Inclusion Criteria:

   - Age 21 - 75

   - Diagnosis of OSAHS with baseline AHI equal or greater than 15 events/hr of sleep

   - Able and willing to provide written informed consent

   - Agreement to try PAP as initial treatment approach

   - Adequate clinical CPAP titration within two weeks of enrollment

Exclusion Criteria:

   - Participation in another interventional research study within the last 30 days

   - The need for more than one titration PSG

   - The use of sedatives or hypnotics during the titration PSG

   - Major medical or psychiatric condition that would interfere with the demands of the
   study, adherence to PAP, or the ability to commit to follow-up assessment.

   - Prior prescription for, or exposure to PAP therapy within the previous year (except
   exposure to CPAP during clinical therapy titration.)

   - Chronic respiratory failure or insufficiency with suspected or known neuromuscular
   disease, moderate or severe COPD or other pulmonary disorders, or any condition with
   an elevation of arterial carbon dioxide levels (>45 mmHG) while awake or participants
   qualifying for oxygen therapy (arterial saturation < or equal to 88% for more than
   five minutes).

   - Surgery of the upper airway, nose, sinus, or middle ear within the previous 90 days

   - Surgery at any time for the treatment of OSAHS such as uvulopalatopharyngoplasty
   (UPPP)

   - Presence of untreated or poorly managed, non-OSAHS related sleep disorders:

      - moderate to severe periodic limb movements (greater or equal to 15 per hour with
      symptoms or arousals)

      - Restless Leg syndrome (greater than 10 per hour)

      - Males experiencing chronic insomnia

   - Use of medications with hypnotic or sedative effects or regular use of night time
   sedatives or sleeping aids greater than or equal to one night per week.

   - Consumption of ethanol more than 4 nights per week (CAGE criteria)

   - Shift workers