Chronic bronchitis leads to accelerated hyperinflation in COPD patients during exercise

Abstract

Background and objective: It is not known whether patients with chronic obstructive pulmonary disease (COPD) have a different exercise capacity with (CB(+) ) or without accompanying chronic bronchitis (CB(-) ).

Methods: We conducted spirometry, a 6-min walk distance test and cardiopulmonary exercise test in 50 age-matched healthy control subjects, 45 COPD patients without CB (CB(-) ) and 37 COPD patients with CB (CB(+) ). A multiple regression model was established to identify factors independently associated with peak oxygen consumption ( V ˙ O 2 ).

Results: Patients with and without CB had similar forced expiratory volume in 1 s (FEV1 ). CB(+) patients had a lower V ˙ O 2 . CB(+) and CB(-) participants had similar increases in tidal volume at peak exercise; however, CB(+) patients had an increased respiratory rate (RR). These patients reached the peak value for ratio of end-expiratory lung volume to total lung capacity (TLC) at a lower work load. A stepwise multiple linear regression analysis identified chronic bronchitis, FEV1 , diffusing capacity for carbon monoxide, the ratio of residual volume to TLC and serum tumour necrosis factor-α as independent predictors of peak V ˙ O 2 .

Conclusions: CB significantly lowers exercise capacity in COPD patients because of dynamic hyperinflation during exercise. The accelerated dynamic hyperinflation may contribute to increased airway and systemic inflammation in COPD patients.

Keywords: cardiopulmonary exercise test; chronic bronchitis; chronic obstructive pulmonary disease; dynamic hyperinflation; exercise capacity.