A pilot study of normobaric oxygen therapy in acute ischemic stroke

Background and Purpose - Therapies that transiently prevent ischemic neuronal death can potentially extend therapeutic time windows for stroke thrombolysis. We conducted a pilot study to investigate the effects of high-flow oxygen in acute ischemic stroke. Methods - We randomized patients with acute stroke (<12 hours) and perfusion-diffusion "mismatch" on magnetic resonance imaging (MRI) to high-flow oxygen therapy via facemask for 8 hours ( n = 9) or room air ( controls, n = 7). Stroke scale scores and MRI scans were obtained at baseline, 4 hours, 24 hours, 1 week, and 3 months. Clinical deficits and MR abnormalities were compared between groups. Results - Stroke scale scores were similar at baseline, tended to improve at 4 hours ( during therapy) and 1 week, and significantly improved at 24 hours in hyperoxia-treated patients. There was no significant difference at 3 months. Mean ( +/- SD) relative diffusion MRI lesion volumes were significantly reduced in hyperoxia-treated patients at 4 hours (87.8 +/- 22% versus 149.1 +/- 41%; P = 0.004) but not subsequent time points. The percentage of MRI voxels improving from baseline "ischemic" to 4-hour "non-ischemic" values tended to be higher in hyperoxia-treated patients. Cerebral blood volume and blood flow within ischemic regions improved with hyperoxia. These "during-therapy" benefits occurred without arterial recanalization. By 24 hours, MRI showed reperfusion and asymptomatic petechial hemorrhages in 50% of hyperoxia-treated patients versus 17% of controls ( P = 0.6). Conclusions - High-flow oxygen therapy is associated with a transient improvement of clinical deficits and MRI abnormalities in select patients with acute ischemic stroke. Further studies are warranted to investigate the safety and efficacy of hyperoxia as a stroke therapy.