On the mechanism of mucosal folding in normal and asthmatic airways

1997 ◽  
Vol 83 (6) ◽  
pp. 1814-1821 ◽  
Author(s):  
Barry R. Wiggs ◽  
Constantine A. Hrousis ◽  
Jeffrey M. Drazen ◽  
Roger D. Kamm
Keyword(s):  
Smooth Muscle ◽  
Muscle Activation ◽  
Composite Model ◽  
Chronic Obstructive ◽  
Airway Wall ◽  
Element Analysis ◽  
Obstructive Pulmonary Disease ◽  
Folding Pattern ◽  
Airway Lumen ◽  
Layer Composite

Wiggs, Barry R., Constantine A. Hrousis, Jeffrey M. Drazen, and Roger D. Kamm. On the mechanism of mucosal folding in normal and asthmatic airways. J. Appl. Physiol. 83(6): 1814–1821, 1997.—Previous studies have demonstrated that the airway wall in asthma and chronic obstructive pulmonary disease is markedly thickened. It has also been observed that when the smooth muscle constricts the mucosa buckles, forming folds that penetrate into the airway lumen. This folding pattern may influence the amount of luminal obstruction associated with smooth muscle activation. A finite-element analysis of a two-layer composite model for an airway is used to investigate the factors that determine the mucosal folding pattern and how it is altered as a result of changes in the thickness or stiffness of the different layers that comprise the airway wall. Results demonstrate that the most critical physical characteristic is the thickness of the thin inner layer of the model. Thickening of this inner layer likely is represented by the enhanced subepithelial collagen deposition seen in asthma. Other findings show a high shear stress at or near the epithelial layer, which may explain the pronounced epithelial sloughing that occurs in asthma, and steep gradients in pressure that could cause significant shifts of liquid between wall compartments or between the wall and luminal or vascular spaces.

scholarly journals Computed tomographic measures of airway morphology in smokers and never-smoking normals

2014 ◽  
Vol 116 (6) ◽  
pp. 668-673 ◽  
Author(s):  
G. R. Washko ◽  
A. A. Diaz ◽  
V. Kim ◽  
R. G. Barr ◽  
M. T. Dransfield ◽  
...  
Keyword(s):  
Chronic Obstructive Pulmonary Disease ◽  
Chronic Obstructive ◽  
Sectional Area ◽  
Airway Wall ◽  
Cross Sectional ◽  
Obstructive Pulmonary Disease ◽  
Wall Area ◽  
Computed Tomographic ◽  
Airway Morphology ◽  
Central Airway

Bronchial wall area percent (WA% = 100 × wall area/total bronchial cross sectional area) is a standard computed tomographic (CT) measure of central airway morphology utilized in smokers with chronic obstructive pulmonary disease (COPD). Although it provides significant clinical correlations, the range of reported WA% is narrow. This suggests limited macroscopic change in response to smoking or that remodeling proportionally affects the airway wall and lumen dimensions such that their ratio is preserved. The objective of this study is to assess central airway wall area (WA), lumen area (Ai), and total bronchial area (Ao) from CT scans of 5,179 smokers and 92 never smoking normal subjects. In smokers, WA, Ai, and Ao were positively correlated with forced expiratory volume in 1 s (FEV1) expressed as a percent of predicted (FEV1%), and the WA% was negatively correlated with FEV1% ( P < 0.0001 for all comparisons). Importantly, smokers with lower FEV1% tended to have airways of smaller cross-sectional area with lower WA. The increases in the WA% across GOLD stages of chronic obstructive pulmonary disease (COPD) can therefore not be due to increases in WA. The data suggest two possible origins for the WA% increases: 1) central airway remodeling resulting in overall reductions in airway caliber in excess of the decreased WA or 2) those with COPD had smaller native airways before they began smoking. In both cases, these observations provide an explanation for the limited range of values of WA% across stages of COPD.

scholarly journals Emerging concepts in smooth muscle contributions to airway structure and function: implications for health and disease

2016 ◽  
Vol 311 (6) ◽  
pp. L1113-L1140 ◽  
Author(s):  
Y. S. Prakash
Keyword(s):  
Smooth Muscle ◽  
Cell Types ◽  
Structure And Function ◽  
Normal Lung ◽  
Future Research ◽  
Chronic Obstructive ◽  
Obstructive Pulmonary Disease ◽  
Health And Disease ◽  
Growth And Aging ◽  
And Function

Airway structure and function are key aspects of normal lung development, growth, and aging, as well as of lung responses to the environment and the pathophysiology of important diseases such as asthma, chronic obstructive pulmonary disease, and fibrosis. In this regard, the contributions of airway smooth muscle (ASM) are both functional, in the context of airway contractility and relaxation, as well as synthetic, involving production and modulation of extracellular components, modulation of the local immune environment, cellular contribution to airway structure, and, finally, interactions with other airway cell types such as epithelium, fibroblasts, and nerves. These ASM contributions are now found to be critical in airway hyperresponsiveness and remodeling that occur in lung diseases. This review emphasizes established and recent discoveries that underline the central role of ASM and sets the stage for future research toward understanding how ASM plays a central role by being both upstream and downstream in the many interactive processes that determine airway structure and function in health and disease.

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