J Appl Physiol 103: 1465, 2007;
doi:10.1152/japplphysiol.00696.2007
8750-7587/07 $8.00
LETTER TO THE EDITOR
Commentary on "The role of the large airways on smooth muscle contraction in asthma"
TO THE EDITOR: 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 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.
FOOTNOTES
Address for reprint requests and other correspondence: B. Thompson, The Alfred Hospital, Melbourne, Victoria, Australia 3004 (e-mail: b.thompson{at}alfred.org.au)
REFERENCES
- 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.[Abstract/Free Full Text]
- Downie SR, Salome CM, Verbanck S, Thompson BR, Berend N, King GG. Ventilation heterogeneity is a major determinant of airway hyper-responsiveness in asthma. Thorax [February 20, 2007] Epub ahead of print.
- 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.[Abstract/Free Full Text]
- Permutt S. The role of the large airways on smooth muscle contraction in asthma. J Appl Physiol; doi:10.1152/japplphysiol.00590.2007.
- 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.[Abstract/Free Full Text]
- Verbanck S, Schuermans D, Paiva M, Vincken W. Non-reversible conductive airways ventilation heterogeneity in mild asthma. J Appl Physiol 94: 1380–1386, 2003.[Abstract/Free Full Text]
Bruce Thompson
Greg King
Richard Harding
Respiratory Medicine, The Alfred Hospital; Woolcock Institute, University of Sydney; and Anatomy and Cell Biology, Monash University, Australia
Copyright © 2007 by the American Physiological Society.
