Gene expression responses to exercise are not significantly different between COPD patients and healthy controls, regardless of desaturation status.

<p><b>A</b> Gene expression inductions (post/pre) for regulators of Oxphen. PPAR, peroxisome proliferator-activated receptor; PGC, PPAR gamma co-activator; PRC, PGC-1-related co-activator; ERRα, estrogen-related receptor α; NRF, nuclear respiratory factor; TFAM, mitochondrial transcription factor A. <b>B</b> Gene expression inductions for metabolic enzymes involved in citric acid cycle, β-oxidation and glycolysis. CS, citrate synthase; HADH, 3-hydroxyacyl-CoA dehydrogenase; COX4-1, cytochrome <i>c</i> oxidase subunit IV isoform 1; HK-II, hexokinase II; PFK, phosphofructokinase muscle isoform. <b>C</b> Gene expression inductions of hypoxia-associated targets. HIF-1α, hypoxia-inducible factor 1 alpha; VEGF-A, vascular endothelial growth factor A; GLUT1, glucose transporter 1. Whiskers indicate minimum and maximum values. Level of significance: ^*p<0.05 for post <i>vs</i>. pre.</p

Main characteristics of subjects.

<p>Values are expressed as mean±SD or median (25th percentile, 75th percentile). Abbreviations: BMI, body mass index; FFMI, fat-free mass index; FEV₁, forced expiratory volume in one second; FVC, forced vital capacity; <i>D</i>_L,CO, diffusion capacity of the lungs for carbon monoxide; <i>S</i>p,o₂, oxygen saturation measured via pulse oximetry. Significance of difference compared to controls: ^*p<0.05, ^**p<0.01, ^***p≤0.001. Level of significance COPD_D<i>vs.</i> COPD_ND patients: ^#p<0.05.</p

Results from the maximal cycle ergometry test.

<p>Values are expressed as median (25th percentile, 75th percentile). Abbreviations: <i>V</i>′o₂, oxygen uptake; <i>V</i>′e, minute ventilation; MVV, maximal voluntary ventilation, calculated as FEV₁×37.5; HR, heart rate; HR predicted calculated as (220 − age); AT<i>V</i>′o₂, <i>V</i>′o₂ at anaerobic threshold; <i>S</i>_p,o₂, oxygen saturation measured via pulse oximetry; <i>S</i>_a,o₂, arterial oxygen saturation. Level of significance of difference <i>vs.</i> controls: ^*p<0.05, ^**p<0.01, ^***p≤0.001. Level of significance of difference COPD_D<i>vs.</i> COPD_ND patients: ^##p<0.01, ^###p≤0.001.</p

Main characteristics of <i>vastus lateralis</i> muscle fibers.

<p>Values are expressed as mean±SD or median (25th percentile, 75th percentile). Abbreviations: CSA, cross-sectional area; CS, citrate synthase; HADH, 3-hydroxyacyl-CoA dehydrogenase; OXPHOS, oxidative phosphorylation; AU, arbitrary units. Significance of difference compared to controls: * p<0.05, ** p<0.01, *** p≤0.001.</p

Change in quadriceps muscle saturation during exercise is not associated with systemic desaturation.

<p>Reliable muscle saturation data was available for 11 COPD_ND, 9 COPD_D patients and 11 healthy controls.</p

Quadriceps desaturation during cycle ergometry.

<p>Values are expressed as median (25th percentile, 75th percentile). Abbreviations: TSI, tissue saturation index; <i>τ</i>, time constant of recovery of muscle oxygen saturation.</p