Airway Airflow Research Articles

Health locus of control related daily living activities during COVID 19 pandemic as an indicator of Bronchial Asthma

Background: Bronchial asthma is a widespread chronic airway inflammatory disease, and it is characterized by paroxysmal or continual respiratory manifestations and airway airflow limitations. Accordingly, coronavirus disease 2019 (COVID-19) impact on quality of life including daily living activities come into views to be highly misjudged, especially in patients who have not been admitted to the hospital. Aim: To find out relationship between health locus of control and daily living activities among adult patients with bronchial asthma during Covid 19 Pandemic at Port- said city in Egypt. Subject and methods: A descriptive cross-sectional study was carried out on a total of 230 adult patients from both sex with bronchial asthma attend medical chest clinics in Alsalam, Por – fouad, Algawhara governmental hospital at Port-said city, Egypt responded to the self-administered survey and excluded patients with co- morbid diseases and were refused to participate in the study using self-administered survey divided into three main parts. First part consist of 8 items related to demographic data, second part: Patient's knowledge regarding bronchial Asthma adapted from Williams., 2005, third part: it adapted from Putman., 2004 to assess the effect of covid 19 on bronchial asthma patient's daily living activities and locus of control. Results: there are a statistically significant relation between total scores of locus of asthma control and smoking pattern ps= (o, oo3) with total Mean scores and SD 28.52 ± 4.43. Also, there are a positive correlation between total daily living activities scores and total locus of control among patients with Bronchial Asthma. Finally, there are a statistically significant relation between total daily living activities scores and Bronchial Asthma patients and their socio-demographic characteristics only in the items related to patient's residence Ps=( 0.082) . Conclusion: Patient with Bronchial Asthma need for receive regular; periodic in-service coping program contains methods of adherence with their daily living activities, knowledge of their disease which indirectly added stressor on patient's life and indirectly affect their disease management and coping especially in the period of Corona virus Pandemic which added stressors of those patients. Further studies are needed to study the coping strategies that influence bronchial Asthma patient's locus of control, management and coping with their disease with a large geographical areas and sampling.

Validated numerical simulation of airflow in child respiratory airways

Both pulmonary airway geometry and breathing pattern evolve from birth to adulthood. These gradual changes significantly influence airflow dynamics and subsequently particle transport and deposition. Regarding the airway structure, the differences between infants and adults are most profound till 5 years of age. Since that age the child airway geometry can be downsized from adult lungs. The objective of the present work was to investigate airflow patterns in child airways. The digital model of male respiratory airways was downsized to dimensionally correspond to a 5–year old child. Airflow simulations with properly validated RANS k–ω turbulence model were performed under steady inhalation boundary conditions. The inspiratory flow rate was 12.5 L/min. The velocity profiles just upstream of the first bifurcation were validated by Laser–Doppler anemometry (LDA) experiments. A replica of the same geometry as the one used in the simulation was 3D printed and part of the trachea was replaced by a glass tube. LDA measurements in several points upstream of the first bifurcation were carried out. The validated flow patterns were compared to the ones obtained in adult lungs.

P9‐69: Persistent airway inflammation and airflow limitation in patients with not well‐controlled asthma even on ICS/LABA therapy

P9‐69: Persistent airway inflammation and airflow limitation in patients with not well‐controlled asthma even on ICS/LABA therapy

Analysis of flow field and turbulence predictions in a lung model applying RANS and implications for particle deposition

Airflow and aerosol deposition in the human airways are important aspects for applications such as pulmonary drug delivery and human exposure to aerosol pollutants. Numerical simulations are widely used nowadays to shed light in airflow features and particle deposition patterns inside the airways. For that purpose, the Euler/Lagrange approach is adopted for predicting flow field and particle deposition through point-particle tracking. Steady-state RANS (Reynolds-averaged Navier-Stokes) computations of flow evolution in an extended lung model applying different turbulence models were conducted and compared to measurements as well as high resolution LES (large-eddy simulations) for several flow rates. In addition, various inlet boundary conditions were considered and their influence on the predicted flow field was analysed. The results showed that the mean velocity field was simulated reasonably well, however, turbulence intensity was completely under-predicted by two-equation turbulence models. Only a Reynolds-stress model (RSM) was able predicting a turbulence level comparable to the measurements and the high resolution LES. Remarkable reductions in wall deposition were observed when wall effects were accounted for in the drag and lift force expressions. Naturally, turbulence is an essential contribution to particle deposition and it is well known that two-equation turbulence models considerably over-predict deposition due to the spurious drift effect. A full correction of this error is only possible in connection with a Reynolds-stress turbulence model whereby the predicted deposition in dependence of particle diameter yielded better agreement to the LES predictions. Specifically, with the RSM larger deposition is predicted for smaller particles and lower deposition fraction for larger particles compared to LES. The local deposition fraction along the lung model was numerically predicted with the same trend as found from the measurements, however the values in the middle region of the lung model were found to be somewhat larger.

The effect of decongestion on nasal airway patency and airflow

Nasal decongestant reduces blood flow to the nasal turbinates, reducing tissue volume and increasing nasal airway patency. This study maps the changes in nasal anatomy and measures how these changes affect nasal resistance, flow partitioning between superior and inferior cavity, flow patterns and wall shear stress. High-resolution MRI was applied to capture nasal anatomy in 10 healthy subjects before and after application of a topical decongestant. Computational fluid dynamics simulated nasal airflow at steady inspiratory flow rates of 15 L.min^{-1} and 30 L.min^{-1}. The results show decongestion mainly increases the cross-sectional area in the turbinate region and SAVR is reduced (median approximately 40% reduction) in middle and lower parts of the cavity. Decongestion reduces nasal resistance by 50% on average, while in the posterior cavity, nasal resistance decreases by a median factor of approximately 3 after decongestion. We also find decongestant regularises nasal airflow and alters the partitioning of flow, significantly decreasing flow through the superior portions of the nasal cavity. By comparing nasal anatomies and airflow in their normal state with that when pharmacologically decongested, this study provides data for a broad range of anatomy and airflow conditions, which may help characterize the extent of nasal variability.

Polydisperse Aerosol Transport and Deposition in Upper Airways of Age-Specific Lung.

A comprehensive understanding of airflow characteristics and particle transport in the human lung can be useful in modelling to inform clinical diagnosis, treatment, and management, including prescription medication and risk assessment for rehabilitation. One of the difficulties in clinical treatment of lung disorders lies in the patients’ variable physical lung characteristics caused by age, amongst other factors, such as different lung sizes. A precise understanding of the comparison between different age groups with various flow rates is missing in the literature, and this study aims to analyse the airflow and aerosol transport within the age-specific lung. ANSYS Fluent solver and the large-eddy simulation (LES) model were employed for the numerical simulation. The numerical model was validated with the available literature and the computational results showed airway size-reduction significantly affected airflow and particle transport in the upper airways. This study reports higher deposition at the mouth-throat region for larger diameter particles. The overall deposition efficiency (DE) increased with airway size reduction and flow rate. Lung aging effected the pressure distribution and a higher pressure drop was reported for the aged lung as compared to the younger lung. These findings could inform medical management through individualised simulation of drug-aerosol delivery processes for the patient-specific lung.

Computational characterization of inhaled droplet transport to the nasopharynx

How human respiratory physiology and the transport phenomena associated with inhaled airflow in the upper airway proceed to impact transmission of SARS-CoV-2, leading to the initial infection, stays an open question. An answer can help determine the susceptibility of an individual on exposure to a COVID-2019 carrier and can also provide a preliminary projection of the still-unknown infectious dose for the disease. Computational fluid mechanics enabled tracking of respiratory transport in medical imaging-based anatomic domains shows that the regional deposition of virus-laden inhaled droplets at the initial nasopharyngeal infection site peaks for the droplet size range of approximately 2.5–19 upmu . Through integrating the numerical findings on inhaled transmission with sputum assessment data from hospitalized COVID-19 patients and earlier measurements of ejecta size distribution generated during regular speech, this study further reveals that the number of virions that may go on to establish the SARS-CoV-2 infection in a subject could merely be in the order of hundreds.

Effects of Modulus of Elasticity on airflow in Human Respiratory airway

In this work, Computational analysis of air flow in human respiratory tract model is done by the use of CFD technique. Fluid Structure Interaction (FSI) method is used on the third-to-sixth generation simplified respiratory tract model for computational study. The modulus of Elasticity is varied in a range of 1 to 5 MPa and its effect on flow-physics is captured inside human airway model. The variation of velocity and its effect on deformation has been captured for both rigid and flexible model and its analysis is carried out. The result from simulation shows that as the Modulus of elasticity increases, wall deformation decreases.

Oxidative Stress and Inflammation Biomarker Expression in Obstructive Sleep Apnea Patients

Obstructive Sleep Apnea Syndrome (OSAS) is a respiratory sleep disorder characterised by repeated episodes of partial or complete obstruction of the upper airway during the night. This obstruction usually occurs with a reduction (hypopnea) or complete cessation (apnea) of the airflow in the upper airways with the persistence of thoracic-diaphragmatic respiratory movements. During the hypopnea/apnea events, poor alveolar ventilation reduces the oxygen saturation in the arterial blood (SaO2) and a gradual increase in the partial arterial pressure of carbon dioxide (PaCO2). The direct consequence of the intermittent hypoxia is an oxidative imbalance, with reactive oxygen species production and the inflammatory cascade’s activation with pro and anti-inflammatory cytokines growth. Tumour necrosis factors, inflammatory cytokines (IL2, IL4, IL6), lipid peroxidation, and cell-free DNA have been found to increase in OSAS patients. However, even though different risk-related markers have been described and analysed in the literature, it has not yet been clarified whether specified inflammatory bio-markers better correlates with OSAS diagnosis and its clinical evolution/comorbidities. We perform a scientific literature review to discuss inflammatory and oxidative stress biomarkers currently tested in OSAS patients and their correlation with the disease’s severity and treatment.

Computational Analysis of Airflow in Upper Airway under Light and Heavy Breathing Conditions for a Realistic Patient Having Obstructive Sleep Apnea

Background: Obstructive sleep apnea is a sleeping disorder that has troubled a sizeable population. There is an active area of research on obstructive sleep apnea that intends to better understand airflow behaviors and therefore treat patients more effectively. This paper aims to investigate the airflow characteristics of the upper airway in an obstructive sleep apnea (OSA) patient under light and heavy breathing conditions by using Turbulent Kinetic Energy (TKE), an accurate method in expressing the flow concentration mechanisms of sleeping disorders. It is important to visualize the concentration of flow in the upper airway in order to identify the severity level of the obstruction during sleep. Methods: Computational fluid dynamic (CFD) analysis was used as a solution tool to evaluate the airflow during light and heavy breathing conditions. A medical imaging technique was used to extract the 3D model from the CT scan images. Additionally, mesh generation and simulation were carried out via CFD software to evaluate the light and heavy breathing characteristics related to obstructive sleep apnea. Steady state Reynold’s averaged Navier-Stoke (RANS) with the k-ω shear stress transport (SST) turbulence model was utilized. The airflow characteristics were quantified using parameters such as pressure distribution, skin friction coefficient, velocity profile, Reynolds number, turbulent Reynolds number and turbulence kinetic energy. Results: Contour plots at different planes were used to visualize the airflow distribution as it passed through different cross-sectional areas of the airway. The results revealed that the presence of a smaller cross-sectional area of the airway caused an increase in airflow parameters, especially during heavy breathing. Furthermore, turbulent airflow conditions along the airway were noticed during heavy breathing. The severity of OSA could be measured by the turbulent kinetic energy which is able to show the behavior and concentration of mean flow. This study is expected to provide crucial and important results by visualizing the concentration of airflow mechanisms and characteristics of a patient’s airway during light and heavy breathing. These findings enable TKE to be used as a new tool for characterizing the severity of obstructive sleep apnea in the upper airways of patients.

Micro-machined stent flow sensor for detecting breathing and heartbeat from airflow in airway of rat

We developed a stent flow sensor using micro-electromechanical systems (MEMS) technology in order to measure airflow in the airways of laboratory animals. An airflow waveform contains a respiration signal produced by lung motion and heartbeats as these functions are physically connected. This enables both respiration and heart functions to be evaluated under unrestrained and unanesthetized conditions during drug development. Using MEMS technology, we fabricated a tube flow sensor based on a thermal principle, and the stent structure was produced by photolithography and wet etching. The fabricated flow sensor and stent were integrated via a connection area on both elements. In the proof-of-concept trial, we verified that the flow sensor was placed in the center of the tube by expanding the stent. We evaluated the flow detection characteristics, sensor output vs flow rate and sensor response and used the developed stent flow sensor to measure the airflow in the airway of a rat. The respiration and heartbeat signals were successfully identified from the airflow waveform by applying Fourier transform analysis.

Forced expiratory flow during 25%-75% of expiration in middle aged obese and non-obese females – A comparitive study

Introduction: Obesity can cause various health hazards in women in many ways. Overweight or being obese is associated with various risk factors like diabetes and coronary artery disease in women. The incidence of obesity is increasing worldwide. Obesity can cause alteration in pulmonary function which may lead to early morbidity and mortality. FEF 25%-75% is one of the most effort independent portion of the curve, more sensitive parameter to airflow in peripheral airways, where disease of chronic airflow obstruction can begin. Reduced Expiratory Flow rate value in obese individuals may be probably due to increase in the total peripheral resistance and airway resistance with obesity. Hence the present study was undertaken to know the impact of obesity on Forced Expiratory Flow rate25%-75% in middle aged obese females. Aims and Objectives: The present study was conducted ` to compare Pulmonary function test parameter FEF 25%-75% in middle aged obese and non-obese females, to determine the impact of obesity on FEF25%-75%. Materials and Methods: Dynamic Pulmonary Function tests (PFTs) of 50 normal, healthy, non-obese middle aged females and 50 healthy but obese middle aged females, age group 30-45 years of Hubli city were determined and were compared with its normal counterparts. Study subjects were classified into obese and non-obese based on WHO classification of BMI. To obtain the dynamic pulmonary function test computerized Spirometer Eazy on-PC model were used. Dynamic PFT parameter FEF25%-75%was used as measure of lung function. Results: In our Study conducted, middle aged obese females had FEF25%-75% (litre) of 2.53± 0.85 compared to corresponding values in controls were 2.77±1.06.Our study showed statistically significant differences between two groups. Conclusion: In our study Dynamic pulmonary function test parameter FEF25%-75% showed statistically significant reduction in obese compared to non-obese middle aged females. Keywords: Obesity, Middle aged obese

Peak Flow Meter with Measurement Analysis

The Peak flow meter is a device used to measure the amount of airflow in the human airway or often referred to as PFR (Peak Flow Rate). Peak Flow Rate (PFR) measurement is a simple and reliable way to detect airway obstruction. PFR measurement is a simple, non-invasive, fast and economic method to assess the strength and speed of expiration in L / min, through maximum expiration of capacity total lung. The results of peak flow data can illustrate early warning signs for an illness that in some cases may show a decrease in lung function 1-3 days before other respiratory symptoms become apparent. This module is designed using MPX5100GP sensor. This sensor has a pressure range of 0-100 Kpa. The Nature module is also equipped with data storage facilities using an SD Card so that the measurement data can be processed using Ms. Excel to find out graph data for further diagnostic purposes. The inspection results can be directly viewed on the display and also automatically stored in the SD Card storage that has been available. This module has the highest error rate of 4.41% and the lowest error value of 0.42% compared to the original device. From the data collection that has been done, it can be concluded that this module can be used for the inspection process.

Inhalation airflow and ventilation efficiency in subject-specific human upper airways

The present numerical study investigated the transportation time of the inhaled chemicals in three realistic human airway models by adopting a methodology from the field of the building ventilation. Two indexes including “scale of ventilation efficiency 3 (SVE3)” and “local purging flow rate (L-PFR)” were used to evaluate the respective arrival time and staying time under different inhalation flow rates. The general trend of the SVE3 was predicted as expected and the exceptions within the nasal cavities were attributed to the uneven allocation of the inhaled flow between the internal channels and the formation of the vortex circulation therein. The complicated situation of the L-PFR was also explained by the structure constrains. Moreover, the variation of the two indexes with the flow rate was sensitive to the inter-subjective differences but the distribution pattern was not changed significantly. By combining the SVE3 and L-PFR, it could help with assessing the potential effect of the inhaled chemicals on the human health for engineering applications to which the relative impacts are more interested than the absolute value. But for the precise evaluation regarding a specific chemical, comprehensive simulation is still necessary with the surface adsorption included under realistic respiration cycles.

Removing of Snoring Segments from Tracheal Breathing Sounds using a Wavelet-based Algorithm.

Tracheal sounds represent information about the upper airway and respiratory airflow, however, they can be contaminated by the snoring sounds. The sound of snoring has spectral content in a wide range that overlaps with that of breathing sounds during sleep. For assessing respiratory airflow using tracheal breathing sound, it is essential to remove the effect of snoring. In this paper, an automatic and unsupervised wavelet-based snoring removal algorithm is presented. Simultaneously with full-night polysomnography, the tracheal sound signals of 9 subjects with different levels of airway obstruction were recorded by a microphone placed over the trachea during sleep. The segments of tracheal sounds that were contaminated by snoring were manually identified through listening to the recordings. The selected segments were automatically categorized based on including discrete or continuous snoring pattern. Segments with discrete snoring were analyzed by an iterative wave-based filtering optimized to separate large spectral components related to snoring from smaller ones corresponded to breathing. Those with continuous snoring were first segmented into shorter segments. Then, each short segments were similarly analyzed along with a segment of normal breathing extracted from the recordings during wakefulness. The algorithm was evaluated by visual inspection of the denoised sound energy and comparison of the spectral densities before and after removing snores, where the overall rate of detectability of snoring was less than 2%.Clinical Relevance- The algorithm provides a way of separating snoring pattern from the tracheal breathing sounds. Therefore, each of them can be analyzed separately to assess respiratory airflow and the pathophysiology of the upper airway during sleep.

Application of patient-specific simulation workflow for obstructive sleep apnea diagnosis and treatment with a mandibular advancement device.

A computational fluid dynamics simulation workflow was developed to analyze the upper airway of patients with obstructive sleep apnea, which is a potentially serious sleep-related breathing disorder. A single characteristic parameter was introduced to assess the severity of sleep apnea on the basis of the numerical results. Additionally, a fluid-structure interaction simulation was applied to study in detail the behavior of compliant pharyngeal walls. An experimental setup was designed to validate the patient-specific upper airway modeling. The suitability of the characteristic parameter was demonstrated in a retrospective analysis of radiological and clinical data of 58 patients as well as a prospective analysis of 22 patients. The simulation workflow was successfully used as part of an ongoing clinical investigation to predict the outcome of the obstructive sleep apnea treatment with a mandibular advancement device. The simulation results provided essential information about the critical region in the pharynx for the selection of an appropriate treatment and readily demonstrated the effect of mandibular protrusion on the air flow in the upper airway.

Helium-Oxygen Mixture Model for Particle Transport in CT-Based Upper Airways.

The knowledge of respiratory particle transport in the extra-thoracic pathways is essential for the estimation of lung health-risk and optimization of targeted drug delivery. The published literature reports that a significant fraction of the inhaled aerosol particles are deposited in the upper airways, and available inhalers can deliver only a small amount of drug particles to the deeper airways. To improve the targeted drug delivery efficiency to the lungs, it is important to reduce the drug particle deposition in the upper airways. This study aims to minimize the unwanted aerosol particle deposition in the upper airways by employing a gas mixture model for the aerosol particle transport within the upper airways. A helium–oxygen (heliox) mixture (80% helium and 20% oxygen) model is developed for the airflow and particle transport as the heliox mixture is less dense than air. The mouth–throat and upper airway geometry are extracted from CT-scan images. Finite volume based ANSYS Fluent (19.2) solver is used to simulate the airflow and particle transport in the upper airways. Tecplot software and MATLAB code are employed for the airflow and particle post-processing. The simulation results show that turbulence intensity for heliox breathing is lower than in the case of air-breathing. The less turbulent heliox breathing eventually reduces the deposition efficiency (DE) at the upper airways than the air-breathing. The present study, along with additional patient-specific investigation, could improve the understanding of particle transport in upper airways, which may also increase the efficiency of aerosol drug delivery.

Physiological and geometrical effects in the upper airways with and without mandibular advance device for sleep apnea treatment

Sleep apnea is a sleep disorder that occurs when the breathing of a person is interrupted during the sleep. This interruption occurs because of the patient has narrowed airways and the upper airways muscles relax, closes in and blocks the airway. Therefore, any forces or reaction originated by the air flow dynamics over the relaxed upper airways muscles could make to close the upper airways, and consequently the air could not flow into your lungs, provoking sleep apnea. Fully describing the dynamic behavior of the airflow in this area is a severe challenge for the physicians. In this paper we explore the dynamic behavior of airflow in the upper airways of 6 patients suffering obstructive sleep apnea with/without a mandibular advancement device using computational fluid dynamics. The development of flow unsteadiness from a laminar state at entry to the pharynx through to the turbulent character in the soft palate area is resolved using an accurate numerical model. Combining the airflow solution with a geometrical analysis of the upper airways reveals the positive effects of mandibular advance device in the air flow behavior (pressure drop). Improved modeling of airflow and positioning of mandibular advance device could be applied to improve diagnosis and treatment of obstructive sleep apnea.

Particle transport and deposition correlation with near-wall flow characteristic under inspiratory airflow in lung airways

Exposure of lung airways to detrimental suspended aerosols in the environment increases the vulnerability of the respiratory and cardiovascular systems. In addition, recent developments in therapeutic inhalation devices magnify the importance of particle transport. In this manuscript, particle transport and deposition patterns in the upper tracheobronchial (TB) tree were studied where the inertial forces are considerable for microparticles. Wall shear stress divergence (WSSdiv) is proposed as a wall-based parameter that can predict particle deposition patterns. WSSdiv is proportional to near-wall normal velocity and can quantify the strength of flow towards and away from the wall. Computational fluid dynamics (CFD) simulations were performed to quantify airflow velocity and WSS vectors for steady inhalation in one case-control and unsteady inhalation in six subject-specific airway trees. Turbulent flow simulation was performed for the steady case using large eddy simulation to study the effect of turbulence. Magnetic resonance velocimetry (MRV) measurements were used to validate the case-control CFD simulation. Inertial particle transport was modeled by solving the Maxey–Riley equation in a Lagrangian framework. Deposition percentage (DP) was quantified for the case-control model over five particle sizes. DP was found to be proportional to particle size in agreement with previous studies in the literature. A normalized deposition concentration (DC) was defined to characterize localized deposition. A relatively strong correlation (Pearson value > 0.7) was found between DC and positive WSSdiv for physiologically relevant Stokes (St) numbers. Additionally, a regional analysis was performed after dividing the lungs into smaller areas. A spatial integral of positive WSSdiv over each division was shown to maintain a very strong correlation (Pearson value > 0.9) with cumulative spatial DC or regional dosimetry. The conclusions were generalized to a larger population in which two healthy and four asthmatic patients were investigated. This study shows that WSSdiv could be used to predict the qualitative surface deposition and relative regional dosimetry without the need to solve a particle transport problem.

An Overview of Experiments and Numerical Simulations on Airflow and Aerosols Deposition in Human Airways and the Role of Bioaerosol Motion in COVID-19 Transmission

Determining the hotspots and deposition efficiencies (DEs) for aerosols in human airways is important for both research and medical purposes. The complexity of the human airways and the breathing process limit the application of in vitro measurements to only two consecutive branches of the human airway. Herein, in-depth information on in vitro experiments and state-of-the-art review on various computational fluid dynamics (CFD) applications and finite element methods on airflow and aerosol motion in both healthy and obstructed human airways are provided. A brief introduction of the application of one-dimensional and two-dimensional mathematical models to investigate airflow and particle motion in the lungs are further discussed. As evident in this review, aerosol deposition in the upper and central human airway regions has been extensively studied under different inhalation statuses and conditions such as humidity as well as different aerosol sizes, shapes, and properties. However, there is little literature on the lower sections of the human airways. Herein, a detailed review of the fundamentals for both in vitro experiments and numerical simulation at different sections of human airways is done. Exceptional features and essential developments in numerical methods for aerosol motion in healthy and diseased human airways are also discussed. Challenges and limitations associated with the applications of in vitro experiments and CFD methods on both human-specific and idealized models are highlighted. The possibility of airborne transmission pathways for COVID-19 has been discussed. Overall, this review provides the most useful approach for carrying out two-phase flow investigations at different sections of the human lungs and under different inhalation statuses. Additionally, new research gaps that have developed recently on the role of bioaerosols motion in COVID-19 transmission, as well as the deposition of aerosols in impaired human airways due to coronavirus (COVID-19) are underlined.