(1175) Diagnostic Accuracy of ROX HR Index in Predicting HFNC Outcome in Hypoxic Respiratory Failure

Introduction: High-flow nasal cannula would decrease the rate of endotracheal intubation among people with acute respiratory failure as compared with the conventional oxygen therapy. But the failure of HFNC would lead to the cause delayed intubation and increased mortality. The ROX index (ratio of pulse oximetry/Fio2to respiratory rate) has been validated to predict HFNC outcomes in patients with pneumonia. Modified ROX criteria that incorporating heart rate appears to be a promising tool in the early identification of patients who are at high risk of HFNC failure .Objective of our study was to determine sensitivity and specificity of ROX HR index in predicting HFNC outcome in acute hypoxemic respiratory failure.

Methods: Single centre, open label, prospective observational study . 83 patients in multi-disciplinary ICU with acute hypoxemic respiratory failure initiated with HFNC therapy were included. ROX HR index was calculated at 4 th hour and 10 th hour after initiation of HFNC. Based on the outcome, patients were divided into two groups, those who liberated from HFNC and those who failed HFNC and progressed to mechanical ventilation. Comparison and analysis of ROX HR index was performed using area under the receiving operating characteristic curve (AUROC) and cutoff value were assessed for prediction of HFNC failure.

Results: Out of 83 patients ,57 patients were liberated from HFNC to ventury mask while 26 patients were initiated on invasive mechanical ventilation. ROX HR index measured at 4th hour and 10th hour were lower in those with failed HFNC compared to those were liberated from HFNC.
Cut off value of ROX HR index at 4 th hour ≤ 8.42 predicts higher risk of HFNC failure with a sensitivity of 76.9 % and specificity of 68.4 % (AUC – 0.722 (0.594 – 0.850), p = 0.001).While ROX HR index at 10 th hour has a cut off value of ≤ 9.51 predicts higher risk of HFNC failure with sensitivity of 65.4% and specificity of 70.2% ( AUC – 0.682 (0.547 – 0.817), p = 0.008)

Conclusions: ROX-HR index at 4 th hour of ≤ 8.42 and 10 th hour ≤ 9.51 were significantly associated with a higher risk of HFNC failure (95% CI 0.594 – 0.850& 0.547 – 0.817respectively). ROX-HR index appears to be a promising tool for early identification of treatment failure in patients initiated on HFNC for acute hypoxemic respiratory failure.