Simulations of Cyclic Breathing in the Conducting Zone of the Human Lung

2012 ◽  
Author(s):  
D. Keith Walters ◽  
Greg W. Burgreen ◽  
Robert L. Hester ◽  
David S. Thompson ◽  
David M. Lavallee ◽  
...  
Keyword(s):  
Mass Flow ◽  
Human Lung ◽  
Air Flow ◽  
Upper Airway ◽  
Flow Distribution ◽  
Whole Body ◽  
Patient Specific ◽  
Cross Sectional ◽  
Scan Data ◽  
Conducting Zone

Computational fluid dynamics (CFD) simulations were performed to predict the air flow in the human lung during cyclic breathing. The study employed a morphologically complex computational geometry generated using a combination of patient-specific CT-scan data for the extrathoracic and upper airway regions and a representative branching geometry for the lower airways that is available in the open literature. The geometry extended throughout the entire conducting zone and includes 16 partially resolved airway generations. For each generation beyond the third, only a fraction of the airway branches were retained, resulting in truncated flow outlets (for inspiratory flow) in generations 414. The inhalation and exhalation air flow boundary conditions were prescribed based on a physiologically realistic ventilation pattern, which was obtained using a whole-body model of human physiology. The flow was driven by specifying time-varying volumetric flowrates applied at each of the distal boundaries, while the oral boundary was maintained at constant (atmospheric) pressure. The study investigated the effectiveness of three different mass flow distribution schemes to drive the air flow. It was found that prescribed mass flow distribution fractions based on the square of the airway cross-sectional area produced the best results in terms of a uniform distal pressure distribution, while all methods produced reasonable results in terms of mass flow distribution throughout the lung airway geometry.

Cyclic Breathing Simulations in Large-Scale Models of the Lung Airway From the Oronasal Opening to the Terminal Bronchioles

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
D. Keith Walters ◽  
Greg W. Burgreen ◽  
Robert L. Hester ◽  
David S. Thompson ◽  
David M. Lavallee ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Mass Flow ◽  
Flow Rate ◽  
Large Scale ◽  
Whole Body ◽  
Patient Specific ◽  
Computational Domain ◽  
Scale Models ◽  
Fully Coupled ◽  
Conducting Zone

Computational fluid dynamics (CFD) simulations were performed using large-scale models of the human lung airway and unsteady periodic breathing conditions. The computational domain included fully coupled representations of the orotracheal region and large conducting zone up to generation four (G4) obtained from patient-specific CT data, and the small conducting zone (to the 16th generation) obtained from a stochastically generated airway tree with statistically realistic morphological characteristics. A reduced-geometry airway model was used, in which several airway branches in each generation were truncated, and only select flow paths were retained to the 16th generation. The inlet and outlet flow boundaries corresponded to the oral opening, the physical inlet/outlet boundaries at the terminal bronchioles, and the unresolved airway boundaries created from the truncation procedure. The total flow rate was specified according to the expected ventilation pattern for a healthy adult male, which was supplied by the whole-body modeling software HumMod. The unsteady mass flow distribution at the distal boundaries was prescribed based on a preliminary steady-state simulation with an applied flow rate equal to the average flow rate during the inhalation phase of the breathing cycle. In contrast to existing studies, this approach allows fully coupled simulation of the entire conducting zone, with no need to specify distal mass flow or pressure boundary conditions a priori, and without the use of impedance or one-dimensional (1D) flow models downstream of the truncated boundaries. The results show that: (1) physiologically realistic flow is obtained in the model, in terms of cyclic mass conservation and approximately uniform pressure distribution in the distal airways; (2) the predicted alveolar pressure is in good agreement with correlated experimental data; and (3) the use of reduced-order geometry modeling allows accurate and efficient simulation of large-scale breathing lung flow, provided care is taken to use a physiologically realistic geometry and to properly address the unsteady boundary conditions.

Cyclic Breathing Simulations in Large Scale Models of the Lung Airway From the Oronasal Opening to the Terminal Bronchioles

2012 ◽  
Author(s):  
D. Keith Walters ◽  
Greg W. Burgreen ◽  
Robert L. Hester ◽  
David S. Thompson ◽  
David M. Lavallee ◽  
...  
Keyword(s):  
Steady State ◽  
Boundary Conditions ◽  
Large Scale ◽  
Whole Body ◽  
Patient Specific ◽  
Cfd Simulations ◽  
Reduced Order ◽  
Scale Models ◽  
Steady State Simulation ◽  
Conducting Zone

Computational fluid dynamics (CFD) simulations were performed for unsteady periodic breathing conditions, using large-scale models of the human lung airway. The computational domain included fully coupled representations of the orotracheal region and large conducting zone up to generation four (G4) obtained from patient-specific CT data, and the small conducting zone (to G16) obtained from a stochastically generated airway tree with statistically realistic geometrical characteristics. A reduced-order geometry was used, in which several airway branches in each generation were truncated, and only select flow paths were retained to G16. The inlet and outlet flow boundaries corresponded to the oronasal opening (superior), the inlet/outlet planes in terminal bronchioles (distal), and the unresolved airway boundaries arising from the truncation procedure (intermediate). The cyclic flow was specified according to the predicted ventilation patterns for a healthy adult male at three different activity levels, supplied by the whole-body modeling software HumMod. The CFD simulations were performed using Ansys FLUENT. The mass flow distribution at the distal boundaries was prescribed using a previously documented methodology, in which the percentage of the total flow for each boundary was first determined from a steady-state simulation with an applied flow rate equal to the average during the inhalation phase of the breathing cycle. The distal pressure boundary conditions for the steady-state simulation were set using a stochastic coupling procedure to ensure physiologically realistic flow conditions. The results show that: 1) physiologically realistic flow is obtained in the model, in terms of cyclic mass conservation and approximately uniform pressure distribution in the distal airways; 2) the predicted alveolar pressure is in good agreement with previously documented values; and 3) the use of reduced-order geometry modeling allows accurate and efficient simulation of large-scale breathing lung flow, provided care is taken to use a physiologically realistic geometry and to properly address the unsteady boundary conditions.

Design and Optimization of the Restrictor of a Race Car

2015 ◽  
Author(s):  
Prithvi Raj Kokkula ◽  
Shashank Bhojappa ◽  
Selin Arslan ◽  
Badih A. Jawad
Keyword(s):  
Fluid Dynamics ◽  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Air Flow ◽  
Intake Manifold ◽  
Maximum Pressure ◽  
Cross Sectional ◽  
Formula Sae

Formula SAE is a student competition organized by SAE International. The team of students design, manufacture and race a car. Restrictions are imposed by the Formula SAE rules committee to restrict the air flow into the intake manifold by putting a single restrictor of 20 mm. This rule limits the maximum engine power by reducing the mass flow rate flowing to the engine. The pull is greater at higher rpms and the pressure created inside the cylinder is low. As the diameter of the flow path is reduced, the cross sectional area for flow reduces. For cars running at low rpm when the engine requires less air, the reduction in area is compensated by accelerated flow of air through the restrictor. Since this is for racing purpose cars here are designed to run at very high rpms where the flow at the throat section reach sonic velocities. Due to these restrictions the teams are challenged to come up with improved restrictor designs that allow maximum pressure drop across the restrictor’s inlet and outlet. The design considered for optimizing a flow restrictor is a venturi type having 20 mm restriction between the inlet and the outlet complying with the rules set by Formula SAE committee. The primary objective of this work is to optimize the flow restriction device that achieves maximum mass flow and minimum pull from the engine. This implies the pressure difference created due to the cylinder pressure and the atmospheric pressure at the inlet should be minimum. An optimum flow restrictor is designed by conducting analysis on various converging and diverging angles and coming up with an optimum value. Venturi type is a tubular pipe with varying diameter along its length, through which the fluid flows. Law of governing fluid dynamics states that the “Velocity of the fluid increases as it passes through the constriction to satisfy the principle of continuity”. An equation can be derived from the combination of Bernoulli’s equation and Continuity equation for the pressure drop due to venturi effect. [1]. A Computational Fluid Dynamics (CFD) tool is used to calculate the minimum pressure drop across the restrictor by running a series of analysis on various converging and diverging angles and calculating the pressure drop. As a result, an optimum air flow restrictor is achieved that maximizes the mass flow rate and minimizes the engine pull.

Numerical Analysis of the VAD Outflow Cannula Positioning on the Blood Flow in the Patient–Specific Brain Supplying Arteries

2020 ◽  
Vol 22 (2) ◽  
pp. 619-636 ◽  
Author(s):  
Zbigniew Tyfa ◽  
Damian Obidowski ◽  
Krzysztof Jóźwik
Keyword(s):  
Blood Flow ◽  
Computer Aided Design ◽  
Volume Flow Rate ◽  
Flow Distribution ◽  
Primary Objective ◽  
Patient Specific ◽  
Blood Flow Distribution ◽  
Reconstruction Process ◽  
Outflow Cannula ◽  
The Brain

AbstractThe primary objective of this research can be divided into two separate aspects. The first one was to verify whether own software can be treated as a viable source of data for the Computer Aided Design (CAD) modelling and Computational Fluid Dynamics CFD analysis. The second aspect was to analyze the influence of the Ventricle Assist Device (VAD) outflow cannula positioning on the blood flow distribution in the brain-supplying arteries. Patient-specific model was reconstructed basing on the DICOM image sets obtained with the angiographic Computed Tomography. The reconstruction process was performed in the custom-created software, whereas the outflow cannulas were added in the SolidWorks software. Volumetric meshes were generated in the Ansys Mesher module. The transient boundary conditions enabled simulating several full cardiac cycles. Performed investigations focused mainly on volume flow rate, shear stress and velocity distribution. It was proven that custom-created software enhances the processes of the anatomical objects reconstruction. Developed geometrical files are compatible with CAD and CFD software – they can be easily manipulated and modified. Concerning the numerical simulations, several cases with varied positioning of the VAD outflow cannula were analyzed. Obtained results revealed that the location of the VAD outflow cannula has a slight impact on the blood flow distribution among the brain supplying arteries.

Incorporating Patient-Specific Variability in the Simulation of Realistic Whole-Body $^{18}{\hbox{F-FDG}}$ Distributions for Oncology Applications

2009 ◽  
Vol 97 (12) ◽  
pp. 2026-2038 ◽  
Author(s):  
Amandine Le Maitre ◽  
William Paul Segars ◽  
Simon Marache ◽  
Anthonin Reilhac ◽  
Mathieu Hatt ◽  
...  
Keyword(s):  
Whole Body ◽  
Patient Specific

scholarly journals Elderly Patients in Primary Care are Still at Risks of Receiving Potentially Inappropriate Medications

2021 ◽  
Vol 12 ◽  
pp. 215013272110350
Author(s):  
Pasitpon Vatcharavongvan ◽  
Viwat Puttawanchai
Keyword(s):  
Primary Care ◽  
Primary Care Clinic ◽  
Clinical Decision ◽  
Cross Sectional Study ◽  
Study Data ◽  
Patient Specific ◽  
Potentially Inappropriate Medications ◽  
Cross Sectional ◽  
Care Clinic ◽  
Inappropriate Medications

Background Most older adults with comorbidities in primary care clinics use multiple medications and are at risk of potentially inappropriate medications (PIMs) prescription. Objective This study examined the prevalence of polypharmacy and PIMs using Thai criteria for PIMs. Methods This study was a retrospective cross-sectional study. Data were collected from electronic medical records in a primary care clinic in 2018. Samples were patients aged ≥65 years old with at least 1 prescription. Variables included age, gender, comorbidities, and medications. The list of risk drugs for Thai elderly version 2 was the criteria for PIMs. The prevalence of polypharmacy and PIMs were calculated, and multiple logistic regression was conducted to examine associations between variables and PIMs. Results Of 2806 patients, 27.5% and 43.7% used ≥5 medications and PIMs, respectively. Of 10 290 prescriptions, 47% had at least 1 PIM. The top 3 PIMs were anticholinergics, proton-pump inhibitors, and nonsteroidal anti-inflammatory drugs (NSAIDs). Polypharmacy and dyspepsia were associated with PIM prescriptions (adjusted odds ratio 2.48 [95% confident interval or 95% CI 2.07-2.96] and 3.88 [95% CI 2.65-5.68], respectively). Conclusion Prescriptions with PIMs were high in the primary care clinic. Describing unnecessary medications is crucial to prevent negative health outcomes from PIMs. Computer-based clinical decision support, pharmacy-led interventions, and patient-specific drug recommendations are promising interventions to reduce PIMs in a primary care setting.

scholarly journals Symptom cluster is associated with prolonged return-to-play in symptomatic athletes with acute respiratory illness (including COVID-19): a cross-sectional study—AWARE study I

2021 ◽  
pp. bjsports-2020-103782
Author(s):  
Martin Schwellnus ◽  
Nicola Sewry ◽  
Carolette Snyders ◽  
Kelly Kaulback ◽  
Paola Silvia Wood ◽  
...  
Keyword(s):  
Online Survey ◽  
Severe Disease ◽  
Univariate Analysis ◽  
Respiratory Illness ◽  
Symptom Cluster ◽  
Return To Play ◽  
Whole Body ◽  
Multiple Model ◽  
Acute Respiratory Illness ◽  
Cross Sectional

BackgroundThere are no data relating symptoms of an acute respiratory illness (ARI) in general, and COVID-19 specifically, to return to play (RTP).ObjectiveTo determine if ARI symptoms are associated with more prolonged RTP, and if days to RTP and symptoms (number, type, duration and severity) differ in athletes with COVID-19 versus athletes with other ARI.DesignCross-sectional descriptive study.SettingOnline survey.ParticipantsAthletes with confirmed/suspected COVID-19 (ARICOV) (n=45) and athletes with other ARI (ARIOTH) (n=39).MethodsParticipants recorded days to RTP and completed an online survey detailing ARI symptoms (number, type, severity and duration) in three categories: ‘nose and throat’, ‘chest and neck’ and ‘whole body’. We report the association between symptoms and RTP (% chance over 40 days) and compare the days to RTP and symptoms (number, type, duration and severity) in ARICOV versus ARIOTH subgroups.ResultsThe symptom cluster associated with more prolonged RTP (lower chance over 40 days; %) (univariate analysis) was ‘excessive fatigue’ (75%; p<0.0001), ‘chills’ (65%; p=0.004), ‘fever’ (64%; p=0.004), ‘headache’ (56%; p=0.006), ‘altered/loss sense of smell’ (51%; p=0.009), ‘Chest pain/pressure’ (48%; p=0.033), ‘difficulty in breathing’ (48%; p=0.022) and ‘loss of appetite’ (47%; p=0.022). ‘Excessive fatigue’ remained associated with prolonged RTP (p=0.0002) in a multiple model. Compared with ARIOTH, the ARICOV subgroup had more severe disease (greater number, more severe symptoms) and more days to RTP (p=0.0043).ConclusionSymptom clusters may be used by sport and exercise physicians to assist decision making for RTP in athletes with ARI (including COVID-19).

Effect of an interval rehabilitation program with home-based, vibration-assisted training on the development of muscle and bone in children with cerebral palsy – an observational study

2020 ◽  
Vol 33 (8) ◽  
pp. 1083-1092 ◽  
Author(s):  
Ibrahim Duran ◽  
Kyriakos Martakis ◽  
Christina Stark ◽  
Leonie Schafmeyer ◽  
Mirko Rehberg ◽  
...  
Keyword(s):  
Cerebral Palsy ◽  
Bone Growth ◽  
Muscle Growth ◽  
Rehabilitation Program ◽  
Whole Body ◽  
Cross Sectional ◽  
Home Based ◽  
Children With Cerebral Palsy ◽  
One Year ◽  
Intensive Rehabilitation

AbstractObjectivesIn children with cerebral palsy (CP), the most common cause of physical impairment in childhood, less muscle and bone growth has been reported, when compared with typically developing children. The aim of this study was to evaluate the effect of an intensive rehabilitation program including physiotherapy in combination with 6 months of home-based, vibration-assisted training on muscle and bone growth in children with CP.MethodsWe included children with CP, who participated in a rehabilitation program utilizing whole-body vibration (WBV). Muscle mass was quantified by appendicular lean mass index (App-LMI) and bone mass by total-body-less-head bone mineral content (TBLH-BMC) assessed by Dual-energy X-ray absorptiometry (DXA) at the beginning of rehabilitation and one year later. To assess the functional muscle-bone unit, the relation of TBLH-BMC to TBLH lean body mass (TBLH-LBM) was used.ResultsThe study population included 128 children (52 females, mean age 11.9 ± 2.7). App-LMI assessed in kg/m2 increased significantly after rehabilitation. The age-adjusted Z-score for App-LMI showed no significant change. TBLH-BMC assessed in gram increased significantly. The Z-scores for TBLH-BMC decreased lesser than expected by the evaluation of the cross-sectional data at the beginning of rehabilitation. The parameter $\frac{TBLH-BMC}{TBLH-LBM}$ did not change relevantly after 12 months.ConclusionsMuscle growth and to a lesser extent bone growth could be increased in children with CP. The intensive rehabilitation program including WBV seemed to have no direct effect on the bone, but the observed anabolic effect on the bone, may only been mediated through the muscle.

scholarly journals Lipid, fatty acid, carnitine- and choline derivative profiles in rheumatoid arthritis outpatients with different degrees of periodontal inflammation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kathrin Beyer ◽  
Stein Atle Lie ◽  
Bodil Bjørndal ◽  
Rolf K. Berge ◽  
Asbjørn Svardal ◽  
...  
Keyword(s):  
Rheumatoid Arthritis ◽  
Fatty Acid ◽  
Mitochondrial Dysfunction ◽  
Inflammatory Diseases ◽  
Whole Body ◽  
Cross Sectional ◽  
Chronic Inflammatory Diseases ◽  
Periodontal Inflammation ◽  
Inflammatory Status ◽  
Lipid Fatty Acid

AbstractRheumatoid arthritis (RA) and periodontitis are chronic inflammatory diseases with several pathogenic pathways in common. Evidence supports an association between the diseases, but the exact underlying mechanisms behind the connection are still under investigation. Lipid, fatty acid (FA) and metabolic profile alterations have been associated with several chronic inflammatory diseases, including RA and periodontitis. Mitochondria have a central role in regulating cellular bioenergetic and whole-body metabolic homeostasis, and mitochondrial dysfunction has been proposed as a possible link between the two disorders. The aim of this cross-sectional study was to explore whole-blood FA, serum lipid composition, and carnitine- and choline derivatives in 78 RA outpatients with different degrees of periodontal inflammation. The main findings were alterations in lipid, FA, and carnitine- and choline derivative profiles. More specifically, higher total FA and total cholesterol concentrations were found in active RA. Elevated phospholipid concentrations with concomitant lower choline, elevated medium-chain acylcarnitines (MC-AC), and decreased ratios of MC-AC and long-chain (LC)-AC were associated with prednisolone medication. This may indicate an altered mitochondrial function in relation to the increased inflammatory status in RA disease. Our findings may support the need for interdisciplinary collaboration within the field of medicine and dentistry in patient stratification to improve personalized treatment. Longitudinal studies should be conducted to further assess the potential impact of mitochondrial dysfunction on RA and periodontitis.

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