4C Mortality Score and high-flow nasal oxygen therapy outcome in COVID-19

ABSTRACT

Background: High-flow nasal oxygen therapy (HFNO) is an established treatment for acute hypoxemic respiratory failure due to COVID-19. However, sometimes this treatment fails to prevent the need for invasive ventilation or evade death. A proposed tool to predict in-hospital mortality in patients with COVID-19 is the 4C Mortality score. Aim(s) To assess the factors related to HFNO failure in patients admitted to ICU for COVID-19. Method(s) In a retrospective analysis of 118 patients treated with HFNO after the failure of conventional oxygen therapy, HFNO failure was defined as either death or the need for invasive or non-invasive ventilation. In all patients, routine blood gases and biochemical blood analyses were performed. The 4C Mortality Score was recorded at admission, taking into account age, sex, number of comorbidities, initial respiratory rate and oxygen saturation, Glasgow coma scale, and levels of urea and C-reactive protein. Result(s) The mean age of the cohort was 59.5+/-1.2 years and mean BMI 32.5+/-6.1 kg/m2;73 (62%) patients were men. In 43 patients (36%), HFNO treatment failed. Patients in whom HFNO failed were older (62.7+/-12.6 vs 57.7+/-13.1 years, P=0.043), had lower PaO2/FiO2 index before HFNO initiation 83.1+/-29.9 vs 114.2+/-62.3, P=0.003), lower ROX index after 48 hours of HFNO treatment (5.7+/-2.4 vs 8.6+/-3.3, P<0.001), and higher 4C Mortality Score (11.1+/-3.2 vs 9.5+/-3.6, P=0.017). One point increase of the 4C score increased 1.15-times the risk of HFNO failure (95%CI 1.02-1.28, P=0.02). Conclusion(s) A complex mortality predictor used in hospitalised COVID-19 patients was associated with HFNO failure besides the baseline severity of the respiratory failure.