Elevated exercise ventilation in mild COPD is not linked to enhanced central chemosensitivity

Background: The purpose of this study was to determine if altered central chemoreceptor characteristics contributed to the elevated ventilation relative to carbon dioxide production (V̇E/V̇CO2) response during exercise in mild chronic obstructive pulmonary disease (COPD). Methods: Twenty-nine mild COPD and 19 healthy age-matched control participants undertook lung function testing followed by symptom-limited incremental cardiopulmonary exercise testing. On a separate day, basal (non-chemoreflex) ventilation (V̇EB), the central chemoreflex ventilatory recruitment threshold for CO2 (VRTCO2), and central chemoreflex sensitivity (V̇ES) were assessed using the modified Duffin's CO2 rebreathing method. Resting arterialized blood gas data were also obtained. Results: At standardized exercise intensities, absolute V̇E and V̇E/V̇CO2 were consistently elevated and the end-tidal partial pressure of CO2 was relatively decreased in mild COPD versus controls (all p < 0.05). There were no between-group differences in resting arterialized blood gas parameters, basal V̇E, VRTCO2, or V̇ES (all p > 0.05). Conclusion: These data have established that excessive exercise ventilation in mild COPD is not explained by altered central chemosensitivity.