Beyond the Lungs: O2 Supplementation Improves Cerebral Oxygenation and Fatigue during Exercise in Interstitial Lung Disease.

Purpose: Cerebral hypoxia may exacerbate the perception of fatigue. We previously demonstrated that exercise-related hypoxemia, a hallmark of fibrotic interstitial lung disease (f-ILD), dose dependently impairs cerebral oxygenation in these patients. It is unknown whether normalizing cerebral oxygenation with O2 supplementation would be associatedwith positive changes in a relevant patient-centered outcome during exercise in f-ILD, such as improved perceived fatigue. Methods: Fourteen patients (12 males, 72 ± 8 yr, 8 with idiopathic pulmonary fibrosis, lung diffusing capacity for carbon monoxide = 44% ± 13% predicted) performed a constant-load (60% peak work rate) cycle test to symptom limitation (Tlim) breathing medical air. Fourteen controls cycled up to Tlim of an age- and sex-matched patient. Patients repeated the test on supplemental O2 (fraction of inspired O2 = 0.41 ± 0.08) for the same duration. Near-infrared spectroscopy and the rating-of-fatigue (ROF) scale assessed prefrontal cortex oxygenation and perceived fatigue, respectively. Results: Patients showed severe exertional hypoxemia (Tlim O2 saturation by pulse oximetry = 80% ± 8%); they had poorer cerebral oxygenation (e.g., oxy-deoxyhemoglobin difference [HbDiff] = -3.5 ± 4.7 [range = -17.6 to +1.9] vs +1.9 ± 1.7 µmol from rest) and greater fatigue (ROF = 6.2 ± 2.0 vs 2.6 ± 2.3) versus controls under air (P < 0.001). Reversal of exertional hypoxemia with supplemental O2 led to improved HbDiff (+1.7 ± 2.4 µmol from rest; no longer differing fromcontrols) and lower ROF scores (3.7 ± 1.2, P < 0.001 vs air) in patients. There was a significant correlation between O2-induced changes inHbDiff and ROF scores throughout exercise in f-ILD (rrepeated-measures correlation = -0.51, P < 0.001). Conclusions: Supplemental O2 improved cerebral oxygenation during exercise in f-ILD, which was moderately associated with lower ratings of perceived fatigue. Reversing cerebral hypoxia with O2 supplementation may thus have positive effects on patients' disablement beyond those expected from lower ventilation and dyspnea in this patient population. [ABSTRACT FROM AUTHOR]