Effects of 100 % oxygen during exercise in patients with interstitial lung disease

Purpose: Hypoxemia limits exercise in some patients with interstitial lung disease (ILD). High levels of supplemental oxygen during exercise might allow physical training at a higher level and more effective pulmonary rehabilitation (PR). Our goals were to use graded cardiopulmonary exercise testing (CPET) to determine whether hyperoxia (F_IO₂≈1.0) increased exercise tolerance in patients with mild to moderate ILD. Methods: We studied 6 patients with ILD, including idiopathic pulmonary fibrosis (IPF) and nonspecific interstitial pneumonia (NSIP). The study population included 3 females and 3 males (age 69 ± 5 [SD] years; FVC 61 ± 14 %; absolute D_LCO 53 ± 19 %). Subjects underwent 2 ramped (15 W/min) CPET protocols on a cycle ergometer (Jaeger Oxycon Pro™, CareFusion Respiratory Care) breathing either air or oxygen (F_IO₂≈1.0) from a Douglas bag in random order. Results: Minute ventilation (VE) increased significantly during CPET breathing air (pre CPET, 18 ± 2 [SEM] L/min; post CPET, 47 ± 6; P = 0.01), but it did not increase significantly breathing oxygen (pre CPET, 15 ± 3 [SEM]; post CPET, 29 ± 9; P = 0.06). Likewise, carbon dioxide production (VCO₂) increased significantly during CPET breathing air (pre CPET, 450 ± 93 [SEM] mL/min; post CPET, 1311 ± 200; P = 0.01), but it did not increase significantly breathing oxygen (pre CPET, 369 ± 129; post CPET, 847 ± 832; P = 0.09). Exercise time during CPET did not differ significantly (P = 0.34) in air (5.6 ± 0.9 [SEM] min) or oxygen (7.0 ± 1.8). Increases in heart rate (HR) and Borg dyspnea index (BDI) after CPET were not affected by breathing oxygen. Conclusion: Exercise-induced increases in VE and VCO₂ were prevented by breathing pure oxygen during CPET, demonstrating both decreased ventilatory drive and more efficient exercise at achieved workloads. Hyperoxia could enhance the ability of patients with ILD to train at higher workloads, resulting in more effective rehabilitation.