Edema has many possible causes: 1  Prolonged standing or sitting, especially in hot weather, can cause excess fluid to accumulate in the feet, ankles and lower legs. 2  Tiny valves inside the veins of the legs can become weakened, causing a common problem called venous insufficiency.
Cars with nitrous-equipped engines can be identified by the purge of the delivery system that most drivers perform prior to reaching the starting line. A separate electrically operated valve is used to release air and gaseous nitrous oxide trapped in the delivery system.
What is Nitrous Oxide. Nitrous oxide use for labor pain is a mixture of 50% nitrous gas and 50% oxygen that is inhaled through a mask or mouthpiece that a woman holds and self-administers, as she wishes. A version of nitrous oxide is used widely in dental offices, where most people know of it as laughing gas.