Evaluation of high intensity NIMV in terms of physiological parameters has been performed in short-term studies in COPD patients. However, the support pressure levels used in exacerbated patients seem contradictory and the muscular discharge levels are uncertain. The objective of study is to determine the discharge level of the inspiratory musculature reached at the same pressure support (PS) values in a group of hospital and domiciliary ventilators. Patients with COPD in at least 6 months of treatment with home NIMV and in stable phase of their disease will be included. Nine commercial ventilators will be used, each patient will use 3 different ventilators. A 5 minute record will be taken at baseline (without NIMV). Subsequently, 5 minutes in NIMV in 3 levels of PS (15/10/20) for each ventilator (15/10/20) and patient with EPAP of 5 cmH2O will be recorded. The results will be compared between the different ventilators and PS values using a general linear model for repeated variables to determine the differences between ventilators and PS levels of respiratory muscular discharge in COPD patients