Nowadays, lung isolation techniques are an essential part of thoracic anesthesia. The two principal devices used in order to achieve one-lung ventilation (OLV) are the double lumen tube (DLT) and the bronchial blocker (BB). Even though DLT and BB have always been considered equally effective in lung isolation, a study recently published by Bussières et al. demonstrated the clear superiority of BB over DLT in terms of rapidity and quality of lung collapse. In order to explain this result, a physiologic study was recently conducted. During this project, some interesting discoveries were made. In fact, during lung isolation, while the chest is closed, there is a buildup of negative pressure in the NVL until pleural opening. Moreover, an absorption of ambient air through the lumen of the DLT or through the internal channel of the BB is observed. Putting all these elements together, a possible explanation for the superiority of BB over DLT was obtained. Indeed, in the first study of Bussières, the internal channel of BB was occluded. By doing so, there were no possible aspiration of ambient air in the NVL. This condition may have accelerated the absorption atelectasis of the NVL that occurs during lung collapse by reducing NVL volume and by conserving a higher alveolar partial pressure of oxygen in it.

The hypothesis is that when using a DLT in OLV, occluding the non-ventilated lung (NVL) lumen will reproduce the BB physiology by accelerating the second phase of lung deflation and giving a better quality of lung collapse compared to usual practice of keeping the non-ventilated lung opened to ambient air.

The main objective is to compare the speed and quality of complete lung deflation occurring during OLV with a DLT when the non-ventilated DLT lumen is occluded vs not occluded.

This randomized study will include a total of 30 patients scheduled for lung resection using video-assisted thoracoscopic surgery (VATS). Fifteen patients will compose the experimental group (NVL lumen occluded) and 15 other patients will be part of the control group (NVL lumen opened to ambient air).

One-lung ventilation (OLV) is a major consideration in thoracic anesthesia. Lung isolation, through the use of double-lumen tube (DLT) or bronchial blocker (BB), offers to the surgeon the intra-thoracic access he needs for the surgery. With the use of a DLT, the non-ventilated lung is isolated by disconnecting its specific lumen from the ventilator and keeping it opened to ambient air. With a BB, the BB cuff is inflated in the bronchus after a brief apnea period. Thereafter, only the dependent lung is ventilated.

Until recently, studies evaluating the quality of lung collapse with the use of DLT versus BB showed contradicting results and were not conclusive. However, in 2016, Bussières' research group obtained a faster lung collapse with the use of a BB with its internal channel occluded and a second period of apnea at pleural opening.

A review of the literature could not explain in details these results. In the 2000s, lung collapse during OLV was described as undergoing two distinct phases; the first phase occuring at the opening of the pleural cavity and corresponding to a quick but partial collapse secondary to the elastic recoil of the lung. The second phase, a slower one, being the reabsorption, by the vascular capillary bed, of the gas contained into the alveoli; the speed of this second phase being directly proportional to the solubility coefficient of the gas.

Since no previous studies had explanation for Bussières' unexpected results, they conducted a physiologic study to extensively determine the physiology of the non-ventilated lung (NVL) during OLV with the use of DLT and BB. Their results demonstrated that during lung isolation, while the chest is closed, there is a buildup of negative pressure in the NVL until pleural opening, when the lumen of the DLT or the internal channel of the BB are occluded. This phenomenon was observed for both lung isolation devices (BB and DLT). They also observed an absorption of ambient air through the lumen of the DLT and the internal channel of the BB when the lumen of both device was open to ambient air. These results probably explain why Bussières obtained a faster lung collapse with BB in their study. By occluding the internal channel of the BB they prevented the aspiration of ambient air in the NVL. This condition may have accelerated the absorption atelectasis of the NVL that occurs during the second phase of lung collapse by obtaining an initial lower lung volume containing a higher alveolar partial pressure of oxygen (PAO2) in the BB group.

Since these recent findings demonstrate that both lung isolation devices cause negative pressure and an aspiration of ambient air, it is possible that the occlusion of the specific lumen of the NVL of a DLT could reproduce the physiology of the lung isolation obtained with a BB with its internal channel occluded.

The hypothesis is that by withholding gas exchange between the NVL and ambient air from the beginning of OLV to the pleural opening, the resorption atelectasis will be facilitated. Consequently, lung collapse of the NVL will occur faster when clamping its specific lumen on the DLT instead of letting it communicate with ambient air like anesthesiologists usually do.

Inclusion Criteria:

• Elective lung resection (lobectomies and segmentectomies) by VATS requiring OLV.
• More than 18 years old.
• Having read, understand and signed the consent form presented at the pre-operative evaluation

Exclusion criteria :

A- Pre-operative

1. Known or anticipated difficult tracheal intubation.
2. Bronchoscopic or CT-scan findings contraindicating the insertion of a DLT.
3. Severe COPD or asthma (FEV1 <50%).
4. Prior intrathoracic surgery (including cardiac surgeries).
5. Pleural or interstitial pathology.
6. Previous chemotherapy or thoracic radiotherapy.
7. Acute or chronic pulmonary infection.
8. Endobronchial mass.
9. Tracheostomy.

B- Post-randomisation

1. Bronchoscopic findings contraindicating the insertion of DLT.
2. VATS findings that cancel the surgery.
3. Severe desaturation (SatO2 < 90%) during the observation period.
4. Any need to reinflate the collapse lung.

Adverse event data were collected from the beginning of the surgery through completion of surgery. Moreover, the first PACU thoracic x-ray of each patient was analyzed by a radiologist in order to detect anomalies.

Post-randomisation exclusions. Most of them due to negative biopsies cancelling the need of a lobectomy/segmentectomy.

The study was single blinded. (the anesthesiologist knew in which group the patient was but the surgeon was blinded)