Contribution of Nasal High Flow in Pneumology Assessed in Acid-Free Hypercapnic Acute Respiratory Failure

Inclusion Criteria: * Major patient ≥ 18 years old * Medical diagnosis of Acute Respiratory Failure less than 48 hours * With partial pressure of carbon dioxide (PaCO2) \> 45 and pH \> 7.35 for less than 48 hours, with no indication of Non-Invasive Ventilation (NIV) placement * Underlying terrain of known or unknown chronic respiratory pathology (may be unknown at time of diagnosis) Examples : COPD, Bronchiectasis, Pulmonary fibrosis, asthma, sequelae pathologies … * All etiologies (infectious, cardiac decompensation, trauma, etc.) * Having given informed consent * Patient under a social security scheme * Possibility to include a patient having already been included in the study but suffering from a new episode of hypercapnic non acidic Acute Respiratory Failure with a free interval of 3 months Exclusion Criteria: * Restrictive chronic neuromuscular or kyphoscoliotic respiratory insufficiencies * Drug-induced Acute respiratory failure * Pneumothorax (X-ray pulmonary detachment) * Oxygen poisoning. In this case, PaCO2 will be asset again later with the purpose to include after oxygenotherapy decrease for a target SpO2 of 92% maximum * Severe Acute Respiratory Syndrome (SARS) Coronavirus 2 (COVII) Pneumonia * Tracheostomy * Prior treatment with chronic or initiated NIV just prior to treatment (e.g. Intensive Care Unit) * Respiratory Severity Criteria for Resuscitation Management * Agitation or non-cooperation * Pregnancy or breastfeeding * Person participating in other biomedical research * Any other reason that the investigator believes may interfere with the evaluation of the study objectives * Person under judicial protection (guardianship, curatorship) * Person deprived of liberty by a judicial or administrative decision