Determine the clinical efficacy in terms of Apnea Hypopnea Index (AHI), excessive daytime sleepiness (EDS), nocturnal oxygenation of a nasal Positive end-expiratory pressure (PEEP) valve "Provent" in obstructive sleep apnea. The hypothesis is the efficacy will be better than dental device.

Inclusion Criteria:

• Symptomatic patients confirmed of OSA by sleep study (PSG according to AASM criteria or validated level 3 portable monitoring devices with AHI > 10/hr)
• Not using CPAP for any reasons or patients on dental device but would like to try alternative treatments for OSA.
• Able to sign informed consent and use the PEEP nasal valve.
• Age between 18-65 years old.
• Willing to attend follow up.

Exclusion Criteria:

• Known nasal problems like deformities or significant rhinitis affecting application of PEEP nasal valve.
• Unable to sign consent or use PEEP nasal valve.
• Significant or unstable co-morbidities requiring other forms of treatment for OSA as priority.
• Coexisting sleep disordered breathing condition other than OSA requiring more complex treatment. E.g. central sleep apnea, significant Cheyne Stokes respiration or hypoventilation syndrome.