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To evaluate cardiac autonomic modulation in patients with COPD during peak exercise.

Fifty-three patients with COPD (mean FEV₁, 35% predicted [SD, 11% predicted]; mean Pao₂, 68 mm Hg [SD, 11 mm Hg]; mean Paco₂, 40 mm Hg [SD, 7 mm Hg]; mean age, 61 years [SD, 10 years]; 26 women and 27 men) and 14 healthy control subjects aged 60 years (SD, 8 years) [seven women and seven men] were studied at rest and during ramped bicycle ergometry to their volitional peak. Patients were not receiving autonomic medications other than inhaled β-agonist agents and/or anticholinergic agents. Control subjects were not receiving any medications. Cardiac autonomic modulation was assessed via time-frequency analysis (Wigner-Ville) of ECG-derived heart rate variability as the power in the low-frequency (LF) band (ie, 0.04 to 0.15 Hz) and the high-frequency (HF) band (ie, > 0.15 to 0.4 …