The investigators aim to assess the respiratory effect of short half-life agents in balanced anesthesia on patients suffering from non-treated or suspected obstructive sleep apnea syndrome (OSA) We will study the impact on OSA of a regimen of remifentanil-desflurane versus a regimen of fentanyl-sevoflurane. Each patient will undergo three respiratory portable polygraphies: the night before the surgery ; the first night following the surgery ; the third night following the surgery.