Inclusion criteria: 1. Patients with stable, symptomatic Chronic Obstructive Pulmonary Disease (COPD) with airflow obstruction of level 2 and 3 according to the current Global initiative for chronic Obstructive Lung Disease (GOLD) strategy (2011). 2. Patients with Forced Expiratory Volume in one second (FEV1) ≥ 30% and <80 % of the predicted normal, and FEV1/FVC < 0.70 when measured 45 min after the inhalation of 84 µg ipratropium bromide.