Nasal Continuous Positive Airway Pressure (CPAP) is the standard therapy for obstructive sleep apnea hypopnea syndrome (OSAHS). This is most commonly administered as a single positive pressure that has been individualized for the patient to prevent obstructive respiratory events. However, the therapeutic pressure may vary by sleep stage and body position within a single night and may change over the course of several nights. One approach to dealing with this variability is the use of automatically adjusting CPAP that responds to patient breathing patterns with alterations in the delivered pressure. This study is designed to determine the effectiveness of using the energy spectrum analysis of flow signals to automatically adjust CPAP pressure and improve sleep variables. Thirty subjects who require CPAP will be recruited from the NYU sleep disorders center. Following diagnostic studies (either split night or full night) the subject will undergo a night of treatment with the Fisher and Paykel Healthcare AutoPAP. Efficacy of treatment will be evaluated based on normalization of sleep disordered breathing while treated with the AutoPAP.