The project will be pursued in our respiratory, autonomic nervous system physiology laboratory (Respiratory, autonomic nervous system physiology laboratory, Department of Pneumology and Intensive Care Medicine, RWTH Aachen University Hospital; Head of Department: Professor Michael Dreher). Overactivity of the sympathetic nerve activity (SNA) axis with centrally increased heart rate and peripheral vasoconstriction is a known phenomenon in patients with systolic heart failure (HF) and has recently been described in patients with primary lung disease as seen in chronic obstructive pulmonary disease (COPD). However, systematic analyses on this clinically relevant topic are currently lacking. Thus, using a comprehensive, multimodal approach and state-of-the-art technology, this research project is designed to determine the extent and nature of increased SNA in COPD (AIM 1) and evaluate the underlying mechanisms (AIM 2). The project will address the following hypotheses: 1. In COPD, concomitant obstructive sleep apnea is independently associated with increased SNA. 2. Precapillary pulmonary hypertension (PH), inspiratory muscle dysfunction and systemic inflammation describe a COPD phenotype characterised by increased SNA with a different subtype.