Our aim was to determine the rate of success of HFNO and its relationship with current treatments for severe COVID-19.

This was a cohort study including patients admitted for HFNO because of respiratory failure despite oxygen therapy through a facial mask. Care was standardized, with systematic use of steroids and prevention or treatment of thromboembolic complications, and tocilizumab when deemed useful. HFNO failure was defined by the requirement for mechanical ventilation and/or death.

In August 2021, among 1397 patients with COVID-19 admitted in the emergency department, 110 (7.8%) received HFNO (mean age 55 years, sex-ratio M/F 1.4). Thirteen patients (12%) had received a steroid treatment before hospital admission. At least one comorbid condition was observed in 57% of the patients. Mean duration of the disease at admission was 8.8 days and mean respiratory rate was 34/min. A CT scan was performed for 101 patients (92%), among whom 13 had a pulmonary embolism. All patients received a steroid treatment, and tocilizumab was prescribed in 79 cases (72%). Failure of HFNO was observed in 54 cases (49%); the only risk factor was the absence of tocilizumab administration: AOR [IC95%] 3.50 [1.40-8.69]. We observed a trend toward failure with steroid use before hospital admission: AOR 3.83 [0.96-16.66].

Success of HFNO, when all therapeutic means of treatment for severe COVID-19 pneumonia were applied, was associated with tocilizumab administration. Our data suggest the interest of a randomized study to determine whether HFNO is the right signal for prescription of anti-IL6 drugs.