A novel non-invasive index of oxygenation and prediction of outcomes for patients on high-flow nasal cannula

Abstract

Introduction/Aim. Acute respiratory failure (ARF) is a major cause of morbidity and mortality. Predicting patient trajectory has important ramifications. Current tools are limited either by invasiveness or unreliable data points. We explored the utility of a novel non‐invasive index of oxygenation (flow x FiO2/SpO2) at predicting outcomes in patients with ARF managed with high flow nasal prongs (HFNP).

Methods. This is a retrospective cohort of patients treated with HFNP from July 2018 to June 2019. Patients were included if they were treated by a respiratory physician, aged 18‐85, and had a diagnosis of ARF. Exclusion criteria included post‐operative use of HFNP, or the indication for HFNP was not clear. The index was compared to the ROX index for external validation.

Results. Preliminary analysis of 39 patients is reported. The average age was 57 years and 54% of patients were female. The most common indication for HFNP was COPD (38%), followed by community acquired pneumonia (20%). HFNP use was successful in avoiding intensive care, mechanical ventilation and non‐invasive ventilation (NIV) in 76.9% of cases., with escalation to NIV the most common outcome in those who failed HFNP. 2 patients died. At 24 hours, the median index score in the success group was 10.7, and 21.5 in the failure group (P = 0.004) with no statistical difference at other time points. Divergence in the ROX index for success vs failure occurred at 2 hours (9.7 vs 15.6, P = 0.004) and continued to 24 hours.

Conclusion. After preliminary analysis, our novel index was able to predict success of HFNP in ARF at 24 hours. The ROX index performed well in this cohort at a different raw value, potentially explained by a different study population. Further patient numbers are required to determine the precise transition point of this new index and further predictors of success.