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

Purpose: We studied the effect of O 2 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% O 2 ) were compared with tests performed breathing 30% O 2 . Oxygen uptake (V̇O 2 ) kinetics were calculated from the constant WR test results.
Results: In the ILD group, peak WR, peak V̇O 2 , and V̇O 2 at the gas exchange threshold improved significantly when breathing 30% O 2 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). O 2 saturation (SpO 2 %) at peak exercise was higher with 30% O 2 (97% ± 4% vs 88% ± 9%, P = 0.002). The time constant (tau) of V̇O 2 kinetics was faster in ILD patients while breathing 30% O 2 (41 ± 10 s) compared with RA (52 ± 14 s, P = 0.003). There was a negative linear relation between tau and SpO 2 % with RA ( r = -0.76, P = 0.006) and while breathing 30% O 2 ( r = -0.68, P = 0.02).
Conclusions: Using a clinically applicable level of O 2 supplementation (30%) improved maximal, aerobic exercise capacity and V̇O 2 kinetics in ILD patients, likely due to increased blood O 2 content subsequently increasing the O 2 delivery to the working muscles.
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