Predicting the effectiveness of high-flow oxygen therapy in COVID-19 patients: a single-centre observational study

BACKGROUND: High-flow nasal cannula (HFNC) therapy is a helpful tool in the treatment of hypoxaemic respiratory failure. However, the clinical parameters predicting the effectiveness of HFNC in coronavirus-19 disease (COVID-19) patients remain unclear. METHODS: Sixteen COVID-19 patients undergoing HFNC in the Asklepios Lung Clinic Munich-Gauting, Germany between 16 March and 3 June 2020 were retrospectively included into the study. Seven patients successfully recovered after HFNC (Group 1), while 9 patients required intubation upon HFNC failure (Group 2). Relevant predictors for an effective HFNC therapy were analysed on day 0 and 4 after HFNC initiation via receiver operating characteristics. RESULTS: The groups did not differ significantly in terms of age, sex, body mass index, and comorbidities. Five patients died in Group 2 upon disease progression and HFNC failure. Group 1 required a lower oxygen supplementation (FiO(2) 0.46 [0.31–0.54] vs. 0.72 [0.54–0.76], P = 0.022) and displayed a higher PaO(2)/FiO(2) ratio (115 [111–201] vs. 93.3 [67.2–145], P = 0.042) on day 0. In Group 2, fever persisted on day 4 (38.5 [38.0–39.4]°C vs. 36.5 [31.1–37.1]°C, P = 0.010). Serum C-reactive protein (CRP) levels > 108 mg L(–1) (day 0) and persistent oxygen saturation < 89% and PaO(2)/FiO(2) ratio < 91 (day 4) were identified as significant predictors for HFNC failure (area under curve 0.929, 0.933, and 0.893). CONCLUSIONS: Elevated oxygen saturation, decreased FiO(2) and reduced serum CRP on day 4 significantly predict HFNC effectiveness in COVID-19 patients. Based on these parameters, larger prospective studies are necessary to further investigate the effectiveness of HFNC in the treatment of COVID-19-associated hypoxaemic respiratory failure.