We tested the respective effect of high-flow and supplemental O2 from nasal high-flow O2 therapy (NHFO2) on dyspnea and exercise tolerance in fibrotic interstitial lung disease. Supplemental O2 and NHFO2 (but not high-flow) provided improvements in these outcomes at "iso-O2 saturation" due to reduced ventilatory requirements. Physiological benefits derived from O2 supplementation are thus likely primary drivers of dyspnea relief and improved exercise tolerance on NHFO2 (vs air) in these patients.
Thivent et al. (Thu,) studied this question.