Evaluation of the success of high flow nasal oxygen therapy in type 1 respiratory failure using ROX index, alveolar-arterial oxygen gradient and HACOR score

In this study, the ability of the ROX index, HACOR score and alveoloarterial oxygen gradient at 0 and 12 hours to predict early treatment success in patients receiving high-flow nasal oxygen therapy due to hypoxemic respiratory failure and the relationship between dynamic changes in these scores and treatment success were investigated. A prospective, observational study was conducted with 75 patients who received high-flow nasal oxygen therapy between March 2023 and January 2025. Demographic information, history, clinical and laboratory data of the patients at the time of admission were recorded and ROX index, HACOR score and alveoloarterial oxygen gradient were calculated at 0 and 12 hours. Success rates in the first 48 hours; intensive care and hospital stays; intensive care, hospital and 28-day mortality were recorded. In this study, treatment was successful in 57 patients in the early period, while it failed in 18 patients. The strongest predictor of treatment failure was the HACOR score at the 12th hour (p=0.002;area under the curve:0.768). When the cut-off value for HACOR score was taken as ≥5, sensitivity was found to be 61,5% and specificity was found to be 82,5%. When the calculated HACOR score change (ΔHACOR=0.hour-12.hour) was evaluated, a significant difference was observed between the successful group and the unsuccessful group (3[1.5-5.0] vs. 1[-3-3]; p=0.02). Although no significant difference was found between the groups in the ROX indexes calculated at 0 and 12 hours; in the subgroup analysis, ROX index showed a significant increase at the 12th hour compared to the beginning of treatment in the successful group (4.89[4.22-5.98]) vs. 9.56[7.88-11.61]; Z:-6.5, p<0.001) A significant increase was also observed in the unsuccessful group (4.88[3.43-6.12] vs. 8.65[5.27-10.8]; Z:-3.10 p<0.001). When the calculated ROX index change (ΔROX=0.hour-12.hour) was evaluated, a significant difference was found between the successful and unsuccessful groups (-4.48[-8.8- -2.90] vs. -2.78[-5.9 - -0.62]; p=0.04). Dynamically monitored ROX and especially HACOR scores have high predictive power for high-flow nasal oxygen therapy success, and focusing on the changes in the scores during follow-up may improve clinical decision-making processes. Keywords: hypoxemic respiratory failure, high-flow nasal cannula, rox index, hacor score