Arterial partial pressure of oxygen ( PaO@ ) and fraction of inspired oxygen ( FIO@ ) were measured before anesthesia induction ( T@ ) , at skin incision ( T@ ) , after administration of heparin ( T@ ) , at @ minutes after CPB weaning ( T@ ) , just before departure from the operating room to the intensive care unit ( ICU ) ( T@ ) , and @ hour after ICU admission ( T@ ) , and PaO@/FIO@ ratio was calculated .