scholarly journals A Conjugate Fluid–Porous Approach for Simulating Airflow in Realistic Geometric Representations of the Human Respiratory System

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Christopher T. DeGroot ◽  
Anthony G. Straatman
Keyword(s):  
Human Lung ◽  
Computational Simulation ◽  
Practical Interest ◽  
Upper Airway ◽  
Upper Airways ◽  
Simulation Techniques ◽  
Airway Trees ◽  
Modeling Paradigm ◽  
Great Practical Interest ◽  
Geometric Representations

Simulation of flow in the human lung is of great practical interest as a means to study the detailed flow patterns within the airways for many physiological applications. While computational simulation techniques are quite mature, lung simulations are particularly complicated due to the vast separation of length scales between upper airways and alveoli. Many past studies have presented numerical results for truncated airway trees, however, there are significant difficulties in connecting such results with respiratory airway models. This article presents a new modeling paradigm for flow in the full lung, based on a conjugate fluid–porous formulation where the upper airway is considered as a fluid region with the remainder of the lung being considered as a coupled porous region. Results are presented for a realistic lung geometry obtained from computed tomography (CT) images, which show the method's potential as being more efficient and practical than attempting to directly simulate flow in the full lung.

Motor responses to positive-pressure breathing in the developing opossum

1985 ◽  
Vol 58 (5) ◽  
pp. 1489-1495 ◽  
Author(s):  
J. P. Farber
Keyword(s):  
Airway Resistance ◽  
Upper Airway ◽  
Abdominal Muscle ◽  
Positive Pressure ◽  
Postnatal Life ◽  
Abdominal Muscles ◽  
Upper Airways ◽  
Motor Responses ◽  
Upper Airway Resistance ◽  
Upper Airway Muscles

The suckling opossum exhibits an expiration-phased discharge in abdominal muscles during positive-pressure breathing (PPB); the response becomes apparent, however, only after the 3rd-5th wk of postnatal life. The purpose of this study was to determine whether the early lack of activation represented a deficiency of segmental outflow to abdominal muscles or whether comparable effects were observed in cranial outflows to muscles of the upper airways due to immaturity of afferent and/or supraspinal pathways. Anesthetized suckling opossums between 15 and 50 days of age were exposed to PPB; electromyogram (EMG) responses in diaphragm and abdominal muscles were measured, along with EMG of larynx dilator muscles and/or upper airway resistance. In animals older than approximately 30 days of age, the onset of PPB was associated with a prolonged expiration-phased EMG activation of larynx dilator muscles and/or decreased upper airway resistance, along with expiratory recruitment of the abdominal muscle EMG. These effects persisted as long as the load was maintained. Younger animals showed only those responses related to the upper airway; in fact, activation of upper airway muscles during PPB could be associated with suppression of the abdominal motor outflow. After unilateral vagotomy, abdominal and upper airway motor responses to PPB were reduced. The balance between PPB-induced excitatory and inhibitory or disfacilitory influences from the supraspinal level on abdominal motoneurons and/or spinal processing of information from higher centers may shift toward net excitation as the opossum matures.

Inspiratory coactivation of the genioglossus enlarges retroglossal space in laryngectomized humans

1996 ◽  
Vol 80 (5) ◽  
pp. 1595-1604 ◽  
Author(s):  
I. Kobayashi ◽  
A. Perry ◽  
J. Rhymer ◽  
B. Wuyam ◽  
P. Hughes ◽  
...  
Keyword(s):  
Upper Airway ◽  
Dependent Manner ◽  
Tongue Movement ◽  
Forward Movement ◽  
Upper Airways ◽  
Posterior Aspect ◽  
Airway Patency ◽  
Significant Movement ◽  
Tongue Position ◽  
Tracheal Stoma

To investigate the relationship between the electrical activity of the genioglossus (GG-EMG) and associated tongue movement, seven laryngectomized subjects breathing through a tracheal stoma (without pressure or flow change in the upper airway) were studied in the supine position. Tongue movement, with the use of lateral fluoroscopy, and GG-EMG expressed as a percentage of maximum voluntary genioglossal activation were monitored simultaneously during 1) spontaneous inspiration (SI), 2) resistive loaded inspiration (LI), and 3) rapid inspiration (RI). Tongue position during each maneuver was compared with its position during spontaneous expiration. Peak GG-EMG during the three maneuvers was significantly different from each other (SI: 5.4 +/- 1.6, LI: 11.9 +/- 1.8, and RI: 51.6 +/- 9.4 (SE) %, respectively). Associated forward movement of the posterior aspect of the tongue was minimum during SI; however, significant movement was observed during LI, and this was increased during RI. Significant covariance existed between peak GG-EMG and this movement. Genioglossal coactivation with inspiration enlarges the glossopharyngeal airway, particularly in its caudal part. In subjects with intact upper airways, this activation may protect or enhance upper airway patency in an effort-dependent manner.

Uvula Dynamic Characteristics

2013 ◽  
Author(s):  
A. M. Al-Jumaily ◽  
S. Ashaat ◽  
B. A. Martin ◽  
R. Heinzer ◽  
J. Haba Rubio ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Structural Model ◽  
Fluid Layer ◽  
Structural Characteristics ◽  
Upper Airway ◽  
Mode Shapes ◽  
Tissue Elasticity ◽  
Upper Airways ◽  
Obstructive Sleep ◽  
Mri Scans

The airway binary fluid layer and the structural characteristics of the upper airways have significant influence on the activity of the airway muscles by changing airway compliance and collapsibility during obstructive sleep apnea trauma. The uvula plays an important role in the collapse process. Using MRI scans, this paper develops a structural model for the uvula and determines its dynamic characteristics in terms of natural frequencies and mode shapes as a preliminary process to determine optimum conditions to therapeutically relieve upper airway obstruction. The effect of the variation of tissue elasticity due to water content is elaborated on.

A MODEL HIERARCHY FOR IONOSPHERIC PLASMA MODELING

2004 ◽  
Vol 14 (03) ◽  
pp. 393-415 ◽  
Author(s):  
CHRISTOPHE BESSE ◽  
PIERRE DEGOND ◽  
FABRICE DELUZET ◽  
JEAN CLAUDEL ◽  
GÉRARD GALLICE ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Plasma Density ◽  
Maxwell Equations ◽  
Ionospheric Plasma ◽  
Practical Interest ◽  
Plasma Modeling ◽  
Model Hierarchy ◽  
Great Practical Interest ◽  
Two Fluid ◽  
Insight Into

This paper deals with the modeling of the ionospheric plasma. Starting from the two-fluid Euler–Maxwell equations, we present two hierarchies of models. The MHD hierarchy deals with large plasma density situations while the dynamo hierarchy is adapted to lower density situations. Most of the models encompassed by the dynamo hierarchy are classical ones, but we shall give a unified presentation of them which brings a new insight into their interrelations. By contrast, the MHD hierarchy involves a new (at least to the authors) model, the massless-MHD model. This is a diffusion system for the density and magnetic field which could be of great practical interest. Both hierarchies terminate with the "classical" Striation model, which we shall investigate in detail.

scholarly journals Sticky Thermals: Evidence for a Dominant Balance between Buoyancy and Drag in Cloud Updrafts

2015 ◽  
Vol 72 (8) ◽  
pp. 2890-2901 ◽  
Author(s):  
David M. Romps ◽  
Alexander B. Charn
Keyword(s):  
Large Eddy Simulation ◽  
Practical Interest ◽  
Momentum Equation ◽  
Severe Weather ◽  
Convective Clouds ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Great Practical Interest ◽  
Natural Boundaries ◽  
Drag Law

Abstract The vertical velocities of convective clouds are of great practical interest because of their influence on many phenomena, including severe weather and stratospheric moistening. However, the magnitudes of forces giving rise to these vertical velocities are poorly understood, and the dominant balance is in dispute. Here, an algorithm is used to extract thousands of cloud thermals from a large-eddy simulation of deep and tropical maritime convection. Using a streamfunction to define natural boundaries for these thermals, the dominant balance in the vertical momentum equation is revealed. Cloud thermals rise with a nearly constant speed determined by their buoyancy and the standard drag law with a drag coefficient of 0.6. Contrary to suggestions that cloud thermals might be slippery, with a dominant balance between buoyancy and acceleration, cloud thermals are found here to be sticky, with a dominant balance between buoyancy and drag.

Computational Biology: Development in the Field of Medicine

2021 ◽  
Keyword(s):  
Mathematical Modeling ◽  
Computational Biology ◽  
Social Systems ◽  
Computational Simulation ◽  
Analytical Data ◽  
Theoretical Methods ◽  
Simulation Techniques

Computational biology involves the development and application of analytical-data and theoretical methods, computational simulation techniques, and mathematical modeling to the study of biological, behavioral, ecological, and social systems.

About injuries with a chemical (ink) pencil

1930 ◽  
Vol 26 (8) ◽  
pp. 841-843
Author(s):  
S. I. Rizvash
Keyword(s):  
Human Tissue ◽  
Practical Interest ◽  
Russian Literature ◽  
Medical Institutions ◽  
Great Practical Interest ◽  
Treatment Of Wounds ◽  
Type Of Injury

In Russian literature, very little attention has been paid to this type of injury. I managed to find only 2 articles in which this issue is treated. In the manuals on general and private surgery, both translated and original, there is no indication of the action of aniline pencils on human tissue. Nothing is said about this even in the largest Russian monographs on the treatment of wounds (Trinkler, Petrov). Meanwhile, the injuries caused by a chemical pencil, due to their peculiar course and often even a difficult outcome, are undoubtedly of great practical interest. This prompts me to report two cases of such an injury, which I observed in different medical institutions at almost the same time.

scholarly journals The Microbiota/Host Immune System Interaction in the Nose to Protect from COVID-19

Life ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 345
Author(s):  
Arianna Di Stadio ◽  
Claudio Costantini ◽  
Giorgia Renga ◽  
Marilena Pariano ◽  
Giampietro Ricci ◽  
...  
Keyword(s):  
Immune System ◽  
Viral Entry ◽  
Upper Airway ◽  
Organ Damage ◽  
Host Immune System ◽  
Upper Airways ◽  
Mucosal Homeostasis ◽  
Resistance To Infection ◽  
Variable Clinical Presentation

Coronavirus disease 2019 (COVID-19) is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and is characterized by variable clinical presentation that ranges from asymptomatic to fatal multi-organ damage. The site of entry and the response of the host to the infection affect the outcomes. The role of the upper airways and the nasal barrier in the prevention of infection is increasingly being recognized. Besides the epithelial lining and the local immune system, the upper airways harbor a community of microorganisms, or microbiota, that takes an active part in mucosal homeostasis and in resistance to infection. However, the role of the upper airway microbiota in COVID-19 is not yet completely understood and likely goes beyond protection from viral entry to include the regulation of the immune response to the infection. Herein, we discuss the hypothesis that restoring endogenous barriers and anti-inflammatory pathways that are defective in COVID-19 patients might represent a valid strategy to reduce infectivity and ameliorate clinical symptomatology.

Mouth and nose resistance in newborn kittens and puppies

1981 ◽  
Vol 51 (3) ◽  
pp. 641-645 ◽  
Author(s):  
J. P. Mortola ◽  
J. T. Fisher
Keyword(s):  
Mechanical Properties ◽  
Airway Obstruction ◽  
Flow Rate ◽  
Muscle Tone ◽  
Upper Airway ◽  
Upper Airway Obstruction ◽  
Upper Airways ◽  
Airway Patency ◽  
The Difference ◽  
Adult Cats

Newborn mammals, including infants, have difficulties in mouth breathing when the nasal passages are occluded. In this study we examined the possibility that differences in the passive mechanical properties of the upper airways could fully explain this behavior. Steady inspiratory flows through the upper airways in anesthetized supine newborn kittens and puppies resulted in upper airway obstruction, even at flows less than those occurring during resting breathing, suggesting that in the unanesthetized condition muscle tone plays an important role in maintaining upper airway patency. Mouth (Rm) and nose (Rn) resistances have been measured during steady expiratory flows with nostrils closed and mouth passively open or nostrils open and mouth closed. In all the newborns, Rn was substantially smaller than Rm. In contrast, the Rn/Rm in adult dogs is greater than unity. In adult cats Rn/Rm is above or below unity depending upon the flow rate, but the ratio is always larger than in newborn kittens. The difference between newborns and adults is entirely due to the small Rn of the newborn, as Rm is not greater in the newborn than in the adult. We conclude that the obligatory nose breathing behavior of newborns is not fully explained by the passive mechanical properties of the upper airways.

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