title: Effects of dynamic hyperinflation on exercise capacity and quality of life in stable COPD patients.
abstract: OBJECTIVE
  Dynamic hyperinflation (DH) is an important pathophysiological characteristic of chronic obstructive pulmonary disease (COPD). There is increasing evidence that DH has negative effects on exercise performance and quality of life. The objective of this study was to explore effects of DH on exercise capacity and quality of life in stable COPD patients.
  
  
  METHODS
  Fifty-eight COPD patients and 20 matched healthy individuals underwent pulmonary function test, 6-min walk test and symptom-limited cardiopulmonary exercise test (CPET). End-expiratory lung volume/total lung capacity ratio (EELVmax/TLC) at peak exercise of CPET was evaluated, and EELVmax/TLC ≥ 75% was defined as 'severe dynamic hyperinflation (SDH)'.
  
  
  RESULTS
  Of the 58 patients studied, 29 (50.0%) presented with SDH (SDH+ group, EELVmax/TLC 79.60 ± 3.60%), having worse maximal exercise capacity reflected by lower peakload, maximal oxygen uptake (VO2 max), maximal carbon dioxide output (VCO2 max) and maximal minute ventilation (VEmax) than did those without SDH (SDH- group, EELVmax/TLC 67.44 ± 6.53%). The EELVmax/TLC ratio at peak exercise had no association with variables of pulmonary function and 6-min walk distance (6MWD), but correlated inversely with peakload, VO2 max, VCO2 max and VEmax (r = -0.300~-0.351, P < 0.05). Although no significant differences were observed, patients with EELVmax/TLC ≥ 75% tended to have higher COPD assessment test score (15.07 ± 6.55 vs 13.28 ± 6.59, P = 0.303).
  
  
  CONCLUSIONS
  DH develops variably during exercise and has a greater impact on maximal exercise capacity than 6MWD, even in those with the same extent of pulmonary function impairment at rest.
authors.affiliation: Department of Respiratory and Critical Care Medicine, Beijing Chaoyang Hospital, Capital Medical University, Beijing Key Laboratory of Respiratory and Pulmonary Circulation, Beijing Institute of Respiratory Medicine, Beijing, China.|Department of Surgery Intensive Care Unit, State Key Laboratory of Cardiovascular Diseases, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
authors.forename: Li
authors.initials: L
authors.lastname: Zhao
authors.affiliation: Department of Respiratory and Critical Care Medicine, Beijing Chaoyang Hospital, Capital Medical University, Beijing Key Laboratory of Respiratory and Pulmonary Circulation, Beijing Institute of Respiratory Medicine, Beijing, China.|Department of Surgery Intensive Care Unit, Beijing Anzhen Hospital, Capital Medical University, Beijing Institute of Heart, Lung and Blood Vessel Disease, Beijing, China.
authors.forename: Liyue
authors.initials: L
authors.lastname: Peng
authors.affiliation: Department of Respiratory and Critical Care Medicine, Beijing Chaoyang Hospital, Capital Medical University, Beijing Key Laboratory of Respiratory and Pulmonary Circulation, Beijing Institute of Respiratory Medicine, Beijing, China.
authors.forename: Baomei
authors.initials: B
authors.lastname: Wu
authors.affiliation: Department of Respiratory and Critical Care Medicine, Beijing Chaoyang Hospital, Capital Medical University, Beijing Key Laboratory of Respiratory and Pulmonary Circulation, Beijing Institute of Respiratory Medicine, Beijing, China. 13641000837@163.com.
authors.forename: Xiaoning
authors.initials: X
authors.lastname: Bu
authors.affiliation: Department of Respiratory Medicine, China-Japan Friendship Hospital, Capital Medical University, National Clinical Research Center for Respiratory Medicine, Beijing, China. cyh-birm@263.net.
authors.forename: Chen
authors.initials: C
authors.lastname: Wang
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D015444:Exercise / Q000502:physiology*; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D007320:Inspiratory Capacity; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D011788:Quality of Life; D012129:Respiratory Function Tests; D014109:Total Lung Capacity; D000070857:Walk Test / Q000379:methods
keywords: COPD assessment test; body composition; cardiopulmonary exercise test; chronic obstructive; dynamic hyperinflation; exercise; pulmonary disease