Blood and other body fluids do boil when their pressure drops below 6.3 kPa (47 Torr), the vapor pressure of water at body temperature.[9] This condition is called ebullism.[10] The steam may bloat the body to twice its normal size and slow circulation, but tissues are elastic and porous enough to prevent rupture.[11] Ebullism is slowed by the pressure containment of blood vessels, so some blood remains liquid.[8] Swelling and ebullism can be reduced by containment in a flight suit. Space Shuttle astronauts wore a fitted elastic garment called a Crew Altitude Protection Suit (CAPS) which prevented ebullism at pressures as low as 2 kPa (15 Torr).[12] Spacesuits are necessary to prevent ebullism above 19 km.[9] Most spacesuits use 20 kPa (150 Torr) of pure oxygen, just enough to sustain full consciousness. This pressure is high enough to prevent ebullism, but simple evaporation of blood, or of gases dissolved in the blood, can still cause decompression sickness (the bends) and gas embolisms if not managed.