Method and apparatus for delivering a biphasic defibrillation pulse with variable energy

Abstract

An apparatus and method for determining an optimal transchest external defibrillation waveform that provides for variable energy in the first or second phase of a biphasic waveform that, when applied through a plurality of electrodes positioned on a patient's torso, will produce a desired response in the patient's cardiac cell membranes. The method includes the steps of providing a quantitative model of a defibrillator circuit for producing external defibrillation waveforms, the quantitative model of a patient includes a chest component, a heart component, a cell membrane component and a quantitative description of the desired cardiac membrane response function. Finally, a quantitative description of a transchest external defibrillation waveform that will produce the desired cardiac membrane response function is computed. The computation is made as a function of the desired cardiac membrane response function, the patient model and the defibrillator circuit model.

What is claimed:  
     
         1 . A method for determining a first and a second phase of a biphasic defibrillation shock pulse, one of said first phase and said second phase having variable energy, wherein upon application of said first phase and said second phase of said biphasic defibrillation shock pulse a desired response is produced in a patient's cardiac cell membrane, comprising: 
 providing a quantitative model of a defibrillator circuit for producing said biphasic defibrillation shock pulse;    providing a quantitative model of a patient that includes a variable heart component;    providing a quantitative description of a predetermined response of said cardiac cell membrane to said shock pulse; and    determining a quantitative description of a first phase and a second phase of said biphasic defibrillation shock pulse by selecting from a group consisting of items (a) and (b) as defined below: 
 (a) determining a quantitative description of a first phase of said biphasic defibrillation shock pulse that will produce said predetermined response of said cardiac cell membrane, wherein the determination is made as a function of said predetermined response of said cardiac cell membrane, said quantitative model of a defibrillator circuit, and said quantitative model of a patient, and wherein the quantitative description of the first phase provides for setting a time duration for said first phase based on said variable heart component, whereby an amount of energy to be delivered by said first phase varies according to the time duration that is set; and  
   determining a quantitative description of a second phase of said biphasic defibrillation shock pulse phase on said first phase; and 
 (b) determining a quantitative description of a first phase of said biphasic defibrillation shock pulse that will produce said predetermined response of said cardiac cell membrane, wherein the determination is made as a function of said predetermined response of said cardiac cell membrane, said quantitative model of a defibrillator circuit, and said quantitative model of a patient; and  
   determining a quantitative description of a second phase of said biphasic defibrillation shock pulse based on said first phase, wherein said quantitative description provides for setting a time duration for said second phase based on said variable heart component whereby an amount of energy to be delivered by said second phase varies according to said time duration that is set.