• Primary efficacy outcome measure is a comparison of the change in NIHSS scores from baseline to 4 hours (during therapy) in the two groups. The primary neuroimaging outcome measure is a similar comparison of the change in MRI ischemic lesion volumes [ Time Frame: 90 days ] [ Designated as safety issue: Yes ]
  
• Primary safety outcome measure is a comparison of the change in NIHSS scores from baseline to 24 hours (during therapy) in the two groups. The primary neuroimaging outcome measure is a similar comparison of the change in MRI ischemic lesion volumes. [ Time Frame: 90 days ] [ Designated as safety issue: Yes ]
  

Stroke is the third leading cause of death and the leading cause of disability in the United States. Ischemic stroke is caused by a blockage of blood flow to one or more brain arteries, usually due to a blood clot. As a result there is a reduced supply of oxygen and other nutrients leading to permanent brain damage. At present the clot-busting drug intravenous tissue plasminogen activator, t-PA, is the only acute stroke treatment approved by the Food and Drug Administration. Unfortunately less than 5 percent of individuals with stroke actually receive t-PA because it has to be administered within 3 hours of stroke onset to be safe and effective. Therefore, it is important to develop new therapies for stroke and strategies that can safely extend the time window for delivering clot-busting drugs.

Normobaric oxygen therapy (NBO, or high-flow oxygen delivered via a facemask) shows promise as a simple, widely accessible, low-cost therapy that can prevent stroke-related brain damage and extend the time window for administering clot-busting drugs.

The primary goal of this trial is to compare the safety and therapeutic efficacy of NBO (started within 9 hours of symptom onset) to standard medical treatment. This trial will also determine the potential of NBO in extending the therapeutic time window for administering such drugs as t-PA. A total of 240 individuals with acute ischemic stroke will be enrolled at the Massachusetts General and Brigham and Women's Hospitals in Boston. Participants will be randomly selected to receive either room air or oxygen therapy administered for 8 hours. Neurological function scores and neuroimaging (magnetic resonance imaging, MRI, or computed tomography, CT, scans) will be obtained before, during, and after therapy until 90 days.

This study is part of the Specialized Program of Translational Research in Acute Stroke (SPOTRIAS), which allows researchers to enhance and initiate translational research that ultimately will benefit individuals with stroke.