Predictors of High-Flow Nasal Oxygen Success in COVID-19 Respiratory Failure: A Retrospective Observational Cohort Study

There is no clear consensus regarding optimal use of oxygen therapy for patients with type 1 respiratory failure secondary to COVID-19. This retrospective observational cohort study evaluates high-flow nasal oxygen (HFNO) delivery in adults with COVID-19 and compares potential predictors of treatment success. Adults receiving HFNO in two tertiary hospitals in Hull, UK, between 1 March 2020 and 1 March 2021 were included. Demographic, clinical, and biochemical data were extracted from hospital records; prognostic scores were calculated retrospectively. HFNO success was defined as an improvement in oxygenation with subsequent discontinuation of HFNO without escalation to non-invasive or mechanical ventilation, or death. In total, 108 patients received HFNO (mean age 64.1 years; 66% male; 94% White/White British). Of the 65% (70/108) considered suitable for ICU, 59% (41/70) achieved HFNO success. Among patients not suitable for ICU (38/108), 24% (9/38) achieved HFNO success. Multivariate analysis identified older age (adjusted OR 1.049, 95% CI 1.015–1.085; p = 0.005) and higher CRP (adjusted OR 1.007, 95% CI 1.002–1.011; p = 0.003) as independent predictors of HFNO failure. The ISARIC 4C score demonstrated 70% positive and 71% negative predictive value for HFNO success (AUROC 0.726, 95% CI 0.628–0.823). These factors may help guide appropriate use of HFNO in patients with COVID-19.