Document g2n26bV4pXQkqxBM6KnddZD3G

620 HEINZ SPECHT ing these structures with the exterior is mechanically adapted to relieve int|| pressure readily. The mechanical effects of atmospheric pressure change on gases en(|f within soft-walled structures, such as the gastrointestinal tract, are quantitat different in the two ranges of pressure, in that the partial pressure of watel hances the volume change on decrease in pressure in inverse proportions absolute pressure. On increase of pressure there is no deleterious effect, The effects of the partial pressure of oxygen with change in atmospheric! sure are qualitatively different in the two ranges of abnormal pressures! creased pressures there is a tendency for "oxygen poisoning" to increase a portion to the absolute pressure above a relatively low limiting value. At dec atmospheric pressure there is, conversely, a progressive asphyxiation due tcfein ference with the oxygen transport to the tissues and finally with the prV labile oxidative processes in the tissues. The effects of the partial-pressure changes of inert gases are qualitati'ycra similar in the two ranges of atmospheric pressure, in that reduction of -prle^mr] leads to supersaturation of the dissolved gases, with the consequent dang|||| formation of bubbles within and without the vascular system. The causaftrf between bubbles and the symptoms of decompression sickness is not wholly; lished, but the immediate relief of symptoms by recompression indicates: relationship. At high atmospheric pressures there is observed an additional effect central .nervous system that has been attributed to the inert gases. A caus. tion of carbon dioxide to it has been suggested in view of the lack.pfiS activity of the inert gases, but neither approach can fully account fqjpfi served effects. At low atmospheric pressures the biologically active gasesjf such marked effects that no observations on the part played by inert gas^ as passive diluters of the oxygen, have been made. At present, there are three extensive bibliographies of the liter^ffl field.42'08'94 It is hoped that the reference/-given here to reports of:fe|tii|e| culation will aid the reader as an indication of the existence of the'f$,oijlr subsequent search of the abstracting journals may reveal the ultima! publication. .. ------05~ECrHoS'and- JrF.-Fulton-,- A-Bibliography oj-Aviation-Medicincv^rhoh 111., 1942, p.,237. "E. C. Hoff and L. J. Greenbaum, Jr., A Bibliographical Sourcebooli of Conlvr Diving and Submarine Medicine, Vol. II. NAVMED-P-5033, Office of Naval^Re|| Bureau of Medicine and Surgery, Department of the Navy, Washington, D. C., CHAPTER XVm idustrial Noise and the Conservation of Hearing* JEROME R. COX, Jr. |jly the best-known case of occupational loss of hearing is that of |||ihe hunchback bellringer of Notre Dame. The events of this famous ^^ifugo. novel took place in France in the year 1482. Centuries later during "sig|al revolution medical science took note of the problem by coining the ^.^^filermaker's deafness." Only during the past few years, however, has jjSli&iiip wbo^e become aware of the barmful effects of extended exposure to rS&ftfnoise. The recent widespread interest in the problem results from a com"Mjo'f .several factors. isjljhf'Von tinued increase in the number of workers exposed to intense noise is 1 *' fEaait` important factor. From the time man first began to work metal he 'Wj) fed sounds different from those~ o" "f h*i*s" n""a*tu""ra*'*l en'v*i*roV*n*m*Ven* Vt.. OAUs Vc*iv' iliza- GiiH^&veloped man has found more and more ways of having, machines do ^rukShd each new machine added to his exposure to noise. Since industrial }lupni{M|trwas-quite-graduab-the increase-in noise was gradual and has, until |gen endured by all concerned without much protest. So great is the jweifnlpeople now affected and so intense are some of the new noise sources, igfrjj.fy can no longer afford to overlook the problem. lj|w|u'[|Md with this increased number of severe noise exposures is a general "'jKjr^^the responsibility for an occupational disability from the worker to ''Mer. With the passage of modern workmen's compensation laws this lBUijBffls,been accomplished for most traumatic injuries and occupational burden of the responsibility for occupational hearing impairment is jffigjind eventually will surely be placed entirely, on. industry. *n resPnsibility would be impractical without certain technological ay^^f.^lJiprfi^elds-of-acoustics-and audiometry. The electronic audiometer has and repeatable hearing measurements possible in clinical circumn^^Improvements in noise-measuring equipment, at last, make it feasible man's noise exposure quantitatively; and the tremendous strides made jl^ijveriR^.tii.u^field...of_:.noisejed.uction promiae a satisfactory, .solution..to the jknVihro.ugh engineering control. ~ rjj,' UMtrations not otherwise credited are furnished through the courtesy of the Liberty .^Insurance Company, where the author was employed during the preparation of a ffiqffthe manuscript. 621 \*' n.f 'stOK HH- m