Bronchodilator therapy in COPD: physiological effects

Educational aims

1. To review current concepts of the mechanisms of symptom relief and improved exercise tolerance following pharmacological treatment in chronic obstructive pulmonary disease (COPD).

2. To examine the relative responsiveness of new physiological outcome parameters in clinical trials.

Summary Bronchodilator therapy is the first step in improving dyspnoea and exercise endurance in patients with COPD. Recent studies have challenged the long-held view that airway obstruction in COPD is irreversible. We now know that even in the setting of minor or no change in traditional spirometry, bronchodilator therapy is associated with consistent, and often impressive, reduction in lung hyperinflation. This pharmacological lung volume reduction is linked to improved inspiratory muscle function and enhanced neuro- mechanical coupling of the respiratory system during activity, even in those with advanced disease. Moreover, these improvements in dynamic mechanics provide a sound physiological rationale for observed bronchodilator-induced improvements in the important patient-centred outcomes of reduced dyspnoea and activity limitation.