Predictive factors for high-flow nasal cannula failure in acute hypoxemic respiratory failure in an intensive care unit

Background and Objective: High-flow nasal cannula (HFNC), a relatively new technique in acute hypoxemic respiratory failure (AHRF), is gaining popularity in intensive care units (ICUs). Our study aims to identify the predictive factors for failure of HFNC. Materials and Methods: This is a 5-year retrospective cohort study in patients with AHRF using HFNC in an ICU of a regional hospital in Hong Kong. The primary outcome is to identify the predictive factors for failure of HFNC which is defined as escalation of treatment to noninvasive ventilation, mechanical ventilation, extracorporeal membrane oxygenation, or death. Results: Of the 124 ICU patients with AHRF, 69 (55.65%) failed in the use of HFNC. The patients failing HFNC had higher Acute physiology and Chronic Health Evaluation IV scores, lower Glasgow Coma Scale scores, lower platelet counts and serum sodium levels upon ICU admission, and higher pH on day of HFNC commencement. They had higher respiratory rates before HFNC and higher heart rates before and 1 h after HFNC. The respiratory rate-oxygenation (ROX) index which is defined as a ratio of SpO(2)/FiO(2) to respiratory rate was significantly lower in the failure group 1 h and 12 h after HFNC. By multivariate binary logistic regression, failure of HFNC is associated with lower ROX index at 12 h after HFNC. Conclusion: ROX index at 12 h serves as a valuable tool to monitor the responsiveness to HFNC treatment. Close monitoring is required to identify patient failing using HFNC.