Document Detail

Breathlessness during acute bronchoconstriction in asthma. Pathophysiologic mechanisms.
MedLine Citation:
PMID:  8256884     Owner:  NLM     Status:  MEDLINE    
The purpose of this study was to examine potential contributing factors to breathlessness during bronchoconstriction, in particular, to evaluate the role of lung hyperinflation. We also wished to elucidate qualitative aspects of the unpleasant sensory experience and to identify factors that contribute to intersubject variability in subjective and objective assessments of airflow obstruction. We studied sensory-mechanical interrelationships during and after induced bronchoconstriction in 21 subjects with mild stable asthma. Breathlessness (Borg scale), spirometry, and inspiratory capacity (IC) were measured after each dose during methacholine bronchoprovocation to a maximal change (delta) in FEV1 of 50%. Breathing pattern, specific airway resistance (SRaw), plethysmographic thoracic gas volume, and maximal inspiratory mouth pressure (MIP) were recorded at baseline, at maximal response, and at full symptom recovery. End-expiratory lung volume (EELV) was derived from IC. Borg increased from 0.4 +/- 0.1 (very, very slight) at baseline to 5.0 +/- 0.5 (severe) at maximal bronchoconstriction (mean +/- SEM, p < 0.001). FEV1 fell significantly (p < 0.001) to 48% predicted at maximal response. Of the 21 subjects, 19 reported increased inspiratory rather than expiratory difficulty and predominantly described sensations of reduced inspiratory capacity and unrewarded inspiratory effort. Stepwise multiple regression analysis using delta Borg (outcome variable) versus changes in spirometry, SRaw, IC, and breathing pattern components, selected delta IC as the principal contributing factor: delta Borg = 0.09 (delta IC, %fall); n = 193, r = 0.86, p < 0.001. delta IC continued to contribute significantly (p < 0.001) to the variance in Borg ratings after accounting for delta FEV1, and it was the strongest predictor of symptom recovery (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
M D Lougheed; M Lam; L Forkert; K A Webb; D E O'Donnell
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The American review of respiratory disease     Volume:  148     ISSN:  0003-0805     ISO Abbreviation:  Am. Rev. Respir. Dis.     Publication Date:  1993 Dec 
Date Detail:
Created Date:  1994-01-11     Completed Date:  1994-01-11     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0370523     Medline TA:  Am Rev Respir Dis     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1452-9     Citation Subset:  AIM; IM    
Department of Medicine, Queen's University, Kingston, Ontario, Canada.
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MeSH Terms
Acute Disease
Asthma / complications,  physiopathology*
Bronchial Provocation Tests
Bronchoconstriction / physiology*
Dyspnea / complications,  physiopathology*
Methacholine Chloride / diagnostic use
Pulmonary Ventilation
Reg. No./Substance:
62-51-1/Methacholine Chloride

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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