Obstructive sleep apnea syndrome (OSAS) is characterized by repetitive collapse of the upper airway during sleep .The obstructive apneic event is associated with considerable breathing efforts against a totally or partially occluded upper airway, and apnea is terminated by an arousal and heavy snoring as airflow is restored. Severity of OSAS is described according to total number of apneas and hyperpneas per hour of sleep, which is named as the apnea-hypopnea index (AHI).