Zero-stress state of intra- and extraparenchymal airways from human, pig, rabbit, and sheep lung

2002 ◽  
Vol 92 (3) ◽  
pp. 1261-1266 ◽  
Author(s):  
Karen O. McKay ◽  
Barry R. Wiggs ◽  
Peter D. Paré ◽  
Roger D. Kamm
Keyword(s):  
Stress State ◽  
Regional Differences ◽  
Computational Models ◽  
Transmural Pressure ◽  
Opening Angle ◽  
Airway Wall ◽  
Small Opening ◽  
Airway Narrowing ◽  
Airway Tree ◽  
Large Opening

Alterations in airway wall anatomic properties and the consequential effects on airway narrowing have been assessed by use of computational models. In these models, it is generally assumed that at zero transmural pressure the airway wall exists in a zero-stress state. Many studies have shown that this is often not the case, as evidenced by a nonzero opening angle. In this study, we measured the opening angle of airway rings at zero transmural pressure to test this assumption. The airway tree was dissected from human, pig, sheep, and rabbit lungs. Airways were excised from the tree, and the opening angle was measured. There were obvious species and regional differences in opening angle. Rabbit airways from both extraparenchymal and intraparenchymal sites exhibited marked opening angles (7–82°). Extraparenchymal airways from sheep had large opening angles (up to 50°), but ovine intraparenchymal airways had small opening angles. Measurable opening angles were rarely observed in human and porcine airways of any size. The assumption of a stable zero-stress state at zero transmural pressure is therefore valid for human and porcine, but not rabbit and sheep, airways.

Airway smooth muscle orientation in intraparenchymal airways

1997 ◽  
Vol 82 (1) ◽  
pp. 70-77 ◽  
Author(s):  
M. Lei ◽  
H. Ghezzo ◽  
M. F. Chen ◽  
D. H. Eidelman
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Serial Sections ◽  
Airway Wall ◽  
Transverse Axis ◽  
Mean Values ◽  
Airway Narrowing ◽  
Human Specimen ◽  
The Mean ◽  
Airway Tree

Lei, M., H. Ghezzo, M. F. Chen, and D. H. Eidelman.Airway smooth muscle orientation in intraparenchymal airways. J. Appl. Physiol. 82(1): 70–77, 1997.—Airway smooth muscle (ASM) shortening is the central event leading to bronchoconstriction. The degree to which airway narrowing occurs as a consequence of shortening is a function of both the mechanical properties of the airway wall as well as the orientation of the muscle fibers. Although the latter is theoretically important, it has not been systematically measured to date. The purpose of this study was to determine the angle of orientation of ASM (θ) in normal lungs by using a morphometric approach. We analyzed the airway tree of the left lower lobes of four cats and one human. All material was fixed with 10% buffered Formalin at a pressure of 25 cmH2O for 48 h. The fixed material was dissected along the airway tree to permit isolation of generations 4–18 in the cats and generations 5–22 in the human specimen. Each airway generation was individually embedded in paraffin. Five-micrometer-thick serial sections were cut parallel to the airway long axis and stained with hematoxylin-phloxine-saffron. Each block yielded three to five sections containing ASM. To determine θ, we measured the orientation of ASM nuclei relative to the transverse axis of the airway by using a digitizing tablet and a light microscope (×250) equipped with a drawing tube attachment. Inspection of the sections revealed extensive ASM crisscrossing without a homogeneous orientation. The θ was clustered between −20° and 20° in all airway generations and did not vary much between generations in any of the cats or in the human specimen. When θ was expressed without regard to sign, the mean values were 13.2° in the cats and 13.1° in the human. This magnitude of obliquity is not likely to result in physiologically important changes in airway length during bronchoconstriction.

scholarly journals Airway Transmural Pressures in an Airway Tree During Bronchoconstriction in Asthma

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Tilo Winkler
Keyword(s):  
Experimental Studies ◽  
Bronchial Tree ◽  
Relative Increase ◽  
Transmural Pressure ◽  
Dynamic Hyperinflation ◽  
Airway Narrowing ◽  
Wilson Model ◽  
Airway Tree ◽  
The Difference ◽  
The Individual

Airway transmural pressure in healthy homogeneous lungs with dilated airways is approximately equal to the difference between intraluminal and pleural pressure. However, bronchoconstriction causes airway narrowing, parenchymal distortion, dynamic hyperinflation, and the emergence of ventilation defects (VDefs) affecting transmural pressure. This study aimed to investigate the changes in transmural pressure caused by bronchoconstriction in a bronchial tree. Transmural pressures before and during bronchoconstriction were estimated using an integrative computational model of bronchoconstriction. Briefly, this model incorporates a 12-generation symmetric bronchial tree, and the Anafi and Wilson model for the individual airways of the tree. Bronchoconstriction lead to the emergence of VDefs and a relative increase in peak transmural pressures of up to 84% compared to baseline. The highest increase in peak transmural pressure occurred in a central airway outside of VDefs, and the lowest increase was 27% in an airway within VDefs illustrating the heterogeneity in peak transmural pressures within a bronchial tree. Mechanisms contributing to the increase in peak transmural pressures include increased regional ventilation and dynamic hyperinflation both leading to increased alveolar pressures compared to baseline. Pressure differences between intraluminal and alveolar pressure increased driven by the increased airway resistance and its contribution to total transmural pressure reached up to 24%. In conclusion, peak transmural pressure in lungs with VDefs during bronchoconstriction can be substantially increased compared to dilated airways in healthy homogeneous lungs and is highly heterogeneous. Further insights will depend on the experimental studies taking these conditions into account.

Research of the Connecting Form about the Spherical Shell and the Nozzle

2011 ◽  
Vol 413 ◽  
pp. 520-523
Author(s):  
Cai Xia Luo
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Finite Element Model ◽  
Spherical Shell ◽  
Maximum Stress ◽  
Peak Stress ◽  
Element Model ◽  
Small Opening ◽  
Large Opening ◽  
Reducing Stress

The Stress Distribution in the Connection of the Spherical Shell and the Opening Nozzle Is Very Complex. Sharp-Angled Transition and Round Transition Are Used Respectively in the Connection in the Light of the Spherical Shell with the Small Opening and the Large One. the Influence of the Two Connecting Forms on Stress Distribution Is Analyzed by Establishing Finite Element Model and Solving it. the Result Shows there Is Obvious Stress Concentration in the Connection. Round Transition Can Reduce the Maximum Stress in Comparison with Sharp-Angled Transition in both Cases of the Small Opening and the Large Opening, Mainly Reducing the Bending Stress and the Peak Stress, but Not the Membrane Stress. the Effect of Round Transition on Reducing Stress Was Not Significant. so Sharp-Angled Transition Should Be Adopted in the Connection when a Finite Element Model Is Built for Simplification in the Future.

scholarly journals Revealing the Mass Loss Structures of Four Key Massive Binaries Using Optical Spectropolarimetry

2014 ◽  
Vol 9 (S307) ◽  
pp. 336-341
Author(s):  
Jamie R. Lomax
Keyword(s):  
Mass Loss ◽  
Binary Systems ◽  
Hot Spot ◽  
Polarized Light ◽  
Opening Angle ◽  
Geometric Information ◽  
Intrinsic Polarization ◽  
Polarization Component ◽  
Circumstellar Material ◽  
Large Opening

AbstractThe majority of massive stars are members of binary systems. However, in order to understand their evolutionary pathways, mass and angular momentum loss from these systems needs to be well characterized. Self-consistent explanations for their behavior across many wavelength regimes need to be valid in order to illuminate key evolutionary phases. I present the results of linear spectropolarimetric studies of three key binaries (β Lyrae, V356 Sgr, V444 Cyg, and WR 140) which reveal important geometric information about their circumstellar material. β Lyrae exhibits a repeatable discrepancy between secondary eclipse in the total and polarized light curves that indicates an accretion hot spot has formed on the edge of the disk in the system. The existence of this hot spot and its relationship to bipolar outflows within the system is important in the understanding of mass transfer dynamics in Roche-lobe overflow binaries. Preliminary work on V356 Sgr suggests the system maybe surrounded by a common envelope. V444 Cyg shows evidence that its shock creates a cone with a large opening angle of missing material around the WN star. This suggests the effects of radiative inhibition or braking, can be significant contributors to the location and shape of the shock within colliding wind binaries. The intrinsic polarization component of WR 140 is likely due to the formation of dust within the system near periastron passages. Continued work on these and additional objects will provide new and important constraints on the mass loss structures within binary systems.

Regional diastolic mechanics of the left ventricle in the conscious dog

1979 ◽  
Vol 236 (2) ◽  
pp. H323-H330 ◽  
Author(s):  
D. Ling ◽  
J. S. Rankin ◽  
C. H. Edwards ◽  
P. A. McHale ◽  
R. W. Anderson
Keyword(s):  
Left Ventricle ◽  
Pressure Gradient ◽  
Regional Differences ◽  
Diastolic Pressure ◽  
Left Ventricular ◽  
Transmural Pressure ◽  
Diastolic Filling ◽  
Rapid Phase ◽  
Conscious Dog ◽  
Dynamic Relationship

In eight chronically instrumented conscious dogs, apical and middle left ventricular transverse diameters were measured with pulse-transit ultrasonic dimension transducers. Intracavitary apical and midventricular pressures and intrapleural pressure were measured with micromanometers. Both diameters were normalized as a percent extension from the dimension at zero transmural pressure, determined during a transient vena caval occlusion. During the rapid phase of diastolic filling, there was a 2--5 mmHg pressure gradient from the midventricle to the apex. During late rapid filling, the apical transmural pressure and diameter increased more rapidly and reached diastasis 17 +/- 4 ms earlier than the corresponding midventricular measurements (P less than 0.01). The static diastolic pressure-dimension characteristics at the apical and midventricular levels were not significantly different (P greater than 0.30). The dynamic diastolic pressure-dimension relationship was also similar at the two levels and could be represented by a model incorporating parallel viscous properties. Because of regional differences in pressures and dimensions, however, the dynamic relationship could not be modeled when pressure was compared to the dimension at a different level. Thus, diastolic pressures should be measured at the same level as dimensions when assessing left ventricular diastolic mechanics.

scholarly journals Decreased airway narrowing and smooth muscle contraction in hyperresponsive pigs

2002 ◽  
Vol 93 (4) ◽  
pp. 1296-1300 ◽  
Author(s):  
Debra J. Turner ◽  
Peter B. Noble ◽  
Matthew P. Lucas ◽  
Howard W. Mitchell
Keyword(s):  
Smooth Muscle ◽  
Airway Hyperresponsiveness ◽  
Porcine Model ◽  
Smooth Muscle Contraction ◽  
Airway Wall ◽  
Muscle Contractility ◽  
Smooth Muscle Contractility ◽  
Airway Narrowing

Increased smooth muscle contractility or reduced smooth muscle mechanical loads could account for the excessive airway narrowing and hyperresponsiveness seen in asthma. These mechanisms were investigated by using an allergen-induced porcine model of airway hyperresponsiveness. Airway narrowing to electric field stimulation was measured in isolated bronchial segments, over a range of transmural pressures (0–20 cmH2O). Contractile responses to ACh were measured in bronchial segments and in isolated tracheal smooth muscle strips isolated from control and test (ovalbumin sensitized and challenged) pigs. Test airways narrowed less than controls ( P < 0.0001). Test pigs showed reduced contractility to ACh, both in isolated bronchi ( P < 0.01) and smooth muscle strips ( P < 0.01). Thus isolated airways from pigs exhibiting airway hyperresponsiveness in vivo are hyporesponsive in vitro. The decreased narrowing in bronchi from hyperresponsive pigs may be related to decreased smooth muscle contractility. These data suggest that mechanisms external to the airway wall may be important to the hyperresponsive nature of sensitized lungs.

scholarly journals Dynamic airway constriction in rats: heterogeneity and response to deep inspiration

2019 ◽  
Vol 317 (1) ◽  
pp. L39-L48
Author(s):  
Thien-Khoi N. Phung ◽  
Scott E. Sinclair ◽  
Patrudu Makena ◽  
Robert C. Molthen ◽  
Christopher M. Waters
Keyword(s):  
Computational Models ◽  
Small Airways ◽  
Respiratory Resistance ◽  
Dynamic Changes ◽  
Airway Narrowing ◽  
Airway Constriction ◽  
X Ray Imaging ◽  
Model Predictions ◽  
Dose Dependent Increase ◽  
Dose Dependent

Airway narrowing due to hyperresponsiveness severely limits gas exchange in patients with asthma. Imaging studies in humans and animals have shown that bronchoconstriction causes patchy patterns of ventilation defects throughout the lungs, and several computational models have predicted that these regions are due to constriction of smaller airways. However, these imaging approaches are often limited in their ability to capture dynamic changes in small airways, and the patterns of constriction are heterogeneous. To directly investigate regional variations in airway narrowing and the response to deep inspirations (DIs), we utilized tantalum dust and microfocal X-ray imaging of rat lungs to obtain dynamic images of airways in an intact animal model. Airway resistance was simultaneously measured using the flexiVent system. Custom-developed software was used to track changes in airway diameters up to generation 19 (~0.3–3 mm). Changes in diameter during bronchoconstriction were then measured in response to methacholine (MCh) challenge. In contrast with the model predictions, we observed significantly greater percent constriction in larger airways in response to MCh challenge. Although there was a dose-dependent increase in total respiratory resistance with MCh, the percent change in airway diameters was similar for increasing doses. A single DI following MCh caused a significant reduction in resistance but did not cause a significant increase in airway diameters. Multiple DIs did, however, cause significant increases in airway diameters. These measurements allowed us to directly quantify dynamic changes in airways during bronchoconstriction and demonstrated greater constriction in larger airways.

scholarly journals BrdU Pulse LabellingIn Vivoto Characterise Cell Proliferation during Regeneration and Repair following Injury to the Airway Wall in Sheep

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
B. Yahaya ◽  
G. McLachlan ◽  
D. D. S. Collie
Keyword(s):  
Cell Proliferation ◽  
Proliferative Activity ◽  
Histological Analysis ◽  
S Phase ◽  
Pulse Labelling ◽  
Airway Wall ◽  
Brush Biopsy ◽  
Cell Proliferative Activity ◽  
Airway Tree

The response of S-phase cells labelled with bromodeoxyuridine (BrdU) in sheep airways undergoing repair in response to endobronchial brush biopsy was investigated in this study. Separate sites within the airway tree of anaesthetised sheep were biopsied at intervals prior to pulse labelling with BrdU, which was administered one hour prior to euthanasia. Both brushed and spatially disparate unbrushed (control) sites were carefully mapped, dissected, and processed to facilitate histological analysis of BrdU labelling. Our study indicated that the number and location of BrdU-labelled cells varied according to the age of the repairing injury. There was little evidence of cell proliferation in either control airway tissues or airway tissues examined six hours after injury. However, by days 1 and 3, BrdU-labelled cells were increased in number in the airway wall, both at the damaged site and in the regions flanking either side of the injury. Thereafter, cell proliferative activity largely declined by day 7 after injury, when consistent evidence of remodelling in the airway wall could be appreciated. This study successfully demonstrated the effectiveness ofin vivopulse labelling in tracking cell proliferation during repair which has a potential value in exploring the therapeutic utility of stem cell approaches in relevant lung disease models.

scholarly journals Hubble Space Telescope Imaging of the Disks and Jets of Taurus Young Stellar Objects

1997 ◽  
Vol 182 ◽  
pp. 355-364 ◽  
Author(s):  
Karl Stapelfeldt ◽  
Christopher J. Burrows ◽  
John E. Krist ◽  
Keyword(s):  
High Spatial Resolution ◽  
Hubble Space Telescope ◽  
Scattered Light ◽  
Young Stellar Objects ◽  
Opening Angle ◽  
Stellar Objects ◽  
Space Telescope ◽  
Spread Function ◽  
Large Opening ◽  
T Tau

We report on Hubble Space Telescope imaging of eleven young stellar objects in the nearby Taurus molecular clouds. The high spatial resolution and stable point spread function of HST reveal important new details of the circumstellar nebulosity of these objects. Three sources (HH 30, FS Tau B, and DG Tau B) are resolved as compact bipolar nebulae without a directly visible star. In all three cases, jet widths near the sources are found to be 50 AU or less. Flattened disk structures are seen in absorption in HH 30 and FS Tau B, and in reflection about GM Aur. Extended envelope structures traced by scattered light are present in HL Tau, T Tau, DG Tau, and FS Tau. The jet in DG Tau exhibits a large opening angle and is already resolved into a bow-like structure less than 3″ from the star.

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