The objective is to assess the impact of a wearable Noninvasive Positive Pressure Ventilation, on physical activity and quality of life in patients with severe COPD, complaining of dyspnea.

In order to avoid the occurrence of uncomfortable dyspnea, patients with Chronic Obstructive Pulmonary Disease (COPD) are locked in a vicious circle of inactivity and social isolation which profoundly affects their quality of life and prognosis. A new wearable non invasive positive pressure ventilation device has been recently proposed; it can be used by intermittence during or after physical activities for reducing dyspnea or for shortening dyspnea- recovery time. The investigators hypothesize that this system, in reducing the inconvenience caused by dyspnea, would stimulate a more active lifestyle and improve quality of life. Their objective is to assess the impact of this device on physical activity and quality of life in patients with severe COPD, complaining of dyspnea.

In this open study with no control group, participants will use the device at their convenience, according to their needs in daily life and for 4 weeks.

Inclusion Criteria:

• Patients with stable severe COPD (with FEV1 ≤50% predicted)
• Patients with mMRC score > ou = 2.

Exclusion Criteria:

• Exacerbate within a month prior.
• Using other non invasive ventilation device > 15h per day.
• Have musculoskeletal or neuromuscular problem affecting balance and walking.
• Have cognitive problem affecting comprehension of the different évaluations or questionnaires.
• Have recently participated in physical training or rehabilitation program (≤ 3 months).
• Medical contra-indication to NIV.
• Evolutionary pathologies (excluding COPD) may be life-threatening in the short term (1 year) (cancer, neuromuscular disease rapidly changing).
• Simultaneously enrolled in an other clinical trial.
• Not affiliated to social security.
• Person deprived of liberty, major protected by law.