Blood samples were taken from radial artery and S-G catheter for blood gas analysis at following intervals : during spontaneous breathing when the patient was awake ( T0 ) , 1 min after tracheal indubation ( T1 ) , 1 min after patient was placed in lateral position ( T2 ) and 15 min after it ( T3 ) , 1 min after ribs was braced ( T4 ) , 30 , 60 , 120 min during the course of OLV ( T5 , T6 , T7 ) , the two lungs were ventilated again for 30 min ( T8 ) and Qs/Qt was calculated .