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The formation of bubbles, especially of water vapor bubbles in biological fluids, owing to reduced ambient pressure.
The boiling of body fluids. The formation of bubbles, with particular reference to water vapor bubbles in biological fluids caused by reduced ambient pressure. When the atmospheric pressure reaches 47 mm of mercury at an altitude of 19.2 km (63,000 ft), the water vapor pressure of body fluids is the same as that of the atmosphere. The manifestations of ebullism include bubble formation in the blood, mucous membranes in the mouth and joints and conjunctiva of the eye, and swelling of the skin as a result of diffuse bubble formation in the tissues. This functional limit can be circumvented only with a full- or partial-pressure suit or a pressurized cabin.