scholarly journals CFD Simulations of Respiratory Airflow in Human Upper Airways Response to Walking and Running

2020 ◽  
Author(s):  
Endalew Getnet Tsega
Keyword(s):  
Upper Airways ◽  
Cfd Simulations ◽  
Respiratory Airflow

scholarly journals The effect of airway motion and breathing phase during imaging on CFD simulations of respiratory airflow

2020 ◽  
Vol 127 ◽  
pp. 104099
Author(s):  
Chamindu C. Gunatilaka ◽  
Andreas Schuh ◽  
Nara S. Higano ◽  
Jason C. Woods ◽  
Alister J. Bates
Keyword(s):  
Cfd Simulations ◽  
Respiratory Airflow

scholarly journals Human upper-airway respiratory airflow: In vivo comparison of computational fluid dynamics simulations and hyperpolarized 129Xe phase contrast MRI velocimetry

PLoS ONE ◽  
2021 ◽  
Vol 16 (8) ◽  
pp. e0256460
Author(s):  
Qiwei Xiao ◽  
Neil J. Stewart ◽  
Matthew M. Willmering ◽  
Chamindu C. Gunatilaka ◽  
Robert P. Thomen ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Phase Contrast ◽  
Upper Airway ◽  
Breathing Patterns ◽  
Cfd Simulations ◽  
Airflow Velocity ◽  
Obstructive Sleep ◽  
Respiratory Airflow

Computational fluid dynamics (CFD) simulations of respiratory airflow have the potential to change the clinical assessment of regional airway function in health and disease, in pulmonary medicine and otolaryngology. For example, in diseases where multiple sites of airway obstruction occur, such as obstructive sleep apnea (OSA), CFD simulations can identify which sites of obstruction contribute most to airway resistance and may therefore be candidate sites for airway surgery. The main barrier to clinical uptake of respiratory CFD to date has been the difficulty in validating CFD results against a clinical gold standard. Invasive instrumentation of the upper airway to measure respiratory airflow velocity or pressure can disrupt the airflow and alter the subject’s natural breathing patterns. Therefore, in this study, we instead propose phase contrast (PC) velocimetry magnetic resonance imaging (MRI) of inhaled hyperpolarized 129Xe gas as a non-invasive reference to which airflow velocities calculated via CFD can be compared. To that end, we performed subject-specific CFD simulations in airway models derived from 1H MRI, and using respiratory flowrate measurements acquired synchronously with MRI. Airflow velocity vectors calculated by CFD simulations were then qualitatively and quantitatively compared to velocity maps derived from PC velocimetry MRI of inhaled hyperpolarized 129Xe gas. The results show both techniques produce similar spatial distributions of high velocity regions in the anterior-posterior and foot-head directions, indicating good qualitative agreement. Statistically significant correlations and low Bland-Altman bias between the local velocity values produced by the two techniques indicates quantitative agreement. This preliminary in vivo comparison of respiratory airway CFD and PC MRI of hyperpolarized 129Xe gas demonstrates the feasibility of PC MRI as a technique to validate respiratory CFD and forms the basis for further comprehensive validation studies. This study is therefore a first step in the pathway towards clinical adoption of respiratory CFD.

scholarly journals Effects of replacing the nasal cavity with a simple pipe like structure in CFD simulations of the airflow within the upper airways of OSA patients with patient individual flow rates

2017 ◽  
Vol 3 (2) ◽  
pp. 795-798
Author(s):  
Christina Hagen ◽  
Pragathi Gurumurthy ◽  
Thorsten M. Buzug
Keyword(s):  
Nasal Cavity ◽  
Upper Airways ◽  
Cfd Simulations ◽  
Flow Rates ◽  
Computational Costs ◽  
Pressure Distributions ◽  
Abnormal Pressure ◽  
Reconstruction Effort ◽  
Simulated Flow ◽  
Good Agreement

AbstractOSA is characterized by repetitive collapses of the upper airways during sleep. Computational fluid dynamics can be used to investigate the abnormal pressure distribution in the patient’s airways. The computational costs and model reconstruction effort can be reduced by focusing the simulations on the pharynx and replacing the nasal cavity by a simple pipe structure. In this work, the effects of the mentioned replacement on the simulated flow are evaluated. Airflow simulations using the k-ω turbulence model are performed in the anatomically correct airway of a patient having a high difference in the inspiratory volume flow rates of both nostrils, as well as in a model with replaced nasal cavity by a simple pipe structure. The simulated pressure distributions of both models are in very good agreement indicating the acceptability of replacing the nasal cavity by simple pipe structures in in-silico airflow analyses of OSA patients.

Humoral factors of innate immunity in the saliva of patients with infectious inflammatory respiratory diseases

2018 ◽  
pp. 13-17
Author(s):  
Oleg Melnikov ◽  
Diana Zabolotnaya ◽  
Alexander Bredun ◽  
Bogdan Bil ◽  
Oksana Rylska ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Chronic Rhinosinusitis ◽  
Inflammatory Diseases ◽  
Activity Level ◽  
Chronic Tonsillitis ◽  
Control Group ◽  
Quantitative Composition ◽  
Upper Airways ◽  
Humoral Factors ◽  
Immune Modulators

Introduction: In recently ears factors of innate immunity both cellular and humoral have been paid considerable attention as they are a protective barrier of a fast response and that is why they are largely concentrated at the intersection of the digestive tract and airways. The data concerning the activity level of factors of innate immunity in the upper airways affected by nonspecific inflammatory processes is insufficient and sparse and therefore the purpose of this research was to study the content of humoral factors of innate immunity in the oropharyngeal secretion (ORS) of patients with chronic infectious inflammatory diseases of the upper airways in remission. Materials and Methods: There was an examination of 16 patients with chronic rhinosinusitis (CRS) of bacterial genesis (15-40 years old), 12 patients with rhinopharyngitis of post-viral genesis (8-16 years old), 12 people with scleroma from 30 tо 52 years of age (atrophic form), 10 patients with chronic tonsillitis in remission (from 10 to 33 years of age) and 11 patients of a control group (practically healthy donors from 12 tо 40 years of age). The content of MIP-1b, defensin-1β, lactoferrin, lysozyme, α-interferon was studied in the nonstimulated OPS. Statistics were carried out using Mann-Whitney U-test. Results: The greatest number of deviations in the decrease in the content of the examined nonspecific protective factors was found in cases of scleroma, chronic tonsillitis and chronic rhinosinusitis (p<0,05). The lack of protective humoral factors of innate immunity can be evidence of local immunodeficiency even in remission, which is a pathophysiological component of the maintenance of chronic inflammation. Conclusion: The decrease int he quantitative composition of factors of innate immunity in the oropharyngeal secretion of patients with chronic infectious inflammatory diseases of the airways is an objective ground not only for a replacement therapy, but also for the use of immune response modifiers from photo-immune modulators to “genuine immune modulators” controlling the state of the factors of both innate immunity and immunoglobulins, primarily of secretory type, the level and functionality of various groups of immunocompetent and accessory cells.

Recent Advances on Nitric Oxide in the Upper Airways

2016 ◽  
Vol 23 (24) ◽  
pp. 2736-2745 ◽  
Author(s):  
Mauro Maniscalco ◽  
Andrea Bianco ◽  
Gennaro Mazzarella ◽  
Andrea Motta
Keyword(s):  
Nitric Oxide ◽  
Upper Airways ◽  
Recent Advances

Comparison of DSMC and CFD Models of Heat Transfer in a Rarefied Two-Dimensional Geometry

2018 ◽  
Author(s):  
Dilesh Maharjan ◽  
Mustafa Hadj-Nacer ◽  
Miles Greiner ◽  
Stefan K. Stefanov
Keyword(s):  
Heat Transfer ◽  
Rarefied Gas ◽  
Complex Geometry ◽  
Direct Simulation Monte Carlo ◽  
Accurate Method ◽  
Vacuum Drying ◽  
Helium Pressure ◽  
Two Dimensional ◽  
Dsmc Method ◽  
Cfd Simulations

During vacuum drying of used nuclear fuel (UNF) canisters, helium pressure is reduced to as low as 67 Pa to promote evaporation and removal of remaining water after draining process. At such low pressure, and considering the dimensions of the system, helium is mildly rarefied, which induces a thermal-resistance temperature-jump at gas–solid interfaces that contributes to the increase of cladding temperature. It is important to maintain the temperature of the cladding below roughly 400 °C to avoid radial hydride formation, which may cause cladding embrittlement during transportation and long-term storage. Direct Simulation Monte Carlo (DSMC) method is an accurate method to predict heat transfer and temperature under rarefied condition. However, it is not convenient for complex geometry like a UNF canister. Computational Fluid Dynamics (CFD) simulations are more convenient to apply but their accuracy for rarefied condition are not well established. This work seeks to validate the use of CFD simulations to model heat transfer through rarefied gas in simple two-dimensional geometry by comparing the results to the more accurate DSMC method. The geometry consists of a circular fuel rod centered inside a square cross-section enclosure filled with rarefied helium. The validated CFD model will be used later to accurately estimate the temperature of an UNF canister subjected to vacuum drying condition.

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