Imperial College London

Dr Laura Nicolaou

Faculty of EngineeringDepartment of Mechanical Engineering

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+44 (0)20 7595 7112laura.nicolaou Website

 
 
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609City and Guilds BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
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25 results found

Checkley W, Williams KN, Kephart JL, Fandiño-Del-Rio M, Steenland NK, Gonzales GF, Naeher LP, Harvey SA, Moulton LH, Davila-Roman VG, Goodman D, Tarazona-Meza C, Miele CH, Simkovich S, Chiang M, Chartier RT, Koehler K, CHAP Trial Investigatorset al., 2021, Effects of a Household Air Pollution Intervention with Liquefied Petroleum Gas on Cardiopulmonary Outcomes in Peru. A Randomized Controlled Trial., Am J Respir Crit Care Med, Vol: 203, Pages: 1386-1397

Rationale: Approximately 40% of people worldwide are exposed to household air pollution (HAP) from the burning of biomass fuels. Previous efforts to document health benefits of HAP mitigation have been stymied by an inability to lower emissions to target levels. Objectives: We sought to determine if a household air pollution intervention with liquefied petroleum gas (LPG) improved cardiopulmonary health outcomes in adult women living in a resource-poor setting in Peru. Methods: We conducted a randomized controlled field trial in 180 women aged 25-64 years living in rural Puno, Peru. Intervention women received an LPG stove, continuous fuel delivery for 1 year, education, and behavioral messaging, whereas control women were asked to continue their usual cooking practices. We assessed for stove use adherence using temperature loggers installed in both LPG and biomass stoves of intervention households. Measurements and Main Results: We measured blood pressure, peak expiratory flow (PEF), and respiratory symptoms using the St. George's Respiratory Questionnaire at baseline and at 3-4 visits after randomization. Intervention women used their LPG stove exclusively for 98% of days. We did not find differences in average postrandomization systolic blood pressure (intervention - control 0.7 mm Hg; 95% confidence interval, -2.1 to 3.4), diastolic blood pressure (0.3 mm Hg; -1.5 to 2.0), prebronchodilator peak expiratory flow/height2 (0.14 L/s/m2; -0.02 to 0.29), postbronchodilator peak expiratory flow/height2 (0.11 L/s/m2; -0.05 to 0.27), or St. George's Respiratory Questionnaire total score (-1.4; -3.9 to 1.2) over 1 year in intention-to-treat analysis. There were no reported harms related to the intervention. Conclusions: We did not find evidence of a difference in blood pressure, lung function, or respiratory symptoms during the year-long intervention with LPG. Clinical trial registered with www.clinicaltrials.gov (NCT02994680).

Journal article

Nicolaou L, Checkley W, 2021, Differences between cigarette smoking and biomass smoke exposure: An in silico comparative assessment of particulate deposition in the lungs, Environmental Research, Vol: 197, Pages: 111116-111116, ISSN: 0013-9351

Journal article

Nicolaou L, Checkley W, 2021, Inequities in air pollution exposure and gaps in air quality monitoring, Journal of Allergy and Clinical Immunology, ISSN: 0091-6749

Journal article

Levitt JE, Festic E, Desai M, Hedlin H, Mahaffey KW, Rogers AJ, Gajic O, Matthay MA, ARREST Pneumonia Clinical Trial Investigatorset al., 2021, The ARREST Pneumonia Clinical Trial. Rationale and Design., Ann Am Thorac Soc, Vol: 18, Pages: 698-708

Patients hospitalized for pneumonia are at high risk for mortality. Effective therapies are therefore needed. Recent randomized clinical trials suggest that systemic steroids can reduce the length of hospital stays among patients hospitalized for pneumonia. Furthermore, preliminary findings from a feasibility study demonstrated that early treatment with a combination of an inhaled corticosteroid and a bronchodilator can improve oxygenation and reduce risk of respiratory failure in patients at risk of acute respiratory distress syndrome. Whether such a combination administered early is effective in reducing acute respiratory failure (ARF) among patients hospitalized with pneumonia is unknown. Here we describe the ARREST Pneumonia (Arrest Respiratory Failure due to Pneumonia) trial designed to address this question. ARREST Pneumonia is a two-arm, randomized, double-blinded, placebo-controlled trial designed to test the efficacy of a combination of an inhaled corticosteroid and a β-agonist compared with placebo for the prevention of ARF in hospitalized participants with severe pneumonia. The primary outcome is ARF within 7 days of randomization, defined as a composite endpoint of intubation and mechanical ventilation; need for high-flow nasal cannula oxygen therapy or noninvasive ventilation for >36 hours (each alone or combined); or death within 36 hours of being placed on respiratory support. The planned enrollment is 600 adult participants at 10 academic medical centers. In addition, we will measure selected plasma biomarkers to better understand mechanisms of action. The trial is funded by the U.S. National Heart Lung and Blood Institute.Clinical trial registered with www.clinicaltrials.gov (NCT04193878).

Journal article

Nicolaou L, FandiñoDelRio M, Koehler K, Checkley Wet al., 2021, Size distribution and lung‐deposited doses of particulate matter from household exposure to biomass smoke, Indoor Air, Vol: 31, Pages: 51-62, ISSN: 0905-6947

Exposure to high concentrations of particulate matter (PM) is associated with a number of adverse health effects. However, it is unclear which aspects of PM are most hazardous, and a better understanding of particle sizes and personal exposure is needed. We characterized particle size distribution (PSD) from biomass‐related pollution and assessed total and regional lung‐deposited doses using multiple‐path deposition modeling. Gravimetric measurements of kitchen and personal PM2.5 (< 2.5 µm in size) exposures were collected in 180 households in rural Puno, Peru. Direct‐reading measurements of number concentrations were collected in a subset of 20 kitchens for particles 0.3–25 µm, and the continuous PSD was derived using a nonlinear least‐squares method. Mean daily PM2.5 kitchen concentration and personal exposure was 1205±942 µg/m3 and 115±167 µg/m3 respectively, and the mean mass concentration consisted of a primary accumulation mode at 0.21 µm and a secondary coarse mode at 3.17 µm. Mean daily lung‐deposited surface area (LDSA) and LDSA during cooking were 1009.6±1469.8 µm2/cm3 and 10,552.5±8261.6 µm2/cm3, respectively. This study presents unique data regarding lung deposition of biomass smoke that could serve as a reference for future studies, and provides a novel, more biologically‐relevant metric for exposure‐response analysis compared to traditional size‐based metrics.

Journal article

Kephart JL, Fandiño-Del-Rio M, Williams KN, Malpartida G, Lee A, Steenland K, Naeher LP, Gonzales GF, Chiang M, Checkley W, Koehler K, CHAP trial Investigatorset al., 2021, Nitrogen dioxide exposures from LPG stoves in a cleaner-cooking intervention trial., Environ Int, Vol: 146

BACKGROUND: Liquefied petroleum gas (LPG) stoves have been promoted in low- and middle-income countries (LMICs) as a clean energy alternative to biomass burning cookstoves. OBJECTIVE: We sought to characterize kitchen area concentrations and personal exposures to nitrogen dioxide (NO2) within a randomized controlled trial in the Peruvian Andes. The intervention included the provision of an LPG stove and continuous fuel distribution with behavioral messaging to maximize compliance. METHODS: We measured 48-hour kitchen area NO2 concentrations at high temporal resolution in homes of 50 intervention participants and 50 control participants longitudinally within a biomass-to-LPG intervention trial. We also collected 48-hour mean personal exposures to NO2 among a subsample of 16 intervention and 9 control participants. We monitored LPG and biomass stove use continuously throughout the trial. RESULTS: In 367 post-intervention 24-hour kitchen area samples of 96 participants' homes, geometric mean (GM) highest hourly NO2 concentration was 138 ppb (geometric standard deviation [GSD] 2.1) in the LPG intervention group and 450 ppb (GSD 3.1) in the biomass control group. Post-intervention 24-hour mean NO2 concentrations were a GM of 43 ppb (GSD 1.7) in the intervention group and 77 ppb (GSD 2.0) in the control group. Kitchen area NO2 concentrations exceeded the WHO indoor hourly guideline an average of 1.3 h per day among LPG intervention participants. GM 48-hour personal exposure to NO2 was 5 ppb (GSD 2.4) among 35 48-hour samples of 16 participants in the intervention group and 16 ppb (GSD 2.3) among 21 samples of 9 participants in the control group. DISCUSSION: In a biomass-to-LPG intervention trial in Peru, kitchen area NO2 concentrations were substantially lower within the LPG intervention group compared to the biomass-using control group. However, within the LPG intervention group, 69% of 24-hour kitchen area samples exceeded WHO indoor a

Journal article

Fandiño-Del-Rio M, Kephart JL, Williams KN, Moulton LH, Steenland K, Checkley W, Koehler K, Cardiopulmonary outcomes and Household Air Pollution trial CHAP Trial Investigatorset al., 2020, Household air pollution exposure and associations with household characteristics among biomass cookstove users in Puno, Peru., Environ Res, Vol: 191

BACKGROUND: Household air pollution (HAP) from combustion of biomass fuel, such as wood and animal dung, is among the leading environmental risk factors for preventable disease. Close to half of the world's population relies on biomass cookstoves for their daily cooking needs. Understanding factors that affect HAP can inform measures to maximize the effectiveness of cookstove interventions in a cost-effective manner. However, the impact of kitchen and household characteristics, as well as the presence of secondary stoves, on HAP concentrations is poorly understood in Puno, Peru. OBJECTIVE: To explore how household characteristics explain variability of kitchen area concentrations and personal exposures to CO, PM2.5 and BC from biomass cookstoves among women in rural Peru. METHODS: Household characteristics (including kitchen materials and layout, wealth, and cooking behaviors) and HAP measurements were collected from 180 households in Puno, Peru, from baseline measurements of a randomized trial. Kitchen area concentrations and personal exposures to carbon monoxide (CO), fine particulate matter (PM2.5) and black carbon (BC) were sampled for 48 h. We implemented simple and multivariable linear regression models to determine the associations between household characteristics and both kitchen area concentration and personal exposure to each pollutant. RESULTS: Mean daily kitchen area concentrations and personal exposures to HAP were, on average, 48 times above World Health Organization indoor guidelines for PM2.5. We found that roof type explained the most variability in HAP and was strongly associated with both kitchen area concentrations and personal exposures for all pollutants after adjusting for other household variables. Personal exposures were 27%-36% lower for PM2.5, CO and BC, in households with corrugated metal roofs, compared to roofs made of natural materials (straw, totora or reed) after adjusting for other factors. Higher kitchen area concentrations w

Journal article

Nicolaou L, Ahmed T, Bhutta ZA, Bessong P, Kosek M, Lima AAM, Shrestha S, Chandyo R, Mduma ER, Murray-Kolb L, Morgan B, Grigsby MR, Checkley Wet al., 2020, Factors associated with head circumference and indices of cognitive development in early childhood, BMJ Global Health, Vol: 5

Background While head circumference (HC) has been related to intracranial volume and brain size, its association with cognitive function remains unclear. We sought to understand the relationship among various biological and socioeconomic risk factors, HC and cognitive development. Methods We analysed data across resource-poor settings in Bangladesh, India, Nepal, Peru, South Africa and Tanzania from the Etiology, Risk Factors and Interactions of Enteric Infections and Malnutrition and the Consequences for Child Health and Development longitudinal birth cohort study. Participating children were enrolled and followed up between 2009 and 2014. A final sample of 1210 children aged 0-24 months were included in the analyses. The main outcomes were HC for age Z-score and cognitive, gross motor and language scores from Bayley Scales of Infant Development-III tests. Length, weight and HC were measured monthly, and cognitive tests were administered at 6, 15 and 24 months of age. To disentangle the associations between risk factors and HC from linear growth and to distinguish the direct and indirect effects of these risk factors on cognitive function, we conducted mediation analysis using longitudinal models to account for all data measured during follow-up. Results Average HC-for-age Z-score (HCAZ) was-0.54 (95% CI-0.47 to-0.62) near birth and-1.01 (95% CI-0.94 to-1.08) at 24 months. Children with higher enrolment weight (p<0.0001), higher socioeconomic score (p=0.00037) and taller mothers (p=0.00084) had higher HCAZ at all ages, while enteropathogen infection (p=0.013) and more febrile episodes (p=0.013) were associated with lower HCAZ. The associations between HCAZ and enrolment weight-for-age, maternal height, socioeconomic status or pathogen burden were partly mediated through their associations with length-for-age. HCAZ showed no association with cognitive, gross motor or language skills at 6, 15 and 24 months of age. Conclusions The main risk factors associated with

Journal article

Nicolaou L, Fandiño del Rio M, Koehler K, Steenland K, Checkley Wet al., 2020, Assessing household air pollution exposure using lung deposition models, American Thoracic Society, Publisher: American Thoracic Society, Pages: A1809-A1809, ISSN: 1073-449X

Conference paper

Singanayagam A, Zhou J, Elderfield RA, Frise R, Ashcroft J, Galiano M, Miah S, Nicolaou L, Barclay WSet al., 2020, Characterising viable virus from air exhaled by H1N1 influenza-infected ferrets reveals the importance of haemagglutinin stability for airborne infectivity, PLoS Pathogens, Vol: 16, Pages: 1-21, ISSN: 1553-7366

The transmissibility and pandemic potential of influenza viruses depends on their ability to efficiently replicate and be released from an infected host, retain viability as they pass through the environment, and then initiate infection in the next host. There is a significant gap in knowledge about viral properties that enable survival of influenza viruses between hosts, due to a lack of experimental methods to reliably isolate viable virus from the air. Using a novel technique, we isolate and characterise infectious virus from droplets emitted by 2009 pandemic H1N1-infected ferrets. We demonstrate that infectious virus is predominantly released early after infection. A virus containing a mutation destabilising the haemagglutinin (HA) surface protein displayed reduced survival in air. Infectious virus recovered from droplets exhaled by ferrets inoculated with this virus contained mutations that conferred restabilisation of HA, indicating the importance of influenza HA stability for between-host survival. Using this unique approach can improve knowledge about the determinants and mechanisms of influenza transmissibility and ultimately could be applied to studies of airborne virus exhaled from infected people.

Journal article

Nicolaou L, 2018, Inertial and gravitational effects on aerosol deposition in the conducting airways, Journal of Aerosol Science, Vol: 120, Pages: 32-51, ISSN: 0021-8502

In most inhaled drug delivery applications, aerosol deposition in the upper airways occurs primarily via impaction. However, the effects of gravity become important as particle size increases and flow rate decreases. Sedimentation can therefore be significant in the smaller airways of the tracheobronchial tree, where velocities decrease due to the large increase in cross-sectional area, as well as the larger airways at low inhalation flow rates. In order to assess the relative importance of impaction and sedimentation, particle transport and deposition is examined under different steady inhalation conditions in a mouth-throat and a bifurcation model, using direct numerical simulations. The results are also compared to computations without the effect of gravity on the particles. Two important parameters characterize particle motion: (i) the Stokes number, StkStk, and (ii) the ratio of the gravitational settling velocity to the fluid velocity, View the MathML sourceVg*. The ratio of these two parameters is the Froude number, which measures the relative importance of inertial to gravitational forces. Instantaneous definitions of the Stokes number, non-dimensional settling velocity and Froude number are derived, based on the local flow properties, which provide a more accurate representation of the particle trajectories compared to the reference parameters based on characteristic flow scales. Results show that, in certain regions of the flow, the instantaneous Froude number can be three to four orders of magnitude smaller than the reference value. In these regions, deposition via sedimentation is shown to be significant, and the reference parameter underestimates gravitational effects. In the extrathoracic airways, particles with high View the MathML sourceVg* deposit primarily in the mouth, via sedimentation, while particles with high StkStk deposit mainly in the larynx and trachea, via impaction. In the bifurcation, different orientation angles of the airway geometry

Journal article

Koullapis P, Nicolaou L, Kassinos SC, 2018, In silico assessment of mouth-throat effects on regional deposition in the upper tracheobronchial airways, Journal of Aerosol Science, Vol: 117, Pages: 164-188, ISSN: 0021-8502

Regional deposition of inhaled medicines is a valuable metric of effectiveness in drug delivery applications to the lung. In silico methods are now emerging as a valuable tool for the detailed description of localized deposition in the respiratory airways. In this context, there is a need to minimize the computational cost of high-fidelity numerical approaches. Motivated by this need, the present study is designed to assess the role of the extrathoracic airways in determining regional deposition in the upper bronchial airways. Three mouth-throat geometries, with significantly different geometric and filtering characteristics, are merged onto the same tracheobronchial tree that extends to generation 8, and Large Eddy Simulations are carried out at steady inhalation flowrates of 30 and View the MathML source. At both flowrates, large flow field differences in the extrathoracic airways across the three geometries largely die out below the main bifurcation. Importantly, localized deposition fractions are found to remain practically identical for particles with aerodynamic diameters of up to View the MathML source and View the MathML source at 30 and View the MathML source, respectively. For larger particles, differences in the localized deposition fractions are shown to be mainly due to variations in the mouth-throat filtering rather than upstream flow effects or differences in the local flow field. Deposition efficiencies in the individual airway segments exhibit strong correlations across the three geometries, for all particle sizes. The results suggest that accurate predictions of regional deposition in the tracheobronchial airways can therefore be obtained if the particle size distribution that escapes filtering in the mouth-throat (ex-cast dose) of a particular patient is known or can be estimated. These findings open the prospect for significant reductions in the computational expense, especially in the context of in silico population studies, where the aerosol

Journal article

Koullapis P, Kassinos SC, Muela J, Perez-Segarra C, Rigola J, Lehmkuhl O, Cui Y, Sommerfeld M, Elcner J, Jicha M, Saveljic I, Filipovic N, Lizal F, Nicolaou Let al., 2017, Regional aerosol deposition in the human airways: the SimInhale benchmark case and a critical assessment of in silico methods, European Journal of Pharmaceutical Sciences, Vol: 113, Pages: 77-94, ISSN: 0928-0987

Regional deposition effects are important in the pulmonary delivery of drugs intended for the topical treatment of respiratory ailments. They also play a critical role in the systemic delivery of drugs with limited lung bioavailability. In recent years, significant improvements in the quality of pulmonary imaging have taken place, however the resolution of current imaging modalities remains inadequate for quantifying regional deposition. Computational Fluid-Particle Dynamics (CFPD) can fill this gap by providing detailed information about regional deposition in the extrathoracic and conducting airways. It is therefore not surprising that the last 15 years have seen an exponential growth in the application of CFPD methods in this area. Survey of the recent literature however, reveals a wide variability in the range of modelling approaches used and in the assumptions made about important physical processes taking place during aerosol inhalation. The purpose of this work is to provide a concise critical review of the computational approaches used to date, and to present a benchmark case for validation of future studies in the upper airways. In the spirit of providing the wider community with a reference for quality assurance of CFPD studies, in vitro deposition measurements have been conducted in a human-based model of the upper airways, and several groups within MP1404 SimInhale have computed the same case using a variety of simulation and discretization approaches. Here, we report the results of this collaborative effort and provide a critical discussion of the performance of the various simulation methods. The benchmark case, in vitro deposition data and in silico results will be published online and made available to the wider community. Particle image velocimetry measurements of the flow, as well as additional numerical results from the community, will be appended to the online database as they become available in the future.

Journal article

Koullapis P, Nicolaou L, Kassinos S, 2017, The effect of mouth-throat geometry on regional deposition in the tracheobronchial tree, 5th International Conference on Computational and Mathematical Biomedical Engineering – CMBE2017, Publisher: CMBE, Pages: 942-945, ISSN: 2227-3085

In silico methods offer a valuable approach to predict localized deposition in the tracheobronchialtree, important in the topical treatment of respiratory diseases and the systemic administration ofdrugs with limited lung bioavailability. In this study, we examine the effect of extrathoracic airwayvariation on regional deposition in order to assess whether standard mouth-throat models canbe adopted for more efficient predictions. Despite large qualitative differences in the extrathoracicairways, deposition patterns and efficiencies in the tracheobronchial region remain largely unaffectedfor particles smaller than 6 microns. The findings suggest that for drug delivery applications, standardmouth-throat models could be adopted to predict deposition in the central airways.

Conference paper

Nicolaou L, Zaki TA, 2016, Characterization of aerosol Stokes number in 90◦ bends and idealized extrathoracic airways, Journal of Aerosol Science, Vol: 102, Pages: 105-127, ISSN: 0021-8502

Prediction of aerosol deposition in the respiratory system is important for improving the efficiency of inhaled drug delivery and for assessing the toxicity of airborne pollutants. Deposition is typically reported as a function of a global Stokes number which is based on a reference flow timescale, or the ratio of the characteristic flow length and velocity scales. In reality however, particles experience varying flow timescales as they are advected through the airways, which motivates the use of an instantaneous Stokes number based on the local properties of the flow field. We then define the effective Stokes number as the time-average of the instantaneous value. This effective Stokes number thus encapsulates the flow history and geometric variability, and provides a more detailed account of the particle trajectory in the flow. Laminar and turbulent flows in a curved pipe are examined first and provide a simplified, or canonical, configuration of the flow in the upper airways. They are followed by a study of turbulent flow in an idealized mouth-throat geometry. Our results demonstrate that the effective Stokes number can deviate significantly from the traditional value based solely on the reference flow timescale. In addition, the effective Stokes number shows a clear correlation with deposition efficiency and can therefore be used to determine optimal aerosol release locations in order to minimize extrathoracic losses.

Journal article

Koullapis P, Nicolaou L, Kassinos S, 2016, In silico assessment of mouth-throat effects on regional deposition in the conducting human airways, 14th International Symposium on Computer Methods in Biomechanics and Biomedical Engineering

Conference paper

Nicolaou L, Zaki T, 2016, The instantaneous Stokes number for aerosol transport and deposition in the respiratory airways, 14th International Symposium on Computer Methods in Biomechanics and Biomedical Engineering

Conference paper

Nicolaou L, Zaki TA, 2016, Deposition characteristics in particle-laden turbulent flows, 9th International Conference on Multiphase Flow

Conference paper

Nicolaou L, Jung SY, Zaki TA, 2015, A robust direct-forcing immersed boundary method with enhanced stability for moving body problems in curvilinear coordinates, Computers and Fluids, Vol: 119, Pages: 101-114, ISSN: 0045-7930

A robust immersed boundary method for semi-implicit discretizations of the Navier-Stokes equations on curvilinear grids is presented. No-slip conditions are enforced via momentum forcing, and mass conservation at the immersed boundary is satisfied via a mass source term developed for moving bodies. The errors associated with an explicit evaluation of the momentum forcing are analysed, and their influence on the stability of the underlying Navier-Stokes solver is examined. An iterative approach to compute the forcing term implicitly is proposed, which reduces the errors at the boundary and retains the stability guarantees of the original semi-implicit discretization of the Navier-Stokes equations. The implementation in generalized curvilinear coordinates and the treatment of moving boundaries are presented, followed by a number of test cases. The tests include stationary and moving boundaries and curvilinear grid problems (decaying vortex problem, stationary cylinder, flow in 90° bend in circular duct and oscillating cylinder in fluid at rest).

Journal article

Nicolaou L, Zaki TA, 2015, On the Stokes number and characterization of aerosol deposition in the respiratory airways, 4th International Conference on Computational and Mathematical Biomedical Engineering - CMBE2015, Pages: 224-227, ISSN: 2227-3085

Aerosol deposition in the respiratory airways has traditionally been examined in terms of the Stokes number based on the reference flow timescale. This choice leads to large scatter in deposition efficiency when plotted against the reference Stokes number because the velocity and length scales experienced by advected particles deviate considerably from the reference values. A time-average of the particle local Stokes number should be adopted instead. Our results demonstrate that this average, or effective, Stokes number can deviate significantly from the reference value, in particular in the intermediate Stokes number range where variation across subjects is largest.

Conference paper

Nicolaou L, Zaki TA, 2014, An in silico laboratory for patient-specific treatment of asthma and COPD, Drug Delivery to the Lungs 25, Publisher: The Aerosol Society

Predictive numerical capabilities have the potential for significant impact in the advancement of therapies for lung disease. Accurate and efficient numerical models can provide a valuable clinical aid to optimise therapies and to define the appropriate treatment, for example in severe asthma and chronic obstructive pulmonary disease (COPD). Geometric variations of the respiratory airways across subjects, however, have a pronounced effect on the airflow and aerosol deposition and, hence, pose a significant hurdle which motivates personalised treatment of respiratory diseases. An in silico framework for patient-specific predictions of the flow and aerosol deposition in the respiratory airways is presented. The proposed computational laboratory efficiently accommodates geometric variation and airway motion in order to optimise pulmonary delivery for patients with severe asthma and COPD. Dynamic airway models conforming to the patient’s breathing are constructed via a non-rigid registration method. The flow solver takes advantage of a novel immersed boundary (IB) approach which efficiently handles realistic airway geometries obtained from medical images of patients’ lungs. The transport and deposition of the aerosol particles in the airways is modelled via a Lagrangian point particle-tracking scheme. Using this method, the flow and aerosol deposition in realistic extrathoracic airways are examined and a patient-specific dynamic lung model is presented.

Conference paper

Nicolaou L, Zaki TA, 2013, An immersed boundary method for patient-specific modelling of flow and aerosol deposition in the extrathoracic airways, 3rd International Conference on Computational and Mathematical Biomedical Engineering - CMBE2013, Pages: 414-417, ISSN: 2227-3085

Conference paper

Nicolaou L, Zaki TA, 2013, An immersed boundary method for patient-specific modelling of flow and aerosol deposition in the respiratory airways, Hong Kong, HK, 3rd International Conference on Computational and Mathematical Biomedical Engineering - CMBE2013, Publisher: CMBE, Pages: 414-417, ISSN: 2227-3085

Conference paper

Nicolaou L, Zaki TA, 2012, Direct numerical simulations of flow in realistic mouth–throat geometries, Journal of Aerosol Science, Vol: 57, Pages: 71-87, ISSN: 1879-1964

The flow in a set of four realistic mouth–throat geometries at a flow rate of 30 L/min is studied in order to determine the effect of intrasubject and intersubject variations on the mean flow patterns and the turbulence fluctuations. Direct numerical simulations (DNS) are performed, which fully resolve all the scales in the flow, without requiring a turbulence model. An immersed boundary method is applied on curvilinear grids which simplifies the task of grid generation for the complex extrathoracic geometries and allows the use of a structured grid solver which increases the efficiency of the numerical scheme. Inspection of the mean, responsible for the convective transport of particles, and the fluctuating component of velocity, responsible for turbulent dispersion, allows us to explain in vitro deposition data in the literature obtained in the same mouth– throat models. The results provide insight as to how geometric variation affects aerosol deposition and explain the scatter in deposition data observed in the literature. Geometric variation is shown to have a large impact on both the mean velocity profiles and the turbulence intensities. Examination of the flow fields in the various mouth– throat geometries allows us to address the origin of the dependence of deposition on Reynolds number, and provide the physical significance of the empirical Reynolds number correction previously proposed in the literature.

Journal article

Nicolaou L, Zaki TA, 2012, Prediction of flow and aerosol deposition in the extrathoracic airways using an implicit immersed boundary method, 9th International ERCOFTAC Symposium on Engineering Turbulence Modeling and Measurements (ETMM9)

The effect of intrasubject variation on the turbulentflow and aerosol deposition in the extrathoracic airwaysis studied in two realistic mouth-throat geometriesfrom the same subject. An immersed boundarymethod is applied which simplifies the task of gridgeneration for the complex extrathoracic geometriesand allows the use of a structured grid solver. Curvilineargrids that roughly follow the shape of the geometriesare adopted, allowing for much higher resolutionwithin the geometries than Cartesian grids commonlyused in IB methods. An added advantage isthat the grid lines are approximately aligned with thestreamlines, which reduces numerical diffusive errors.The numerical simulations allow us to explain in vitroaerosol deposition data in the literature for the samemouth-throat models. The position of the tongue duringinhalation is shown to have a significant impact onboth the mean flow patterns and the turbulence intensities,which in turn affects extrathoracic deposition.

Conference paper

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