1969 Reevaluation of Lethal Electric Currents

Low-frequency electric currents of a few milliamperes flowing through the body cause muscular contractions. In the arm such an effect may make a subject unable to let go of a live conductor. The highest currents which 99.5 percent of men and 99.5 percent of women are able to let go have been shown to be 9 and 6 mA, respectively. Currents somewhat larger than this, in the range of 20 to 40 mA, passing across the chest may arrest respiration leading to asphyxia, unconsciousness, and even death. The most common cause of death in electric shock probably is ventricular fibrillation, a condition in which the circulation is arrested and death ensues very rapidly. An analysis of available experimental data indicates that body weight and shock duration are important factors in determining the maximum current not likely to cause ventricular fibrillation. Taking a weight of 50 kg as the average for a human victim it is suggested that the relationship between current shock duration is given by I = 116/??7, where I is the current in milliamperes and T is the time in seconds. It must be stressed that this has only been shown to be valid within the range of 8 ms to 5 seconds. Currents flowing through the nerve centers controlling respiration may cause respiratory inhibition, which sometimes persists for a long time after the current has been interrupted. Other effects produced by high currents, such as burning, etc., are not discussed in this paper.