Dysbarism: a Jet Age Problem of All Physicians.

focused on space efforts and the appearance of commercial jet aviation, medical subjects, which formerly concerned only aviation medicine specialists, now have become of considerable interest to all physicians. One example of the degree of interest has been the establishment of the Committee on Aerospace Medicine by the American College of Chest Physicians. Much attention has been given to the problem of altitude hypoxia in the event of cabin depressurization of commercial jet aircraft, and the emergency oxygen equipment , which is available in the aircraft can be used to minimize oxygen want. However, little has been published about the adverse effects of reduced barometric presure, per Se, except in physiology or aviation medicine journals. The adverse effects of changes in barometric pressure are known as dysbarism. When the differential is between the pressure at sea level and greater pressure, these adverse effects are commonly called caisson disease, long a problem for deep sea divers. Altitude dys-barism occurs when barometric pressure is less than that at sea level inasmuch as barometric pressure decreases progressively with increase in altitude. For example, the mass of air which presses down upon us at sea level weighs approximately twice as much as that at 18,000 feet and approximately three times as much as that at 27,500 feet altitude. Two consequences of the physical properties of gases are important to recall. First, a volume of gas contained in an elastic membrane, such as a balloon, will increase *This paper represents the personal viewpoints of the authors and is not to be construed as a statement of official Air Force policy. in size as the surrounding (ambient) barometric pressure is reduced. Second, the solubility of a gas in solution is proportional to the partial pressure of that gas in the surrounding atmosphere, and when this pressure is reduced, the dissolved gas will come out of solution and tend to form bubbles. An example of this phenomenon is experienced daily when the top is removed from a bottle of soda pop. Probably these two physical properties of gases are the most significant causes of dysbarism, which manifests itself in several ways (Table 1). Body cavities which are open to the outside, either constantly or intermittently, contain gases. If with changes in altitude the communication is maintained, air will escape or enter these spaces as the enclosed gases contract or expand, and no pressure will be built up. …