Chronic obstructive pulmonary disease (COPD) is characterized by irreversible airflow obstruction with chronic airway inflammation and emphysematous changes in the lung parenchyma, thus leading to air-trapping, as well as extional dyspnea. The mechanism underlying desaturation during 6MWT in patients with COPD is multifactorial involving dynamic hyperinflation and impaired gas exchange that worsens ventilation-perfusion mismatch. Previous studies have shown that oxygen desaturation during the 6MWT predicts mortality and increases the risk of adverse outcomes in COPD patients. However, there is a paucity of studies that have looked at effective treatments to counter the consequences of hypoxemia during exertion.
The investigators have established a hospital-based maintenance pulmonary rehabilitation program together with NPV for COPD, and the investigators have shown that the benefits of NPV improves lung function and exercise capacity, and reduces acute exacerbation and medical costs. The investigators now sought to determine whether long-term maintenance NPV improves long-term clinical outcomes and reduces mortality in COPD.
