Selective lobar blockade (SLB) is a specific technique that allows collapse of the operated lobe during thoracic surgery while the other lobes are ventilated. It is associated with the improvement of arterial oxygenation during one lung ventilation (OLV) for thoracic with providing adequate surgical access. The purpose of this study is to compare the efficacy of three bronchial blockers, namely an Arndt® wire-guided endobronchial blocker, a Cohen Flexi-tip endobronchial blocker or a Fuji Uni-blocker, for achieving selective lobar collapse.