Predicting the Outcome of Nasal High-Flow Therapy: A Proposed Representation of the Data and a Supplemental Analysis

To the Editor:

I read with interest the paper by Roca and colleagues that followed up on their initial publication in 2016 (1, 2). One aspect of the report that makes interpreting the results difficult is that the authors did not provide graphs with the individual data points for the respiratory rate, the oxygen saturation as measured by pulse oximetry (Sp_O2)/Fi_O2, and the ROX to compare successes and failures, and only provided comparisons of summary data in the tables. In a manner similar to the graph used by Yang and Tobin when they validated the frequency-to-Vt ratio to predict extubation success (3), I suggest that Roca and colleagues provide a graph with the respiratory rate on the x-axis and the Sp_O2/Fi_O2 on the y-axis, plot the failures and the successes in different symbols, and mark the isopleth with a slope of 4.88. Such a graph allows the reader to see the positions of successes and failures in relation to the cut point of 4.88 and the role that tachypnea and hypoxemia played in those positions. I also suggest to the authors testing the index with the respiratory rate squared. The range of the respiratory rate is narrow. This transformation increases the range of the denominator and might create clearer separation between the successes and the failures.