Ebullism

Acute hypoxia, possibly aggravated by ebullism (the vaporization of body fluids at ambient pressures below 47 mm Hg), may always be a major potential medical emergency in space.

The ebullism syndrome arises when an individual is exposed to an ambient pressure that is less than the vapor pressure of body fluids at normothermic temperature, about 6kPa [197]. Whereas DCS is primarily characterized by the formation in tissues of the gas phase of inert gas, ebullism is characterized by the formation of the gas phase of water.

Exposure to 63 000 feet introduces the additional hazard of ebullism. At this altitude, ambient pressure (47mmHg, 6.25 kPa) equals the saturated vapour pressure of water at body temperature (37°C) and spontaneous boiling and degassing of bodily fluids and tissues will occur (ebullism).