Ultrafine particle transport and deposition in the upper airways of a CT-based realistic lung

© 2018 Australasian Fluid Mechanics Society. All rights reserved. The understanding of the toxic pollutant particles transport and deposition is important for dosimetry and respiratory health effects analysis. The studies over the last few decades for ultrafine particle transport and deposition improves the understanding of the drug-aerosol impacts in the extrathoracic airways. A limited number of studies has also considered upper airways and almost all of those studies used the non-realistic smooth surface for upper airway model. However, the smooth surface anatomical model is far from the realistic lung and it is important to consider realistic lung model for better prediction of ultrafine particle deposition. This study aims to simulate the ultrafine particle transport and deposition in the upper airways of a highly asymmetric CT-based model. The anatomically explicit digital airway model is generated from the high-resolution CT data of a healthy adult. Unstructured tetrahedral mesh throughout the geometry and fine inflation layer mesh near the wall is generated. Euler-Lagrange (E-L) approach and ANSYS Fluent solver (18.2) are used to investigate the ultrafine particle transport and deposition. A wide range of diameter (1 ≤ nm ≤ 1000) and different flow rates are considered for the ultrafine particle simulation. Pressure drop is calculated for right and left lobes which might be helpful for the therapeutic purpose of the asthma patient. The numerical study shows that the deposition efficiency in the right lung and the left lung is different for dissimilar flow rates, which could help the health risk assessment of the respiratory diseases and eventually could help the targeted drug delivery system

A macroscopic particle modelling approach for non-isothermal solid-gas and solid-liquid flows through porous media

© 2019 Elsevier Ltd The complexity of multiphase flows in many engineering systems such as heat exchangers signify the need to develop new and advanced numerical models to analyse the interactions the working fluid and unwanted solid foulants. Fouling is present in a myriad of industrial and domestic processes and it has a negative impact on the economy and the environment. The mechanisms that govern non-isothermal solid-fluid flow through porous metal foam heat exchangers are complex and poorly understood. In this research, a coupled finite volume method (FVM) and macroscopic particle model (MPM) is developed and implemented in ANSYS Fluent to examine the transient evolution of a non-isothermal multiphase solid-fluid flow and the interaction between coupled interactions of solid particles, fluid, and porous media. The maximum particle temperature is dependent on the fluid and solid particle thermo-physical properties in addition to the temperature of the cylindrical ligaments of the porous media. The present results show that the smallest solid particles reach the highest temperatures in the porous heat exchanger and at low inlet velocities, the highest particle temperatures are realized. The results pertaining to maximum particle temperatures are prevalent in many industrial processes and acquiring knowledge of the maximum particle temperature serves as a steppingstone for comprehending complex multiphase solid-fluid flows such as the cohesiveness between the particles and the particle adhesion with the walls. The results of these studies could potentially be used in the future to optimize metal foam heat exchanger designs

Aerosol particle transport and deposition in a CT-scan based mouth-throat model

© 2019 Author(s). A precise understanding of the aerosol particle transport and deposition (TD) in the realistic mouth-throat model is important for the respiratory health risk assessment and effective delivery of the aerosol medicine to the targeted positions of the lung. A wide range of studies have developed the particle TD framework for both idealized and non-idealized extra-thoracic airways. However, all of the existing in silico and experimental model reports a significant amount of aerosol particles are deposit at the extra-thoracic airways and the existing drug delivery device can deliver only 12 percent of the aerosol drug to the targeted position of the lung. This study aims to increase the efficiency of the targeted drug delivery by developing a realistic particle transport model for CT-Scan based mouth-throat replica. A 3-D realistic mouth-throat model is developed from the CT-Scan DiCom images of a healthy adult cast. High-Quality computational cells are generated for the replica model and the proper grid refinement test has been performed. ANSYS Fluent (19.1) solver is used for the particle TD computation. Tecplot and MATLAB software are used for the post-processing purpose. The numerical results report that the breathing pattern and particle diameter influences the overall particle TD in the mouth-throat model. The numerical results also depict different deposition hot spots for the mouth-throat model, which will eventually help to design a better drug delivery device. The numerical results reported that only 13.67 percent of the 10-μm diameter particles are deposited at the mouth-throat model at 15 lpm flow rate and which indicate that the remaining particles will move to the beyond airways. The present results along with more case studies will develop the understanding of the realistic particle deposition in the extrathoracic airways

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

Survey of Hypertension in Dhaka, Bangladesh: Changing Prescribing Patterns

Purpose: To assess changes in the prescribing pattern of antihypertensive drugs and lifestyle factors associated with hypertensive patients in Dhaka, Bangladesh.Methods: A cross-sectional study was conducted among 50 hypertensive patients in various heart disease hospitals and the consulting rooms of 10 cardiologists in the city of Dhaka to determine changes in prescribing patterns of antihypertensive drugs. Respondents were distributed more or less equally between males and the females.Results: Female patients aged 30 to 40 years (8 %) as well as male patients aged 50 to 60 years (54 %) and 60 to 70 years (12 %) were prone to hypertension. However, patients of both sexes whose age ranged from 40 to 50 (40 %) and 50 to 60 (36 %) were more prone to hypertension. It was observed that 46 % of the patients were overweight. A majority of the patients had diabetes with hypertension (28 %). Moreover, most of the patients (80 %) did not indulge in any physical exercise and were non-smokers but had a family history of hypertension. Combined antihypertensive drugs, especially thiazide diuretics with angiotensin II receptor blockers, calcium antagonists, and angiotensin-converting enzyme (ACE) inhibitors were the first choice of drugs by physicians. The prescribing rate of β-blockers (28.36 %) and combined antihypertensive preparations (40 %) was higher than that of older antihypertensives, viz loop diuretics, propranolol and enalapril.Conclusion: Combination therapy is favored by all doctors who compared with the past prescribing practice of a single medication for hypertension.Keywords: Hypertension, Prescribing pattern, Antihypertensive drugs, Lifestyle factors, Family histor

Ultrafine particle transport and deposition in a large scale 17-generation lung model

© 2017 Elsevier Ltd To understand how to assess optimally the risks of inhaled particles on respiratory health, it is necessary to comprehend the uptake of ultrafine particulate matter by inhalation during the complex transport process through a non-dichotomously bifurcating network of conduit airways. It is evident that the highly toxic ultrafine particles damage the respiratory epithelium in the terminal bronchioles. The wide range of in silico available and the limited realistic model for the extrathoracic region of the lung have improved understanding of the ultrafine particle transport and deposition (TD) in the upper airways. However, comprehensive ultrafine particle TD data for the real and entire lung model are still unavailable in the literature. Therefore, this study is aimed to provide an understanding of the ultrafine particle TD in the terminal bronchioles for the development of future therapeutics. The Euler-Lagrange (E-L) approach and ANSYS fluent (17.2) solver were used to investigate ultrafine particle TD. The physical conditions of sleeping, resting, and light activity were considered in this modelling study. A comprehensive pressure-drop along five selected path lines in different lobes was calculated. The non-linear behaviour of pressure-drops is observed, which could aid the health risk assessment system for patients with respiratory diseases. Numerical results also showed that ultrafine particle-deposition efficiency (DE) in different lobes is different for various physical activities. Moreover, the numerical results showed hot spots in various locations among the different lobes for different flow rates, which could be helpful for targeted therapeutical aerosol transport to terminal bronchioles and the alveolar region

Industrial metal pollution in water and probabilistic assessment of human health risk

© 2016 Elsevier Ltd Concentration of eight heavy metals in surface and groundwater around Dhaka Export Processing Zone (DEPZ) industrial area were investigated, and the health risk posed to local children and adult residents via ingestion and dermal contact was evaluated using deterministic and probabilistic approaches. Metal concentrations (except Cu, Mn, Ni, and Zn) in Bangshi River water were above the drinking water quality guidelines, while in groundwater were less than the recommended limits. Concentration of metals in surface water decreased as a function of distance. Estimations of non-carcinogenic health risk for surface water revealed that mean hazard index (HI) values of As, Cr, Cu, and Pb for combined pathways (i.e., ingestion and dermal contact) were >1.0 for both age groups. The estimated risk mainly came from the ingestion pathway. However, the HI values for all the examined metals in groundwater were 1 × 10−4 for adult and children, respectively. Deterministic and probabilistic estimations of cancer risk through exposure to groundwater were well below the safety limit. Overall, the population exposed to Bangshi River water remained at carcinogenic and non-carcinogenic health threat and the risk was higher for adults. Sensitivity analysis identified exposure duration (ED) and ingestion rate (IR) of water as the most relevant variables affecting the probabilistic risk estimation model outcome

Airflow and particle transport prediction through stenosis airways

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. Airflow and particle transport in the human lung system is influenced by biological and other factors such as breathing pattern, particle properties, and deposition mechanisms. Most of the studies to date have analyzed airflow characterization and aerosol transport in idealized and realistic models. Precise airflow characterization for airway stenosis in a digital reference model is lacking in the literature. This study presents a numerical simulation of airflow and particle transport through a stenosis section of the airway. A realistic CT-scan-based mouth–throat and upper airway model was used for the numerical calculations. Three different models of a healthy lung and of airway stenosis of the left and right lung were used for the calculations. The ANSYS FLUENT solver, based on the finite volume discretization technique, was used as a numerical tool. Proper grid refinement and validation were performed. The numerical results show a complex-velocity flow field for airway stenosis, where airflow velocity magnitude at the stenosis section was found to be higher than that in healthy airways. Pressure drops at the mouth–throat and in the upper airways show a nonlinear trend. Comprehensive pressure analysis of stenosis airways would increase our knowledge of the safe mechanical ventilation of the lung. The turbulence intensities at the stenosis sections of the right and left lung were found to be different. Deposition efficiency (DE) increased with flow rate and particle size. The findings of the present study increase our understanding of airflow patterns in airway stenosis under various disease conditions. More comprehensive stenosis analysis is required to further improve knowledge of the field