Gas Flow in Occluded Respiratory Tree: A New Matrix-Based Approach

2021 ◽  
Author(s):  
Bharat Soni ◽  
Ameeya K. Nayak ◽  
Antonio Miguel
Keyword(s):  
Gas Exchange ◽  
Gas Flow ◽  
Early Stage ◽  
Bronchial Tree ◽  
System A ◽  
Respiratory Tree ◽  
Local Ventilation ◽  
Ventilation Pattern ◽  
Block Based ◽  
Modified Block

Abstract Studies suggest that both the size of airways and the number of bifurcations of the respiratory tree provide the best structural design to accomplish its function. However, constrictions and occlusions due to inflammation and pulmonary edema of the airways can inhibit normal air flowing through the respiratory tree, affecting gas exchange. It results in heterogeneity in gas exchange (and pulmonary perfusion) with adverse risk factors. In this study, we propose a methodology based on the airway tree admittance (reciprocal of impedance) to study this problem. This methodology is distinct from the traditional quantification, based on overall impedance using lump parameter models, and applies to a matrix formed by admittances of each airway of the entire conducting part of the bronchial tree. The generated system admittance matrix is highly sparse in nature, and thus to solve the same system, a modified block-based LU decomposition method is proposed to improve the space-time trade-off. Our approach enables the determination of the local ventilation pattern and reduces the mis-evaluation, mainly in the cases that characterize the early-stage obstructive disorders. The key finding of the present study is to show that how the position and intensity of local obstruction in an airway can affect the overall as well as regional ventilation which can lead to impaired gas exchange.

Patterns of gas flow in the upper bronchial tree

1959 ◽  
Vol 14 (5) ◽  
pp. 753-759 ◽  
Author(s):  
J. B. West ◽  
P. Hugh-Jones
Keyword(s):  
Gas Flow ◽  
Lower Lobe ◽  
Bronchial Tree ◽  
High Flow ◽  
Human Beings ◽  
Lobe Bronchus ◽  
Flow Rates ◽  
Expiratory Flow ◽  
Different Gases ◽  
Expiratory Flow Rates

Patterns of gas flow in the upper bronchial tree have been studied by observing the flow of dye and different gases through a lung cast, and by measurements made on open-chested dogs and on human beings at bronchoscopy. Flow is completely laminar throughout the bronchial tree at low expiratory flow rates (up to 10 l/min.) and completely turbulent, proximal to the segmental bronchi, at high flow rates (80 l/min.). Both at low and high expiratory flow rates, gas from segmental bronchi was not uniformly mixed in the lobar or main bronchi which they supplied. The composition of a catheter sample in these airways would therefore not be representative of the alveolar gas in the corresponding lobe or lung unless the alveolar gas in all areas distal to the sampling tube was homogeneous. Penetration of the left upper lobe bronchus by gas from the lower lobe was demonstrated in the model and a normal subject at bronchoscopy. Submitted on September 3, 1958

scholarly journals Thermally stimulated oxygen desorption in Sr2FeMoO6-δ

2018 ◽  
Vol 4 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Nikolay A. Kalanda
Keyword(s):  
Activation Energy ◽  
Oxygen Diffusion ◽  
Gas Flow ◽  
Oxygen Vacancies ◽  
Early Stage ◽  
Diffusion Activation Energy ◽  
Energy Calculation ◽  
Heating Rates ◽  
Oxygen Desorption ◽  
Diffusion Activation

Polycrystalline Sr2FeMoO6-δ specimens have been obtained by solid state synthesis from partially reduced SrFeO2,52 and SrMoO4 precursors. It has been shown that during oxygen desorption from the Sr2FeMoO6-δ compound in polythermal mode in a 5%H2/Ar gas flow at different heating rates, the oxygen index 6-δ depends on the heating rate and does not achieve saturation at T = 1420 K. Oxygen diffusion activation energy calculation using the Merzhanov method has shown that at an early stage of oxygen desorption from the Sr2FeMoO6-δ compound the oxygen diffusion activation energy is the lowest Еа = 76.7 kJ/mole at δ = 0.005. With an increase in the concentration of oxygen vacancies, the oxygen diffusion activation energy grows to Еа = 156.3 kJ/mole at δ = 0.06. It has been found that the dδ/dt = f (Т) and dδ/dt = f (δ) functions have a typical break which allows one to divide oxygen desorption in two process stages. It is hypothesized that an increase in the concentration of oxygen vacancies Vo•• leads to their mutual interaction followed by ordering in the Fe/Mo-01 crystallographic planes with the formation of various types of associations.

Use of Self-Induced Zernike Filters Based on Saturation Effect in Gas Flow Schlieren Diagnostics

2014 ◽  
Vol 9 (1) ◽  
pp. 15-28
Author(s):  
Alexey Pavlov ◽  
Aleksandr Pavlov ◽  
Maxim Golubev
Keyword(s):  
Focal Plane ◽  
Quantitative Data ◽  
Gas Flow ◽  
Organic Dyes ◽  
Thin Layers ◽  
Saturable Absorption ◽  
Use Of Self ◽  
Absorption Effect ◽  
System A ◽  
Schlieren System

New self-induced Zernike filters (adaptive visualizing transparencies) based on the saturable absorption effect are suggested. The transparencies are thin layers made of translucent absorbing substance, and are placed in the focal plane of the receiving lens of a schlieren system. A possibility to create the transparencies having low response time (10−4 –10−5 s), which significantly reduces liability of the system to vibrations, is demonstrated. Obtainable images are equal to infinitefringe interference patterns allow getting a quantitative data. Examples of application of the organic dyes transparencies in aerophysic experiments are presented

scholarly journals Impact of Heterogeneity on the Transient Gas Flow Process in Tight Rock

Energies ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 3559 ◽  
Author(s):  
Jia ◽  
Tsau ◽  
Barati ◽  
Zhang
Keyword(s):  
History Matching ◽  
Gas Flow ◽  
Preferential Flow ◽  
Early Stage ◽  
Ideal Gas ◽  
Flow Path ◽  
Flow Process ◽  
The Core ◽  
Porosity And Permeability ◽  
Preferential Flow Path

There exits a great challenge to evaluate the flow properties of tight porous media even at the core scale. A pulse-decay experiment is routinely used to measure the petrophysical properties of tight cores including permeability and porosity. In this study, 5 sets of pulse-decay experiments are performed on a tight heterogeneous core by flowing nitrogen in the forward and backward directions under different pressures under pore pressures approximately from 100 psi to 300 psi. Permeability values from history matching are from about 300 nD to 600 nD which shows a good linear relationship with the inverse of pore pressure. A preferential flow path is found even when the microcrack is absent. The preferential path causes different porosity values using differential initial upstream and downstream pressure. In addition, the porosity values calculated based on the forward and backward flow directions are also different, and the values are about 1.0% and 2.3%, respectively, which is the primary novelty of this study. The core heterogeneity effect significantly affects the very early stage of pressure responses in both the upstream and downstream but the permeability values are very close in the late-stage experiment. We proposed that that there are two reasons for the preferential flow path: the Joule–Thomson effect for non-ideal gas and the core heterogeneity effect. Based on the finding of this study, we suggest that very early pressure response in a pulse-decay experiment should be closely examined to identify the preferential flow path, and failure to identify the preferential flow path leads to significant porosity and permeability underestimation.

scholarly journals The Effects of Inhomogeneous Elasticity and Dislocation on Thermodynamics and the Kinetics of the Spinodal Decomposition of a Fe-Cr System: A Phase-Field Study

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1209
Author(s):  
Wooseob Shin ◽  
Jeonghwan Lee ◽  
Kunok Chang
Keyword(s):  
Spinodal Decomposition ◽  
Phase Field ◽  
Early Stage ◽  
Field Method ◽  
Phase Field Method ◽  
Precipitate Size ◽  
System A ◽  
Phase Separation Kinetics ◽  
Cr Concentration ◽  
Cr System

The effects of inhomogeneous elasticity and dislocation on the microstructure evolution of α′ precipitate in a Fe-Cr system was investigated using a Computer Coupling of Phase Diagrams and Thermochemistry (CALPHAD)-type free energy incorporated phase-field method. In order to simulate the precipitation behavior by phase-field modeling in consideration of inhomogeneous elasticity, a Multiphysics Object-Oriented Simulation Environment (MOOSE) framework was used, which makes it easy to use powerful numerical means such as parallel computing and finite element method (FEM) solver. The effect of inhomogeneous elasticity due to the compositional inhomogeneity or the presence of dislocations affects the thermodynamic properties of the system was investigated, such as the lowest Cr concentration at which spinodal decomposition occurs. The effect of inhomogeneous elasticity on phase separation kinetics is also studied. Finally, we analyzed how inhomogeneous elasticity caused by compositional fluctuation or dislocation affects microstructure characteristics such as ratio between maximum precipitate size with respect to the average on early stage and later stage, respectively.

Respiratory and inert gas exchange during high-frequency ventilation

1982 ◽  
Vol 52 (3) ◽  
pp. 683-689 ◽  
Author(s):  
H. T. Robertson ◽  
R. L. Coffey ◽  
T. A. Standaert ◽  
W. E. Truog
Keyword(s):  
Gas Exchange ◽  
High Frequency ◽  
Gas Flow ◽  
Inert Gases ◽  
Inert Gas ◽  
High Frequency Ventilation ◽  
Physiological Dead Space ◽  
Volume Ventilation ◽  
Frequency Ventilation ◽  
Carrier Gases

Pulmonary gas exchange during high-frequency low-tidal volume ventilation (HFV) (10 Hz, 4.8 ml/kg) was compared with conventional ventilation (CV) and an identical inspired fresh gas flow in pentobarbital-anesthetized dogs. Comparing respiratory and infused inert gas exchange (Wagner et al., J. Appl. Physiol. 36: 585--599, 1974) during HFV and CV, the efficiency of oxygenation was not different, but the Bohr physiological dead space ratio was greater on HFV (61.5 +/- 2.2% vs. 50.6 +/- 1.4%). However, the elimination of the most soluble inert gas (acetone) was markedly enhanced by HFV. The increased elimination of the soluble infused inert gases during HFV compared with CV may be related to the extensive intraregional gas mixing that allows the conducting airways to serve as a capacitance for the soluble inert gases. Comparing as exchange during HFV with three different density carrier gases (He, N2, and Ar), the efficiency of elimination of Co2 or the intravenously infused inert gases was greatest with He-O2. However, the alveolar-arterial partial pressure difference for O2 on He-O2 exceeded that on N2-O2 by 5.4 Torr during HFV. The finding agrees with similar observations during CV, suggesting that this aspect of gas exchange is not substantially altered by HFV.

How Tree Roots Gather Oxygen from Soil for Energy Supply by Respiration

1997 ◽  
Vol 52 (11-12) ◽  
pp. 824-827 ◽  
Author(s):  
Hans-Joachim Frick ◽  
Dietrich Woermann ◽  
Wolfgang Grosse
Keyword(s):  
Gas Exchange ◽  
Root System ◽  
Gas Flow ◽  
Molar Mass ◽  
Soil Surface ◽  
Alnus Glutinosa ◽  
Tree Roots ◽  
Convective Gas Flow ◽  
Old Trees ◽  
Convective Volume

Abstract The gas exchange between the root system of the European alder (Alnus glutinosa (L.) Gaertn.) and the surrounding soil is studied using four-year-old trees. For the experiments the root system connected to its stump is exposed to gases of different molar mass. The stump is cut above the soil surface and in contact with the external atmosphere. A net convective volume flow of gas from the soil into the roots and out of the stump is observed if the mean molar mass of the gas present in the soil is lower than that present in the intercellular space of the roots. The direction of the convective gas flow can be reversed by increasing the molar mass of the gas present in the soil. These phenomena are governed by Graham 's law of diffusion. They demonstrate the importance of gas convection for the gas exchange in tree roots.

Breath-by-breath variation of FRC: effect on VO2 and VCO2 measured at the mouth

1979 ◽  
Vol 46 (6) ◽  
pp. 1122-1126 ◽  
Author(s):  
H. U. Wessel ◽  
R. L. Stout ◽  
C. K. Bastanier ◽  
M. H. Paul
Keyword(s):  
Steady State ◽  
Gas Exchange ◽  
Gas Flow ◽  
Co2 Gas ◽  
Mean Values ◽  
Gas Uptake ◽  
Source Data ◽  
Alveolar Level ◽  
Age Range

We examined breath-by-breath (B-B) variations of FRC (delta FRC) and their effect on measured O2 and CO2 gas exchange in 52 2- to 4-min segments of continuous air breathing obtained in 29 patients (age range 6--50 yr). Respiratory frequency ranged from 13 to 43 breaths/min, VE from 6.7 to 22.5 l/min (BTPS), and expired VT from 234 to 1,370 ml (BTPS). Computer analysis was based on the following source data measured at the mouth: inspired (VI) and expired (VE) gas flow, FN2, FO2 and FCO2. The analysis provides B-B evaluation of VI, VE, delta FRC in terms of VN2, and VO2 and VCO2 at the mouth and at the alveolar level, i.e., after correction for delta FRC. Significant B-B variations of FRC were found in all studies. delta FRC ranged from +360 to -360 ml (BTPS). For single respiratory cycles VI - VE is primarily a function of N2 exchange at the mouth (VMN2). VO2 and VCO2, uncorrected for delta FRC, are significantly more dispersed about mean values than the corrected gas uptakes (P less than 0.0005). The data support the view that the assumption of VIN2 = VEN2 is invalid for single respiratory cycles. Determination of breath-by-breath VO2 and VCO2 should therefore, not be based on steady-state gas uptake equations. It requires measurement of both inspired and expired breath volumes and evaluation of N2 gas exchange.

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