Oxygen Uptake Recovery Kinetics after the 6-Minute Walk Test in Patients with Chronic Obstructive Pulmonary Disease.

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 (VO2) 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 (T1/2 VO2) 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), T1/2 VO2 was significantly associated with 6MWD (p = 0.002). CONCLUSIONS: T1/2 VO2 can be used to reflect exercise capacity in patients with COPD. As T1/2 VO2 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.