Utility and timing of the ROX 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, delay in intubation leading to poor overall outcomes has been noticed in subgroup of patients on HFOT. 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. Seventy 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%). Nineteen (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). ROX index was significantly different between the HFOT success versus failure group at baseline, 2, 4, 6, 12 and 24 h. The best cut-off of ROX index at baseline and 2 h were 4.4 (sensitivity 91.7%, specificity 86.7%) and 4.3 (sensitivity 94.4% and specificity 86.7%), respectively. ROX index was found to be an efficient tool in predicting HFOT failure in cases with AHRF with infective etiology.