Oxygen Concentration Target in Stroke Endovascular Treatment

The goal of this clinical trial is to compare the effects of different concentrations of normobaric oxygen on early neurological improvement in acute ischemic stroke (AIS) patients receiving endovascular therapy (EVT). The main questions it aims to answer are: * Evaluating the impact of normobaric high-concentration oxygen versus low-concentration oxygen on early neurological function after EVT. * Evaluating the safety of high and low normobaric oxygen concentration in patients with ischemic stroke. Participants will (1) receive EVT under general anesthesia; (2) be randomly assigned 1:1 to receive oxygen therapy with FiO2=80% or FiO2=30% through endotracheal intubation during the operation, and the gas flow rate was set at 4L /min.