 Chronic obstructive pulmonary disease COPD is associated with progressive decline in lung function with resultant chronic respiratory failure. This leads to significant rates of hospitalization, disability, and death. COPD is also associated with sleep disordered breathing and nocturnal hypoventilation, resulting in nocturnal and daytime hypoxemia and hypercapnia. These, in turn, can contribute to fatigue, dyspnea and impaired quality of life. Presence of hypercapnia is associated with a 33 5-year survival. Nocturnal NPPV can theoretically rest overloaded respiratory muscles, prevent nocturnal hypoventilation, and reset central respiratory drive in patients with hypercapnia. The use of non-invasive positive pressure ventilation NPPV in late stage COPD appears logical to change this inexorable course, to alleviate symptoms and to improve quality of life. While NPPV has a definite role in the management of acute hypercapnic respiratory failure, its role in the management of late stage stable COPD is controversial. Multiple studies have shown no survival benefit for nocturnal NPPV in chronic hypercapnic stable COPD patients. The effects on quality of life and dyspnea scores in such patients have been inconsistent. The variable efficacy might have been due to late administration of the intervention in the course of disease, in the presence of advanced hypercapnic respiratory failure. We sought to assess the effect of applying NPPV on indices of health-related quality of life in patients with relative normocapnia. We hypothesized that patients with stable severe COPD have improved quality of life and reduced dyspnea with the use of NPPV. 