B3)blood-gas Type I:PaO2↓ Type I:PaO2↓+PaCO2 (4 ) pathogenesis ventilation blood gas exchange: diffusion v/Q anatomy shunt(3)blood-gas Type I : PaO2  Type II: PaO2  + PaCO2  (4)pathogenesis ventilation blood gas exchange: diffusion V/Q anatomy shunt