Effects of Bronchodilators in Mild Chronic Obstructive Pulmonary Disease (COPD)

In people with mild COPD, the ability to exhale air from the lungs is partly limited because of narrowing and collapse of the airways. This results in the trapping of air within the lungs and over-distention of the lungs and chest - this is known as lung hyperinflation. We believe that breathing at high lung volumes (hyperinflation) is an important cause of breathing discomfort (dyspnea) in people with COPD. Bronchodilators help to relax muscles in the airways or breathing tubes. Bronchodilators are often prescribed if a cough occurs with airway narrowing; this medication can reduce coughing, wheezing and shortness of breath. Bronchodilators can be taken orally, through injection or through inhalation and begin to act almost immediately but with the effect only lasting 4-6 hours. The main purpose of this study is to examine the effects of inhaled bronchodilators on breathing discomfort and exercise endurance in patients with mild COPD. Each subject will attend 4 visits to the laboratory. Visit 1 (screening visit) will involve a record of medical history, medications used, anthropometrics measurements, questionnaires, breathing tests, an incremental cycle exercise test and a constant-workload cycle exercise test. Visit 2 will involve breathing tests and a constant-workload cycle exercise test. Visits 3 and 4 will involve breathing tests and a constant-workload cycle exercise test after subjects have been randomized to either placebo or Atrovent. These visits will be done on separate days and subjects will receive the two above treatments in random order.