Abstract
Dyspnoea differs between subjects with chronic obstructive pulmonary disease (COPD) and asthma, partly because the underlying mechanisms for bronchoconstriction differ. This study investigated the possible role of inflammation and the contribution of clinical variables on dyspnoea in subjects with COPD and asthma. Forty-eight smoking subjects with COPD and 21 nonsmoking subjects with asthma, were challenged with adenosine 5'-monophosphate (AMP) and methacholine. The Borg score was assessed before and after each challenge. Mean increases in Borg score (per percentage decrease in baseline forced expiratory volume in one second (FEV1)) were significantly smaller in COPD than in asthma (p<0.01), values being 0.055 and 0.045 in COPD and 0.122 and 0.093 in asthma respectively. This difference was largely due to the fact that one-third of the subjects with COPD did not increase their Borg score during bronchoconstriction. The increase in Borg tended to be larger during AMP than during methacholine challenge, both in asthma and COPD. Changes in Borg scores were explained by age in COPD and by the Borg score before AMP challenge in asthma. The authors conclude that perception of dyspnoea during adenosine 5'-monophosphate and methacholine induced bronchoconstriction is lower in chronic obstructive pulmonary disease than in asthma and that age contributes to this difference. As adenosine 5'-monophosphate is regarded as an indirect marker of airway inflammation, the results suggest that inflammation is not important because both groups showed similar responses on such provocations.
