title: Is asymptomatic peripheral arterial disease associated with walking endurance in patients with COPD?
abstract: 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 (r (2)=-0.667, P<0.001), followed by oxygen-cost diagram (r (2)=0.582, P<0.001) and forced expiratory volume in 1 second (r (2)=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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Chang Gung University of Science and Technology, Taiwan, Republic of China ; Department of Respiratory Care, Chang Gung University of Science and Technology, Taiwan, Republic of China.
authors.forename: Kuo-Shao
authors.initials: KS
authors.lastname: Sun
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Chang Gung University of Science and Technology, Taiwan, Republic of China ; Department of Respiratory Care, Chang Gung University of Science and Technology, Taiwan, Republic of China.
authors.forename: Ming-Shian
authors.initials: MS
authors.lastname: Lin
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Chang Gung University of Science and Technology, Taiwan, Republic of China ; Department of Respiratory Care, Chang Gung University of Science and Technology, Taiwan, Republic of China.
authors.forename: Yi-Jen
authors.initials: YJ
authors.lastname: Chen
authors.affiliation: Department of Internal Medicine, Ditmanson Medical Foundation Chia-Yi Christian Hospital, Chiayi, Taiwan, Republic of China.
authors.forename: Yih-Yuan
authors.initials: YY
authors.lastname: Chen
authors.affiliation: Department of Medical Research, Ditmanson Medical Foundation Chia-Yi Christian Hospital, Chiayi, Taiwan, Republic of China.
authors.forename: Solomon Chih-Cheng
authors.initials: SC
authors.lastname: Chen
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Chang Gung University of Science and Technology, Taiwan, Republic of China ; College of Nursing, Dayeh University, Changhua, Taiwan, Republic of China ; Department of Respiratory Therapy, China Medical University, Taichung, Taiwan, Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D055109:Ankle Brachial Index; D058070:Asymptomatic Diseases; D016009:Chi-Square Distribution; D003430:Cross-Sectional Studies; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D016014:Linear Models; D008168:Lung / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010092:Oximetry; D058729:Peripheral Arterial Disease / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D012307:Risk Factors; D014797:Vital Capacity; D016138:Walking
keywords: 6-minute walk tests; COPD; ankle-brachial index; peripheral arterial disease