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MedLine Citation:
PMID:  21852298     Owner:  NLM     Status:  Publisher    
ABSTRACT BACKGROUND: To better understand the inter-relationships between disease severity, inspiratory capacity, breathing pattern and dyspnea, we studied responses to symptom-limited cycle exercise in a large cohort with COPD. METHODS: Analysis was conducted on data from two previously published replicate clinical trials in 427 hyperinflated patients with COPD. Patients were divided into disease severity quartiles based on FEV(1) %predicted. Spirometry, plethysmographic lung volumes and physiological and perceptual responses to constant work rate (CWR) cycle exercise at 75% of the peak incremental work rate were compared. RESULTS: Age, body size and COPD duration were similar across quartiles. As FEV(1) quartile worsened (means of 62, 49, 39 and 27 % predicted): FRC increased (144, 151, 164 and 185 %predicted), IC decreased (86, 81, 69 and 60 %predicted), peak incremental cycle work rate decreased (66, 55, 50, 44 %predicted) and CWR endurance time was 9.7, 9.3, 8.2 and 7.3 min, respectively. During CWR exercise as FEV(1) quartile worsened, peak ventilation (V(E)) and tidal volume (V(T)) decreased, while an inflection or plateau of the tidal volume response occurred at a progressively lower V(E) (p<0.0005), similar percentage of peak V(E) (82-86%) and similar V(T)/IC ratio (73-77 %). Dyspnea intensity at this inflection point was also similar across quartiles (3.1-3.7 Borg units) but accelerated steeply to intolerable levels thereafter. CONCLUSION: Progressive reduction of the resting IC with increasing disease severity was associated with the appearance of critical constraints on V(T) expansion and a sharp increase in dyspnea to intolerable levels at a progressively lower ventilation during exercise.
Denis E O'Donnell; Jordan A Guenette; François Maltais; Katherine A Webb
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-8-18
Journal Detail:
Title:  Chest     Volume:  -     ISSN:  1931-3543     ISO Abbreviation:  -     Publication Date:  2011 Aug 
Date Detail:
Created Date:  2011-8-19     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0231335     Medline TA:  Chest     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
1Respiratory Investigation Unit, Department of Medicine, Queen's University & Kingston General Hospital, Kingston, Ontario, Canada.
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