Some patients with Chronic Obstructive Pulmonary Disease (COPD) report that they are uncertain whether they achieve clinical benefit using a dry-powder inhaler (DPI). One possible explanation is that the patient is unable to inhale the dry powder bronchodilator medication into the lower respiratory tract due to a low peak inspiratory flow rate (PIFR). A PIFR < 60 l/min is considered to be suboptimal flow for a DPI, including the Diskus device. The hypothesis of the study is that the forced expiratory volume in 1 second (FEV1) measured at two hours after inhalation of the study medication will be higher with arformoterol solution (15 mcg) from a nebulizer compared with salmeterol dry powder (50 mcg) inhaled from the Diskus.

Inclusion Criteria:

• male or female patient 60 years of age or older; diagnosis of COPD; current or former smoker; previous or current use of Diskus device; PIFR < 60 l/min using the In-check DIAL against the resistance of the Diskus device; clinically stable.

Exclusion Criteria:

• any patient who has a concomitant disease that might interfere with study procedures or evaluation; inability to withhold short-acting and long-acting bronchodilators on the days of testing