Physiological studies have shown that, in stable hypercapnic COPD patients, NPPV in pressure support mode is able to improve alveolar ventilation by increasing the tidal volume and reducing the respiratory rate [1].

There is evidence that noninvasive inspiratory pressure is able to unload the inspiratory muscles, whereas the application of positive end-expiratory pressure (PEEP) counteracts the intrinsic PEEP (PEEPi) associated with hyperinflation in these patients [2], an effect more evident in acute exacerbations.

There is evidence that, compared with long-term oxygen therapy (LTOT) alone, addition of NPPV at night resulted in significant improvements in daytime arterial oxygen (PaO₂) and carbon dioxide (PaCO₂) tension, total sleep time, sleep efficiency, and overnight PaCO₂. Quality of life with LTOT plus NPPV was significantly better than with LTOT alone. The degree of improvement in daytime PaCO₂ was significantly correlated with an improvement in mean overnight PaCO₂ [3].

Night-time NPPV applied over 3 months may improve heart rate variability, reduce circulating natriuretic peptide levels, and enhance the functional performance of patients with advanced but stable COPD, suggesting that nocturnal NPPV may reduce the impact of cardiac comorbidities in COPD patients [4].