Compliance of peripheral airways deduced  from morphometry

Okazawa, Mitsushi; Paré, Peter D.; Lambert, Robert A.

doi:10.1152/jappl.2000.89.6.2373

Cited by 23 publications

(23 citation statements)

References 22 publications

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“…Our experimental design differed from that of Wang et al, in that bronchial mucosa was used and different regions of the strain-stress relation and their relation to epithelial folds and distension were investigated. Pressurevolume properties of peripheral bronchioles, predominantly comprising the mucosa, have also been reported (9) and are in broad agreement with our findings, showing regions of low and high stress at 0 -10 cmH 2 O. There was considerable hysteresis in the mucosal strain-stress curve reported here.…”

Section: Discussionsupporting

confidence: 93%

Elastic properties of the bronchial mucosa: epithelial unfolding and stretch in response to airway inflation

Noble¹,

Sharma²,

McFawn³

et al. 2005

Journal of Applied Physiology

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The bronchial mucosa contributes to elastic properties of the airway wall and may influence the degree of airway expansion during lung inflation. In the deflated lung, folds in the epithelium and associated basement membrane progressively unfold on inflation. Whether the epithelium and basement membrane also distend on lung inflation at physiological pressures is uncertain. We assessed mucosal distensibility from strain-stress curves in mucosal strips and related this to epithelial length and folding. Mucosal strips were prepared from pig bronchi and cycled stepwise from a strain of 0 (their in situ length at 0 transmural pressure) to a strain of 0.5 (50% increase in length). Mucosal stress and epithelial length in situ were calculated from morphometric data in bronchial segments fixed at 5 and 25 cmH2O luminal pressure. Mucosal strips showed nonlinear strain-stress properties, but regions at high and low stress were close to linear. Stresses calculated in bronchial segments at 5 and 25 cmH2O fell in the low-stress region of the strain-stress curve. The epithelium of mucosal strips was deeply folded at low strains (0 -0.15), which in bronchial segments equated to Յ10 cmH2O transmural pressure. Morphometric measurements in mucosal strips at greater strains (0.3-0.4) indicated that epithelial length increased by ϳ10%. Measurements in bronchial segments indicated that epithelial length increased ϳ25% between 5 and 25 cmH2O. Our findings suggest that, at airway pressures Ͻ10 cmH2O, airway expansion is due primarily to epithelial unfolding but at higher pressures the epithelium also distends. mucosal folds; epithelium; airway mechanics THE AIRWAY MUCOSA HAS SEVERAL important roles in airway and lung biology. The mucosa contributes to mechanical properties of the airway wall that may influence the degree of airway expansion produced by lung inflation and the extent to which the airway narrows in response to bronchoconstrictor substances. The mucosa comprises the epithelium (with its basement membrane), lamina propria glands, vascular tissue, and an elastic matrix. The epithelium is a continuous layer of cells, with numerous folds that deepen on lung deflation or airway smooth muscle (ASM) contraction (9, 12). By its position internal to ASM, the mucosa imposes an afterload on ASM that may be substantial enough to restrict ASM shortening and, thus, active airway narrowing in response to bronchoconstrictor substances (5, 12). Elastic properties of the mucosa also contribute to the pressure-volume behavior of the airway wall. On lung inflation, the airway lumen expands and the depth of epithelial folds is progressively reduced, which help accommodate the increased volume of the airway lumen (4, 5, 10).Structural and mechanical properties of the mucosa potentially affect the response of the airway wall to lung inflation, deflation, and ASM contraction.Folding properties of the epithelium relevant to ASM contraction have been widely studied (4 -6, 10, 12). The mechanisms of mucosal expansion during lung inflation are less ...

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Section: Discussionsupporting

confidence: 93%

Elastic properties of the bronchial mucosa: epithelial unfolding and stretch in response to airway inflation

Noble¹,

Sharma²,

McFawn³

et al. 2005

Journal of Applied Physiology

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“…One possibility is that stimulation changes the shape of the airway, from oval to circular. Studies in pulmonary airways show that when the pressure surrounding a circular, collapsible tube is greater than the pressure inside the tube, the tube assumes an oval shape (43). Once this critical event is initiated, the tube becomes progressively flatter as the transmural pressure difference continues to increase.…”

Section: Velopharyngeal Cdyn and Critical Collapsing Pressure: Passivmentioning

confidence: 99%

Regional velopharyngeal compliance in the rat: influence of tongue muscle contraction

et al. 2007

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The velopharynx is the most collapsible segment of the upper airway in patients with obstructive sleep apnea. However, we do not know if velopharyngeal compliance is uniform throughout its length, or if compliance is modified by contraction of upper airway muscles. We tested the hypothesis that rostral and caudal velopharyngeal (VP) compliance differs, and that tongue muscle contraction reduces compliance. High-resolution MR images of the VP were made at nasopharyngeal pressures ranging from -9 to 9 cmH(2)O in anesthetized rats. Images were obtained twice at each pressure, once with and once without bilateral hypoglossal nerve stimulation. The volume of the caudal and rostral VP was computed at each pressure. The caudal VP was significantly (P = 0.0058) more compliant than the rostral VP, but electrical stimulation of the tongue muscles did not change compliance. VP critical pressure (Pcrit; pressure at zero airway volume) averaged -25.2 and -12.1 cmH(2)O in the rostral and caudal VP, respectively (P < 0.0001). Coactivation of tongue protrudor and retractor muscles or contraction of protrudor muscles alone dilated the VP and made Pcrit more negative (P < 0.0001), but only in the caudal VP. In the rat, the caudal VP is more collapsible than the rostral VP, and either coactivation of tongue protrudor and retractor muscles or contraction of protrudor muscles alone makes this region more difficult to close. Thus, tongue muscle contraction protects the caudal VP, which appears to be a particularly vulnerable segment of the nasopharyngeal airway. With suitable modification, the methods described here, including tongue muscle stimulation at different pharyngeal pressures, may be appropriate for experiments in human subjects.

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“…In the previous works, three methods were reported to evaluate the localized airway deformations. One approach is to visualize dehydrated and fixed preparations by using optical microscopy (Klingele and Staub, 1971;Okazawa et al, 2000). Another approach is to insufflate a metal powder into a lung as a contrast agent and visualized using bronchogram (Hughes et al, 1972;Menkes et al, 1972;Sittipong et al, 1974).…”

Section: Introductionmentioning

confidence: 99%

Morphometric Deformations of Small Airways and Alveoli under Quasi-static Inflation Process

Sera¹,

Uesugi²,

Yagi³

2005

J. Physiol. Anthropol.

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Localized morphometric deformations of small airways and alveoli during respiration have many biomedical and physiological implications. We developed fast synchrotron radiation CT system to visualize the small airways and alveoli of an intact mouse lung without fixation and dehydration, and analyzed their localized morphometric deformations between functional residual capacity (FRC) and total lung capacity (TLC). In the diameter behavior, the averaged and range values were significantly larger for smaller airways (68.8%, range: 0.36-0.89) than larger airways (45.2%, range: 0.40-0.57). These results indicated that the airway did not deformed in same manner and that these morphological differences characterized the heterogeneous lung function.

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Compliance of peripheral airways deduced from morphometry

Cited by 23 publications

References 22 publications

Elastic properties of the bronchial mucosa: epithelial unfolding and stretch in response to airway inflation

Elastic properties of the bronchial mucosa: epithelial unfolding and stretch in response to airway inflation

Regional velopharyngeal compliance in the rat: influence of tongue muscle contraction

Morphometric Deformations of Small Airways and Alveoli under Quasi-static Inflation Process

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