High-flow nasal oxygen therapy in the treatment of acute respiratory failure in severe COVID-19 pneumonia: a prospective observational study

A significant proportion of patients with COVID‑19 present with a rapidly progressing severe acute respiratory failure. We aimed to assess the efficacy of high‑flow nasal oxygen (HFNO) therapy in severe acute respiratory failure in the course of COVID‑19 in a noncritical care setting as well as to identify predictors of HFNO failure. This prospective observational study was conducted between March and December 2020. We enrolled all consecutive patients hospitalized with confirmed SARS‑CoV‑2 infection in whom HFNO therapy was used. The primary outcome was death or endotracheal intubation within 30 days from admission. Of the 380 patients with COVID‑19 hospitalized at our tertiary center, 116 individuals (30.5%) requiring HFNO due to severe pneumonia were analyzed. The primary outcome occurred in 54 patients (46.6%). The overall 30‑day mortality rates were 30.2% (35 out of 116 patients) in the entire cohort and 64.7% (34 out of 51 patients) among individuals requiring endotracheal intubation. A multivariable analysis revealed that the ROX index (the ratio of oxygen saturation / fraction of inspired oxygen to respiratory rate) below 3.85 measured within the first 12 hours of therapy was related to increased mortality (hazard ratio, 5.86; 95% CI, 3.03-11.35) compared with the ROX index of 4.88 or higher. The results of our study suggest that nearly half of patients treated with HFNO due to severe COVID‑19 pneumonia will require mechanical ventilation. The ROX index is a useful tool for predicting HFNO failure in this population.