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. In this study, the investigators will randomize the patients receiving VATS operation with EBB into two groups: one group will receive the conventional bronchoscopic guided EBBs placement, the other group receive two step procedure without confirmation by fiberoptic bronchoscopy.