Airway Tree Model Of Lung Recruitment: Effect Of Alveolar Compliance On Pressure Volume Fluctuations

2010 ◽  
Author(s):  
Samir Amin ◽  
Henrique T. Moriya ◽  
Béla Suki ◽  
Adriano M. Alencar
Keyword(s):  
Lung Recruitment ◽  
Tree Model ◽  
Volume Fluctuations ◽  
Airway Tree ◽  
Recruitment Effect

Stochastic model of the pulmonary airway tree and its implications for bronchial responsiveness

1993 ◽  
Vol 75 (6) ◽  
pp. 2493-2499 ◽  
Author(s):  
J. H. Bates
Keyword(s):  
Theoretical Calculations ◽  
Distribution Functions ◽  
Relative Width ◽  
Tree Model ◽  
Bronchial Responsiveness ◽  
Probability Distribution Functions ◽  
Conducting Airway ◽  
Generation Number ◽  
Airway Tree ◽  
The Individual

The resistance of the pulmonary conducting airway tree (Raw) is a consequence of the resistances of its component airways and how they are connected together. To date, theoretical calculations of Raw have been performed with the aid of mathematical models of the airway tree that are purely deterministic. That is, the mechanical properties of the component airways in these models are precisely defined functions of generation number. Such models take no account of the fact that the airways of a given generation are not all exactly the same but rather exhibit a spectrum of wall thicknesses, amounts of smooth muscle, and number of parenchymal attachments. In the present study, the properties of a 10-generation stochastic airway tree model are investigated. The lengths and radii of the airways in the tree are drawn randomly from probability distribution functions (PDFs), the means of which are deterministic functions of generation number and the standard deviations are assigned various values. Monte Carlo simulation is used to estimate the PDF of Raw itself in various conditions. We show that the relative width of the PDF of Raw may be comparable to that of the PDFs from which the individual airway radii were drawn. It is also shown that when bronchoconstriction is simulated by narrowing each airway by a random amount the resulting PDF for Raw may increase in width many times. We conclude that the variations in airway responsiveness seen in nature can only be properly understood when the distribution of airway properties within the lung are taken into account.

scholarly journals Transient Dynamics Simulation of Airflow in a CT-Scanned Human Airway Tree: More or Fewer Terminal Bronchi?

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Shouliang Qi ◽  
Baihua Zhang ◽  
Yueyang Teng ◽  
Jianhua Li ◽  
Yong Yue ◽  
...  
Keyword(s):  
Flow Pattern ◽  
Temporal Variations ◽  
Area Ratio ◽  
Dynamics Simulation ◽  
Tree Model ◽  
Computational Fluid Dynamics Cfd ◽  
Airway Tree ◽  
The Difference ◽  
Cfd Method ◽  
Airway Model

Using computational fluid dynamics (CFD) method, the feasibility of simulating transient airflow in a CT-based airway tree with more than 100 outlets for a whole respiratory period is studied, and the influence of truncations of terminal bronchi on CFD characteristics is investigated. After an airway model with 122 outlets is extracted from CT images, the transient airflow is simulated. Spatial and temporal variations of flow velocity, wall pressure, and wall shear stress are presented; the flow pattern and lobar distribution of air are gotten as well. All results are compared with those of a truncated model with 22 outlets. It is found that the flow pattern shows lobar heterogeneity that the near-wall air in the trachea is inhaled into the upper lobe while the center flow enters the other lobes, and the lobar distribution of air is significantly correlated with the outlet area ratio. The truncation decreases airflow to right and left upper lobes and increases the deviation of airflow distributions between inspiration and expiration. Simulating the transient airflow in an airway tree model with 122 bronchi using CFD is feasible. The model with more terminal bronchi decreases the difference between the lobar distributions at inspiration and at expiration.

scholarly journals The Role of Airway Shunt Elastance on the Compartmentalization of Respiratory System Impedance

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Jason H. T. Bates
Keyword(s):  
Respiratory System ◽  
Upper Airway ◽  
Inverse Model ◽  
Tree Model ◽  
Upper Airways ◽  
Peripheral Airways ◽  
Pulmonary Airways ◽  
Peripheral Airway ◽  
In Series ◽  
Airway Tree

An inverse model consisting of two elastic compartments connected in series and served by two airway conduits has recently been fit to measurements of respiratory impedance in obese subjects. Increases in the resistance of the distal conduit of the model with increasing body mass index have been linked to peripheral airway compression by mass loading of the chest wall. Nevertheless, how the two compartments and conduits of this simple model map onto the vastly more complicated structure of an actual lung remain unclear. To investigate this issue, we developed a multiscale branching airway tree model of the respiratory system that predicts realistic input impedance spectra between 5 and 20 Hz with only four free parameters. We use this model to study how the finite elastances of the conducting airway tree and the proximal upper airways affect impedance between 5 and 20 Hz. We show that progressive constriction of the peripheral airways causes impedance to appear to arise from two compartments connected in series, with the proximal compartment being a reflection of the elastance of upper airway structures proximal to the tracheal entrance and the lower compartment reflecting the pulmonary airways and tissues. We thus conclude that while this simple inverse model allows evaluation of overall respiratory system impedance between 5 and 20 Hz in the presence of upper airway shunting, it does not allow the separate contributions of central versus peripheral pulmonary airways to be resolved.

Numerical simulation of the tree higro-thermal response in forest fire environment

2020 ◽  
pp. 57-65
Author(s):  
Eusébio Conceiçã ◽  
João Gomes ◽  
Maria Manuela Lúcio ◽  
Jorge Raposo ◽  
Domingos Xavier Viegas ◽  
...  
Keyword(s):  
Forest Fire ◽  
Numerical Study ◽  
Thermal Response ◽  
View Factor ◽  
Tree Model ◽  
Pine Tree ◽  
Surface Temperatures ◽  
Fire Environment ◽  
Fire Front ◽  
Heat Exchanges

This paper refers to a numerical study of the hypo-thermal behaviour of a pine tree in a forest fire environment. The pine tree thermal response numerical model is based on energy balance integral equations for the tree elements and mass balance integral equation for the water in the tree. The simulation performed considers the heat conduction through the tree elements, heat exchanges by convection between the external tree surfaces and the environment, heat exchanges by radiation between the flame and the external tree surfaces and water heat loss by evaporation from the tree to the environment. The virtual three-dimensional tree model has a height of 7.5 m and is constituted by 8863 cylindrical elements representative of its trunks, branches and leaves. The fire front has 10 m long and a 2 m high. The study was conducted taking into account that the pine tree is located 5, 10 or 15 m from the fire front. For these three analyzed distances, the numerical results obtained regarding to the distribution of the view factors, mean radiant temperature and surface temperatures of the pine tree are presented. As main conclusion, it can be stated that the values of the view factor, MRT and surface temperatures of the pine tree decrease with increasing distance from the pine tree in front of fire.

The Arabic Origins of English and Indo-European “Definite Articles”: A Radical Linguistic Theory Approach

2016 ◽  
Vol 4 (6) ◽  
pp. 26
Author(s):  
Zaidan Ali Jassem
Keyword(s):  
Comparative Method ◽  
Linguistic Theory ◽  
General Level ◽  
Theory Approach ◽  
Tree Model ◽  
Linguistic Change ◽  
European Languages ◽  
The Family ◽  
Different Types ◽  
Definite Articles

This paper traces the Arabic origins or cognates of the “definite articles” in English and Indo-European languages from a radical linguistic (or lexical root) theory perspective. The data comprises the definite articles in English, German, French, Spanish, Portuguese, Italian, Romanian, Latin, Greek, Macedonian, Russian, Polish, Sanskrit, Hindi, Bengali, Persian, and Arabic. The results clearly indicate that five different types of such articles emerged in the data, all of which have true Arabic cognates with the same or similar forms and meanings, whose differences are due to natural and plausible causes and different routes of linguistic change, especially lexical, semantic, or morphological shift. Therefore, the results support the adequacy of the radical linguistic theory according to which, unlike the Family Tree Model or Comparative Method, Arabic, English, German, French, Latin, Greek, and Sanskrit not only belong to the same language family, renamed Eurabian or Urban family, but also are dialects of the same language, with Arabic being their origin all because only it shares the whole cognates with them all and because it has a huge phonetic, morphological, grammatical, and lexical variety. They also manifest fundamental flaws and grave drawbacks which plague English and Indo-European lexicography for ignoring Arabic as an ultimate ancestor and progenitor not only in the treatment of the topic at hand but in all others in general. On a more general level, they also show that there is a radical language from which all human languages stemmed and which has been preserved almost intact in Arabic, thus being the most conservative and productive language

Assessing the Risk of Noncompliance in Wastewater Treatment

1992 ◽  
Vol 26 (5-6) ◽  
pp. 1411-1420 ◽  
Author(s):  
S. H. Choudhury ◽  
S. L. Yu ◽  
Y. Y. Haimes
Keyword(s):  
Wastewater Treatment ◽  
Wastewater Treatment Plant ◽  
Fault Tree ◽  
Treatment Plant ◽  
Risk Identification ◽  
System Component ◽  
System Failure ◽  
Tree Model ◽  
Risk Quantification ◽  
Failure Probabilities

This paper presents an integrated methodology that allows determining the probability of noncompliance for a given wastewater treatment plant. The methodology applies fault-tree analysis, which uses failure probabilities of individual components, to predict the overall system failure probability. The methodology can be divided into two parts : risk identification and risk quantification. In risk identification, the key components in the system are determined by analyzing the contribution of individual component failures toward system failure (i.e., noncompliance). In risk quantification, a fault-tree model is constructed for the particular system, component failure probabilities are estimated, and the fault-tree model is evaluated to determine the probability of occurrence of the top event (i.e., noncompliance). A list can be developed that ranks critical events on the basis of their contributions to the probability of noncompliance. Such a ranking should assist managers to determine which components require most attention for a better performance of the entire system. A wastewater treatment plant for treating metal-bearing rinse water from an electroplating industry is used as an example to demonstrate the application of this methodology.

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