FORMATION OF BUBBLES IN BOVINE SERUM AND SYNOVIAL FLUID BY RAPID DECOMPRESSION

It is believed that the symptoms of decompression sickness are initiated by the formation of gas microbubbles in tissue which have become supersaturated as a result of too rapid reduction of ambient pressure. However, it is still uncertain where the bubbles form in the body. Since it is unlikely that tissue supersaturation of sufficient magnitude to allow random bubble formation through the thermodynamic activity of gas molecules can exist in vivo, it is necessary to examine the characteristics of tissues and tissue fluids to understand the probabilities that bubbles will form under real conditions of exposure and decomposition. Bovine serum and synovial fluid were exposed to physiologically inert gases (helium and nitrogen) at pressures of 50, 100, 150, and 250 psig. The fluids were exposed to CO(,2) at these same pressures and to a mixture of 5 percent CO(,2) and 95 percent nitrogen. Synovial fluid to which additional albumin and to which 70,000 molecular weight dextran had been added was also exposed to these pressures. Following exposure, samples were decompressed rapidly and bubbles were counted using a light microscope and photographed with an inverted microscope adapted for attachment of a 35 mm camera. The results indicate that for inert gases, the number of bubbles which form in serum is related to the maximum exposure pressure prior to decompression. For synovial fluid, bubble formation number is not dependent on exposure pressure for pressures investigated, but bubbles increase in size with increasing maximum pressure prior to decompression. CO(,2) exposure inhibits formation of bubbles following decompression of serum, but increases bubble formation in synovial fluid. The addition of albumin in synovial fluid in sufficient quantity to make the concentration equivalent to that in serum, makes the synovial fluid behave more like serum, producing increased numbers of bubbles at increased exposure pressure. A similar effect is found when dextran is added to synovial fluid or when dextran is added to serum exposed to high pressure of CO(,2). It is concluded that serum contains sufficient nucleation sites to allow decompression bubbles to form whenever a sufficient quantity of gas is dissolved in the fluid. Synovial fluid has fewer nucleation sites, decreasing the probability that bubbles will form there at any particular exposure-decompression profile. The existance of nucleation sites appears to be related to the concentration of large molecules in the fluid such as protein or albumin