Document Detail

A novel hypothesis to explain the bronchconstrictor effect of deep inspiration in asthma.
MedLine Citation:
PMID:  11828039     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: In healthy subjects deep inspiration transiently dilates the airways, while many asthmatic subjects show bronchoconstriction by a mechanism which is incompletely understood. We hypothesised that the negative intrathoracic pressure associated with deep inspiration occurring in the context of increased leakiness of the airway vasculature may temporarily increase airway oedema and thus reduce luminal diameter in subjects with asthma. METHODS: The effects of non-forced deep inspiration and forced deep inspiration through resistance (generating enhanced negative intrathoracic pressure) on specific airway conductance (sGaw) were compared in 10 asthmatic and 11 healthy subjects. Each performed two respiratory manoeuvres: (1) sGaw was measured immediately after three deep inspirations without added resistance, each performed at a predetermined rate (equal to that when performed maximally through resistance); and (2) sGaw was measured immediately after three forced inspirations through resistance. RESULTS: Compared with deep inspiration without added resistance, sGaw was significantly reduced after deep inspiration through resistance in the asthmatic group by a mean (SD) of -13.5 (11.0)% (p=0.003) but was unchanged in the control group (-0.5 (12.4)%, p=0.67). CONCLUSIONS: Given the similar time-volume relationship in the two manoeuvres, the reduction in sGaw is unlikely to be due to differences in smooth muscle behaviour. It is suggested that the enhanced negative intrathoracic pressure acting across the airway capillaries increases airway wall oedema and reduces airway calibre. Such a mechanism operational during normal rapid deep inspiration might contribute to bronchoconstriction after deep inspiration in subjects with asthma.
G P Burns; G J Gibson
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Thorax     Volume:  57     ISSN:  0040-6376     ISO Abbreviation:  Thorax     Publication Date:  2002 Feb 
Date Detail:
Created Date:  2002-02-05     Completed Date:  2002-04-15     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  0417353     Medline TA:  Thorax     Country:  England    
Other Details:
Languages:  eng     Pagination:  116-9     Citation Subset:  IM    
Department of Respiratory Medicine, Freeman Hospital, Newcastle upon Tyne NE7 7DN, UK.
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MeSH Terms
Airway Resistance / physiology
Asthma / physiopathology*
Bronchoconstriction / physiology*
Forced Expiratory Volume / physiology
Functional Residual Capacity / physiology
Pilot Projects
Thorax / physiology
Vital Capacity / physiology
Comment In:
Thorax. 2002 Aug;57(8):751; author reply 751   [PMID:  12149541 ]

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