Short-term effects of supplemental oxygen during exercise in patients with idiopathic pulmonary fibrosis (IPF)

Background: International guidelines recommend the use of supplemental oxygen (O2) in IPF patients who suffer from exercise-induced hypoxemia (EIH). As short-term effects of O2 during exercise are not known in IPF patients yet, the aim of our study was to investigate the effects of O2 on the endurance walking capacity in hypoxemic IPF patients. Methods: 53 IPF patients with EIH were investigated in a prospective double-blinded randomized-controlled cross-over trial. Following an initial incremental shuttle walk test (ISWT) which assess the individual maximum gait speed, each patient performed 3 endurance shuttle walk tests (ESWT) at 85%max under following conditions: (A) with medical air (compressed room air)(ESWTMA), (B) with 2 liters/min O2 (ESWT2L) and (C) with 4 liters/min O2 (ESWT4L). Walking endurance time during ESWT was the primary outcome. Data of secondary outcomes (oxygen saturation [SpO2], heart rate [HR], breathing frequency [BF]) were compared at the end of the shortest ESWT ("isotime"). Results: 50 patients (69 y, FVC 72%pred., DLCO 33%pred., ISWT: 389m) completed the study. Endurance walking time was longer during ESWT4L> ESWT2L >ESWTMA (585 sec vs. 462 sec vs. 404 sec, F=3.483, p=0.03). SpO2ISO was higher by breathing O2 and by using a higher flow rate (ESWT4L 88% vs. ESWT2L 85% vs. ESWTMA 80%, F=123.204, p<0.0001), whereas BFISO and HRISO tended to be lower (p=n.s.). Discussion: O2 showed significant and clinically relevant benefits on walking capacity and oxygen saturation compared to compressed room air in IPF patients with EIH. A dose-dependent effect has been found showing higher vs. lower oxygen flow rates to be more beneficial.