Abstract
Background: There is a growing interest in exercise parameters capable of objectively evaluating the functional capacity of patients with chronic obstructive pulmonary disease (COPD). Objectives: The purpose of the present study was to analyze breath-by-breath cardiopulmonary and gas exchange recovery responses of patients with COPD after a 6-minute walk test (6MWT). Methods: Oxygen uptake (VO<sub>2</sub>) kinetics of patients were obtained using mobile telemetric cardiopulmonary monitoring during and after a 6MWT. Recovery kinetics were modelled using a 4-parameter nonlinear logistic model. Multiple linear regression was performed to assess the association between the half-time of recovery of oxygen consumption (T<sub>1/2</sub> VO<sub>2</sub>) and exercise capacity (6-minute walking distance, 6MWD). Results: Sixty-nine patients with COPD (28 females) with a mean age of 65 ± 10 years took part in the study. After adjustment for covariates (body mass index, forced expiratory volume in 1 s, forced vital capacity, and age), T<sub>1/2</sub> VO<sub>2</sub> was significantly associated with 6MWD (p = 0.002). Conclusions: T<sub>1/2</sub> VO<sub>2</sub> can be used to reflect exercise capacity in patients with COPD. As T<sub>1/2</sub> VO<sub>2</sub> mostly depends on the rate of increase in pulmonary blood flow, the results of the present study underline the importance of cardiocirculatory impairment for exercise intolerance in patients with COPD.
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