Tiotropium Handihaler vs. Tiotropium Respimat in COPD

Inclusion Criteria: Outpatients of either gender, age > 40. Willing and able to give informed consent and adhere to visit/protocol schedules. (Consent must be given before any study procedures are performed) Women of childbearing potential must have a negative urine pregnancy test. This will be confirmed before participation in this investigational protocol. Clinical diagnosis of COPD confirmed by post-bronchodilator spirometry demonstrating FEV1/FVC < 0.70 in all GOLD stages (http://www.goldcopd.org/). Patients who are tiotropium naïve or whose tiotropium can be withheld for 2 weeks before screening visit/visit 1 Exclusion Criteria: Upper respiratory tract infection within 6 weeks (in this case, we will re-screen the patient after 6 weeks) 24/7 oxygen use Previous history of pneumothorax Evidence of interstitial, occupational or chronic infectious lung disease by imaging studies For women of child bearing potential, positive pregnancy test. Major chronic illnesses which in the judgement of the study physician would interfere with participation in the study History of claustrophobia