High Flow Nasal Oxygen for Severe Hypoxemia: Oxygenation Response and Outcome in COVID-19 Patients.

RATIONALE The "Berlin definition" of acute respiratory distress syndrome (ARDS) does not allow inclusion of patients receiving high-flow nasal oxygen (HFNO). However, several articles proposed that criteria for defining ARDS should be broadened to allow inclusion of patients receiving HFNO. OBJECTIVE To compare the proportion of patients fulfilling ARDS criteria during HFNO and soon after intubation, and 28-day mortality between patients treated exclusively with HFNO and patients transitioned from HFNO to IMV. METHODS From previously published studies we analyzed COVID-19 patients who had PaO2/FiO2 ≤300 while treated with HFNO ≥40 L/min, or NIV with PEEP ≥5 cmH2O (comparator). In patients transitioned from HFNO/NIV to invasive mechanical ventilation (IMV), we compared ARDS severity during HFNO/NIV and soon after IMV. We compared 28-day mortality in patients treated exclusively with HFNO/NIV vs. transitioned to IMV. MEASUREMENTS AND MAIN RESULTS We analyzed 184 and 131 patients receiving HFNO or NIV, respectively. 112 HFNO, and 69 NIV patients transitioned to IMV. 104 (92.9%) HFNO patients and 66 (95.7%) NIV patients continued to have PaO2/FiO2 ≤300 under IMV. 28-day mortality in patients who remained on HFNO was 4.2% (3/72) while in patients transitioned from HFNO to IMV it was 28.6% (32/112) (p<0.001). 28-day mortality in patients who remained on NIV was 1.6% (1/62), while in patients who transitioned from NIV to IMV it was 44.9% (31/69) (p<0.001). Overall mortality was 19.0% (35/184) and 24.4% (32/131) for HFNO and NIV, respectively (p=0.2479). CONCLUSIONS Broadening ARDS definition to include HFNO patients with PaO2/FiO2 ≤300 may identify patients at earlier stages of disease but with lower mortality. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/).