The medical practitioner who is interested in electrical trauma should have an understanding of the engineering aspects of the system which caused the injury. It is also important that the electrical parameters which determine the severity and consequences of the shock also are understood.

History

Prior to Edison's development of the electric lamp in 1879, electrical shock, except from lightning, was a rare phenomenon because there were few electrical devices available which could provide a shock. The explosive growth in the use of electrical systems from 1880 to 1900 led to many cases of electrical shock and to subsequent studies as to how electricity kills or causes injuries. Some of these studies were applied in designing the electric chair for the first legal electrocution at Auburn Prison, New York, in 1890. By about 1900, it was finally determined that the usual mode of death in electrocution was ventricular fibrillation.

All electric chairs used for electrocuting criminals use a head and calf electrode. The application cycle for the electricity is not standardized between states. In Alabama, a 60 Hz sinusoidal voltage is applied as follows: 1800 V for 22 seconds, a voltage reduction to 700 to 800 V in 12 seconds, an increase in voltage to 1800 V in 5 seconds, and then the power is turned off. There is a current of about 7 A when the 1800 V is applied.

Electrical terminology

There are various electrical terms which must be understood in order to follow any discussion of the engineering aspects related to the cause of electrical trauma.

Voltage

Voltage, with the units of volts, is a measure of the electrical potential difference between any two points.