HCRT and chronic obstructive pulmonary disease: Plasma orexin-A levels in COPD patients were found to correlate significantly with BMI (r = 0.589, P = .000) (Figure 1(a)), %fat (r = 0.367, P = .020) (Figure 1(b)), PaO2 (r = −0.738, P = .000) (Figure 1(c)), and SaO2 (r = −0.616, P = .000) (Figure 1(d)).