Obstructive sleep apnea (OSA) is a condition of disordered breathing characterised by intermittent partial and/or complete upper airway obstruction during sleep. The participants, naive to nasal continuous positive airway pressure (CPAP), recently diagnosed with OSA, will undergo two automatic CPAP titration studies with collection of polysomnographic (PSG) data. The data will be analysed to assess effectiveness of Compumedics auto-CPAP device in the normalisation of sleep disordered breathing in OSA patients, with respect to another auto-CPAP device.