<prompt> What will be the PA O2 when FiO2 is 0.5?100150250.500  <response>: FiO2 fraction of O2 in inspired 50 Pressure at sea level 760 mm Hg According to law to paial pressures of gases, Pressures exeed by a gas in a mixture is propoional : if 50 of air is O2 PAO2 50 of 760 380 mm Hg. 