oxygen saturation < or = 88% or PaO2 < or = 55 mm Hg
oxygen saturation < or = 88% or pao2 < or = 55 mm hg
oxygen saturation < or = 88% or PaO2 < or = 55 mm Hg
oxygen saturation < or = 88% or pao2 < or = 55 mm hg