Methods: We searched 4 electronic databases (Pubmed, EMBASE, Scopus, and Web of Science) to identifyrandomized controlled trials (RCTs) comparing the effects of HFNC with either COT or NIV on rates of 1) treatmentfailure and 2) intubation/reintubation in adult critically ill patients.Results: We identified 18 RCTs ( n = 4251 patients) in pooled analyses. As a primary mode of support, HFNCtreatment reduced the risk of treatment failure [Odds Ratio (OR) 0.65; 95% confidence interval (CI) 0.43 – 0.98;p = 0.04; I2= 32%] but had no effect on preventing intubation