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 ( T@ ) , @ min after tracheal indubation ( T@ ) , @ min after patient was placed in lateral position ( T@ ) and @ min after it ( T@ ) , @ min after ribs was braced ( T@ ) , @ , @ , @ min during the course of OLV ( T@ , T@ , T@ ) , the two lungs were ventilated again for @ min ( T@ ) and Qs/Qt was calculated .