginfo_p15.html � � http://www.medical.philips.com/main/products/resuscitation/biphasic_techno sic_techno http://www.medical.philips.com/main/products/resuscitation/bipha logy/understanding_electricity.html logy/understanding_electricity.html
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