Inclusion Criteria:  • Large vessel occlusion anterior circulation stroke (terminal carotid artery and/or middle cerebral artery M1-M2 segment) eligible to mechanical thrombectomy under general anesthesia  Exclusion Criteria :  Active smoker Chronic respiratory failure with ambulatory oxygen supplementation Obesity with BMI>40Kg/ m2 Intubation before the procedure Heart failure with intolerance to decubitus Severe renal failure Suspected elevated intracranial pressure Pregnant or breastfeeding women