Decompression sickness: a review.
Work in compressed air is a dangerous activity, whether it is carried on under water in a conventional diving suit, in self-contained breathing apparatus or in a diving bell, or in relatively dry conditions in a caisson or an underwater tunnel. Surprisingly large numbers of men have worked at one time or another in compressed air in tunnels or caissons and it is the dangers which arise to the health of these men that are considered here. When a tunnel is driven through water-logged strata or through porous ground under a river, the open end of the tunnel must be sealed off and air pumped in to balance the hydrostatic pressure, should there be any danger of water flooding in and bringing with it unmanageable quantities of silt or sand. A pier of a bridge may be constructed in deep water by means of a caisson (Fr. caisse, a box), which is a compressed air chamber in which a gang of men excavate foundations. In both tunnels and caissons men come and go through an air lock and must be compressed on entering and decompressed at the end of the work period. Although working conditions in these circumstances have much improved over the last 6o years, our understanding of the reactions of the human body to atmospheric pressures greater than the normal and of the pathogenesis of decompression sickness is still insufficient to prevent illness completely. In engineering practice it is customary for working pressure to be expressed as gauge pressure in pounds per square inch (p.s.i.g.) which is the pressure over and above the normal atmospheric pressure of I4-7 p.S.i. (I 03 kg./cm.2). For certain calculations absolute pressure (gauge pressure plus atmospheric pressure) is used, and for clarity it must always be stated whether gauge or absolute pressure is referred to. In naval practice it is usual to think in terms of feet of sea water, each 33 feet of depth corresponding to about one atmosphere or approximately I5 p.s.i. Sometimes the unit of pressure used is the atmosphere (atm.). On the
Aviation Medicine in Its Preventive Aspects
AVIATION MEDICINE IN ITS PREVENTIVE ASPECTS. An Historical Survey. By John F. Fulton. New York, Oxford University Press, 1948. 174 pp., illus. $3.00. It seems proper that a physiologist should have wvritten a book about aviation medicine, dealing as it does with I. Altitude Sickness and Acclimatization: The History of Oxygen; II. Decompression Sickness: The Genesis of the Tissue Bubble; III. Pressure Cabins and Explosive Decompression; The Spring of the Air; IV. Effects of Acceleration: DimOut and Black-Out; Protective Measures; and V. Man and the Machine: Problems of Safety in Flight. If you enjoy reading for pleasure, open Dr. Fulton's book at any page and start in. Well-written and readable, it blends history and science in a way which might serve as an example of excellence to many of our medical writers. You will quickly discover that the pilot or the passenger in an aircraft can take to the air and land safely only if the designer as well as the pilot do their work within the limitations of man's physiology. You will find that the pioneer in this field was a man who never saw an airplane. Robert Boyle wrote The Spring of the Air about three hundred years ago, discussed altitude sickness, and first mentioned the occurrence of tissue bubbles in animals confined in low pressure chambers. Since Boyle's time, the practical applications of his and subsequent physiological observations have become apparent. One might conclude with Dr. Fulton that one of the first things to consider in developing a new engineering discovery would be the way in which the human organism nmight be affected by the physical and physiological forces involved. Thus, designers should logically ask for consultation from physiologists and other miiedical scientists early in their labors. That this was not always so is attested to by Dr. Fulton's report of ". . . Air Marshal Harris's expostulations in 1940-1 over the size of the tailgunner's compartment in our early B-17 bombers-compartments which to man would require the development of a race of pygmies-. . . [and] ... his infinite delight on witnessing an aircraft designer stuck and unable to move in attempting to seat himself at the rear-gunner's station." This special medical field in which the environmental factors have a vital bearing upon the health of people who fly has expanded largely through the application of sound scientific principles to the problems at hand. This lesson must be applied to every occupational field if we are to succeed in teaching man to live safely and in good health in his industrialized world.
The Inca Occupation of the South Coast of Peru
like the others, however; it forks into several nearly parallel ravines of which the largest are Huayuri, Rio Grande-Palpa, Ingenio (called Collao in ancient times), Nasca proper (the ancient Caxamarca), Taruga, and Poroma. Due to peculiarities of the local topography, the irrigated areas in Ica and the ravines of Nasca are located inland, at the foot of the mountains, rather than at the mouths of the rivers as is more usual in Peruvian coastal valleys. No sharp natural or cultural boundary separates the valley of Chincha from the valleys of Cafiete (ancient Huarco and Runahuana), Asia, and Mala, the next valleys going up the coast to the northwest. At the other end of the area we are considering, however, there is a sharp break; beyond Yauca the Andean foothills reach out to the sea, natural conditions are quite different, and there are important differences in the archaeological picture as well. The historical sources which mention the south coast are not particularly helpful, except in so far as they provide us with a few dates. To begin with, no chronicler gives an explicit account of the political organization of the south coast at the time it came into contact with the Incas. It can, perhaps, be inferred from Cabello Balboa's statements about common policy toward the Inca invaders that there was some sort of political connection between the valleys of Mala, Cafiete, and Chincha, but the connection need have been no more than a temporary military alliance. Cabello makes no mention at all of Pisco. The valleys of Ica, Nasca, and 125