Normobaric Hyperoxia Combined With Endovascular Treatment for Acute Ischemic Stroke

Inclusion Criteria: * age≥18; * Suspected lage vessel occlusion of acute anterior circulation occlusion; i.e. either the ICA or the M1/M2-segment of the MCA; * Stroke symptom onset has been more than 6 hours but not more than 24 hours,and imaging confirmed the existenceof ischemic penumbra; * NIHSS score≥6; * Alberta Stroke Program Early CT score (ASPECTS) of 6-10 on non- contrast CT; * (Level of consciousness) NIHSS score of 0 or 1 * mRS score was 0-1 before stroke; * Informed consent obtained; Exclusion Criteria: * Rapid improvement in neurological status to an NIHSS \< 6 or evidence of vessel recanalization prior to randomization; * Seizures at stroke onset; * Intracranial hemorrhage; * Systolic pressure greater than 185 mm Hg or diastolic pressure greater than 110 mm Hg, or aggressive treatment intravenous medication)necessary to reduce blood pressure to these limits; * Symptoms rapidly improving; * Symptoms suggestive of subarachnoid hemorrhage, even if CT scan was normal; * Platelet count of less than 100,000 per cubic millimeter; * CT showed a multiple infarction (low density area greater than 1/3 cerebral hemisphere); * severe hepatic or renal dysfunction; * active and chronic obstructive pulmonary disease or acute respiratory distress syndrome; * \>3 L/min oxygen required to maintain peripheral arterial oxygen saturation (SaO2)#95% as per current stroke management guidelines; * medically unstable; * inability to obtain informed consent; * Life expectancy\<90 days; * Pregnant or breast-feeding women; * Unwilling to be followed up or poor compliance for treatment; * Patients being enrolled or having been enrolled in other clinical trial within 3 months prior to this clinical trial; * Evidence of intracranial tumor; * Baseline blood glucose of \< 50 mg/dL (2.78 mmol) or \> 400 mg/dL (22.20 mmol); * Patients with upper gastrointestinal bleeding or nausea and vomiting who cannot use oxygen masks; * Other circumstances requiring emergency oxygen inhalation;