{'fraction_non_alphanumeric': 0.03892733564013841, 'fraction_numerical': 0.01773356401384083, 'mean_word_length': 5.302452316076295, 'pattern_counts': {'":': 0, '<': 3, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Relationship between exercise capacity and clinical measures in patients with chronic obstructive pulmonary disease

Context: The 6-min walk distance test (6MWT) is commonly used to assess the exercise tolerance and to identify functional changes resulting from disease progression or therapeutic intervention in patients with chronic obstructive pulmonary disease (COPD). Understanding the factors related to exercise capacity can create a way to a better understanding of physical activity limitations. Aims: The aim of this study was to determine the relationship between 6MWT, dyspnea, quality of life (HRQL), and disease severity and identify the predictors of 6MWT in COPD patients. Settings and Design: A cross-sectional study was developed on COPD patients referred to the outpatient pulmonary clinic of the Ahvaz Jundishapur University of Medical Sciences. Materials and Methods: A total of 72 patients with mild to very severe COPD participated in this study. The 6MWT was performed based on American Thorax Society′s protocol. Disease severity was evaluated using spirometry. The health-related quality of life (HRQL) was assessed by the St George′s Respiratory Questionnaire (SGRQ), and exertional dyspnea was measured by Borg score. Statistical Analysis Used: The data were evaluated using Pearson′s linear correlation coefficient, Spearman′s correlation coefficient, and multivariate linear regression. Results: The 6-min walk distance (6MWD) correlated positively with forced expiratory volume in 1 s (FEV 1 ) (r = 0.36, P < 0.05) and forced vital capacity (FVC) (r = 0.37, P < 0.05), whereas there was no significant correlation between disease severity based on Global Initiative for Chronic Obstructive Lung Disease (GOLD) classification and 6MWD. Moreover, no statistically significant correlation was found between exertional dyspnea and 6MWT. A negative correlation was observed between 6MWD and total score of QOL, activity, and impact domain, respectively (r = −0.39, r = −0.44, r = −0.40, P < 0.01). Multiple regression analysis indicated that the age was identified as independent predictor of the 6MWD. Conclusions: This study showed that there is stronger relationship between 6MWD and HRQL (activity and impact) compared with physiological measures of disease severity such as FEV 1 .