| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
1 Woolcock Institute of Medical Research, Camperdown, NSW, Australia; Cooperative Research Centre for Asthma, Camperdown, NSW, Australia
2 Woolcock Institute of Medical Research, Camperdown, NSW, Australia; Cooperative Research Centre for Asthma, Camperdown, NSW, Australia; Department of Medicine, The University of Sydney, Sydney, NSW, Australia
* To whom correspondence should be addressed. E-mail: williamt{at}med.usyd.edu.au.
Using the forced oscillation technique we track airway resistance continuously during quiet breathing (QB) and deep inspiration (DI), thus observing fluctuations in resistance that may reflect mechanisms of airway stretch and renarrowing. After DI however, the resistance may be depressed for a period not related to volume changes. We hypothesized that this gradual increase in resistance following DI-induced dilation was determined by a simple time constant. Furthermore, to the extent that this effect reflects dynamic characteristics of airway renarrowing, the resistance change after each tidal inspiration should also be constrained by this temporal limit. A model relating resistance fluctuations to the breathing pattern, including both instantaneous and delayed effects, was developed and applied to data from 14 non-asthmatic and 17 asthmatic subjects (respectively mean±SD FEV1 103±13 and 83±12%predicted) following methacholine challenge (dose 145±80 and 3.0±3.4umol respectively) that resulted in respective FEV1 reductions of 16±7% and 24±6% from baseline. Resistance was measured continuously for one minute of quiet breathing, a deep inspiration, followed by a further minute of quiet breathing. Resistance values at end expiration (Ree) and end inspiration (Rei) were calculated. We found that the sequence of Ree following DI was best modeled by a power-law function of time rather than an exponential decay (r2=0.82±0.18 compared to 0.63±0.16, p<.01). Furthermore, the coefficient characterizing this "renarrowing function" was close to equal to the coefficient characterizing the equivalent function of resistance change between each Rei and subsequent Ree during quiet breathing, particularly in the non-asthmatics for which the intra-class correlation was 0.66. This suggests that the same time-dependent factors determine renarrowing after both large and small breaths.
This article has been cited by other articles:
|
|
 |
|
  D. G. Chapman, N. Berend, G. G. King, B. E. McParland, and C. M. Salome Deep inspirations protect against airway closure in nonasthmatic subjects J Appl Physiol, August 1, 2009; 107(2): 564 - 569. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Agrawal, S. K. Singh, V. P. Singh, E. Murphy, and I. Parikh Partitioning of nasal and pulmonary resistance changes during noninvasive plethysmography in mice J Appl Physiol, December 1, 2008; 105(6): 1975 - 1979. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. M. Slats, K. Janssen, A. van Schadewijk, D. T. van der Plas, R. Schot, J. G. van den Aardweg, J. C. de Jongste, P. S. Hiemstra, T. Mauad, K. F. Rabe, et al. Bronchial Inflammation and Airway Responses to Deep Inspiration in Asthma and Chronic Obstructive Pulmonary Disease Am. J. Respir. Crit. Care Med., July 15, 2007; 176(2): 121 - 128. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Diba, C. M. Salome, H. K. Reddel, C. W. Thorpe, B. Toelle, and G. G. King Short-term variability of airway caliber--a marker of asthma? J Appl Physiol, July 1, 2007; 103(1): 296 - 304. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. S. An, T. R. Bai, J. H. T. Bates, J. L. Black, R. H. Brown, V. Brusasco, P. Chitano, L. Deng, M. Dowell, D. H. Eidelman, et al. Airway smooth muscle dynamics: a common pathway of airway obstruction in asthma Eur. Respir. J., May 1, 2007; 29(5): 834 - 860. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Schweitzer, L. T. T. Vu, Y. T. Nguyen, C. Chone, B. Demoulin, and F. Marchal Estimation of the bronchodilatory effect of deep inhalation after a free run in children Eur. Respir. J., July 1, 2006; 28(1): 89 - 95. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. H. T. Bates, S. S. Wagers, R. J. Norton, L. M. Rinaldi, and C. G. Irvin Exaggerated airway narrowing in mice treated with intratracheal cationic protein J Appl Physiol, February 1, 2006; 100(2): 500 - 506. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
| Visit Other APS Journals Online |
