Tiotropium Respimat Versus HandiHaler on SaO2 and Sleep in COPD Patients

Inclusion Criteria: * Male or female patients aged \>=40 years old * current or ex-smokers with a smoking history of at least 10 pack-years * mild to moderate stable COPD (Global Initiative for Chronic Obstructive Lung Disease \[GOLD\] Stage I and II according to the 2010 GOLD guidelines (a post-bronchodilator forced expiratory volume in the first second (FEV1) ≥80% of predicted for stage I and 50% ≤ FEV1 \< 80% of predicted for stage II, with a post-bronchodilator FEV1/forced vital capacity (FVC) ratio \<0.70 at screening) * waking arterial oxygen tension (PaO2) ≥60 mmHg Exclusion Criteria: * refusal to participate * respiratory tract infection within 4 weeks prior to screening * COPD exacerbations requiring treatment with antibiotics and/or oral corticosteroids and/or hospitalization within 6 weeks prior to screening * concomitant pulmonary diseases other than COPD * asthma * evidence of sleep apnea on baseline sleep studies * obesity hypoventilation syndrome * respiratory failure * congestive heart failure * a history of life-threatening arrhythmias * cardiomyopathy * long-QT syndrome or QTc \>450 ms at screening * diabetes * long-term oxygen therapy * symptomatic prostatic hyperplasia * bladder-neck obstruction * moderate/severe renal impairment * urinary retention * narrow-angle glaucoma * family or personal history of mental illness * drug or alcohol abuse * severe cognitive impairment * concurrent oncological diseases * history of narcolepsy or restless legs syndrome * known history of alpha-1 antitrypsin deficiency * participation in the active phase of a supervised pulmonary rehabilitation program * hypersensitivity to any of the test ingredients * history of adverse reactions to inhaled anticholinergics.