Role of Respiratory Rate Oxygenation (ROX) Index in Predicting Outcomes of Non-Invasive Ventilation in Patients with Acute Hypercapnic Respiratory Failure

Agmy, Gamal; Mahmoud, Manal A.; Zakaria, Kholoud; Adam, Mohamed F.

doi:10.21608/jcmrp.2025.383212.1266

Role of Respiratory Rate Oxygenation (ROX) Index in Predicting Outcomes of Non-Invasive Ventilation in Patients with Acute Hypercapnic Respiratory Failure

Document Type : Original Article

Authors

¹ Department of Chest Diseases and Tuberculosis, Assiut University Hospitals, Faculty of Medicine, Assiut University, Assiut, Egypt.

² Department of Chest Diseases, Al-Mabarra Hospital, Assiut, Egypt.

10.21608/jcmrp.2025.383212.1266

Abstract

Background and Aim: Non-invasive ventilation (NIV) plays a vital role in managing acute hypercapnic respiratory failure, yet its failure remains a major clinical challenge. Early identification of patients at risk of NIV failure is essential to prevent delays in invasive mechanical ventilation. The ROX index, calculated as the ratio of SpO₂/FiO₂ to respiratory rate, has emerged as a potential non-invasive tool for guiding clinical decision-making. This study evaluated the predictive value of the ROX index in determining the success of non-invasive ventilation in patients with acute hypercapnic respiratory failure.
Methods: A prospective observational study was conducted on 100 adult patients admitted to the respiratory intensive care unit with acute hypercapnic respiratory failure requiring NIV. ROX index and arterial blood gases were recorded at baseline and multiple time points (1, 12, 24, 36, and 48 hours).
Results: NIV was successful in 80% of patients, while 20% experienced failure. The ROX index was significantly higher at all time points in the successful group (p < 0.001). An ROX index < 5.11 and a baseline respiratory rate > 28 breaths/min were identified as independent predictors of NIV failure. At a cut-off point of < 5.19, the ROX index had an overall diagnostic accuracy of 87.2% in predicting NIV failure.
Conclusion: The ROX index serves as a straightforward and practical bedside parameter for assessing the likelihood of noninvasive ventilation (NIV) success in patients presenting with acute hypercapnic respiratory failure. Regular evaluation of the ROX index can support timely clinical decisions regarding the need for endotracheal intubation.

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