AUTHOR=Müller Julian , Lichtblau Mona , Saxer Stéphanie , Calendo Luigi-Riccardo , Carta Arcangelo F. , Schneider Simon R. , Berlier Charlotte , Furian Michael , Bloch Konrad E. , Schwarz Esther I. , Ulrich Silvia 

TITLE=Effect of Breathing Oxygen-Enriched Air on Exercise Performance in Patients With Pulmonary Hypertension Due to Heart Failure With Preserved Ejection Fraction: A Randomized, Placebo-Controlled, Crossover Trial

JOURNAL=Frontiers in Medicine

VOLUME=8

YEAR=2021

URL=https://www.frontiersin.org/journals/medicine/articles/10.3389/fmed.2021.692029

DOI=10.3389/fmed.2021.692029

ISSN=2296-858X

ABSTRACT=<p><bold>Objective:</bold> To evaluate the effects of breathing oxygen-enriched air (oxygen) on exercise performance in patients with pulmonary hypertension due to heart failure with preserved ejection fraction (PH-HFpEF).</p><p><bold>Methods:</bold> Ten patients with PH-HFpEF (five women, age 60 ± 9 y, mPAP 37 ± 14 mmHg, PAWP 18 ± 2 mmHg, PVR 3 ± 3 WU, resting SpO<sub>2</sub> 98 ± 2%) performed two-cycle incremental exercise tests (IET) and two constant-work-rate exercise test (CWRET) at 75% maximal work-rate (<italic>W</italic><sub>max</sub>), each with ambient air (FiO<sub>2</sub> 0.21) and oxygen (FiO<sub>2</sub> 0.5) in a randomized, single-blinded, cross-over design. The main outcomes were the change in <italic>W</italic><sub>max</sub> (IET) and cycling time (CWRET) with oxygen vs. air. Blood gases at rest and end-exercise, dyspnea by Borg CR10 score at end-exercise; continuous SpO<sub>2</sub>, minute ventilation (V'E), carbon dioxide output (V'CO<sub>2</sub>), and cerebral and quadricep muscle tissue oxygenation (CTO and QMTO) were measured.</p><p><bold>Results:</bold> With oxygen vs. air, <italic>W</italic><sub>max</sub> (IET) increased from 94 ± 36 to 99 ± 36 W, mean difference (95% CI) 5.4 (0.9–9.8) W, <italic>p</italic> = 0.025, and cycling time (CWRET) from 532 ± 203 to 680 ± 76 s, +148 (31.8–264) s, <italic>p</italic> = 0.018. At end-exercise with oxygen, Borg dyspnea score and V'E/V'CO<sub>2</sub> were lower, whereas PaO<sub>2</sub> and end-tidal PaCO<sub>2</sub> were higher. Other parameters were unchanged.</p><p><bold>Conclusion:</bold> Patients with PH-HFpEF not revealing resting hypoxemia significantly improved their exercise performance while breathing oxygen-enriched air along with less subjective dyspnea sensation, a better blood oxygenation, and an enhanced ventilatory efficiency. Future studies should investigate whether prolonged training with supplemental oxygen would increase the training effect and, potentially, daily activity for PH-HFpEF patients.</p><p><bold>Clinical Trial Registration:</bold> [<ext-link ext-link-type="uri" xlink:href="http://clinicaltrials.gov/" xmlns:xlink="http://www.w3.org/1999/xlink">clinicaltrials.gov</ext-link>], identifier [NCT04157660].</p>