New conducted electrical weapons: Thoracic cage shielding effects

Introduction: The TASER
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conducted electrical weapon (CEW) delivers electrical pulses that can temporarily incapacitate subjects. For existing CEW models, we have previously presented the distribution of currents in tissues posterior to the sternum and their likelihood of triggering cardiac arrhythmias. New models, the eXperimental Rotating-Field (XRF) waveform CEW (in development) and the X2 CEW (released) have not been investigated. Both the XRF and X2 CEWs target a precise amount of delivered charge per pulse, 64 μC and 62 μC, respectively. The goal of this study was to numerically model the thoracic cage attenuation of currents and electric fields delivered by the new CEWs and to find whether the heart is shielded from the induction of any dangerous arrhythmias. Methods and Results: Finite element modeling (FEM) was used to approximate the current density and electric field strength in tissues around the thoracic cage. FEM boundary conditions were set to correspond to output waveforms of the new CEWs, the XRF and the X2. We analyzed a CEW dart deployment scenario that had both darts located over the anterior aspect of the sternum. We found that the sternum and thoracic cage provided significant attenuation of currents and electrical fields. Conclusion: The sternum and the thoracic cage significantly attenuated currents and electric fields delivered by XRF and X2 CEWs. These tissues `shielded' the heart against potentially dangerous cardiac arrhythmias. The shorter durations and reduced amount of charged delivered by the XRF and the X2 CEWs resulted in increased cardiac safety margins.