Traumatic brain injury (TBI) is one of the world’s leading causes of death and disability, leading to over 500 billion Canadian dollars in societal costs annually. Impaired blood flow to the brain has be recently identified as a main cause for ongoing brain damage after TBI. Control of brain blood flow is termed cerebral autoregulation (CA). Our ability to accurately measure CA in patients at the bedside in the intensive care unit (ICU), is limited to invasive techniques that require neurosurgery expertise and carry risk.