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ROX Index for High-Flow Nasal Cannula Failure Prediction Calculator

ROX = (SpO₂ / FiO₂) / RR — threshold ≥ 4.88 predicts HFNC success.

Compute the ROX index, a validated tool for predicting high-flow nasal cannula (HFNC) failure in acute hypoxaemic respiratory failure: ROX = (SpO₂ % / FiO₂ fraction) / respiratory rate. Values < 2.85 at 2 h or < 3.47 at 6 h or < 3.85 at 12 h after HFNC initiation predict failure (intubation needed). The "success threshold" ≥ 4.88 is widely cited.

Marcus Laurent By Marcus Laurent
Published Last reviewed 1 min read

Inputs

%
breaths/min

Results

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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

ROX = (SpO₂ / FiO₂) / RR.

In depth

Compute the ROX index, a validated tool for predicting high-flow nasal cannula (HFNC) failure in acute hypoxaemic respiratory failure: ROX = (SpO₂ % / FiO₂ fraction) / respiratory rate. Values < 2.85 at 2 h or < 3.47 at 6 h or < 3.85 at 12 h after HFNC initiation predict failure (intubation needed). The "success threshold" ≥ 4.88 is widely cited.