Wearable Defibrillator With A Multivector Shock Waveform

Abstract

A transthoracic defibrillator for external defibrillation comprises at least three electrodes configured to be attached to the thorax of a patient to establish at least two electrical paths across the thoracic cavity and through the heart of the patient. In addition, a defibrillator circuit contained in a defibrillator housing has the capability to deliver a different defibrillation waveform across each of the at least two electrical paths.

1 . A transthoracic defibrillator for external defibrillation, comprising:
 at least three electrodes configured to be attached to a patient to establish at least two electrical paths across the thoracic cavity and through the heart of the patient; and   a defibrillator circuit ( 700 ) comprising a discharge circuit ( 755 ) including a half-bridge circuit for each of said at least three electrodes, and an energy storage capacitor ( 752 ) coupled to the discharge unit, wherein each half-bridge circuit is operatively connected to a corresponding one of the at least three electrodes, and wherein the defibrillator circuit is configured to deliver a defibrillation waveform across each of the at least two electrical paths;   wherein the discharge circuit is controllable to cause stored energy to be discharged to the electrodes to create multiphasic pulses forming the defibrillation waveform across each of the at least two electrical paths;   wherein each of the at least three electrodes is incorporated into a garment or belt that can be worn by the patient.   
     
     
         2 . The defibrillator of  claim 1 , wherein:
 the defibrillator circuit further comprises a measurement circuit ( 720 ) configured to determine the number of currently established electrical paths between the at least three electrodes;   wherein the defibrillator circuit is configured to deliver the defibrillation waveform across only one currently established electrical path if only one electrical path is currently established.   
     
     
         3 . The defibrillator of  claim 1 , wherein:
 the defibrillator circuit is configured to accept input from a user to indicate which pairs of electrodes form designated electrical paths and which defibrillation waveforms are used on which designated electrical paths; and   the defibrillator circuit is configured to deliver the indicated defibrillation waveforms across the designated electrical paths.   
     
     
         4 . The defibrillator of  claim 1 , wherein:
 the defibrillator circuit further comprises a measurement circuit ( 720 ) configured to measure an impedance between at least two pairs of electrodes.   
     
     
         5 . The defibrillator of  claim 4 , wherein the defibrillator circuit is configured to measure impedance simultaneously across at least two pairs of the electrodes using carrier frequencies that differ by at least 5 kHz between each of the simultaneously tested pairs. 
     
     
         6 . The defibrillator of  claim 4 , wherein the defibrillator circuit is configured to measure impedance sequentially between different pairs of the electrodes. 
     
     
         7 . The defibrillator of  claim 4 , wherein:
 the defibrillator circuit is configured to measure impedance at least once at a time that is after the defibrillator is put on the patient and before the patient is in cardiac arrest.   
     
     
         8 . The defibrillator of  claim 4 , wherein the vectors are chosen by the defibrillator circuit to be the two pairs of electrodes with highest measured impedance. 
     
     
         9 . The defibrillator of  claim 4 , wherein a parameter of the defibrillation waveform along each vector is influenced by a measured impedance between the electrodes of a vector. 
     
     
         10 . The defibrillator of  claim 9 , wherein the parameter is the energy delivered. 
     
     
         11 . The defibrillator of  claim 9 , wherein the parameter is the waveform duration. 
     
     
         12 . The defibrillator of  claim 11 , wherein the defibrillator circuit is configured to:
 measure the impedance along one vector;   determine the pulse width of the defibrillation waveform across each vector based at least in part on the impedance measurement; and   cause the duration of the of the waveform along each vector to be substantially the same.   
     
     
         13 . The defibrillator of  claim 11 , wherein the defibrillator circuit is configured to control the waveform duration along each vector to cause the energy delivered along each vector to be substantially the same. 
     
     
         14 . The defibrillator of  claim 9 , wherein the parameter is the waveform tilt. 
     
     
         15 . The defibrillator of  claim 14 , wherein the defibrillator circuit is configured to control the waveform duration along each vector to cause the waveform tilt along each vector to be substantially the same. 
     
     
         16 . The defibrillator of  claim 9 , wherein a parameter of the defibrillation waveform along at least one vector is influenced by the measured impedance between the electrodes of that vector. 
     
     
         17 . The defibrillator of  claim 9 , wherein a parameter of the defibrillation waveform along at least one vector is influenced by the measured impedance between the electrodes of a different vector. 
     
     
         18 . The defibrillator of  claim 4 , wherein there is only one designated vector;
 and the designated vector corresponds to the lowest measured impedance amongst all pairs of electrodes.   
     
     
         19 . The defibrillator of  claim 1 , wherein two electrical paths form a first vector and a second vector; and the defibrillation waveforms comprise a sequence of non-zero voltages including a positive shock on the first vector, followed by a positive shock on the second vector, followed by a negative shock on the first vector, followed by a negative shock on the second vector. 
     
     
         20 . The defibrillator of  claim 19 , wherein the defibrillator contains a single capacitor in an energy storage module; and the duration of the shock on each vector is determined by the impedance between the electrodes of that vector. 
     
     
         21 . The defibrillator of  claim 1 , wherein two electrical paths form a first vector and a second vector; and the defibrillation waveforms comprise a sequence of non-zero voltages including a positive shock on the first vector, followed by a positive shock on the second vector, followed by a negative shock simultaneously on the first and second vectors. 
     
     
         22 . The defibrillator of  claim 1 , wherein the defibrillator circuit is configured to measure the patient's electrocardiogram via the electrodes also used to deliver the defibrillation waveforms. 
     
     
         23 . The defibrillator of  claim 22 , wherein two of the at least three electrodes are used to measure the electrocardiogram signal and a third of the at least three electrodes is used as a reference electrode. 
     
     
         24 . The defibrillator of  claim 1 , wherein:
 the at least three electrodes include exactly four electrodes providing six possible electrical paths; and   a first set of vectors are two electrical paths chosen from the six possible electrical paths;   a second set of vectors are two lectrical paths chosen from the six possible electrical paths, wherein the second set of vectors is different from the first set of vectors; and   if the first set of defibrillation waveforms delivered across the first set of vectors fail to establish a regular heart rhythm in the patient, the defibrillator circuit is configured to deliver a second set of defibrillation waveforms across the second set of vectors.   
     
     
         25 - 26 . (canceled) 
     
     
         27 . A transthoracic defibrillator for external defibrillation, comprising:
 four electrodes configured to be attached to a patient and establish electrical paths across a thoracic cavity and through the heart of the patient;   wherein a first pair of the four electrodes, when attached to the patient, forms a first electrical path for a first shock vector; and   wherein a second pair of the four electrodes, when attached to the patient, forms a second electrical path for a second shock vector; and   a defibrillator circuit, wherein:   the defibrillator circuit is operatively connected to the four electrodes;   the defibrillator circuit contains an energy storage module with a single capacitor to supply both shock vectors;   the defibrillator circuit is configured to measure an impedance across the electrodes of both shock vectors;   the defibrillator circuit is configured to deliver a first defibrillation waveform through the first shock vector, where the duration of the first defibrillation waveform is proportional to the impedance measured across the first pair of electrodes; and   the defibrillator circuit is configured to deliver a second defibrillation waveform through the second shock vector, where the duration of the second defibrillation waveform is proportional to the impedance measured across the second pair of electrodes.   
     
     
         28 . The defibrillator of  claim 27 , wherein the defibrillator circuit includes a single capacitor in the energy storage module.