ICU care of patients considered "palliative" but without contraindications to admission to intensive care, for whom a do-not intubate order decision was made upon admission represents a particular target for non-invasive oxygenation techniques. The benefits of non invasive ventilation (NIV) in this population are debated especially in cancer patients. The more recently used nasal humidified high flux canula oxygenation (HFNC) therapy may have benefits over NIV in these patients. It is supposed to have better tolerance and could allow better compliance and thus higher efficiency. These potential benefits are major for such a population for which tolerance and symptomatic relief are priority goals

Observational prospective multicenter study Primary outcome: To analyze the efficacy and tolerance of NIV and HFNC in patients admitted to intensive care unit, or intermediate catre unit for acute respiratory insufficiency for whom a a do-not intubate order decision was taken upon admission or after extubation if the patient initially received mechanical ventilation.

Secondary outcomes: To analyze the efficacy and tolerance of NIV and HFNC according to the following reason for ICU admission: chronic obstructive pneumopathy decompensated COPD, severe heart failure, evolutive cancer or hematologic malignancy; to analyze tolerance and acceptability of different techniques; to analyze the duration of the oxygenation methods use; to analyze the modalities of eventual withdrawing life support therapies and the associated sedative and opioid treatments; to analyze the satisfaction for the use of the non invasive technique by the relatives and the caregivers; to analyze mortality at D28 and D90 and quality of life at 3 and 6 months in surviving patients

Inclusion Criteria:

• acute respiratory failure defined by respiratory rate>25/min and or hypoxemia (sPO2 <92% with O2 >3l/min)
• admission in ICU or intermediate care unit
• decision to not intubate the patient or to not re-intubate the patient
• indication to NIV or HFNC-O2
• French social security affiliation

Exclusion Criteria:

• refusal to participate
• legal protection
• pregnancy
• prophylactic treatment by VNI or HFNC-O2 after extubation

• patient admitted in ICU or intermediate care with decision of a do-not intubate order on admission or after extubation (for patients receiving invasive mechanical ventilation)
• with acute respiratory failure criteria (respiratory rate >25/min; contraction of accessory respiratory muscles or hypoxemia requiering > 3L/min O2 to obtain SpO2 >92%)
• and having indication for NIV or HFNC-O2