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Journal of Allergy
Volume 2012 (2012), Article ID 157047, 8 pages
http://dx.doi.org/10.1155/2012/157047
Review Article

Airway Smooth Muscle Dynamics and Hyperresponsiveness: In and outside the Clinic

1Centre for Neonatal Research and Education, School of Women’s and Infants’ Health, The University of Western Australia, Crawley 6009, Australia
2School of Anatomy, Physiology, and Human Biology, The University of Western Australia, Crawley 6009, Australia
3Department of Pulmonary Physiology, West Australian Sleep Disorders Research Institute, Sir Charles Gairdner Hospital, Nedlands 6009, Australia
4School of Medicine and Pharmacology, The University of Western Australia, Crawley 6009, Australia

Received 27 July 2012; Accepted 5 September 2012

Academic Editor: Michael M. Grunstein

Copyright © 2012 Peter B. Noble et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The primary functional abnormality in asthma is airway hyperresponsiveness (AHR)—excessive airway narrowing to bronchoconstrictor stimuli. Our understanding of the underlying mechanism(s) producing AHR is incomplete. While structure-function relationships have been evoked to explain AHR (e.g., increased airway smooth muscle (ASM) mass in asthma) more recently there has been a focus on how the dynamic mechanical environment of the lung impacts airway responsiveness in health and disease. The effects of breathing movements such as deep inspiration reveal innate protective mechanisms in healthy individuals that are likely mediated by dynamic ASM stretch but which may be impaired in asthmatic patients and thereby facilitate AHR. This perspective considers the evidence for and against a role of dynamic ASM stretch in limiting the capacity of airways to narrow excessively. We propose that lung function measured after bronchial provocation in the laboratory and changes in lung function perceived by the patient in everyday life may be quite different in their dependence on dynamic ASM stretch.