The objective of the study is to evaluate the efficacy of home High Flow Oxygen for the reduction of severe exacerbation following admission for a severe exacerbation of COPD or death against standard oxygen therapy.

Inclusion Criteria:

1. Patient with a diagnosis of COPD defined by GOLD guidelines

2. Admitted in hospital for AECOPD

3. 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

4. Patients affiliated or, beneficiary of a social security cover

5. Patient who has read and understood the information letter and signed the consent form

6. 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

7. For menopausal woman: confirmatory diagnosis (amenorrhea not medically induced for at least 12 months before the inclusion visit)

Exclusion Criteria:

1. Age <18 or > 85 years

2. Patient treated with chronic NIV with ongoing treatment

3. 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.

4. BMI > 35 kg/m2

5. Patient admitted for an acute COVID-19 infection

6. Hypercapnic respiratory failure justifying NIV defined as

   1. An Arterial Blood Gas (ABG) PaCO2 > 7 kPa in stable condition within 6 months
   2. Patients with ABG PaCO2 > 7 kPa at hospital discharge and that remained hypercapnic between 2- and 4-weeks following discharge

7. Pregnancy (blood pregnancy test positive) or lactation ongoing

8. Significant psychiatric disorder or dementia that would prevent adherence to study protocol

9. Tobacco use < 10 pack-year

10. Expected survival < 12 months due to any situation other than COPD disease

11. Refusal of high-flow oxygen therapy

12. Person deprived of liberty by administrative or judicial decision or placed under judicial protection (guardianship or supervision)

13. Patients already involved in a research protocol that would impact with the outcome measured in the current protocol