Role and limitations of high-flow nasal oxygen therapy in COVID-19 patients: An observational study

The management of acute respiratory failure in COVID-19 patients and the role and limitations of high-flow nasal oxygen therapy (HFNOT) remain unclear.

This study aimed to investigate the effect of HFNOT, identify the characteristics of patients who will benefit from therapy, and determine monitoring strategies to decide on endotracheal intubation for patients with COVID-19.

We conducted a prospective observational study of COVID-19 patients who were admitted to the intensive care unit (ICU) and required HFNOT for at least 2 days between 20 March 2020 and 20 June 2020. The exclusion criteria were a severe respiratory failure, reduced levels of consciousness, combination with other noninvasive ventilation strategies, and exhaustion. The patients were followed up until ICU discharge. The primary outcome was the proportion of patients with COVID-19 who were successfully weaned from HFNOT, whereas failure comprised intubation or death on HFNOT.

Thirty-five subjects (24 males, mean-age: 61.62, standard deviation: 14.9 yr.) were included in the study. A total of 20/35 (57.1%) subjects survived to discharge. C-reactive-protein (CRP) and interleukin-6 (IL-6) levels were significantly increased in the treatment failure group (CRP; effect size (r):0.35, P: 0.037, IL-6; r: 0.37, P: 0.03). Although there was a difference between repeated measures of partial-pressure-of-oxygen/fraction-of-inspired-oxygen (PaO₂/FiO₂:P/F) rates (partial-eta-squared (η_p²):0.79, P < 0.001), no difference was found between carbon dioxide levels (η_p²:0.29, p: 0.44). There was also no difference between ROX (ratio-of-oxygen-saturation/FiO₂ to respiratory-rate) rates (Kendall's W: 0.33 P = 0.310).

In COVID-19 patients with mild-to-moderate dyspnea and hypoxemia who are nonresponsive to conventional-oxygen-therapies, the initial approach may involve the use of HFNOT. In this study, patient monitoring could be performed with ROX and P/F ratios, and the effectiveness of the treatment could be decided by looking at these rates in the second hour. Prolongation of the period and awake prone positioning did not improve the outcome.