Effect of Supplemental Oxygen on Physiological Responses to Exercise in Fibrotic Interstitial Lung Disease

Purpose We studied the effect of O2 supplementation on physiological response to exercise in patients with moderate to severe interstitial lung disease (ILD). Methods Thirteen patients (age 66 ± 10 yr, 7 males) with ILD (total lung capacity, 71% ± 22% predicted; carbon monoxide diffusion capacity, 44% ± 16% predicted) and 13 healthy individuals (age 50 ± 17 yr, 7 males) were tested. ILD patients performed symptom-limited cardiopulmonary exercise tests and constant work rate (WR) tests at 80% of the WR at the gas exchange threshold. Tests breathing room air (RA; 21% O2) were compared with tests performed breathing 30% O2. Oxygen uptake (VO2) kinetics were calculated from the constant WR test results. Results In the ILD group, peak WR, peak VO2, and VO2 at the gas exchange threshold improved significantly when breathing 30% O2 compared with RA (mean ± SD, 75 ± 26 vs 66 ± 23 W, 17 ± 4 vs 15 ± 2 mL·kg-1·min-1, and 932 ± 245 vs 854 ± 232 mL·min-1; P = 0.004, P = 0.001, and P = 0.01, respectively). O2 saturation (SpO2%) at peak exercise was higher with 30% O2 (97% ± 4% vs 88% ± 9%, P = 0.002). The time constant (tau) of VO2 kinetics was faster in ILD patients while breathing 30% O2 (41 ± 10 s) compared with RA (52 ± 14 s, P = 0.003). There was a negative linear relation between tau and SpO2% with RA (r = -0.76, P = 0.006) and while breathing 30% O2 (r = -0.68, P = 0.02). Conclusions Using a clinically applicable level of O2 supplementation (30%) improved maximal, aerobic exercise capacity and VO2 kinetics in ILD patients, likely due to increased blood O2 content subsequently increasing the O2 delivery to the working muscles.