Is asymptomatic peripheral arterial disease associated with walking endurance in patients with COPD?

Abstract

Kuo-Shao Sun,1,2* Ming-Shian Lin,1,2* Yi-Jen Chen,1,2 Yih-Yuan Chen,3 Solomon Chih-Cheng Chen,4 Wei Chen1,5,6 1Division of Pulmonary and Critical Care Medicine, 2Department of Respiratory Care, Chang Gung University of Science and Technology, 3Department of Internal Medicine, 4Department of Medical Research, Ditmanson Medical Foundation Chia-Yi Christian Hospital, Chiayi, 5College of Nursing, Dayeh University, Changhua, 6Department of Respiratory Therapy, China Medical University, Taichung, Taiwan, Republic of China *These authors contributed equally to this work Objective: Symptomatic peripheral arterial disease (PAD) is associated with impaired walking endurance in patients with chronic obstructive pulmonary disease (COPD). However, it is unknown whether asymptomatic PAD is associated with impaired walking endurance in patients with COPD. Methods: This prospective cross-sectional study enrolled 200 COPD patients (mean age: 70.9 years) who volunteered to perform ankle-brachial index (ABI) and 6-minute walk test (6MWT) consecutively. Demographic data, lung function, dyspnea scales, and cardiovascular risk factors were recorded. The ABI was used to detect PAD (ABI <0.90). All patients were free of PAD symptoms at enrollment. Results: Of the 200 COPD patients, 17 (8.5%) were diagnosed with asymptomatic PAD. The COPD patients without asymptomatic PAD did not walk significantly further on the 6MWT than the COPD patients with asymptomatic PAD (439±86 m vs 408±74 m, P=0.159). The strongest correlation with the distance walked on the 6MWT was Medical Research Council dyspnea scale (r2=-0.667, P<0.001), followed by oxygen-cost diagram (r2=0.582, P<0.001) and forced expiratory volume in 1 second (r2=0.532, P<0.001). In multivariate linear regression analysis, only age, forced expiratory volume in 1 second, and baseline pulse oximetry were independently correlated with the distance covered on the 6MWT (P<0.05). However, body mass index, baseline heart rate, and ABI were not correlated with the distance covered on the 6MWT. Conclusion: Asymptomatic PAD is not associated with walking endurance in patients with COPD. Therefore, it is important to detect and treat asymptomatic PAD early so that COPD patients do not progress to become exercise intolerant. Limited by the small sample size and predominantly male (99%) population in the study, further large-scale prospective studies are needed to verify the results. Keywords: peripheral arterial disease, COPD, ankle-brachial index, 6-minute walk tests