Pulmonary Acinus

2020 ◽  
Author(s):  
Keyword(s):  
Pulmonary Acinus

Hamiltonian Chaos in a Model Alveolus

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
F. S. Henry ◽  
F. E. Laine-Pearson ◽  
A. Tsuda
Keyword(s):  
Reynolds Number ◽  
Fixed Point ◽  
Lyapunov Exponent ◽  
Fine Particles ◽  
Hamiltonian Dynamics ◽  
Maximal Lyapunov Exponent ◽  
Poincaré Sections ◽  
Pulmonary Acinus ◽  
Hamiltonian Chaos ◽  
Poincare Sections

In the pulmonary acinus, the airflow Reynolds number is usually much less than unity and hence the flow might be expected to be reversible. However, this does not appear to be the case as a significant portion of the fine particles that reach the acinus remains there after exhalation. We believe that this irreversibility is at large a result of chaotic mixing in the alveoli of the acinar airways. To test this hypothesis, we solved numerically the equations for incompressible, pulsatile, flow in a rigid alveolated duct and tracked numerous fluid particles over many breathing cycles. The resulting Poincaré sections exhibit chains of islands on which particles travel. In the region between these chains of islands, some particles move chaotically. The presence of chaos is supported by the results of an estimate of the maximal Lyapunov exponent. It is shown that the streamfunction equation for this flow may be written in the form of a Hamiltonian system and that an expansion of this equation captures all the essential features of the Poincaré sections. Elements of Kolmogorov–Arnol’d–Moser theory, the Poincaré–Birkhoff fixed-point theorem, and associated Hamiltonian dynamics theory are then employed to confirm the existence of chaos in the flow in a rigid alveolated duct.

Roentgenographic Appearance of the Human Pulmonary Acinus

1971 ◽  
Vol 6 (3) ◽  
pp. 171-175 ◽  
Author(s):  
G. Gamsu ◽  
W. M. Thurlbeck ◽  
P. T. Macklem ◽  
R. G. Fraser
Keyword(s):  
Pulmonary Acinus

Deposition of Submicron Particles by Chaotic Mixing in the Pulmonary Acinus

2021 ◽  
pp. 145-161
Author(s):  
Akira Tsuda ◽  
Frank S. Henry
Keyword(s):  
Fluid Particle ◽  
Submicron Particles ◽  
Chaotic Mixing ◽  
Breathing Frequency ◽  
Particle Trajectories ◽  
Recirculating Flow ◽  
Pulmonary Acinus ◽  
Inhaled Particles ◽  
Hamiltonian Chaos ◽  
Qualitative Changes

In this review, the authors outline the evidence that emerged some 30 years ago that the mechanisms thought responsible for the deposition of submicron particles in the respiratory region of the lung were inadequate to explain the measured rate of deposition. They then discuss the background and theory of what is believed to be the missing mechanism, namely chaotic mixing. Specifically, they outline how that the recirculating flow in the alveoli has a range of frequencies of oscillation and some of these resonate with the breathing frequency. If the system is perturbed, the resonating frequencies break into chaos, and they discuss a number of practical ways in which the system can be disturbed. The perturbation of fluid particle trajectories results in Hamiltonian chaos, which produces qualitative changes in those trajectories. They end the review with a discussion of the effects of chaotic mixing on the deposition of inhaled particles in the respiratory region of the lung.

Gas mixing in a model of the pulmonary acinus with asymmetrical alveolar ducts

1982 ◽  
Vol 52 (3) ◽  
pp. 624-633 ◽  
Author(s):  
C. Bowes ◽  
G. Cumming ◽  
K. Horsfield ◽  
J. Loughhead ◽  
S. Preston
Keyword(s):  
Molecular Diffusion ◽  
Dimensional Change ◽  
Normal Subjects ◽  
Mixing Efficiency ◽  
Gas Mixing ◽  
Alveolar Plateau ◽  
Pulmonary Acinus ◽  
Simple Boundary ◽  
Alveolar Duct ◽  
Asymmetrical Model

An asymmetrical model of the human pulmonary acinus is described, in which elements of volume are represented by nodes joined by conductors permitting convective flow and molecular diffusion. The method of analysis permits simultaneous convection, diffusion, and dimensional change in any direction and requires only simple boundary conditions. Inspiration of O2 into a resident gas of 79% N2 followed by expiration was simulated at two flows. On expiration the slope of the alveolar plateau was 1.7%, and the alveolar N2 mixing efficiency was 97.0%. A symmetrical but otherwise similar model gave a slope of zero and a mixing efficiency of 99.9%. The patterns of gas concentration within the asymmetrical acinus during the respiratory cycle confirm and extend previous observations on the interactions between simultaneous convection and diffusion in asymmetrical structures (16, 21, 22). Even though these in combination within alveolar duct asymmetry can account for the slope of the alveolar plateau, they are insufficient to account for the failure of complete gas mixing found in normal subjects.

scholarly journals Perfusion heterogeneity in the pulmonary acinus

1998 ◽  
Vol 84 (3) ◽  
pp. 933-938 ◽  
Author(s):  
Nobuhiro Tanabe ◽  
Thomas M. Todoran ◽  
Gerald M. Zenk ◽  
Brenda R. Bunton ◽  
Wiltz W. Wagner ◽  
...  
Keyword(s):  
Blood Flow ◽  
Fluorescence Microscopy ◽  
Capillary Blood ◽  
Fluorescent Dye ◽  
Time Difference ◽  
Appearance Time ◽  
Pulmonary Acinus ◽  
The Mean ◽  
The Difference ◽  
Dilution Curves

There is little information on the distribution of acinar perfusion because it is difficult to resolve blood flow within such small regions. We hypothesized that the known heterogeneity of arteriolar blood flow and capillary blood flow would result in heterogeneous acinar perfusion. To test this hypothesis, the passage of fluorescent dye boluses through the subpleural microcirculation of isolated dog lobes was videotaped by using fluorescence microscopy. As the videotapes were replayed, dye-dilution curves were recorded from each of the tributary branches of Y-shaped venules that drained an acinus. From the dye curves, we calculated the mean appearance time of each curve. The difference in mean appearance times between venular tributary branches was small in most cases. In 43% of the observed venular branch pairs, the dye curves were essentially superimposable (the mean appearance-time difference was <5%); and in another 42%, the mean appearance-time difference between curves was 5–10%. From these results, we conclude that acinar perfusion is unexpectedly homogeneous.

scholarly journals A Semiautomatic Segmentation Algorithm for Extracting the Complete Structure of Acini from Synchrotron Micro-CT Images

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Luosha Xiao ◽  
Toshihiro Sera ◽  
Kenichiro Koshiyama ◽  
Shigeo Wada
Keyword(s):  
Statistical Analysis ◽  
Gas Exchange ◽  
Ct Images ◽  
Segmentation Algorithm ◽  
Micro Ct ◽  
Complete Structure ◽  
Pulmonary Acinus ◽  
Semiautomatic Segmentation ◽  
Binary Image Processing ◽  
Processing Techniques

Pulmonary acinus is the largest airway unit provided with alveoli where blood/gas exchange takes place. Understanding the complete structure of acinus is necessary to measure the pathway of gas exchange and to simulate various mechanical phenomena in the lungs. The usual manual segmentation of a complete acinus structure from their experimentally obtained images is difficult and extremely time-consuming, which hampers the statistical analysis. In this study, we develop a semiautomatic segmentation algorithm for extracting the complete structure of acinus from synchrotron micro-CT images of the closed chest of mouse lungs. The algorithm uses a combination of conventional binary image processing techniques based on the multiscale and hierarchical nature of lung structures. Specifically, larger structures are removed, while smaller structures are isolated from the image by repeatedly applying erosion and dilation operators in order, adjusting the parameter referencing to previously obtained morphometric data. A cluster of isolated acini belonging to the same terminal bronchiole is obtained without floating voxels. The extracted acinar models above 98% agree well with those extracted manually. The run time is drastically shortened compared with manual methods. These findings suggest that our method may be useful for taking samples used in the statistical analysis of acinus.

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