What are the predictors of failure in high-flow nasal cannula oxygen?

Updated: Jun 18, 2020
  • Author: Guy W Soo Hoo, MD, MPH; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Although the focus has been on noninvasive ventilation (NIV), there has been increasing use of high-flow nasal cannula (HFNC) oxygen in clinical situations where NIV had previously been used. This also warrants objective measures that may identify patients in whom HFNC oxygen support fails and who require intubation. This is important, as delayed intubation of patients with progressive hypoxemic respiratory failure has been associated with increased mortality. This led to the identification of the ROX index, defined as the ratio of pulse oximetry oxygen saturation and fraction of inspired oxygen to respiratory rate [(SpO2/FIO2)/RR]. In an inception and validation cohort of patients with pneumonia and on HFNC oxygen, values of the ROX index greater than 4.88 measured at 2, 6, and 12 hours, 18 and 24 hours after initiation of HFNC were found to identify those patients who would not need intubation. [9] Lower ROX index scores not only identified those requiring intubation, but was also associated with poor outcomes, specifically mortality. The authors identified the hours between the 12th and 24th hours as the most vulnerable in their cohort, with an increased risk of failure in those with ROX index scores lower than 3.85.

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