Approach: In the study described above, we will determine the Modified Rankin Scale (mRS) at hospital discharge. We will compare proportions of good neurological outcome [defined as a mRS ≤ 3] between subjects enrolled in REOX II (i.e. receive the study intervention, rapid FiO2 optimization) vs. those enrolled in REOX I (i.e. do not receive the study intervention), using binomial test.