Respiratory Support in Chronic Obstructive Pulmonary Disease (COPD) Patients

Inclusion Criteria: * 1\) Patients with COPD, GOLD C or D and Forced expiratory volume in one second (FEV1)\<65%; * 2\) AHRF (pH\<7,35 and PaCO2≥45mm Hg (≥6kPa) treated more than 24h with Ventilation (non-invasive or invasive); * 3\) 48h to 2 weeks with pH\>7.35, and PaCO2\>45 (\>6kPa) after NIV withdrawal, during daytime at rest without oxygen or ventilatory support (or with O2 if patients are not able to avoid O2 with immediate desaturation below 80%). Exclusion Criteria: 1. Patient treated with chronic NIV or continuous positive airway pressure (CPAP) device, with ongoing treatment; 2. Primary diagnosis of restrictive lung disease causing hypercapnia i.e. obesity hypoventilation and chest wall disease, however these patients will be included if the "FEV1/Forced vital capacity (FVC)" ratio is \<60% and the FEV1 \<50% if the predominant defect is considered to be obstructive by the center clinician; 3. BMI \> 35 kg/m2; 4. Sedative medication causing hypercapnia (\> 3 drugs or more than 20mg of morphine/day); 5. Polygraphic diagnosis of Obstructive Sleep Apnoea Syndrome (AHI\>30/h (French criteria); 6. Cognitive impairment that would prevent informed consent into the trial 7. Pregnancy; 8. Tobacco use \< 10 pack-year; 9. Psychiatric disease necessitating anti-psychotic medication, ongoing treatment for drug or alcohol addiction, persons of no fixed abode post-discharge; 10. Unstable coronary artery syndrome; 11. Age \<18 years; 12. Inability to comply with the protocol; 13. Expected survival\<12 months due to any situation other than COPD disease; 14. Duration of ICU stay\>10 days; 15. No affiliated to national health insurance; 16. Measure of legal protection (guardianship, wardship or judicial protection) for patients over the age of majority.