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

The aim of the PIRAHNA study is to compare patients treated with Nasal High Flow in association with conventional standard treatment versus patients treated only with conventional standard treatment. Primary objective : To demonstrate the therapeutic superiority of Nasal High Flow in hypercapnic Acute Respiratory Failure without acidosis, in combination with conventional standard treatment Secondary objectives : 1. Identify the characteristics (etiologies) of responder patients (defined by a decrease in capnia and a failure to develop acidosis within two weeks of hospitalization) 2. Identify the etiology (trigger) of the Acute Respiratory Failure of responder patients 3. Compare the evolution of respiratory rate between the two treatment groups 4. Compare the evolution of dyspnea between the two treatment groups 5. Compare the evolution of gas exchanges between the two treatment groups 6. Compare the length of stay between the two groups 7. Compare the evolution of patients comfort state in the two treatment groups