Inclusion Criteria:  both sexes aged eighteen or over already have baseline polysomnography showing a severe Apnea-Hypopnea Index (AIH), defined according to the current criteria of the American Academy of Sleep Medicine (AASM) as 30 events / hour of sleep or more already be using a continuous positive pressure device (CPAP) at a pressure equal to or greater than 9 cmH2O with good adherence, defined as an average use equal to or greater than 4 hours per day.  Exclusion Criteria:  Patients with:  severe or decompensated respiratory or cardiac diseases previous pharyngeal surgery or other sleep disorders, such as parasomnias, narcolepsy or primary insomnia users of sedative medications such as opioids, benzodiazepines and muscle relaxants uncontrolled diabetes or hyperthyroidism