High flow nasal oxygen versus conventional oxygen therapy in patients with COVID-19 pneumonia and mild hypoxemia: a randomized controlled trial.

Rationale- In COVID-19 patients with mild hypoxemia, the clinical benefit of high flow nasal oxygen (HFNO) remains unclear. We aimed to examine whether HFNO compared with conventional oxygen therapy (COT) could prevent escalation of respiratory support in this patient population. Methods- In this multicentre, randomised, parallel-group, open-label trial, COVID-19 patients with peripheral oxygen saturation (SpO2) ≤92% who required oxygen therapy were randomised to HFNO or COT. The primary outcome was the rate of escalation of respiratory support (i.e., continuous positive airway pressure, noninvasive ventilation or invasive mechanical ventilation) within 28 days. Among secondary outcomes, clinical recovery was defined as the improvement in oxygenation (SpO2 ≥96% with FiO2 ≤30% or PaO2/FiO2 ratio >300 mmHg). Results- Among 364 randomised patients, 55 (30.3%) of 181 patients assigned to HFNO and 70 (38.6%) of 181 patients assigned to COT underwent escalation of respiratory support, with no significant difference between groups (absolute risk difference -8.2% [95%CI -18 +1.4]; RR 0.79 [95%CI, 0.59-1.05]; p= 0.09). There was no significant difference in clinical recovery (69.1% vs 60.8%; absolute risk difference 8.2 [95%CI -1.5% to +18.0%], RR 1.14 [95%CI 0.98 to 1.32]), ICU admission (7.7% vs 11.0%, mean difference -0.2 days [95%CI -1.2 to +0.7], absolute risk difference -3.3% [95%CI -9.3% to +2.6]), in hospital length of stay (11 [IQR 8-17] vs 11 [IQR 7-20] days, absolute risk difference -1.0% [95%CI -3.0% to +1.0]). Conclusions- Among patients with COVID-19 pneumonia and mild hypoxemia, the use of HFNO did not significantly reduce the likelihood of escalation of respiratory support.