Severe obstructive sleep apnea (OSA) is associated with increased cardiovascular morbidity and mortality. Endothelial dysfunction, an early marker of vascular disease has been demonstrated in OSA. Regular treatment of OSA by continuous positive airway pressure (CPAP) improves endothelial function and is associated with a reduction in cardiovascular risk. Approximately 40% of patients with OSA are intolerant or insufficiently adherent to CPAP. Alternative treatments or adjuvants to the CPAP are needed.