Oral unintentional leak is a common side effect of continuous positive airway pressure (CPAP) for obstructive sleep apnea (OSA) treatment. Management of oral unintentional leakage has not been standardized and the effectiveness of potential approaches have not been studied in controlled studies. Higher levels of CPAP are associated with higher leak. In the present study, a sequential approach to control excessive unintentional leak will be tested. In study A, the reduction of therapeutic CPAP level will be tested. In study B, oronasal CPAP will be compared to nasal CPAP with a chinstrap.

Study B will consist of a controlled crossover trial to compare unintentional leak during the use of an oronasal mask versus a nasal mask with a chinstrap, among subjects who remain with excessive leak at the end of study A. The order of interventions will be randomized. One of the groups will initially use an oronasal mask for 10 days. A washout period of 7 days under nasal CPAP will follow. After washout, subjects will continue using a nasal mask and will be asked to use a chinstrap for another 10 days. In the other group, the order of interventions will be the opposite.

Inclusion Criteria:

• Diagnosis of moderate and severe obstructive sleep apnea;
• Use of CPAP with a nasal mask;
• 95th percentile of unintentional leak from the last 7 days above 24 l/min, or at least 4 sudden drops of leak over one night of nasal CPAP
• Persistence of excessive leak at the end of Study A.

Exclusion Criteria:

• Patients who experience unintentional leakage from the mask/accessories.
• Diagnostic polysomnography examination with a predominance of central apnea;
• Patients with unstable heart disease, bedridden, neurodegenerative diseases, severe psychiatric disorders and COPD;
• Previous surgery for obstructive sleep apnea;
• Severe nasal obstruction (NOSE questionnaire score equal or greater then 55 points).