Sensitive swine and TASER electronic control devices

Ventricular fibrillation risk estimation for conducted electrical weapons: critical convolutions

The TASER® Conducted Electrical Weapon (CEW) is used by law enforcement agencies about 900 times per day worldwide and has been shown to reduce suspect and officer injuries by about 65%. However, since a CEW delivers rapid electrical pulses through injected probes, the risk of inducing ventricular fibrillation (VF) has been considered. Animal studies have shown that the tip of the probe must come within a few millimeters of the surface of the heart for the CEW to induce VF in a typical animal application. Early calculations of the CEW VF risk in humans used sophisticated 3-D chest models to determine the size of the probe landing areas that had cardiac tissue within a given distance of the inner surface of the ribs. This produced a distribution of area (cm(2)) vs. mm of depth. Echocardiography was then used to determine the shortest distance from the skin surface to the cardiac surface. This produced a population distribution of skin-to-heart (STH) distances. These 2 distributions were then convolved to arrive at a probability of inducing VF for a typical human CEW application. With 900, 000 probe-mode field uses to date, epidemiological results have shown that these initial VF risk estimates were significant overestimates. We present model refinements that take into account the gender and body-mass-index (BMI) of the target demographics and produce VF risk estimates concordant with the epidemiological results. The risk of VF is estimated at 0.4 per million uses with males.

Cardiac effects of varying pulse charge and polarity of TASER conducted electrical weapons

The TASER(R) CEW (Conducted Electrical Weapon) is rapidly replacing the club in the English-speaking world for assisting in the arrest of resistant subjects and is now used by the majority of law enforcement agencies in the USA, Canada, and the UK. Animal safety studies of the CEW have focused on the risk of VF. We sought to determine the difference in cardiac capture and VF risk between the approximately 102 +/- 8 microC of the ubiquitous X26 and a me-tered 72 microC charge from an experimental device. It is well established from the bidomain theory and experimental data that a pacing electrode will capture the heart with significantly lower charge when the electrode touching the cardiac tissue is a cathode However, experimental data show that there is no difference in the ability of the anode vs the cathode to induce VF. We sought to evaluate the effect of polarity changes on cardiac capture and the induction of VF. Small swine ( approximately 20.0 kg) were anesthetized and ventilated. The apex of the heart was located via echocar-diography and a CEW probe was fully inserted towards the apex. Echocardiography was used to monitor cardiac contractions to determine cardiac capture. Both the X26 and the 72 microC pulses were delivered at both polarities to test for cardiac capture. Higher charge pulses (375 microC) were then delivered with both polarities to test for VF risk. The 72 microC experimental unit was unable to cause cardiac capture even in small swine with fully inserted probes directly over the apex of the heart. We found no polarity effect in the risk of VF in small swine with larger charge ( approximately 5x) pulses.