The need of fiberoptic bronchoscopy for placing an endobronchial blocker. Endobronchial blockers (EBB) have been presented effective and safe alternative for lung separation in vedio-assisted thoracoscopic (VATS) operations. However, there were previous reports showed that it takes longer time to position the EBB versus the double lumen tubes. Placing EBBs need three-step procedure (one is placing an endotracheal tube, the second is inserting the EBB, the third is confirmation of the position by fiberoptic bronchoscopy). In this study, the investigators will randomize the patients receiving VATS operation with EBB into two groups: one group will receive the conventional 3-step procedure, the other group receive two step procedure without confirmation by fiberoptic bronchoscopy.