Sara Hefton1, Nikolay Bogush2, Robert S Crawford3, Robert M Reed4. 1. Department of Neurology, University of Maryland Medical Center, Baltimore, Maryland, USA. 2. University of Maryland, Baltimore, Maryland, USA. 3. Department of Vascular Surgery & Anesthesiology, University of Maryland, Baltimore, Maryland, USA. 4. Department of Pulmonary and Critical Care Medicine, University of Maryland, Baltimore, Maryland, USA.