Muscle Dysfunction in Patients With Chronic Obstructive Lung Disease (COPD): the Role of Sympathetic Activation

Inclusion Criteria: * Diagnosis of COPD II or III according to the GOLD guidelines * FEV1 of less than 60% of the predicted value * RV/TLC \> 45% * Optimal stable medication according to the GOLD guidelines for at least 2 weeks * The last exacerbation must not be more recent than three weeks * Stable sinus rhythm * The subgroup on NIV should be stable on NIV for \> 1 month Exclusion Criteria: * not willing or unable to sign the informed consent before the study begins * Age under 30 or over 80 years * paO2\< 55 mmHg or PaCO2 \> 45 mmHg on arterial blood gas analysis (For patients on NIV, PaCO2 values of up to 55 mmHg are acceptable.) * Treatment with drugs having direct sympathomimetic activity (e.g. theophylline, moxonidine, clonidine) * Oral medication with beta2 sympathomimetics (therapy with long-acting inhaled beta2 sympathomimetics is permitted) * History of sleep apnoea or documented evidence of \> 15 episodes of apneas and/or hypopnea per hour during sleep. An episode of apnea is defined as the cessation of inspiratory airflow for 10 s or more. Hypopnea is defined as a reduction in airflow (\> 50%) lasting for more than 10 s in comparison with the maximum airflow recorded during the preceding breathing cycle. * Myocardial infarction (MI) or a coronary revascularization procedure within the previous 2 calendar months * Clinically evident polyneuropathy * Diabetes mellitus necessitating any pharmacologic therapy * Severe (i.e., life-limiting) concomitant disease, including life-threatening malignancy (cancer likely to reduce life expectancy to less than 5 years), acquired immune deficiency syndrome, or any other life-threatening disease. * Diuretics should not be taken before measurements