Upon completion of these baseline visits, the COPD patients will be randomly assigned to a standard dose of Tiotropium once-daily (18 µg) or placebo for 4 weeks (or until study completion as visits 2-4 may require 1-2 wks to complete). Patients otherwise will receive usual care, except (as noted) for discontinuing other anticholinergic bronchodilators and theophylline. They will also discontinue long acting beta agonists for 48 hours prior to performing each of the designated visits. At the end of this intervention period, the procedures outlined in Visits 2-4 will be repeated (on the COPD patients only). All post intervention visits will be timed so that the primary measures will be made 1.5 to 2 hrs post dose of Tiotropium.