Decompression sickness (bends) is generally considered to be due to the effects of bubbles which originate from supersaturated gas dissolved in the blood and other tissues.
The bubbles in the tissues are formed from pre-exisiting gas nuclei. The gas initially diffused into the gas nuclei in the tissue and is then forced out by decompression, depending on the difference between the inside tension of the gas nuclei and the surrounding tension of the tissue.
Mammalian gelatin samples were first used according to this theory by LeMessurier in 1972 as a model in the etiology of bends, and further careful research has been carried out by Beckman, Yount, Mano and their co-workers. Mano et al. have evaluated the relative effectiveness of standard decompression tables in reducing bubble formation using the agarose gel bubble technique under rigorously controlled conditions.
Bubble formation is mainly due to the decompression ratio, accompanied by hyperbaric exposure; however, the variation of exposure temperatures also influences the formed bubbles even though there are no decompression steps.
Therefore, to understand the relation between the temperature and bubble formation, research was undertaken. This bubble work is composed of two groups of experiments. One involved saturation experiments, and the relation between the number of bubbles and different saturation pressures was obtained as a regression line. The temperature was controlled at 20.0±1.0°C.
In the other experiments, the environmental temperature was changed between 5 and 30°C. Agarose gel samples, with 15 cells in a set, were exposed to the same bottom pressure but the environmental temperature was varied in each set of conditions.
The number of bubbles was counted in each sample and the cells were heated to 30°C for 30min and bubble counting was then done. The exposure time at the bottom pressure was 30, 60, or 120min in the non-saturation experiments and 6 hours in the saturation experiments. The phenomena of bubble formation according to the variations of the temperature were investigated in detail, and, eventually, significant regression equations could be obtained with good relations in all defferent conditions of hyperbaric exposure.
This result gives us much information on bubble formation phenomena, which can aid us in carrying out our basic research on decompression sickness, especially as concerns the influence of environmenal temperature, although there are differences between in vitro and in vivo phenomena. Moreover, the standard decompression table by the Ministry of Labour could be evaluated by this bubble counting technique. The safety of the table was questionable, and it was recognized that the table was not necessarily correct. This research will be applied to various fields of diving or compressed air work in the future.
