Document EqO3JG7DD84QM8yMzr7vKEwYV

596 HEINZ SPECHT holding may result in compression of the lungs to such an extent that onlyiwff considerable difficulty can sufficient positive pressure be created by the thdfaT musculature to release the glottal closure. Such cases have been observ||l recompression from negative pressure, as will be discussed later. It is import especially in experimental work, that warning against breath holding bel mulgated during indoctrination and in the course of work while rapid compr|l is being effected. Other effects of compression that are partly of a mechanical nature, the transient accumulation of carbon dioxide in the lungs and blood duringflip of gas on rapid compression of the atmosphere, as described by Beafffflj discussed under subsequent headings. The extension of mechanical effects to conditions of pathology is not in this presentation, but reports of injury.to pathological areas in the compression are found in the literature80 and argue strongly for thorough, employment medical examinations in occupations involving atmospheric changes. 2. Solution oj Gases in the Body As indicated in the section on the solubility of atmospheric gases, the .clj of the blood and. tissues for taking up gases is determined by twqM characteristics that respond to partial pressure. That is, both the simplefjl solution of gases in fluids and the pressure-labile chemical association .p|| of them with solutes in the fluids and their cells are concomitantly afflcj changes -in-pressure. -Relatively "small - quantities 'off"gas~'aTe~take watery portion of the blood, as is seen from Table 2, but it must mind that all gases passing to and from the tissues pass through thb phase in the course off their transfer between tissue and atmosphere. In|fffl at every stage of the transfer of gases there is, inescapably, a series .offml through which gas exchange takes place, each of which has its owncoefncie diffusion, permeability, partition, and the lijce, which set up the the tissue-gas relationship with external pressure. Smith and Morales48 describe at least four phases in the attainrr?en!$! saturation of tissues with inert gases by way of the lungs. Their analysisTM a curve of uptake with respect to time that, instead of having a uniformh/clf in sloper-is-chaTacterized-by--an-inflection-or"flattening-in-what-ttmyrcrS'lM^s|' stage of gas transfer. At this time the blood is taking in gas affa unitonnlf since it is presented at the lung surface at a limited rate, in conformity yuff speed of circulation. These transient phenomena are of interest here mainly they show the system to be first serially, then conoomitantly-r-'-affcctcdi.. pressure changes during an increase in pressure. It is evident, fiirtlii ' virtue of these limiting phases the degree of saturation or concenl rat l-miq fora in the tissues is limited with respect to time. Although the general nature of the uptake of gases in the different u-u- "R. E. Smith and M. F. Morales, Bull. Math. Biophys., 6, 141 (1944). 1' EFFECTS OF ABNORMAL ATMOSPHERIC PRESSURE 597 S& 1 igksimilar, the effectiveness of the distributing system varies and this hobs the time required for saturation. The partition of gases among ffifiular, neural, and muscular tissues is obviously dependent at equilibMlsolubility of . the gases in the various materials comprising the cell efS',$he protoplasm, and the inclusions, but at any time short of equilibrium ~r|actrs other than those controlling diffusion (i.e., invasion and 15 may be considered to be the transport and access of the gases olfphese factors are usually spoken of as the vascularization of the tissue. Mplshown that the ratio of capillary surface to the total cell volume llilsues is 51.9 and of tissues poor in fat is 222.2. He indicates further that ggrity is due to the included fat alone, since the same ratio on the basis Sn^ojgactive protoplasm exceeds that found for muscle, sentially it is seen that the fat depots are large nitrogen reservoirs with .eWhjccess and thus require a longer time for charging than do the lean S. Rate of Change of Pressure * glregoing facts indicate that complete saturation requires a definite Safe, and thus on theoretical grounds alone short deep dives may be Sh less chance of sequelae due to excess inert gas than may long SpfivFrom experience and experimentation the relations of these pressure factors have been summarized in diving tables.48,46 jmfbediate effects limiting the rate of compression are mainly those of a ffipiature bn'the ears, sinuses, and'"otEer "isolated gas phases within " Gastrointestinal. gases apparently play no role in -compression but Kp'iffias;k;en into account in view of the ultimate decompression. The effects jffnt'tluvt sinuses are not expressible in quantitative form because of the yidual nature of the response. ,hci'nii|y indication that rapid compression may have some other limiting AisJinifhe observation of Bean80 that the influx offgas into the lungs may j*jji. funMent retardation of the CO2 elimination and thus temporarily elevate Sspft&tb in the alveoli and blood-tissue complex. Bean found complete fal^.eolar gas outflow in human subjects during such rapid compression, 1^p|eievation of pCO* in catheterized lungs of dogs under anesthesia. " .................... f-liVEFEECTS OF MAINTAINED POSITIVE ATMOSPHERIC PRESSURE JBBffisb... 1. State of Saturation of the Several Body Tissues J sippying. tables46 indicate that saturation at any level is rarely. attained "r"Trr' ` ..................... ".. `` ` ........ ` ' ~ ` ^B'Ai/tjr^OersB' and M. A. Still, Naval Med. Research Inst., Research Project X-284, Rept. W H^K|?isher W. A. White, Jr., Naval Med. Research Inst., Rept. No. 86 (1944). SnsfiM1^i^jManual, 1948. Navy Dept., Bureau of Ships, U. S. Government Printing Office, *\ikln^on !. C.