Document KRJg52599x2yKvqM7MdnNy416

598 HEINZ SPECHT decompression increases throughout with increased stay at the working The phenomenally long decompressions necessary for even short stays depths prove to be a limiting factor in the amount of useful work thai^ffi effected, even under the best possible conditions; for example, a 20-minuff of 300 feet on compressed air requires a total time of 3 hours. The limitations on the stay at working level are, however, legion: electric heating of suits to maintain the body temperature and improvemg construction of the suits to increase mobility and reduce the fatigue of mat ing the diving rig have been effective in improving the performance of di^rii length of stay at the feasible work depths is still short. The resistances* ment and the difficulty of working against water movements is so telliff| strength of divers that effective work cannot be carried out for the recoifiirfl periods except under very favorable conditions of weather and currents^! In caisson work the periods of work are longer in general, and as afl pressures encountered are limited by the nature of the operations. Pressurgf equivalent to about 100 feet probably are not often encountered andml period of 1.5 hours twice a day has been used at such levels.47 Since tnegflsii; tions for performing useful work are in most cases better for caisson worker for divers, some difference is understandable. On the other hand, thtpcH worker is undoubtedly more nearly saturated than is the diver uti'di practices and thus more subject to sequelae if proper decompression^! carried out. It has been the practice in this country for caisson Crews's divided shifts.42 The incidence of bends reported by Jones et ql.t8. thousand "decompressions after a 1.5-hour shift but, because of the-relu'c' workers to report mild cases or to have treatment on their own ti&'el some question whether complete coverage was obtained. It was fbunli tests of prophylaxis, where attention was directed to reporting ali'lcl where no-stigma was attached to such reporting, the incidence wits thousand despite the complete lack of any severe cases. Other grdufi incidences of 2.49 to 2.24 per thousand when no treatment or interested personnel was maintained. The latter higher incidencei-isaf^Pm| related to the extremely casual manner in which decompression' is ^barn at the insistence of the men themselves. -S7'Effects~an~the~'Gircutatim In an academic sense, the blood can carry in phyfficaii:iiBluti6 oxygen to supply tissue respiration when the inspired partial pressurefelp is equivalent to 3 atm.,16 whereas while breathing 1 atm. of air, less,fffiai|||||| -of-th,e-oxygBii-carr-ied--by-the^blo0d-4s-in-physioal-solu;ffonR::iTKe;YjRijffi^ capacity of the hemoglobin is attained, however, with only siightiif " Occupation and Health. International Labour Office, Geneva,'1930. " R. R. Jones, J. W. Crosson, F. E. Griffith, R. R. Sayers, H. H. Sehrenkga^^S J. Ind. Hyg. Toxicol., 22, 427 (1940). V. ;,S ' ' L :JSlt EFFECTS OF ABNORMAL ATMOSPHERIC PRESSURE 599 H>V Therefore, it would seem that oxygen transport per se is more than ipressed air atmospheres. Si!tiqn with regard to C02 is by the same token not so favorable. This ipphe fact that the carbon dioxide from the tissues is less readily taken ffiemoglobin under these conditions and a rise in venous pC02 occurs Sglyby a fall in pH with the attainment of the buffer capacity of the |||||q,et of.48 showed that the. change in pH at 4 atm. of oxygen amounted papaa.Venous blood. As indicated above a further temporary enhanceii|effect may follow rapid compression.80 geltijalythe pulse pressure and circulation are not uniformly changed by ||||kjmqspheric pressure, but when very high partial pressures of oxygen lained^complicating effects from the impaired carbon dioxide transport g|changes. It is probable that dilation of cerebral and peripheral vessels S. Oxygen Poisoning 3 to 4 atm. of oxygen, or corresponding oxygen pressure in air, nStor disturbances of cerebrocortical origin develop. The syndrome is loxygen poisoning" and may show only minor twitches but usually pro- ,1-blown convulsions within a short time. This is an acute condition qualitatively to symptoms known to affect individuals maintained at a Ipsure of oxygen above about 600 mm: Hg for periods of several days.60 effects at normal atmospheric pressure seem to be a pulmonary i&esulting-in-substernabdistress-and-coughing-with-a~clinical picture onfestion, while the acute conditions brought on by. exposure to high litres of oxygen over short intervals at increased atmospheric pressures Central nervous system, causing seizures, loss of consciousness, narrow- :ual fields through scotomata, and so forth, which overshadow the |of' less spectacular symptoms. The modus operandi of oxygen poisonafiderable dispute at the present time sinoe bothsC02 and 02 are known inactive effects on isolated systems at increasedpressure.80 Studies tend fiat irreversible or incompletely reversible changes take place in all ^Sfereactions and particularly in the central -nervous system, and there ifcin to believe that the normal gas-handling systems involving enpramately^affected:ao~Itrhas-been-shown-recently-that-oxygen toxicity , Bitialijd by interference with the transport of carbon dioxide from tissues SSI- 4. Inert Oas Effects SpffifcJyiitii). .. ......... .......... ...... ... r ...................... ................... |0^j.m^TM7experimentarhwork-on"deep=seardrving-and-saivagerit'was-repqrted- ^.iiwBehnke, L. A. Shaw, C. W. Shilling, R. M. Thompson, and A. C. Messer, Am. J. llpS (1934). Beeker-Freyseng and H. G. Clamann, Lujtlahrtmedizin, 7, 272 (1942). riljertsen et a!., J. Appl: Physiol., 6, No. 6, 358 (1953).