Association between peak oxygen consumption and static hyperinflation in patients with chronic obstructive pulmonary disease

Abstract

Introduction: Chronic Obstructive Pulmonary Disease (COPD) is a pathology with a major impact on morbidity and mortality, leading to functional limitations and progressive deterioration of lung function and quality of life. Medium-term inactivity triggers physical deconditioning, limiting exercise endurance. Physical activity is an important component of rehabilitation programs for patients with COPD, and studies in the last decade have correlated this limitation of physical activity with the phenomenon of lung hyperinflation, which is the increase in lung volume at the end of expiration. In stable patients with COPD, the inspiratory capacity/total lung capacity (IC/TLC) ratio and the degree of dyspnea are better predictors of exercise capacity. For this reason, our study aims to correlate static hyperinflation (IC/TLC) with exercise capacity represented by peak oxygen consumption (VO2 peak), measured during the cardiopulmonary exercise test. Methods: This project was approved by the Research Ethics Committee (CEP) of the Augusto Motta University Center under number 012/2011. Sixteen patients of both sexes participated in the study, 8 of whom were male, aged 70.68 ± 9.56 years, weighing 54.41 ± 16.34 kg, height 1.62 ± 0.12 m, BMI 20.45 ± 3.84, and diagnosed with moderate to very severe COPD. The patients underwent spirometry, plethysmography, and cardiopulmonary exercise testing. Correlation of variables was performed using Pearson's test. Analyses were performed using SigmaStat for Windows, version 3.5 (Systat Softaware, Inc., Chicago, IL, USA), and p-values ​​< 0.05 were considered statistically significant. Results: There was a correlation between spirometric variables and peak VO2 (normalized by body mass) with TLC (r = -0.508; p = 0.044); FRC (r = -0.551; p = 0.027); RV (r = -0.539; p = 0.031) and CI/TLC (r = 0.512; p = 0.042). Associations were also observed between VO2 (L/min) and the following variables: TLC (r = -0.572; p = 0.020); FRC (r = -0.614; p = 0.011); RV (r = -0.589; p = 0.016) and CI/TLC (r = 0.774; p = 0.0004). Conclusion: COPD patients with a lower CI/TLC ratio have worse peak oxygen consumption.