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ROX Index HFNO Failure Prediction — FRCA Final MCQ

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ModerateIntensive Care MedicineROX Index HFNO Failure PredictionFRCA Final

A 55-year-old woman (ASA III) in ICU with community-acquired pneumonia develops acute respiratory failure. She is placed on high-flow nasal oxygen (HFNO) at 60 L/min, FiO2 0.6. The ROX index (SpO2/FiO2 divided by RR) is calculated at 2 hours as 3.2. What does this predict?

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Correct answer: B — High risk of HFNO failure requiring intubation

The ROX index = (SpO2/FiO2) / respiratory rate. It was developed to predict HFNO failure in acute hypoxaemic respiratory failure. A ROX index <2.85 at 2 hours, <3.47 at 6 hours, or <3.85 at 12 hours predicts HFNO failure requiring intubation. A ROX of 3.2 at 2 hours is above the 2-hour threshold but should prompt continued close monitoring and reassessment at 6 and 12 hours. Delayed intubation after HFNO failure is associated with increased mortality, so early identification of patients unlikely to succeed is critical.

Reference: Roca O et al – 2019 – ROX index validation; ICS – 2023 – HFNO guidelines