The investigators hypothesis is that obstructive sleep apnea (OSA) patients with a low arousal threshold may wake up too early during a respiratory event, before upper airway muscles can be activated to achieve stable ventilation. Thus, strategies to manipulate the respiratory arousal threshold could potentially improve the quality of sleep and sleep disordered breathing. Agents that raise arousal threshold are therefore likely to benefit some patients with OSA. The overall goal of this project is to determine the importance of the arousal threshold in OSA, determine which patients might benefit from a raised arousal threshold, and test this hypothesis by using pharmacological manipulation of the arousal threshold to achieve this goal.