Lung isolation is primordial in thoracic surgery. To achieve it, two techniques are used: the double lumen tube (DLT) and the bronchial blocker (BB). Left-sided DLT (L-DLT) is use by the majority of anesthesiologists for both left and right thoracic surgeries. Standard right-sided DLT (Rs-DLT) is rarely use since it is dif¬ficult to properly position it and that there is a risk of misalignment between the lateral orifice of the tube and the origin of the right upper lobe (RUL) bron¬chus. In 2007, the investigators have published results suggesting enlarging the Rs-DLT's lateral orifice. The modified R-DLT (Rm-DLT) was more frequently in an adequate position: 77% vs 37% of patients (p = 0.0121), and easier to reposition: 97% vs 74% of patients (p= 0.0109) in comparison to the standard R-DLT group. The data suggest the superiority of the Rm-DLT compared to Rs-DLT for optimal positioning to facilitate one-lung ventilation (OLV) during thoracic surgery. It is believed that DLT tend to provide quicker and better quality of lung collapse than BB. In 2013, investigators have demonstrated an equivalent quality of lung collapse (LC) between L-DLT and BB used with two apnea periods when initiating OLV. Complementary analysis showed a significative difference to obtain complete LC (CLC) between L-DLT for left thoracoscopy and L-DLT for right thoracoscopy and BB in right or left surgery. The investigator hypothesis is that, when using L-DLT for left video-assisted thoracoscopic surgery (VATS), LC of the isolated lung will be slower and of poorer quality compare to the use of the Rm-DLT. The primary objective is to compare the delay between pleural opening (PO) and CLC in left VATS when using three lung isolation devices: 1) L-DLT and 2) Rm-DLT. Secondary objectives are: 1) to evaluate quality of LC, 2) to evaluate the level of obstruction of the lumen of the left bronchus, 3) to evaluate the quality of OLV (PaO2) 4) To collect blind surgeon's opinion about de device used and 5) to measure the delay between OLV and PO for evaluating the role of absorption atelectasis in obtaining CLC. After obtaining IRB approval, the investigators propose a study of 40 patients undergoing an elective left VATS at IUCPQ involving one lung ventilation. They will have to be 21 years or more, to read, understand and sign an informed consent at their pre-operative evaluation. This study will be prospective, randomized, and blind to thoracic surgeons.