Predictors of high-flow nasal cannula (HFNC) failure in severe community-acquired pneumonia or COVID-19.

The aim was to identify predictors for early identification of HFNC failure risk in patients with severe community-acquired (CAP) pneumonia or COVID-19. Data from adult critically ill patients admitted with CAP or COVID-19 and the need for ventilatory support were retrospectively analysed. HFNC failure was defined as the need for invasive ventilation or death before intubation. 60 patients with CAP and 185 with COVID-19 were included. 27 (45%) patients with CAP and 69 (37.3%) patients with COVID-19 showed HFNC failure. Lower oxygenation index, lower respiratory oxygenation (ROX) index, and higher respiratory rate at the start of HFNC were significantly associated with HFNC failure. ROC-analysis identified a respiratory rate of 27/min as the optimal cut-off for predicting HFNC failure, with a specificity of 59% and a sensitivity of 75%, and an oxygenation index after HFNC initiation of 99.6 (specificity 81%, sensitivity 74%). In COVID-19, an elevated CRB65-score at hospital admission and at HFNC-initiation was significantly associated with HFNC failure. In CAP and COVID patients an oxygenation index < 99.6, a respiratory rate > 27/min and a ROX index < 4.88 were predictors for HFNC failure whereas a CRB65 score > 3 at hospital admission and > 2 at HFNC start was predictive for HFNC failure in COVID-19.