Field current sources for electric defibrillation

UNDER certain conditions, the heart may lose its rhythmic pumping action and cease the circulation of blood. This situation is known as ventricular fibrillation and may occur during surgical procedures or as a consequence of electric shock. Normal heart action may be restored by passing an electric current of suitable characteristics through the heart. In the operating room, defibrillation is accomplished by applying electrodes to the heart directly and passing a 60-cycle alternating-current of from 1.5 to 2 amperes through the heart (120 to 135 volts). When fibrillation results from an electric shock received under field conditions, electrodes cannot be applied to the heart directly but may be applied to the surface of the body to permit sufficient current to flow through the heart to effect defibrillation. In animal experiments with electrodes at the chest,
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defibrillation has been accomplished reliably by the use of 60-cycle alternating-current, 480 volts, 15 amperes applied for periods up to about 1 second. Such a current first brings the heart to a standstill; upon interruption of the current, the heart will usually resume its pumping action provided the elapsed time between the onset of fibrillation and the application of defibrillation current is not excessive.