SCUBA - Self-Contained Underwater Breathing Apparatus 14
SCUBA - Self-Contained Underwater Breathing Apparatus 14 : Effects of Breathing High Pressure Gas: See also: Breathing gases at high ambient pressure. Decompression sickness: Decompression sickness. The prolonged exposure to breathing gases at high partial pressure will result in increased amounts of non-metabolic gases, usually nitrogen and/or helium, (referred to in this context as inert gases) dissolving in the bloodstream as it passes through the alveolar capillaries, and thence carried to the other tissues of the body, where they will accumulate until saturated. This saturation process has very little immediate effect on the diver. However when the pressure is reduced during ascent, the amount of dissolved inert gas that can be held in stable solution in the tissues is reduced. This effect is described by Henry's Law. As a consequence of the reducing partial pressure of inert gases in the lungs during ascent, the dissolved gas will be diffused back from the bloodstream to the gas in the lungs and exhaled. The reduced gas concentration in the blood has a similar effect when it passes through tissues carrying a higher concentration, and that gas will diffuse back into the bloodsteam, reducing the loading of the tissues. As long as this process is gradual, all will go well and the diver will reduce the gas loading by diffusion and perfusion until it eventually re-stabilises at the current saturation pressure. The problem arises when the pressure is reduced more quickly than the gas can be removed by this mechanism, and the level of supersaturation rises sufficiently to become unstable
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