Electrocution and Electrical Injury Study Guide

Critical vocabulary terms and definitions covering the physics, epidemiology, pathology, and devices related to electrocution and lightning injury.

Electrocution

Death caused by the passage of electrical current through the body.

The Three Requirements for an Electrocution

1. A charged source (voltage); 2. A current pathway through the body; 3. A ground (return path to earth).

Ground

A reference point in an electrical circuit from which voltages are measured and a common return path for electric current; it has an electric potential of zero.

Voltage

The electrical potential difference, measured in volts ($V$).

High Voltage

Electrical potential generally considered to be greater than $1,000\,V$.

Current

The rate of flow of charges through a conductor resulting from a voltage difference, measured in Amperes ($A$).

Alternating Current (AC)

Current where the direction of electron flow reverses cyclically; it is used in homes and can cause tetany and repeated muscular contractions.

Direct Current (DC)

Current where electrons flow in a single direction; common sources include batteries, defibrillators, and lightning.

Resistance

Anything that impedes the flow of electricity through a conductor, measured in Ohms ($\Omega$).

Ohm’s Law

The principle that Current equals Voltage divided by Resistance ($I = V / R$).

Amperage

The amount of current flowing through the body; described as the single most important factor determining injury severity.

No let go threshold

Amperage level of $15\text{--}17\,mA$ where muscles contract such that the victim cannot release the source.

Ventricular Fibrillation (V-FIB)

The characteristically fatal heart rhythm caused by $75\text{--}100\,mA$ in low-voltage fatalities.

Arc

An electrical discharge created through the air, often occurring with high voltage.

Short circuit

An electrical circuit that follows an unintended path, such as when a person touches a device electrified by a frayed wire.

GFI (Ground Fault Interrupter)

A safety device that monitors current flow in a circuit.

Electrical mark

A shallow crater with a ridge of raised skin, a pale white center, and hyperemic (reddened) borders.

Joule burn

Darkened, charred, and blistered skin resulting from heat generated by electrical resistance in tissue.

Arc burn

High-voltage injury causing a "crocodile skin" appearance with multiple spark burns due to current passing through high-temperature air.

Flame burn

A secondary heat source injury in electrocution cases occurring when clothing catches fire.

Tetanic asphyxia

Mechanical asphyxia caused by the sustained contraction of respiratory muscles in low-voltage electrocution cases.

Central apnea

Cessation of breathing that occurs if electrical current passes through the respiratory center of the brain.

Linear burns

First- to second-degree lightning burns ($1\text{--}4\,cm$) caused by vaporization of water where sweat accumulates, such as in the axilla or mid-chest.

Punctate burns

Lightning injuries involving pinpoint lesions clustered together on the epidermis and dermis, often on the soles or tips of the toes.

Lichtenberg figures

Arborizing, fernlike skin marks (feathering) seen in $20\text{--}30\%$ of lightning cases; they are not true burns and fade within hours.

Direct strike

The most fatal type of lightning contact where the discharge hits the body directly.

Side flash

Lightning contact where the entire current is transferred from a struck object by air, ground, or wiring to a nearby person.

Tympanic membrane rupture

Injury found in $50\text{--}80\%$ of lightning cases due to high pressure generated at the moment of the strike.

EMD (Electro-Muscular Disruption)

Battery-operated tools used in law enforcement that deliver short-duration, high-voltage, low-amperage current along low-resistance routes.

Stun Gun

A hand-held device powered by a $9\,V$ battery that delivers brief high-peak pulses (up to $50,000\,V$) to cause pain and muscle contraction.

TASER

Acronym for Thomas A. Swift Electric Rifle; it propels two wired darts that deliver current between the barbs.

Nerve and muscle capture

The extent to which TASER current engages the body, determined by the spread (distance) between the probes.