G. G. Knickerbocker

A-C shocks of varying parameters affecting the heart

It is well known that both the human and the dogs heart may be thrown into ventricular fibrillation by 60-cycle a-c shocks, resulting in the cessation of circulation followed by death. There are, however, little data available as to the magnitude of the current of various durations that will result in fibrillation, nor is there much information as to how the induction of fibrillation is influenced by the timing of the shock in the heart cycle. Ferris, Williams, Spence, and King1 found that the sheeps heart was most vulnerable to shocks that fell during the T phase of the electrocardiogram of the heart.

Exposure of Mice to a Strong AC Electric Field - An Experimental Study

Twenty-two male mice were exposed to a 60-Hz ac electric field by placing them, in cages, between parallel plates energized to create a field, initially unperturbed, of 4 kV/in. In the course of 10?months, each animal had an accumulated exposure time of nearly 1500 hours. These animals, and a parallel control group (essentially identically handled but receiving no exposure to electric fields), were repeatedly bred and observed to determine whether there were any effects, harmful or beneficial, as a result of the exposure.

Medical Evaluation of Man Working in AC Electric Fields

This paper covers an investigation of the effects of HV 60-Hz ac fields on human beings. Experimental results of the intensity of the electric fields to which linemen are subjected when doing maintenance work on energized HV lines are presented. The protection offered by Faraday screens is discussed. The results of a series of physiological examinations that were carried out on 11 linemen, some of whom used conventional hot stick methods and others worked barehanded from an aerial bucket connected to an energized conductor, are presented. The examinations, which extended over a 42-month period, were conducted by members of the staff of The Johns Hopkins Hospital, Baltimore, Md.

A Portable Defibrillator

A portable electric defibrillator has been designed, capable of being operated from 115 volts a-c or from 6-or 12-volt storage or dry batteries. Features have been incorporated to insure safety, to both the operator and the victim. Prototypes of this type of equipment have been tested extensively on animals, . and have been used successfully on six human victims of ventricular fibrillation in the hospital. The defibrillator discussed here has been successfully employed once.

Cardiac Responses to Transthoracic Capacitor Discharges in the Dog

Many previous investigators have presented data suggesting that the processes involved in excitation and recovery in heart muscle limit the “vulnerable period” to a relatively small part of the heart cycle in late systole. Evidence presented in this report indicates that there are exceptions to this rule, at least in the intact animal, since under some conditions multiple extrasystoles and ventricular fibrillation can be elicited by single stimuli of short duration and high voltage applied at almost any time in systole or diastole.

Status of Closed Chest Cardiac Massage

This paper describes the steps in the development of the closed chest defibrillator which led to the discovery that, by applying external heart massage to the closed chest with concomitant artificial respiration, it is possible to provide sufficient artificial circulation of oxygenated blood to maintain the heart and brain alive for an hour or more. The results of the application of cardiopulmonary resuscitation to 301 patients at The Johns Hopkins Hospital are also presented and discussed.

Electrical techniques and the heart in health and disease

Some interesting examples are presented of electrical measuring techniques in three principal areas of medical science: basic physiology; diagnosis of disease; and treatment of disease. Intracellular recordings, electrocardiography, flow-recording techniques, pacemaking, and defibrillation are among the specific methods discussed.

Field treatment in electric shock cases - II

Electric shocks of the order of 0.1 ampere can throw the heart into a twitching state of ventricular fibrillation. Several amperes, on the other hand, simply contract the heart and paralyze the breathing which artificial respiration can relieve, Ventricular fibrillation, however, can be ended only by sending sufficient current through the heart by electrodes on the skin of the chest.