What will be the PA O2 when FiO2 is 0.5?: (A) >100, (B) >150, (C) >250, (D) .>500
Answer is C. 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.