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

Rationale: In patients with COVID-19 pneumonia and mild hypoxaemia, 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, patients with COVID-19 pneumonia and 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 (ie, continuous positive airway pressure, non-invasive ventilation or invasive mechanical ventilation) within 28 days. Among secondary outcomes, clinical recovery was defined as the improvement in oxygenation (SpO2 ≥96% with fractional inspired oxygen (FiO2) ≤30% or partial pressure of arterial carbon dioxide/FiO2 ratio >300 mm Hg). 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% to +1.4%); RR 0.79 (95% CI 0.59 to 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)), intensive care unit admission (7.7% vs 11.0%, absolute risk difference -3.3% (95% CI -9.3% to +2.6%)), and in hospital length of stay (11 (IQR 8-17) vs 11 (IQR 7-20) days, absolute risk difference -1.0% (95% CI -3.1% to +1.1%)). Conclusions: Among patients with COVID-19 pneumonia and mild hypoxaemia, the use of HFNO did not significantly reduce the likelihood of escalation of respiratory support. Trial registration number: NCT04655638.