Dosimetry considerations for electrical stun devices

Abstract

Electrical dosimetry issues are discussed in relation to electrical stun devices (ESDs). A measure of effectiveness is based on a 'threshold factor,' F(T), calculated with a myelinated nerve model that simulates stimulation of a reference-case neuron (20 microm diameter, 1 cm distant). Several ESDs were measured in the laboratory using resistive loads of 100-1000 Omega; some included air gaps bridged via an electric arc. Conducted current waveform parameters and the associated threshold factors depend on the resistance of the load. Thresholds were also determined for ideal monophasic and biphasic square-wave stimuli, and compared with measured ESD waveforms. Although F(T) is proposed as a metric of strength, an approximate surrogate is the charge within the largest phase of the current versus time waveform. The approximation is reasonably accurate for monophasic waveforms with phase durations below about 100 micros, and for charge-balanced biphasic square-wave stimuli with phase durations between about 40 and 100 micros.

Ventricular myocyte injury by high-intensity electric field: Effect of pulse duration

“…We used the stimulation safety factor (SSF), i.e., the ratio between E 50 and E T , to evaluate this relationship. SSF was calculated as the "safety factor" (Oliveira et al 2008) and the "threshold factor" (Reilly et al 2009) but considering as reference the E T of each cell instead of a reference-case neuron. SSF gives a numerical rating that provides a measure of effectiveness to any form of electrical stimulation.…”

Numerically simulated cardiac exposure to electric current densities induced by TASER X-26 pulses in adult men

“…Measurements confirmed that delivered pulses depend on load impedance (Ben-Yaakov 2006, Reilly et al 2009. Their amplitude and time course may vary considerably.…”

“…Their amplitude and time course may vary considerably. Between 500 and 11 200 the electric charge varied from 108 to 30 μC which is about two orders of magnitudes higher than the threshold charge 0.67 μC for nerval stimulation by short pulses (Reilly et al 2009). Overall, load resistances varied between 170 and 3600 and increased nonlinearly with increasing electrode separation distances.…”

“…Either single pulses or a series of electric high tension pulses are delivered to cause muscular contraction and incapacitate subjects. The most widely used ESDs are TASER R devices, usually TASER M26 and, more recently, type X26 with somewhat greater stimulation strength based on a metric developed by Reilly et al (2009).…”

Comments on ‘The discrepancy between human peripheral nerve chronaxie times as measured using magnetic and electric field stimuli: the relevance to MRI gradient coil safety’

“…One can directly measure the current waveform for electric stimulation and the dB/dt waveform for magnetic stimulation. If these waveforms depart significantly from ideal square waves, it is necessary to analyze the possible impact of the waveform distortions, as suggested in Reilly (2009).…”