Utility and timing of the respiratory rate-oxygenation index in the prediction of high-flow oxygen therapy failure in acute hypoxemic respiratory failure of infective etiology: a prospective observational study.

During and following the COVID-19 pandemic, the world has witnessed a surge in high-flow oxygen therapy (HFOT) use. The ability to provide high oxygenation levels with remarkable comfort levels has been the grounds for the same. Despite the advantages, delays in intubation leading to poor overall outcomes have been noticed in subgroups of patients on HFOT. The respiratory rate-oxygenation (ROX) index has been proposed to be a useful indicator to predict HFOT success. In this study, we have examined the utility of the ROX index prospectively in cases of acute hypoxemic respiratory failure (AHRF) due to infective etiologies. A total of 70 participants were screened, and 55 were recruited for the study. The majority of participants were males (56.4%), with diabetes mellitus being the most common comorbidity (29.1%). The mean age of the study subjects was 46.27±15.6 years. COVID-19 (70.9%) was the most common etiology for AHRF, followed by scrub typhus (21.8%). 19 (34.5%) experienced HFOT failure, and 9 (16.4%) subjects died during the study period. Demographic characteristics did not differ between either of the two groups (HFOT success versus failure and survived group versus expired group). The ROX index was significantly different between the HFOT success versus failure group at baseline, 2, 4, 6, 12, and 24 hours. The best cut-offs of the ROX index at baseline and 2 hours were 4.4 (sensitivity 91.7%, specificity 86.7%) and 4.3 (sensitivity 94.4% and specificity 86.7%), respectively. The ROX index was found to be an efficient tool in predicting HFOT failure in cases of AHRF with infective etiology.