Date of Award
5-1988
Document Type
Dissertation - Restricted
Degree Name
Doctor of Philosophy (PhD)
Department
Biomedical Engineering
First Advisor
Anthony Sances
Second Advisor
John H. Linehan
Third Advisor
Alfred P. Szews
Fourth Advisor
Martin A. Seitz
Fifth Advisor
Joel Myklebust
Abstract
Studies were conducted to further an understanding of injuries due to contact with low voltage 60 Hz alternating currents. The impedance characteristics of circular and elliptical stainless steel electrodes, with areas of 0.3 to 20 cm2 and circumferences of 2 to 28 cm, were analyzed in a saline tank. The saline tank resistance was inversely proportional to the product of electrode area to the one-quarter power and electrode circumference to the one-half power. To analyze the effects of contact geometry and duration on the cross-body resistance, which includes interface effects and body resistance, 100 volts was applied across the hindquarters of anesthetized hogs, between one of eight electrodes and a metal plate. The resulting current rose sharply to half the maximum, gradually reached the maximum, and then rapidly diminished to approximately zero. Average current durations varied from 24 to 326 seconds, and minimum cross-body resistances varied from 242 to 64 ohms, as the electrode size increased. Minimum cross-body resistance varied more with electrode circumference than area. To analyze the effects of contact voltage on the cross-body resistance, a voltage between 75 and 250 volts was applied across the hindquarters of anesthetized hogs, between a 2.5 cm diameter electrode and a metal plate. The voltage was applied until a cessation of current flow was observed. As the applied voltage increased from 75 to 250 volts, average current durations decreased from 225 to 4 seconds, and minimum cross-body resistances increased from 93 to 180 ohms. To measure the temperature distributions in an experimental electrical injury, thermistors were implanted prior to application of 100 volts across the hindquarters of anesthetized hogs between a 5.0 cm diameter electrode and a metal plate. Tissue temperatures were recorded every 10 seconds during the application and post-insult until all temperatures returned below 40°C. Temperatures in excess of 100°C were recorded beneath the edge of the electrode. Temperatures were significantly higher under the electrode edge than center. Two-dimensional axisymmetric finite element models of voltage and temperature distributions resulting from a disk in contact with a semi-infinite medium were developed in three stages: steady-state thermal, steady-state electrical, and transient thermoelectrical.