Introduction:The effect of high-flow nasal cannula (HFNC) on adult post cardiothoracic operation remains controversial. We conducted a meta-analysis of randomized controlled trials to evaluate the effect of HFNC and conventional oxygen therapy (COT) on postcardiothoracic surgery.Methods:A search was conducted in Embase, MEDLINE, Ovid, and Cochrane databases until December, 2017 for all the controlled study to compare HFNC with COT in adult postcardiothoracic surgery. Two authors extracted data and assessed the quality of each study independently. The meta-analysis was performed by using RevMan 5.3. The primary outcome was the rate of escalation of respiratory support rate and pulmonary complications; secondary outcome included the length of intensive care unit (ICU) stay and length of hospital stay and the rate of intubation.Results:Four studies that involved 649 patients were included in the analysis. No significant heterogeneity was found in outcome measures. Compared with COT, HFNC were associated with a significant reduction in the escalation of respiratory support (odds ratio [OR] = 0.44, 95% confidence interval [CI] = 0.29−0.66, P < .001) and pulmonary complications (OR = 0.28, 95% CI = 0.13−0.6, P = .001). There were no significant differences in the reintubation rate (OR = 0.33, 95% CI = 0.02−5.39, P = .43), length of ICU stay (weighted mean difference = 0.11; 95% CI = −0.44 −0.26, P = .14) or length of hospital stay (weighted mean difference = −0.15, 95% CI = −0.46 −0.17, P = .36) between the 2 groups. No severe complications were reported in either group.Conclusion:The HFNC could reduce respiratory support and pulmonary complications, and it could be safely administered for adult postcardiothoracic surgery. Further large-scale, randomized, and controlled trials are needed to update this finding.