In COPD patients, significant correlations (p < 0.05) were observed between oxygen desaturation after 6MWT and endothelin-1 (ρ = −0.32, p = 0.018), as well as between oxygen saturation and lung volume on CT (ρ = 0.28, p = 0.041). The gene discussed is EDN1; the disease is chronic obstructive pulmonary disease.