ABSTRACT
This study was conducted with the aim of determining the range of normal value of respiratory centre sensitivity and exercise tolerance in healthy Thais and any divergence from the normal range in those with COPD. Findings in healthy subjects disclosed that the end-tidal PCO2 and tidal volume response to CO2 were higher and exercise tolerance was lower among the elderly compared with younger subjects; only in young males was the ventilatory response to CO2 higher than in females. In the group of Thai COPD patients, all data were comparable to those of the match healthy subjects, with the exception that one-third of the patients experienced stronger ventilatory drive while breathing room air and a lower musculo-ventilation transfer index during room-air breathing as well as CO2 rebreathing.