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Force Oscillations Simulating Breathing Maneuvers do not Prevent Force Adaptation.
MedLine Citation:
PMID:  22323367     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Airway inflammation in asthmatics exposes the airway smooth muscle (ASM) to a variety of spasmogens. These spasmogens increase ASM tone, which can lead to force adaptation. It has been shown that length oscillations of ASM, which occur in vivo due to breathing maneuvers, can attenuate force adaptation. However, in the presence of tone, the force oscillations required to achieve these length oscillations may be unphysiologic. Herein, we applied force oscillations simulating the tension oscillations experienced by the airway wall during tidal breathing with or without deep inspirations (DI) to ASM. The goal was to investigate whether force adaptation occurs in conditions mimicking breathing maneuvers. Tone was induced by carbachol (average of 20nM) and the force-generating capacity of the ASM was assessed at 5-min intervals before and after carbachol administration using electrical field stimulations (EFS). The results show that force oscillations applied prior to the introduction of tone had a small effect on the force produced by EFS (declined to 96.8%, p>0.05, and 92.3%, p<0.05, with and without DI respectively). The tone induced by carbachol transiently decreased after a DI and declined significantly (p<0.05) due to tidal breathing oscillations (25%). However, these force oscillations did not prevent force adaptation (gain of force of 11.2 ± 2.2 vs. 13.5 ± 2.7 and 11.2 ± 3.0% in static vs. dynamic conditions with or without DI respectively). The lack of effect of simulated breathing maneuvers on force adaptation suggests that this gain in ASM-force may occur in vivo and could contribute to airway hyperresponsiveness.
Authors:
Chris Pascoe; Yuekan Jiao; Chun Y Seow; Peter D Paré; Ynuk Bossé
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-2-9
Journal Detail:
Title:  American journal of respiratory cell and molecular biology     Volume:  -     ISSN:  1535-4989     ISO Abbreviation:  -     Publication Date:  2012 Feb 
Date Detail:
Created Date:  2012-2-10     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8917225     Medline TA:  Am J Respir Cell Mol Biol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
University of British Columbia James Hogg Research Center, St. Paul's Hospital, Vancouver, Canada.
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