Both acute O2 supplementation and nasal high-flow O2 therapy (NHFO2) result in improvements in exertional dyspnoea and exercise tolerance at “iso-O2 saturation” in severely hypoxemic patients with fibrotic interstitial lung disease (f-ILD), driven primarily by a similar decline in ventilatory requirements, reports a study.
Sixteen patients performed endurance tests in a randomized order under the following conditions: air, supplemental O2 (face mask, 9–12 L·min−1), NHFair (50–70 L·min−1; inspired fraction of O2 [FiO2] = 0.21), and NHFO2 (50–70 L·min−1; FiO2 = 0.5). The investigators then compared endurance time and O2 saturation (SpO2), breathing pattern (respiratory plethysmography), and dyspnea (Borg CR-10) across conditions.
Supplemental O2 and NHFO2 led to an increase in isotime SpO2 compared with air (98 percent and 99 percent vs 87 percent, respectively; p<0.001). Likewise, O2 and NHFO2 improved exercise time relative to air and NHFair (683 and 690 vs 346 and 319, respectively; p<0.001; O2 vs NHFO2: p=0.117). [Respirology 2026;31:732-744]
Compared with air, supplemental O2 and NHFO2 also reduced isotime ventilation (63 vs 47 and 44 L·min−1; p<0.001), driven by the reduced respiratory rates (44, 36, 37 10 br·min−1; p<0.001), as well as isotime dyspnoea (7 vs 4 and 3.5; p<0.001; NHFO2 vs NHFair: 3.5 vs 6; p=0.016).
Furthermore, NHFair reduced isotime ventilation (9.0 L·min−1; p=0.012) but failed to improve dyspnoea and exercise time relative to air.
“Our study suggests that physiological benefits derived from supplemental O2 are presumably the primary drivers of dyspnoea relief and improved exercise tolerance on NHFO2 vs air in f-ILD, with no added benefit of NHFair,” the investigators said
“Yet, further research is required to confirm these preliminary findings with adequate sample size due to the number of experimental conditions we compared,” they added.
Unique design
In previous studies, researchers examined the benefits of NHFO2 in reversing exertional hypoxemia, reducing dyspnoea, and improving exercise capacity in patients with f-ILD. [Respiratory Medicine 2021;186:106523; Respirology 2022;27:144-151; BMC Pulmonary Medicine 2020;20:51; BMC Pulmonary Medicine 2021;21:355; Respirology 2024;29:497-504]
“Our study innovates by specifically comparing four distinct experimental conditions,” the investigators said. “[T]his unique design allowed us to ‘isolate’ the physiological and perceptual effects of respiratory support from improved oxygenation in patients with f-ILD and severe activity-related hypoxemia.”
Despite differences in methodology, the cited studies comparing room air and NHFO2 were consistent in reporting symptomatic relief and longer exercise endurance time under the latter in f-ILD. Whether NHFO2 yields superior benefits to O2 therapy, however, remains to be determined.
“In fact, supplemental O2 delivered at low flow rates (4 L·min−1 via nasal cannula) has been shown inappropriate to fully correct hypoxemia in f-ILD,” the investigators said.
“[G]reater dyspnoea alleviation and exercise tolerance on NHFO2 may therefore reflect a larger improvement in systemic oxygenation and/or a specific effect of NHF-related respiratory support but does not allow teasing out any separate contribution in this study,” they added. [Respiratory Medicine 2021;186:106523]
NHFO2 is a promising alternative to O2 therapy, the standard treatment to f-ILD, which is characterized by severe hypoxemia, heightened dyspnoea, and exercise limitation, according to the investigators.