Objective     To study the correlation between exertional dyspnea and dynamic hyperinflation in patients with chronic obstructive pulmonary diseases (COPD).      Methods     Routine lung ventilation function

diffusing function

lung volume and symptom-limited progressive cycle ergometer exercise were tested in 34 stable COPD patients and 10 healthy controls. Two-thirds of their symptom-limited peak work rate was used to conduct high-intensity CWRE test. Borg dyspnea score

TBFV curve and inspiratory capability (IC) were detected every 1 min at rest and exercise.      Results     The IC was significantly lower in COPD patients at peak exercise than at rest (1.56±0.29 L vs 2.07±0.38 L

t=-5.642，P0.01). The ΔBorg was negatively correlated with the ΔIC in COPD patients (r=-0.59

P0.01). The mean expiratory flow and time were significantly lower in COPD patients than in healthy controls at peak exercise time (P0.05).      Conclusion     Dynamic hyperinflation is one of the important factors for dyspnea in stable COPD patients during high-intensity CWRE exercise. The decreased mean expiratory flow and time may be the reason for dynamic hyperinflation in COPD patients during exercise.