Obstructive sleep apnea (OSA), is a condition characterized by several stops and starts in breathing during sleep. This is caused by the collapse and re-opening of throat muscles. Unfortunately, the estimated one in four men and one in ten women who suffer from this condition are four times more likely to suffer from a stroke. The reasons for this phenomenon are not clear; however one likely explanation is an impaired ability among people with OSA to maintain normal blood pressure. In healthy individuals, when blood pressure increases the body reacts with a series of processes in order to bring blood pressure back down to normal levels. These processes are collectively called the baroreflex. However, the baroreflex is impaired in people with OSA, which results in dangerously high blood pressure and consequently, an increased risk for stroke. To-date, research has shown that baroreflex function is not only a powerful predictor of stroke, but also has strong prognostic value following a stroke. Indirect suggestions have been made of a potential improvement of the baroreflex in healthy humans when breathing supplemental oxygen (i.e. breathing high levels of oxygen). However, this remains to be investigated in people with OSA. In what is the first study to evaluate the effectiveness of supplemental oxygen in improving the baroreflex function in OSA, Jordan Querido is evaluating cardoirespiratory variables, including ventilated oxygen and carbon dioxide levels, sympathetic outflow, blood pressure, stroke volume, and heart rate, in both OSA patients and a group of healthy controls. Additionally, he will investigate the mechanisms which place OSA patients at greater risk for stroke, thereby potentially reducing their risk of stroke, and improving the prognosis following stroke.