smooth muscle contraction in asthma" Commentary ...

Commentary on "The role of the large airways on smooth muscle contraction in asthma" Bruce Thompson, Greg King and Richard Harding

J Appl Physiol 103:1465, 2007. doi:10.1152/japplphysiol.00696.2007 You might find this additional info useful... This article cites 4 articles, 4 of which can be accessed free at: http://jap.physiology.org/content/103/4/1465.full.html#ref-list-1 Updated information and services including high resolution figures, can be found at: http://jap.physiology.org/content/103/4/1465.full.html Additional material and information about Journal of Applied Physiology can be found at: http://www.the-aps.org/publications/jappl

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Journal of Applied Physiology publishes original papers that deal with diverse areas of research in applied physiology, especially those papers emphasizing adaptive and integrative mechanisms. It is published 12 times a year (monthly) by the American Physiological Society, 9650 Rockville Pike, Bethesda MD 20814-3991. Copyright © 2007 by the American Physiological Society. ISSN: 0363-6143, ESSN: 1522-1563. Visit our website at http://www.the-aps.org/.

J Appl Physiol 103: 1465, 2007; doi:10.1152/japplphysiol.00696.2007.

Letters To The Editor

Commentary on “The role of the large airways on smooth muscle contraction in asthma” Bruce Thompson, Greg King, and Richard Harding Respiratory Medicine, The Alfred Hospital; Woolcock Institute, University of Sydney; and Anatomy and Cell Biology, Monash University, Australia TO THE EDITOR:

Address for reprint requests and other correspondence: B. Thompson, The Alfred Hospital, Melbourne, Victoria, Australia 3004 (e-mail: b.thompson @alfred.org.au).

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study under discussion that the small airways were involved in the increase in residual volume produced by the BSMT, we would suggest that the techniques employed to measure small airway function were not sensitive enough to measure any change. It is highly likely that significant small airway involvement would have been demonstrated if measures specific for the small airways were employed. REFERENCES 1. Dame Carroll JR, Chandra A, Jones AS, Berend N, Magnussen JS, King GG. Airway dimensions measured from micro-computed tomography and high-resolution computed tomography. Eur Respir J 28: 712–720, 2006. 2. Downie SR, Salome CM, Verbanck S, Thompson BR, Berend N, King GG. Ventilation heterogeneity is a major determinant of airway hyperresponsiveness in asthma. Thorax [February 20, 2007] Epub ahead of print. 3. Nakano Y, Wong JC, de Jong PA, Buzatu L, Nagao T, Coxson HO, Elliott WM, Hogg JC, Pare PD. The prediction of small airway dimensions using computed tomography. Am J Respir Crit Care Med 171: 142–146, 2005. 4. Permutt S. The role of the large airways on smooth muscle contraction in asthma. J Appl Physiol; doi:10.1152/japplphysiol.00590.2007. 5. Verbanck S, Schuermans D, Noppen M, Van Muylem A, Paiva M, Vincken W. Evidence of acinar airway involvement in asthma. Am J Respir Crit Care Med 159: 1545–1550, 1999. 6. Verbanck S, Schuermans D, Paiva M, Vincken W. Non-reversible conductive airways ventilation heterogeneity in mild asthma. J Appl Physiol 94: 1380 –1386, 2003.

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In a recent article in which Solbert Permutt (4) discussed the role of the large airways on smooth muscle contraction, he states he found no evidence that the small airways were involved in the significant increase in residual volume. We would suggest that measures of static lung volumes and HRCT described in the study under discussion are not sufficiently sensitive (1, 5, 6) to detect the significant contribution that the small airways are likely to be having on ventilatory function, following changes in baseline smooth muscle tension (BSMT). There is mounting evidence demonstrating significant increases in ventilatory heterogeneity in both the conducting and acinar regions of the lung as measured by the multiple breath nitrogen washout technique (5, 6). HRCT is also insensitive to small airway dimensions due to limitations in resolution. It is likely that remodeling measured by Brown et al. (3) of large airways represents similar changes in small airways. There is also very recent evidence that the baseline heterogeneity in the conducting small airways is related to bronchial hyperresponsiveness and therefore muscle tone (2). Therefore, despite no evidence being presented in the