Military roentgenology / War Department.

Date:
[1944]
Catalogue details

Licence: Public Domain Mark

Credit: Military roentgenology / War Department. Source: Wellcome Collection.

    89/470 page 79
    102. GENERAL. In dealing with X-ray equipment, two types of hazards must be respected: electrical dangers and X-radiation dangers. These concern the roentgenologist, technicians, and patients. 103. ELECTRICAL HAZARDS. a. The use of shockproof equipment is now so prevalent that electrical dangers have been almost eliminated. However, the safety provided by this type equip- ment is of itself a danger because it is likely to relieve too completely the mind of the operator. After handling trustworthy shockproof equipment, there is considerable likelihood that novice X-ray technicians may fail to recognize the electrical hazards which exist as far as the operation of non- shockproof equipment is concerned. Moreover, everyone should realize that regardless of self- contained tube heads (that is, when the X-ray tube is Immersed in oil and contained in the same tank which accommodates the high tension transformer), or with the use of shockproof cables, one is still handling currents of exceptionally high voltage which under certain conditions might overcome the pro- tective provisions. Therefore, even with modern shockproof equipment, the possibilities of electrical hazards should be respected. b. Physiological effects. Death may result from any one of four physiological effects: (1) The ventricles of the heart may be thrown into fibrillation from which, in the human, they seldom or never recover. ratus may occur with resultant fixation of the muscles of the thorax and the diaphragm in the phase of deep inspiration. (3) The brain centers concerned with constriction of blood vessels may be so stimulated as suddenly to produce extremely high blood pressure with resultant hemorrhages. (4) The resistance on the part of the tissues to the flow of the electrical current may be so great as to produce extreme accumulations of heat with the result of actual charring. c. Voltage versus current factors. Contrary to gen- eral belief, voltage is not the factor directly respon- sible for any of these effects. It is amperage that causes fatalities, and of greatest importance is the amount of current which is effective upon the heart. It has been estimated that for the frequencies of current utilized with most roentgenographic equip- ment (60-cycle), the human heart will tolerate no more than 6 to 15 milliamperes. The heart is involved to the greatest extent when the electrical contacts include one upper extremity and the opposite lower extremity, for with such a contact, approximately 10 percent of the total current involves the heart. Interpreted as total current flowig through the body, by such a route, a minimal lethal value would amount to between 60 and 150 milliamperes. Some individuals have idiosyncrasies (either because of defects in their heart or because of an overly excit- able nervous mechanism), and they cannot tolerate even the lower of these values. It is estimated that approximately 90 percent of injuries incident to electrical shock are those concerned with the heart— hence, the importance of these considerations. With high voltage and very low amperage (that Is, milli- amperage), there is a tendency for an individual to be thrown for a distance. With lesser voltage and sufficient current to stimulate muscle contraction, a complete gripping contact is likely. A certain amount of voltage is required to overcome the resistance of the skin and superficial tissues. This value varies, depending upon the dryness of the skin, the thickness of it, and the amount of fat contained in the sub- cutaneous tissues. With very moist skin and a thin individual, it has been estimated that only 65 volts are required to overcome all body resistance. d. First aid. Regardless of the unfavorable possi- bilities, every effort should be made to restore a victim from electrical shock. However, one should never directly grasp the individual, because by so doing the result will most ltkely be suicide with the accomplishment of no aid whatsoever to the first victim. Instead of plunging to one’s own death, the first objective should be to break the electrical circuit by opening a switch. Perhaps the victim might be disentangled by throwing over him, a sheet or rope or some other nonconductor and then forcibly removing him from the contacts. There- after, he should be treated as a victim of shock. He should be placed in the lying position, prone, with his face turned to one side and chin resting on the back of one of his hands—to provide for freedom of breathing. His collar and other clothing should be loosened and then the Schaefer method of resuscita- 719
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