Obstructive sleep apnea (OSA) is a common condition where airway blockages disrupt breathing during sleep.  Low oxygen levels during sleep can also occur without OSA and may be due to lung problems.  Prior studies have shown that OSA and low oxygen levels during sleep may worsen pulmonary hypertension.  In addition, OSA disrupts sleep causing daytime sleepiness which reduces quality of sleep and quality of life in general.  The standard treatment for OSA is continuous positive airway pressure (CPAP) at night which delivers a flow of air under pressure through a nasal or nasal/oral mask which prevents airway blockages.  This treatment has been shown to improve sleep quality and daytime quality of life in patients with OSA.  A low oxygen level during sleep without OSA is treated with supplemental oxygen during the night. 

The main purpose of this study is to determine if treatment of OSA with CPAP, or low oxygen levels during sleep with oxygen therapy, improves the quality of sleep and overall quality of life in patients with both pulmonary hypertension and OSA or pulmonary hypertension and low oxygen levels at night without OSA. In addition, this study hopes to determine how patients with pulmonary hypertension tolerate and use CPAP or oxygen therapy at night. Blood tests will be performed to determine if treatment of OSA or low oxygen levels at night improves substances in the blood which might affect pulmonary hypertension.