Abstract
BackgroundActivities of daily living in patients with chronic obstructive pulmonary disease (COPD) are limited by exertional dyspnea and reduced exercise capacity. The aims of the study were to examine longitudinal changes in peak oxygen uptake (V̇O2peak), peak minute ventilation (V̇Epeak) and breathing pattern over four years in a group of COPD patients, and to examine potential explanatory variables of change.MethodsThis longitudinal study included 63 COPD patients, aged 44-75 years, with a mean forced expiratory volume in one second (FEV1) at baseline of 51 % of predicted (SD = 14). The patients performed two cardiopulmonary exercise tests (CPETs) on treadmill 4.5 years apart. The relationship between changes in V̇O2peak and V̇Epeak and possible explanatory variables, including dynamic lung volumes and inspiratory capacity (IC), were analysed by multivariate linear regression analysis. The breathing pattern in terms of the relationship between minute ventilation (V̇E) and tidal volume (VT) was described by a quadratic equation, VT = a + b∙V̇E + c∙V̇E2, for each test. The VTmax was calculated from the individual quadratic relationships, and was the point where the first derivative of the quadratic equation was zero. The mean changes in the curve parameters (CPET2 minus CPET1) and VTmax were analysed by bivariate and multivariate linear regression analyses with age, sex, height, changes in weight, lung function, IC and inspiratory reserve volume as possible explanatory variables.ResultsSignificant reductions in V̇O2peak (p < 0.001) and V̇Epeak (p < 0.001) were related to a decrease in resting IC and in FEV1. Persistent smoking contributed to the reduction in V̇O2peak. The breathing pattern changed towards a lower VT at a given V̇E and was related to the reduction in FEV1.ConclusionIncreasing static hyperinflation and increasing airway obstruction were related to a reduction in exercise capacity. The breathing pattern changed towards more shallow breathing, and was related to increasing airway obstruction.
Highlights
Activities of daily living in patients with chronic obstructive pulmonary disease (COPD) are limited by exertional dyspnea and reduced exercise capacity
We have found that the V E-VT relationship can be satisfactorily described by a quadratic model in COPD patients exercising on treadmill [18]
The major findings of this study of a group of COPD patients who were followed over a mean time of 4.5 years were a reduction in V O2peak and V Epeak which were related to a decrease in resting inspiratory capacity (IC) and FEV1, and persistent smoking during the observation period
Summary
Activities of daily living in patients with chronic obstructive pulmonary disease (COPD) are limited by exertional dyspnea and reduced exercise capacity. The aims of the study were to examine longitudinal changes in peak oxygen uptake (VO2peak), peak minute ventilation (VEpeak) and breathing pattern over four years in a group of COPD patients, and to examine potential explanatory variables of change. A reduction in exercise capacity measured as peak oxygen uptake (V O2peak) has Studies of longitudinal changes in V O2peak, peak minute ventilation (V Epeak) and breathing pattern in COPD are scarce. Frisk et al BMC Pulmonary Medicine (2015) 15:93 was found to be related to a reduction in maximal tidal volume (VTmax) and V Epeak, and the decrease in V O2peak was associated with the decrease in FEV1. We are not aware of any studies that have examined the longitudinal changes in V O2peak and breathing pattern in COPD patients of Caucasian origin including both genders
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