Inclusion Criteria:  Patient with a diagnosis of COPD defined by GOLD guidelines Admitted in hospital for AECOPD  With severe respiratory impairment defined by one of the following criteria (long-term oxygen therapy (LTOT) criteria):  Previously established on long-term oxygen therapy according to the following criteria: PaO2 < 7.3kPa or <8kPa with polycythemia, pulmonary hypertension or right heart failure on room air in stable condition Or PaO2 < 7.3kPa or <8kPa with polycythemia, pulmonary hypertension or right heart failure on room air after clinical stabilization during the index admission Patients affiliated or, beneficiary of a social security cover Patient who has read and understood the information letter and signed the consent form For woman of childbearing potential, use of an effective contraception (oestro-progestatives or intra-uterine device or tubal ligation) since at least 1 month and an blood pregnancy test by β-HCG negative at the screening visit, during the duration of the study For menopausal woman: confirmatory diagnosis (amenorrhea not medically induced for at least 12 months before the inclusion visit)  Exclusion Criteria:  Age <18 or > 85 years Patient treated with chronic NIV with ongoing treatment Patients diagnosed with obstructive sleep apnea (OSA) treated with CPAP. Diagnosis of OSA will be over-ruled in patient that had a previous overnight polygraphy. For patients who never had an overnight polygraphy, screening for OSA will be made using the STOP-BANG questionnaire. If the results of the STOP-BANG questionnaire (Appendix 1) is >3, an Apnea-link recording will be performed. If AHI>30/h, patient will be excluded. BMI > 35 kg/m2 Patient admitted for an acute COVID-19 infection  Hypercapnic respiratory failure justifying NIV defined as  An Arterial Blood Gas (ABG) PaCO2 > 7 kPa in stable condition within 6 months Patients with ABG PaCO2 > 7 kPa at hospital discharge and that remained hypercapnic between 2- and 4-weeks following discharge Pregnancy (blood pregnancy test positive) or lactation ongoing Significant psychiatric disorder or dementia that would prevent adherence to study protocol Tobacco use < 10 pack-year Expected survival < 12 months due to any situation other than COPD disease Refusal of high-flow oxygen therapy Person deprived of liberty by administrative or judicial decision or placed under judicial protection (guardianship or supervision) Patients already involved in a research protocol that would impact with the outcome measured in the current protocol