High Flow Nasal Oxygen for Acute Hypoxemic Respiratory Failure in the Emergency Room

Inclusion criteria

• Age ≥ 18 years;
• PaO2/FiO2 ratio between 250 and 150 mmHg or SpO2/FiO2 ratio between 190 and 274, after at least 15 minutes of spontaneous breathing through a Venturi mask (VM), with a FiO2 targeted at a SpO2 94-97%;
• Respiratory rate(RR)≤35breaths/min,afteratleast15minutesofspontaneous breathing through a VM, with a FiO2 targeted at a SpO2 94-97%;
• PaCO2 ≤ 45 mmHg;
• Unilateral or bilateral infiltrate(s), as detected with chest radiography and/or computed tomography and/or with lung ultrasound not fully explained by effusions, atelectasis, or nodules/masses. Infiltrates at lung ultrasound are defined as presence of focal B-lines, consolidations (with irregular marginal contour, air bronchogram, air trapping sign) and irregularity of the pleural line.

Exclusion criteria

• Respiratory failure due to:

• Acute asthma or COPD exacerbation,
• Cardiac failure or fluid overload as primary cause of respiratory failure;
• Unstable angina or ongoing acute myocardial infarction;
• Acute respiratory acidosis with pH < 7.35 and PaCO2 > 45 mmHg;
• Hemodynamic instability and/or use of vasopressors/inotropes;
• Altered mental status (Kelly >3), see Figure 1;(18)
• Contraindications to NIV (high risk of aspiration pneumonia, impaired airways protection, head-facial trauma and/or burns, uncooperative patient, cranial/thoracic/abdominal open wounds);
• Indications to urgent intubation performed according to the clinician in charge;
• Body Mass Index > 35 kg/m2;
• Pregnancy;
• Patient's refusal to participate.