Effects of a New Interface for NIV on Respiratory Drive

Inclusion Criteria: * presence of hypoxemic Acute Respiratory Failure, as defined by a respiratory rate greater than 25 breaths/min, an acute onset (within 1 week) of respiratory distress, an arterial oxygen tension (PaO2) and inspiratory oxygen fraction (FiO2) ratio (PaO2/FiO2) lower than 200 mmHg during HFNC, an evidence of bilateral pulmonary infiltrates in the chest X-ray or computed tomography scan, and an absence of history of chronic respiratory failure or moderate-to-severe cardiac insufficiency (New York Heart Association greater than grade 2 or left ventricular ejection fraction \<50%). Exclusion Criteria: * reduced level of consciousness, as indicated by a Glasgow Coma Scale \< 12 * severe respiratory distress (i.e. respiratory rate \> 35 breaths/min) * hemodynamic instability, (i.e. systolic arterial pressure \<90 mmHg or mean systolic pressure \<65 mmHg despite fluid repletion) * need for vasoactive agents, i.e. vasopressin or epinephrine at any dosage, or norepinephrine \>0.3 mcg/kg/min or dobutamine\>5 mcg/kg/min * life-threatening arrhythmias or electrocardiographic signs of ischemia * acute respiratory failure secondary to neurological disorders, status asthmaticus, chronic obstructive pulmonary disease (COPD), cardiogenic pulmonary oedema * presence of tracheotomy * uncontrolled vomiting * more than 2 acute organ failures * body mass index \>30 kg/m2 * documented history or suspicion of obstructive sleep apnoea * contraindications to placement of a nasal-…