Predicting success of high-flow nasal cannula in pneumonia patients with hypoxemic respiratory failure: The utility of the ROX index

J Crit Care. 2016 Oct:35:200-5. doi: 10.1016/j.jcrc.2016.05.022. Epub 2016 May 31.


Purpose: The purpose of the study is to describe early predictors and to develop a prediction tool that accurately identifies the need for mechanical ventilation (MV) in pneumonia patients with hypoxemic acute respiratory failure (ARF) treated with high-flow nasal cannula (HFNC).

Materials and methods: This is a 4-year prospective observational 2-center cohort study including patients with severe pneumonia treated with HFNC. High-flow nasal cannula failure was defined as need for MV. ROX index was defined as the ratio of pulse oximetry/fraction of inspired oxygen to respiratory rate.

Results: One hundred fifty-seven patients were included, of whom 44 (28.0%) eventually required MV (HFNC failure). After 12 hours of HFNC treatment, the ROX index demonstrated the best prediction accuracy (area under the receiver operating characteristic curve 0.74 [95% confidence interval, 0.64-0.84]; P<.002). The best cutoff point for the ROX index was estimated to be 4.88. In the Cox proportional hazards model, a ROX index greater than or equal to 4.88 measured after 12 hours of HFNC was significantly associated with a lower risk for MV (hazard ratio, 0.273 [95% confidence interval, 0.121-0.618]; P=.002), even after adjusting for potential confounding.

Conclusions: In patients with ARF and pneumonia, the ROX index can identify patients at low risk for HFNC failure in whom therapy can be continued after 12 hours.

Keywords: Acute respiratory failure; High flow nasal cannula; Hypoxemia; Nasal high flow; Oxygen therapy; Pneumonia.

Publication types

  • Observational Study

MeSH terms

  • Adult
  • Aged
  • Catheterization / methods*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Nose
  • Oximetry
  • Oxygen / metabolism
  • Oxygen Inhalation Therapy / methods*
  • Pneumonia / complications
  • Pneumonia / therapy*
  • Proportional Hazards Models
  • Prospective Studies
  • Respiration, Artificial / statistics & numerical data
  • Respiratory Insufficiency / etiology
  • Respiratory Insufficiency / therapy*
  • Respiratory Rate / physiology
  • Severity of Illness Index*
  • Treatment Failure


  • Oxygen