Document Detail

CT and physiologic determinants of dyspnea and exercise capacity during the six-minute walk test in mild COPD.
MedLine Citation:
PMID:  23313036     Owner:  NLM     Status:  Publisher    
OBJECTIVES: We aimed to explore physiological responses to the six-minute walk test (6MWT) and assess computed tomographic (CT) features of the lungs and thigh muscle in order to determine contributors to dyspnea intensity and exercise limitation in dyspneic and non-dyspneic subjects with GOLD-1 COPD and controls. METHODS: We compared Borg dyspnea ratings, ventilatory responses to 6MWT, and CT-measures of emphysema, airway lumen caliber, and cross-sectional area of the thigh muscle (RTM(CT-CSA)) in 19 dyspneic, 22 non-dyspneic, and 30 control subjects. RESULTS: Dyspneic subjects walked less and experienced greater exertional breathlessness than non-dyspneic (105 m less and 2.4 Borg points more, respectively) and control subjects (94 m less and 2.6 Borg points more, respectively (P < 005 for all comparisons). At rest, dyspneic subjects had significant greater expiratory airflow obstruction, air trapping, ventilation/perfusion mismatch, burden of emphysema, narrower airway lumen, and lower RTM(CT-CSA) than comparison subjects. During walking dyspneic subjects had a decreased inspiratory capacity (IC) along with high ventilatory demand. Dyspneic subjects exhibited higher end-exercise tidal expiratory flow limitation and oxygen saturation drop than comparison subjects. In regression analysis, dyspnea intensity was best explained by ΔIC and forced expiratory volume in 1 s %predicted. RTM(CT-CSA) and ΔIC were independent determinants of distance walked. CONCLUSIONS: Among subjects with mild COPD, those with daily-life dyspnea have worse exercise outcomes; distinct lung and thigh muscle morphologic features; and different pulmonary physiologic characteristics at rest and exercise. ΔIC was the main contributor to dyspnea intensity and ΔIC and thigh muscle wasting were determinants of exercise capacity.
Alejandro A Díaz; Arturo Morales; Juan C Díaz; Cristóbal Ramos; Julieta Klaassen; Fernando Saldías; Carlos Aravena; Rodrigo Díaz; Carmen Lisboa; George R Washko; Orlando Díaz
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-1-8
Journal Detail:
Title:  Respiratory medicine     Volume:  -     ISSN:  1532-3064     ISO Abbreviation:  Respir Med     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-1-14     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8908438     Medline TA:  Respir Med     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2012 Elsevier Ltd. All rights reserved.
Division of Pulmonary and Critical Care, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
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