Arterial oxygen pressure ( PaO@ ) , arterial carbondioxide tension ( PaCO@ ) , O@ saturation ( SPO@ ) , mean arterial pressure ( MAP ) , heart rate ( HR ) , anesthetic effect , time of spontaneous breathing recovery , and time of resuscitation were recorded before operation ( T@ ) , immediately after skin incision ( T@ ) , immediately after sternotomy ( T@ ) , before suspension of cardiopulmonary bypass ( CPB , T@ ) , immediately after cardiac re-beating ( T@ ) , immediately after CPB cessation ( T@ ) , and at the end of surgery ( T@ ) .