Document mBERXodmjOgqgwQEY8j6e19JZ

616 HEINZ SPECHT The time of onset of symptoms of decompression sickness is inversely -re'!* to the. rate of ascent, as described previously,69 and is further relatedjEc$|| product of altitude and duration of exposure at each altitude.11 Thus, uhleH precaution of thorough denitrogenation is taken before ascent, there is aiwiJvS possibility of the formation of bubbles provided the altitude is great ;:affip stay protracted. In view of these considerations it seems desirable to asstiml bubble nuclei are always present or at least are being continuoUsly^fcji| in the various tissues of the body and that their chances of survival and J"""~ are enhanced in proportion to the concentration of inert gases. The sit^'fesii'J activity may well be the loci at which the respiratory gases are handiedi]Bo^a by each tissue, thus accounting for the low incidence of patent bubbles'ijfi cells, where gas exchange is diffuse, as compared with the high inciden^l&tl blood, where the intensity of gas exchange is of a very high order. ,| Harvey's theory 84 that hydrostatic factors are basically responsibl&tfq initiation of bubble nuclei is based on the observations that exercise and^t^iiSm are accelerating factors in bubble formation and that the accompanyin||M carbon dioxide concentration is less effective. It is a well-documente&ia|| performance of muscular exercise is a predisposing factor for bends aijjSr a variable in the determination of the time of onset of decompressioi|i<5 symptoms.11,84,85,87 ., The effect of temperature on the production of symptoms of deconif sickness has not been conclusively demonstrated at altitude,11 but the^Tajc a predisposition to such symptoms in caisson workers subject to chilli'rii&!| shown58 leads to the assumption of a conservative'point of view. Thejm&mte of comfortable skin temperatures by electrical heating for the preservation highest degree of co-ordination in the performance of flight duties obvia1|f in the case of accident, the need for consideration of the effects of cold on,J pression sickness. The rationale of the effect of cold at altitude is'bnscildpr^ vasoconsiricting action of cold in the skin, inducing an interference, -wa elimination of inert gases, and the production of shivering, which ten'dlTM gerate the effects of muscular tension over those normally found., There are at least two other variables that have been found to'V'n'! directly with the incidence of decompression sickness: age and. line^TOi (i.e., pounds per unit height).11 Similar relations have been..^de^tii^i^F decbfflpiessiqri "frdm~ BiglT-presaure atmospheres?*'*8 The increases the incidence of symptoms is not clear except circulatory resiliency of young individuals may minimize effects,. .thatSw reported as noticeable in older men. It would be more understandably differential-were-only in the RevBrity_.:of .symptnms_:b.eegirsgrtlagdf capillary vessels of older men would be expected to be more drastic, of linear density is undoubtedly tied up with body fat and thwmo^ difference in vascularization of the tissue. As shown by Gersh,88 tneil|:fM\,i:_)^':i are poorly ventilated because the effective ratio of capillary surface 1 V&Ass* ; w -t EFFECTS OF ABNORMAL ATMOSPHERIC PRESSURE 617 r as compared with tissues such as muscle, which are known to be ^avascular bubbles. fe6. Acclimatization ted or continuous exposure of individuals to high altitudes has been If in connection with mountaineering and in connection with a few ^ _JTas the Andean sulfur mining in Chile.88 The effects noted were j|jj||nc,erned with the reduction of the partial pressure of oxygen, since `Mailing altitude levels decompression effects would not appear. The vaccomplished by the body under prolonged hypoxia of mild degree ^*j;y|n;an increase in the number of red cells and their hemoglobin content, itpflal volume and rate of ventilation of the lungs', as well as changes in nilory efficiency: all directed to the more adequate transport of oxygen sues.1!1,84 Under high altitude- conditions, that is, where great stresB is the, organism even on an intermittent basis, the reactions invoked |ijiadaptive and in certain respects impose further stresses that may lerious damage to the circulatory system, particularly the heart.89 At atddevels some of these responses may attain, and recede from, a maxii||ihder continuing stimulation.99 Ruff and Strughold laid great em- |&ese reactions and recommended the regular exposure of aviators to "nhtions at mountain rest camps.6 It is apparent, however, that the use fentary oxygen at the great heights attained by present aircraft largely the desirability of such acclimatization. It would be of value at Mevels only for protracted sojourn, such as described above. These e place with the passage of time in normal individuals though not SEBEsymptoms and temporary disabilities, cyclic breathing, nausea, S3?, collectively known as mountain sickness. Itiv fcn\RGING OF THE BODY WITH GAS IN DESCENT:' RECOMPRESSION : Re-solution of Oases. Relief of Decompression Sickness he most comforting aspects of exposure to decreased barometric ^^P^K&fac1^that.mos.t-,of_the..dangers,;inv0l.v.e'd-ih3ihi8i.cohdltipnh'cah.be [hl^eljm'inited by recompression to atmospheric pressure. The exceptions (j5jsfc?."j$re*e a shocklike condition has developed to the point of collapse or gjigntodf' it, and where the simple restitution of high partial pressure of Minot.correct the trauma to the peripheral vascular bed_ari^the attend- TEtlonrBefidS pain, biTBkes, and even serious central effects will- JjjlgiHly to recompression if recompression is instituted early enough. The IpglL, j&ppill. A/c, Heat, and Altitude. Harvard Univ. Press, Cambridge, Mass., 1938. ^DgAHland and B. Highman, Am. J. Physiol., 167, 261 (1951). ^pMarshall and H. Specht., Am. J. Physiol, 163, No. 3 (1950). ' .1