Liao H, et al. - This study examined the changes in mortality, acute exacerbation, exercise capacity, symptoms and significant physiological parameters (lung function, respiratory muscle function and gas exchange) consequent to long-term noninvasive positive pressure ventilation (NPPV) in stable hypercapnic COPD patients with respiratory failure. Findings suggested that in this patient population, long-term NPPV not only decreased the partial pressure of arterial carbon dioxide (PaCO₂) but also improved mortality with the aim of reducing PaCO₂.