ABSTRACT
Chronic obstructive pulmonary disease (COPD) is a multisystem disorder with its primary effects in the lungs but with significant functional consequences in other systems. Even in the lungs there are a number of different pathophysiological processes, each of which may be present to a varying degree. Breathlessness is the characteristic symptomof COPD. It is associated with inspiration and has a complex etiology that is linked to the work of breathing [1]. With increasing lung volume a greater respiratory effort is needed to maintain tidal breathing. Bronchodilator-induced reductions in breathlessness at rest have been shown to correlate better with changes in forced inspiratory flow thanwith changes in forced expiratory volume (FEV1) [2]. Static lung volumes are increased in COPD, although this is only moderately correlated with worsening expiratory airflow limitation [3], There is a further rise in functional residual capacity at exercise onset, otherwise known as dynamic hyperinflation. The reduction in breathlessness during exercise following bronchodilators correlates better with improvement in inspiratory capacity during exercise than improvement in FEV1 [4,5].
