Azadeh Akhavan Taheri Borojeni | University of California, San Diego (original) (raw)

Papers by Azadeh Akhavan Taheri Borojeni

Research paper thumbnail of Aerosol Transport Modeling: The Key Link Between Lung Infections of Individuals and Populations

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2022

The recent COVID-19 pandemic has propelled the field of aerosol science to the forefront, particu... more The recent COVID-19 pandemic has propelled the field of aerosol science to the forefront, particularly the central role of virus-laden respiratory droplets and aerosols. The pandemic has also highlighted the critical need, and value for, an information bridge between epidemiological models (that inform policymakers to develop public health responses) and within-host models (that inform the public and health care providers how individuals develop respiratory infections). Here, we review existing data and models of generation of respiratory droplets and aerosols, their exhalation and inhalation, and the fate of infectious droplet transport and deposition throughout the respiratory tract. We then articulate how aerosol transport modeling can serve as a bridge between and guide calibration of withinhost and epidemiological models, forming a comprehensive tool to formulate and test hypotheses about respiratory tract exposure and infection within and between individuals.

Research paper thumbnail of A hierarchical stepwise approach to evaluate nasal patency after virtual surgery for nasal airway obstruction

Clinical Biomechanics, 2019

Background: Despite advances in medicine and expenditures associated in treatment of nasal airway... more Background: Despite advances in medicine and expenditures associated in treatment of nasal airway obstruction, 25-50% of patients undergoing nasal surgeries complain of persistent obstructive symptoms. Our objective is to develop a "stepwise virtual surgery" method that optimizes surgical outcomes for treatment of nasal airway obstruction. Methods: Pre-surgery radiographic images of two subjects with nasal airway obstruction were imported into Mimics imaging software package for three-dimension reconstruction of the airway. A hierarchical stepwise approach was used to create seven virtual surgery nasal models comprising individual (inferior turbinectomy or septoplasty) procedures and combined inferior turbinectomy and septoplasty procedures via digital modifications of each subject's pre-surgery nasal model. To evaluate the effects of these procedures on nasal patency, computational fluid dynamics modeling was used to perform steady-state laminar inspiratory airflow and heat transfer simulations in every model, at resting breathing. Airflow-related variables were calculated for virtual surgery models and compared with dataset containing results of healthy subjects with no symptoms of nasal obstruction.

Research paper thumbnail of In Silico Quantification of Intersubject Variability on Aerosol Deposition in the Oral Airway

Pharmaceutics, Jan 3, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Virtual Surgery for the Nasal Airway

JAMA Facial Plastic Surgery, 2018

IMPORTANCE Nasal airway obstruction (NAO) is a common problem that affects patient quality of lif... more IMPORTANCE Nasal airway obstruction (NAO) is a common problem that affects patient quality of life. Surgical success for NAO correction is variable. Virtual surgery planning via computational fluid dynamics (CFD) has the potential to improve the success rates of NAO surgery. OBJECTIVE To elicit surgeon feedback of a virtual surgery planning tool for NAO and to determine if this tool affects surgeon decision making. DESIGN, SETTING, AND PARTICIPANTS For this cross-sectional study, 60-minute face-to-face interviews with board-certified otolaryngologists were conducted at a single academic otolaryngology department from September 16, 2016, through October 7, 2016. Virtual surgery methods were introduced, and surgeons were able to interact with the virtual surgery planning tool interface. Surgeons were provided with a patient case of NAO, and open feedback of the platform was obtained, with emphasis on surgical decision making. MAIN OUTCOMES AND MEASURES Likert scale responses and qualitative feedback were collected for the virtual surgery planning tool and its influence on surgeon decision making. RESULTS Our 9 study participants were all male, board-certified otolaryngologists with a mean (range) 15 (4-28) number of years in practice and a mean (range) number of nasal surgeries per month at 2.2 (0.0-6.0). When examined on a scale of 1 (not at all) to 5 (completely), surgeon mean (SD) score was 3.4 (0.5) for how realistic the virtual models were compared with actual surgery. On the same scale, when asked how much the virtual surgery planning tool changed surgeon decision making, mean (SD) score was 2.6 (1.6). On a scale of 1 (strongly disagree) to 7 (strongly agree), surgeon scores for perceived usefulness of the technology and attitude toward using it were 5.1 (1.1) and 5.7 (0.9), respectively. CONCLUSIONS AND RELEVANCE Our study shows positive surgeon experience with a virtual surgery planning tool for NAO based on CFD simulations. Surgeons felt that future applications and areas of study of the virtual surgery planning tool include its potential role for patient counseling, selecting appropriate surgical candidates, and identifying which anatomical structures should be targeted for surgical correction. LEVEL OF EVIDENCE NA.

Research paper thumbnail of Aerosol Transport Modeling: The Key Link Between Lung Infections of Individuals and Populations

Frontiers in Physiology

The recent COVID-19 pandemic has propelled the field of aerosol science to the forefront, particu... more The recent COVID-19 pandemic has propelled the field of aerosol science to the forefront, particularly the central role of virus-laden respiratory droplets and aerosols. The pandemic has also highlighted the critical need, and value for, an information bridge between epidemiological models (that inform policymakers to develop public health responses) and within-host models (that inform the public and health care providers how individuals develop respiratory infections). Here, we review existing data and models of generation of respiratory droplets and aerosols, their exhalation and inhalation, and the fate of infectious droplet transport and deposition throughout the respiratory tract. We then articulate how aerosol transport modeling can serve as a bridge between and guide calibration of within-host and epidemiological models, forming a comprehensive tool to formulate and test hypotheses about respiratory tract exposure and infection within and between individuals.

Research paper thumbnail of Normative ranges of nasal airflow variables in healthy adults

International Journal of Computer Assisted Radiology and Surgery, 2019

Purpose: Virtual surgery planning based on computational fluid dynamics (CFD) simulations of nasa... more Purpose: Virtual surgery planning based on computational fluid dynamics (CFD) simulations of nasal airflow has the potential to improve surgical outcomes for patients with nasal airway obstruction (NAO). Virtual surgery planning requires normative ranges of airflow variables, but few studies to date have quantified inter-individual variability of nasal airflow among healthy subjects. This study reports CFD simulations of nasal airflow in 47 healthy adults. Methods: Anatomically-accurate 3-dimensional nasal models were reconstructed from cone beam computed tomography (CBCT) scans and used for steady-state inspiratory airflow

Research paper thumbnail of Influence of Alveolar Mixing and Multiple Breaths of Aerosol Intake on Particle Deposition in the Human Lungs

SSRN Electronic Journal, 2022

Research paper thumbnail of Creation of an idealized nasopharynx geometry for accurate computational fluid dynamics simulations of nasal airflow in patient-specific models lacking the nasopharynx anatomy

International journal for numerical methods in biomedical engineering, May 15, 2016

Virtual surgery planning based on computational fluid dynamics (CFD) simulations has the potentia... more Virtual surgery planning based on computational fluid dynamics (CFD) simulations has the potential to improve surgical outcomes for nasal airway obstruction (NAO) patients, but the benefits of virtual surgery planning must outweigh the risks of radiation exposure. Cone beam computed tomography (CBCT) scans represent an attractive imaging modality for virtual surgery planning due to lower costs and lower radiation exposures compared with conventional CT scans. However, to minimize the radiation exposure, the CBCT sinusitis protocol sometimes images only the nasal cavity, excluding the nasopharynx. The goal of this study was to develop an idealized nasopharynx geometry for accurate representation of outlet boundary conditions when the nasopharynx geometry is unavailable. Anatomically-accurate models of the nasopharynx created from thirty CT scans were intersected with planes rotated at different angles to obtain an average geometry. Cross sections of the idealized nasopharynx were app...

Research paper thumbnail of Low re-inhalation of the exhaled flow during normal nasal breathing in a pediatric airway replica

Building and Environment, 2016

To estimate the fraction of the exhaled airflow that is re-inhaled during normal nasal breathing,... more To estimate the fraction of the exhaled airflow that is re-inhaled during normal nasal breathing, experiments were carried out in a water tank with an anatomically accurate respiratory tract model of a 4year-old child. The velocity of respiratory flow was scaled using similarity laws between air and water. Breath simulation was performed via a computer-controlled piston-cylinder system. Food-dye visualization allows a qualitative analysis of the re-inhaled fraction of this exhaled flow. For the quantitative analysis, neutrally buoyant particles were added to the water medium, and illuminated by the laser which illuminates the whole breathing region of the respiratory model, such that the trajectory and quantity of the re-inhaled particles can be recorded and counted. The experimental results in the pediatric airway replica show that a negligible fraction (<0.06%) of the exhaled airflow is re-inhaled during normal nasal breathing in the absence of the rising thermal plume. The artificial plume generated by a heated aluminium brick at the tank bottom increases the re-inhalation ratio by 4 times under the investigated case (albeit still at a very low value of 0.15%). Our results thus reveal that during normal nasal breathing in the present pediatric subject, the vast majority of human exhaled airflow escapes from the inhalation zone and is not re-inhaled.

Research paper thumbnail of Investigating the 3D flow structure downstream of a fence

In this research the experiments were performed in the water tunnel at the Laboratory for Aero an... more In this research the experiments were performed in the water tunnel at the Laboratory for Aero and Hydrodynamics to investigate the 3D flow structure over roughness elements as a model for the flow over urban environment. It represents the first phase in an extended study on the dispersion of pollutants in an urban environment, which process is governed by the mentioned flow structure. This is an urgent problem as the air quality in cities is decreasing due to increasing pollution from cars and industrial activity. If we can improve the understanding of the dispersion of these gases, we can possibly improve this situation or at least better predict these problems. The principal experimental technique that will be employed is Tomographic-PIV , which is a state-of-the-art experimental technique to measure the flow velocity in a 3D volume. So far it has been applied mainly to investigate the flow structures in some classic turbulence cases: a cylinder wake and turbulent boundary layer ...

Research paper thumbnail of Measurements of total aerosol deposition in intrathoracic conducting airway replicas of children

Journal of Aerosol Science, 2014

The objective of this research was to obtain a correlation that quantitatively predicts micromete... more The objective of this research was to obtain a correlation that quantitatively predicts micrometer-sized aerosol particle deposition in the upper conducting airways (trachea to generation 3) of children. Experiments were conducted using steady inhalation air flow rates to measure the deposition of monodisperse particles with diameters of 3.5-5.5 μm in replicas of the upper tracheobronchial airways of 11 children aged 2-8 years. The total deposition of particles was measured in each replica using gravimetry. Validation was performed by also measuring deposition in five adult replicas and the Alberta Idealized Throat and comparing with existing published data. Although there is considerable intersubject variability in our data, the empirical correlation of Chan & Lippmann (1980) was found to predict total deposition reasonably well in all of our adult and child replicas.

Research paper thumbnail of Correlation between Subjective Nasal Patency and Intranasal Airflow Distribution

Otolaryngology–Head and Neck Surgery, 2017

Objectives (1) Analyze the relationship between intranasal airflow distribution and subjective na... more Objectives (1) Analyze the relationship between intranasal airflow distribution and subjective nasal patency in healthy and nasal airway obstruction (NAO) cohorts using computational fluid dynamics (CFD). (2) Determine whether intranasal airflow distribution is an important objective measure of airflow sensation that should be considered in future NAO virtual surgery planning. Study Design Cross-sectional. Setting Academic tertiary medical center and academic dental clinic. Subjects and Methods Three-dimensional models of nasal anatomy were created based on computed tomography scans of 15 patients with NAO and 15 healthy subjects and used to run CFD simulations of nasal airflow and mucosal cooling. Subjective nasal patency was quantified with a visual analog scale (VAS) and the Nasal Obstruction Symptom Evaluation (NOSE). Regional distribution of nasal airflow (inferior, middle, and superior) was quantified in coronal cross sections in the narrowest nasal cavity. The Pearson correla...

Research paper thumbnail of An idealized branching airway geometry that mimics average aerosol deposition in pediatric central conducting airways

Journal of Aerosol Science, 2015

ABSTRACT The objective of this work was to design an idealized pediatric central conducting airwa... more ABSTRACT The objective of this work was to design an idealized pediatric central conducting airway model that mimics average total particle deposition in the airways of 4–8 year old children. Dimensions of the idealized model were selected based on analytical prediction of deposition in scaled versions of existing adult airway geometries. Validation experiments were then conducted using steady inhalation air flow rate to measure the deposition of monodisperse particles with mass median diameters (MMD) of 3.5, 4.5, 5 and 5.2 mm in the idealized pediatric model. The total deposition of particles was measured using gravimetry. Experimental data confirmed that aerosol deposition in the idealized pediatric central conducting airway geometry was consistent with the average deposition previously measured in 10 realistic airway replicas for children 4–8 years old.

Research paper thumbnail of Nasal versus oral aerosol delivery to the “lungs” in infants and toddlers

Pediatric Pulmonology, 2014

The oral route has been considered superior to the nasal route for aerosol delivery to the lower ... more The oral route has been considered superior to the nasal route for aerosol delivery to the lower respiratory tract (LRT) in adults and children. However, there are no data comparing aerosol delivery via the oral and nasal routes in infants. The aim of this study was to compare nasal and oral delivery of aerosol in anatomically correct replicas of infants&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; faces containing both nasal and oral upper airways. Three CT-derived upper respiratory tract (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;URT&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;) replicas representing infants/toddlers aged 5, 14 and 20 months were studied and aerosol delivery to the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;lower respiratory tract&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; (LRT) by either the oral or nasal route for each of the replicas was measured at the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;tracheal&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; opening. A radio-labeled (99mDTPA) normal saline solution aerosol was generated by a soft-mist inhaler (SMIRespimat® Boehringer Ingelheim, Germany) and aerosol was delivered via a valved holding chamber (Respichamber® TMI, London, Canada) and an air-tight mask (Unomedical, Inc., McAllen, TX). A breath simulator was connected to the replicas and an absolute filter at the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;tracheal&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; opening captured the aerosol representing &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;LRT&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; dose. Age-appropriate mask dimensions and breathing patterns were employed for each of the airway replicas. Two different tidal volumes (Vt ) were used for comparing the nasal versus oral routes. Nasal delivery to the LRT exceeded that of oral delivery in the 5- and 14-month models and was equivalent in the 20-month model. Differences between nasal and oral delivery diminished with &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;age&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;/size. Similar findings were observed with lower and higher tidal volumes (Vt ). Nasal breathing for aerosol delivery to the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;LRT&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; is similar to, or more efficient than, mouth breathing in infant/toddler models, contrary to what is observed in older children and adults. Pediatr Pulmonol. © 2014 Wiley Periodicals, Inc.

Research paper thumbnail of Measurements of Total Aerosol Deposition and Validation of Airway Resistance Models in Anatomically Realistic Intrathoracic Conducting Airway Replicas of Children

Research paper thumbnail of Validation of airway resistance models for predicting pressure loss through anatomically realistic conducting airway replicas of adults and children

Journal of biomechanics, Jan 7, 2015

This work describes in vitro measurement of the total pressure loss at varying flow rate through ... more This work describes in vitro measurement of the total pressure loss at varying flow rate through anatomically realistic conducting airway replicas of 10 children, 4 to 8 years old, and 5 adults. Experimental results were compared with analytical predictions made using published airway resistance models. For the adult replicas, the model proposed by van Ertbruggen et al. (2005. J. Appl. Physiol. 98, 970-980) most accurately predicted central conducting airway resistance for inspiratory flow rates ranging from 15 to 90L/min. Models proposed by Pedley et al. (1970. J. Respir. Physiol. 9, 371-386) and by Katz et al. (2011. J. Biomech. 44, 1137-1143) also provided reasonable estimates, but with a tendency to over predict measured pressure loss for both models. For child replicas, the Pedley and Katz models both provided good estimation of measured pressure loss at flow rates representative of resting tidal breathing, but under predicted measured values at high inspiratory flow rate (60L/...

Research paper thumbnail of Appendix/Supplementary Material

Virtual surgery planning based on computational fluid dynamics (CFD) simulations has the potentia... more Virtual surgery planning based on computational fluid dynamics (CFD) simulations
has the potential to improve surgical outcomes for nasal airway obstruction patients,
but the benefits of virtual surgery planning must outweigh the risks of radiation
exposure. Cone beam computed tomography (CT) scans represent an attractive
imaging modality for virtual surgery planning due to lower costs and lower radiation
exposures compared with conventional CT scans. However, to minimize the radiation exposure, the cone beam CT sinusitis protocol sometimes images only the nasal cavity, excluding the nasopharynx. The goal of this study was to develop an idealized nasopharynx geometry for accurate representation of outlet boundary conditions when the nasopharynx geometry is unavailable. Anatomically accurate
models of the nasopharynx created from 30 CT scans were intersected with planes
rotated at different angles to obtain an average geometry. Cross sections of the idealized nasopharynx were approximated as ellipses with cross‐sectional areas and
aspect ratios equal to the average in the actual patient‐specific models. CFD simulations were performed to investigate whether nasal airflow patterns were affected when the CT‐based nasopharynx was replaced by the idealized nasopharynx in 10 nasal airway obstruction patients. Despite the simple form of the idealized geometry, all biophysical variables (nasal resistance, airflow rate, and heat fluxes) were very similar in the idealized vs patient‐specific models. The results confirmed the expectation that the nasopharynx geometry has a minimal effect in the nasal airflow patterns during inspiration. The idealized nasopharynx geometry will be useful in future CFD studies of nasal airflow based on medical images that exclude the nasopharynx.

Research paper thumbnail of Creation of an idealized nasopharynx geometry for accurate computational fluid dynamics simulations of nasal airflow in patient‐specific models lacking the nasopharynx anatomy

Virtual surgery planning based on computational fluid dynamics (CFD) simulations has the potentia... more Virtual surgery planning based on computational fluid dynamics (CFD) simulations has the potential to improve surgical outcomes for nasal airway obstruction patients, but the benefits of virtual surgery planning must outweigh the risks of radiation exposure. Cone beam computed tomography (CT) scans represent an attractive imaging modality for virtual surgery planning due to lower costs and lower radiation exposures compared with conventional CT scans. However, to minimize the radiation exposure, the cone beam CT sinusitis protocol sometimes images only the nasal cavity, excluding the nasopharynx. The goal of this study was to develop an ideal-ized nasopharynx geometry for accurate representation of outlet boundary conditions when the nasopharynx geometry is unavailable. Anatomically accurate models of the nasopharynx created from 30 CT scans were intersected with planes rotated at different angles to obtain an average geometry. Cross sections of the ide-alized nasopharynx were approximated as ellipses with cross‐sectional areas and aspect ratios equal to the average in the actual patient‐specific models. CFD simulations were performed to investigate whether nasal airflow patterns were affected when the CT‐based nasopharynx was replaced by the idealized nasopharynx in 10 nasal airway obstruction patients. Despite the simple form of the idealized geometry, all biophysical variables (nasal resistance, airflow rate, and heat fluxes) were very similar in the idealized vs patient‐specific models. The results confirmed the expectation that the nasopharynx geometry has a minimal effect in the nasal airflow patterns during inspiration. The idealized nasopharynx geometry will be useful in future CFD studies of nasal airflow based on medical images that exclude the nasopharynx.

Research paper thumbnail of Investigation of the adjoint method in aerodynamic optimization using various shape parameterization techniques

Journal of the Brazilian Society …, 2010

This paper studies the effect of design variables vector on automatic aerodynamic shape optimizat... more This paper studies the effect of design variables vector on automatic aerodynamic shape optimization in the adjoint method. Three shape techniques are studied: surface points, relations of the NACA 4-digit airfoil series and Hicks-Henne "Bump" Functions. First, this paper presents the ...

Research paper thumbnail of Correlation between subjective nasal patency

Objectives. (1) Analyze the relationship between intranasal airflow distribution and subjective n... more Objectives. (1) Analyze the relationship between intranasal airflow distribution and subjective nasal patency in healthy and nasal airway obstruction (NAO) cohorts using computational fluid dynamics (CFD). (2) Determine whether intranasal airflow distribution is an important objective measure of airflow sensation that should be considered in future NAO virtual surgery planning.

Research paper thumbnail of Aerosol Transport Modeling: The Key Link Between Lung Infections of Individuals and Populations

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2022

The recent COVID-19 pandemic has propelled the field of aerosol science to the forefront, particu... more The recent COVID-19 pandemic has propelled the field of aerosol science to the forefront, particularly the central role of virus-laden respiratory droplets and aerosols. The pandemic has also highlighted the critical need, and value for, an information bridge between epidemiological models (that inform policymakers to develop public health responses) and within-host models (that inform the public and health care providers how individuals develop respiratory infections). Here, we review existing data and models of generation of respiratory droplets and aerosols, their exhalation and inhalation, and the fate of infectious droplet transport and deposition throughout the respiratory tract. We then articulate how aerosol transport modeling can serve as a bridge between and guide calibration of withinhost and epidemiological models, forming a comprehensive tool to formulate and test hypotheses about respiratory tract exposure and infection within and between individuals.

Research paper thumbnail of A hierarchical stepwise approach to evaluate nasal patency after virtual surgery for nasal airway obstruction

Clinical Biomechanics, 2019

Background: Despite advances in medicine and expenditures associated in treatment of nasal airway... more Background: Despite advances in medicine and expenditures associated in treatment of nasal airway obstruction, 25-50% of patients undergoing nasal surgeries complain of persistent obstructive symptoms. Our objective is to develop a "stepwise virtual surgery" method that optimizes surgical outcomes for treatment of nasal airway obstruction. Methods: Pre-surgery radiographic images of two subjects with nasal airway obstruction were imported into Mimics imaging software package for three-dimension reconstruction of the airway. A hierarchical stepwise approach was used to create seven virtual surgery nasal models comprising individual (inferior turbinectomy or septoplasty) procedures and combined inferior turbinectomy and septoplasty procedures via digital modifications of each subject's pre-surgery nasal model. To evaluate the effects of these procedures on nasal patency, computational fluid dynamics modeling was used to perform steady-state laminar inspiratory airflow and heat transfer simulations in every model, at resting breathing. Airflow-related variables were calculated for virtual surgery models and compared with dataset containing results of healthy subjects with no symptoms of nasal obstruction.

Research paper thumbnail of In Silico Quantification of Intersubject Variability on Aerosol Deposition in the Oral Airway

Pharmaceutics, Jan 3, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Virtual Surgery for the Nasal Airway

JAMA Facial Plastic Surgery, 2018

IMPORTANCE Nasal airway obstruction (NAO) is a common problem that affects patient quality of lif... more IMPORTANCE Nasal airway obstruction (NAO) is a common problem that affects patient quality of life. Surgical success for NAO correction is variable. Virtual surgery planning via computational fluid dynamics (CFD) has the potential to improve the success rates of NAO surgery. OBJECTIVE To elicit surgeon feedback of a virtual surgery planning tool for NAO and to determine if this tool affects surgeon decision making. DESIGN, SETTING, AND PARTICIPANTS For this cross-sectional study, 60-minute face-to-face interviews with board-certified otolaryngologists were conducted at a single academic otolaryngology department from September 16, 2016, through October 7, 2016. Virtual surgery methods were introduced, and surgeons were able to interact with the virtual surgery planning tool interface. Surgeons were provided with a patient case of NAO, and open feedback of the platform was obtained, with emphasis on surgical decision making. MAIN OUTCOMES AND MEASURES Likert scale responses and qualitative feedback were collected for the virtual surgery planning tool and its influence on surgeon decision making. RESULTS Our 9 study participants were all male, board-certified otolaryngologists with a mean (range) 15 (4-28) number of years in practice and a mean (range) number of nasal surgeries per month at 2.2 (0.0-6.0). When examined on a scale of 1 (not at all) to 5 (completely), surgeon mean (SD) score was 3.4 (0.5) for how realistic the virtual models were compared with actual surgery. On the same scale, when asked how much the virtual surgery planning tool changed surgeon decision making, mean (SD) score was 2.6 (1.6). On a scale of 1 (strongly disagree) to 7 (strongly agree), surgeon scores for perceived usefulness of the technology and attitude toward using it were 5.1 (1.1) and 5.7 (0.9), respectively. CONCLUSIONS AND RELEVANCE Our study shows positive surgeon experience with a virtual surgery planning tool for NAO based on CFD simulations. Surgeons felt that future applications and areas of study of the virtual surgery planning tool include its potential role for patient counseling, selecting appropriate surgical candidates, and identifying which anatomical structures should be targeted for surgical correction. LEVEL OF EVIDENCE NA.

Research paper thumbnail of Aerosol Transport Modeling: The Key Link Between Lung Infections of Individuals and Populations

Frontiers in Physiology

The recent COVID-19 pandemic has propelled the field of aerosol science to the forefront, particu... more The recent COVID-19 pandemic has propelled the field of aerosol science to the forefront, particularly the central role of virus-laden respiratory droplets and aerosols. The pandemic has also highlighted the critical need, and value for, an information bridge between epidemiological models (that inform policymakers to develop public health responses) and within-host models (that inform the public and health care providers how individuals develop respiratory infections). Here, we review existing data and models of generation of respiratory droplets and aerosols, their exhalation and inhalation, and the fate of infectious droplet transport and deposition throughout the respiratory tract. We then articulate how aerosol transport modeling can serve as a bridge between and guide calibration of within-host and epidemiological models, forming a comprehensive tool to formulate and test hypotheses about respiratory tract exposure and infection within and between individuals.

Research paper thumbnail of Normative ranges of nasal airflow variables in healthy adults

International Journal of Computer Assisted Radiology and Surgery, 2019

Purpose: Virtual surgery planning based on computational fluid dynamics (CFD) simulations of nasa... more Purpose: Virtual surgery planning based on computational fluid dynamics (CFD) simulations of nasal airflow has the potential to improve surgical outcomes for patients with nasal airway obstruction (NAO). Virtual surgery planning requires normative ranges of airflow variables, but few studies to date have quantified inter-individual variability of nasal airflow among healthy subjects. This study reports CFD simulations of nasal airflow in 47 healthy adults. Methods: Anatomically-accurate 3-dimensional nasal models were reconstructed from cone beam computed tomography (CBCT) scans and used for steady-state inspiratory airflow

Research paper thumbnail of Influence of Alveolar Mixing and Multiple Breaths of Aerosol Intake on Particle Deposition in the Human Lungs

SSRN Electronic Journal, 2022

Research paper thumbnail of Creation of an idealized nasopharynx geometry for accurate computational fluid dynamics simulations of nasal airflow in patient-specific models lacking the nasopharynx anatomy

International journal for numerical methods in biomedical engineering, May 15, 2016

Virtual surgery planning based on computational fluid dynamics (CFD) simulations has the potentia... more Virtual surgery planning based on computational fluid dynamics (CFD) simulations has the potential to improve surgical outcomes for nasal airway obstruction (NAO) patients, but the benefits of virtual surgery planning must outweigh the risks of radiation exposure. Cone beam computed tomography (CBCT) scans represent an attractive imaging modality for virtual surgery planning due to lower costs and lower radiation exposures compared with conventional CT scans. However, to minimize the radiation exposure, the CBCT sinusitis protocol sometimes images only the nasal cavity, excluding the nasopharynx. The goal of this study was to develop an idealized nasopharynx geometry for accurate representation of outlet boundary conditions when the nasopharynx geometry is unavailable. Anatomically-accurate models of the nasopharynx created from thirty CT scans were intersected with planes rotated at different angles to obtain an average geometry. Cross sections of the idealized nasopharynx were app...

Research paper thumbnail of Low re-inhalation of the exhaled flow during normal nasal breathing in a pediatric airway replica

Building and Environment, 2016

To estimate the fraction of the exhaled airflow that is re-inhaled during normal nasal breathing,... more To estimate the fraction of the exhaled airflow that is re-inhaled during normal nasal breathing, experiments were carried out in a water tank with an anatomically accurate respiratory tract model of a 4year-old child. The velocity of respiratory flow was scaled using similarity laws between air and water. Breath simulation was performed via a computer-controlled piston-cylinder system. Food-dye visualization allows a qualitative analysis of the re-inhaled fraction of this exhaled flow. For the quantitative analysis, neutrally buoyant particles were added to the water medium, and illuminated by the laser which illuminates the whole breathing region of the respiratory model, such that the trajectory and quantity of the re-inhaled particles can be recorded and counted. The experimental results in the pediatric airway replica show that a negligible fraction (<0.06%) of the exhaled airflow is re-inhaled during normal nasal breathing in the absence of the rising thermal plume. The artificial plume generated by a heated aluminium brick at the tank bottom increases the re-inhalation ratio by 4 times under the investigated case (albeit still at a very low value of 0.15%). Our results thus reveal that during normal nasal breathing in the present pediatric subject, the vast majority of human exhaled airflow escapes from the inhalation zone and is not re-inhaled.

Research paper thumbnail of Investigating the 3D flow structure downstream of a fence

In this research the experiments were performed in the water tunnel at the Laboratory for Aero an... more In this research the experiments were performed in the water tunnel at the Laboratory for Aero and Hydrodynamics to investigate the 3D flow structure over roughness elements as a model for the flow over urban environment. It represents the first phase in an extended study on the dispersion of pollutants in an urban environment, which process is governed by the mentioned flow structure. This is an urgent problem as the air quality in cities is decreasing due to increasing pollution from cars and industrial activity. If we can improve the understanding of the dispersion of these gases, we can possibly improve this situation or at least better predict these problems. The principal experimental technique that will be employed is Tomographic-PIV , which is a state-of-the-art experimental technique to measure the flow velocity in a 3D volume. So far it has been applied mainly to investigate the flow structures in some classic turbulence cases: a cylinder wake and turbulent boundary layer ...

Research paper thumbnail of Measurements of total aerosol deposition in intrathoracic conducting airway replicas of children

Journal of Aerosol Science, 2014

The objective of this research was to obtain a correlation that quantitatively predicts micromete... more The objective of this research was to obtain a correlation that quantitatively predicts micrometer-sized aerosol particle deposition in the upper conducting airways (trachea to generation 3) of children. Experiments were conducted using steady inhalation air flow rates to measure the deposition of monodisperse particles with diameters of 3.5-5.5 μm in replicas of the upper tracheobronchial airways of 11 children aged 2-8 years. The total deposition of particles was measured in each replica using gravimetry. Validation was performed by also measuring deposition in five adult replicas and the Alberta Idealized Throat and comparing with existing published data. Although there is considerable intersubject variability in our data, the empirical correlation of Chan & Lippmann (1980) was found to predict total deposition reasonably well in all of our adult and child replicas.

Research paper thumbnail of Correlation between Subjective Nasal Patency and Intranasal Airflow Distribution

Otolaryngology–Head and Neck Surgery, 2017

Objectives (1) Analyze the relationship between intranasal airflow distribution and subjective na... more Objectives (1) Analyze the relationship between intranasal airflow distribution and subjective nasal patency in healthy and nasal airway obstruction (NAO) cohorts using computational fluid dynamics (CFD). (2) Determine whether intranasal airflow distribution is an important objective measure of airflow sensation that should be considered in future NAO virtual surgery planning. Study Design Cross-sectional. Setting Academic tertiary medical center and academic dental clinic. Subjects and Methods Three-dimensional models of nasal anatomy were created based on computed tomography scans of 15 patients with NAO and 15 healthy subjects and used to run CFD simulations of nasal airflow and mucosal cooling. Subjective nasal patency was quantified with a visual analog scale (VAS) and the Nasal Obstruction Symptom Evaluation (NOSE). Regional distribution of nasal airflow (inferior, middle, and superior) was quantified in coronal cross sections in the narrowest nasal cavity. The Pearson correla...

Research paper thumbnail of An idealized branching airway geometry that mimics average aerosol deposition in pediatric central conducting airways

Journal of Aerosol Science, 2015

ABSTRACT The objective of this work was to design an idealized pediatric central conducting airwa... more ABSTRACT The objective of this work was to design an idealized pediatric central conducting airway model that mimics average total particle deposition in the airways of 4–8 year old children. Dimensions of the idealized model were selected based on analytical prediction of deposition in scaled versions of existing adult airway geometries. Validation experiments were then conducted using steady inhalation air flow rate to measure the deposition of monodisperse particles with mass median diameters (MMD) of 3.5, 4.5, 5 and 5.2 mm in the idealized pediatric model. The total deposition of particles was measured using gravimetry. Experimental data confirmed that aerosol deposition in the idealized pediatric central conducting airway geometry was consistent with the average deposition previously measured in 10 realistic airway replicas for children 4–8 years old.

Research paper thumbnail of Nasal versus oral aerosol delivery to the “lungs” in infants and toddlers

Pediatric Pulmonology, 2014

The oral route has been considered superior to the nasal route for aerosol delivery to the lower ... more The oral route has been considered superior to the nasal route for aerosol delivery to the lower respiratory tract (LRT) in adults and children. However, there are no data comparing aerosol delivery via the oral and nasal routes in infants. The aim of this study was to compare nasal and oral delivery of aerosol in anatomically correct replicas of infants&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; faces containing both nasal and oral upper airways. Three CT-derived upper respiratory tract (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;URT&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;) replicas representing infants/toddlers aged 5, 14 and 20 months were studied and aerosol delivery to the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;lower respiratory tract&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; (LRT) by either the oral or nasal route for each of the replicas was measured at the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;tracheal&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; opening. A radio-labeled (99mDTPA) normal saline solution aerosol was generated by a soft-mist inhaler (SMIRespimat® Boehringer Ingelheim, Germany) and aerosol was delivered via a valved holding chamber (Respichamber® TMI, London, Canada) and an air-tight mask (Unomedical, Inc., McAllen, TX). A breath simulator was connected to the replicas and an absolute filter at the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;tracheal&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; opening captured the aerosol representing &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;LRT&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; dose. Age-appropriate mask dimensions and breathing patterns were employed for each of the airway replicas. Two different tidal volumes (Vt ) were used for comparing the nasal versus oral routes. Nasal delivery to the LRT exceeded that of oral delivery in the 5- and 14-month models and was equivalent in the 20-month model. Differences between nasal and oral delivery diminished with &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;age&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;/size. Similar findings were observed with lower and higher tidal volumes (Vt ). Nasal breathing for aerosol delivery to the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;LRT&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; is similar to, or more efficient than, mouth breathing in infant/toddler models, contrary to what is observed in older children and adults. Pediatr Pulmonol. © 2014 Wiley Periodicals, Inc.

Research paper thumbnail of Measurements of Total Aerosol Deposition and Validation of Airway Resistance Models in Anatomically Realistic Intrathoracic Conducting Airway Replicas of Children

Research paper thumbnail of Validation of airway resistance models for predicting pressure loss through anatomically realistic conducting airway replicas of adults and children

Journal of biomechanics, Jan 7, 2015

This work describes in vitro measurement of the total pressure loss at varying flow rate through ... more This work describes in vitro measurement of the total pressure loss at varying flow rate through anatomically realistic conducting airway replicas of 10 children, 4 to 8 years old, and 5 adults. Experimental results were compared with analytical predictions made using published airway resistance models. For the adult replicas, the model proposed by van Ertbruggen et al. (2005. J. Appl. Physiol. 98, 970-980) most accurately predicted central conducting airway resistance for inspiratory flow rates ranging from 15 to 90L/min. Models proposed by Pedley et al. (1970. J. Respir. Physiol. 9, 371-386) and by Katz et al. (2011. J. Biomech. 44, 1137-1143) also provided reasonable estimates, but with a tendency to over predict measured pressure loss for both models. For child replicas, the Pedley and Katz models both provided good estimation of measured pressure loss at flow rates representative of resting tidal breathing, but under predicted measured values at high inspiratory flow rate (60L/...

Research paper thumbnail of Appendix/Supplementary Material

Virtual surgery planning based on computational fluid dynamics (CFD) simulations has the potentia... more Virtual surgery planning based on computational fluid dynamics (CFD) simulations
has the potential to improve surgical outcomes for nasal airway obstruction patients,
but the benefits of virtual surgery planning must outweigh the risks of radiation
exposure. Cone beam computed tomography (CT) scans represent an attractive
imaging modality for virtual surgery planning due to lower costs and lower radiation
exposures compared with conventional CT scans. However, to minimize the radiation exposure, the cone beam CT sinusitis protocol sometimes images only the nasal cavity, excluding the nasopharynx. The goal of this study was to develop an idealized nasopharynx geometry for accurate representation of outlet boundary conditions when the nasopharynx geometry is unavailable. Anatomically accurate
models of the nasopharynx created from 30 CT scans were intersected with planes
rotated at different angles to obtain an average geometry. Cross sections of the idealized nasopharynx were approximated as ellipses with cross‐sectional areas and
aspect ratios equal to the average in the actual patient‐specific models. CFD simulations were performed to investigate whether nasal airflow patterns were affected when the CT‐based nasopharynx was replaced by the idealized nasopharynx in 10 nasal airway obstruction patients. Despite the simple form of the idealized geometry, all biophysical variables (nasal resistance, airflow rate, and heat fluxes) were very similar in the idealized vs patient‐specific models. The results confirmed the expectation that the nasopharynx geometry has a minimal effect in the nasal airflow patterns during inspiration. The idealized nasopharynx geometry will be useful in future CFD studies of nasal airflow based on medical images that exclude the nasopharynx.

Research paper thumbnail of Creation of an idealized nasopharynx geometry for accurate computational fluid dynamics simulations of nasal airflow in patient‐specific models lacking the nasopharynx anatomy

Virtual surgery planning based on computational fluid dynamics (CFD) simulations has the potentia... more Virtual surgery planning based on computational fluid dynamics (CFD) simulations has the potential to improve surgical outcomes for nasal airway obstruction patients, but the benefits of virtual surgery planning must outweigh the risks of radiation exposure. Cone beam computed tomography (CT) scans represent an attractive imaging modality for virtual surgery planning due to lower costs and lower radiation exposures compared with conventional CT scans. However, to minimize the radiation exposure, the cone beam CT sinusitis protocol sometimes images only the nasal cavity, excluding the nasopharynx. The goal of this study was to develop an ideal-ized nasopharynx geometry for accurate representation of outlet boundary conditions when the nasopharynx geometry is unavailable. Anatomically accurate models of the nasopharynx created from 30 CT scans were intersected with planes rotated at different angles to obtain an average geometry. Cross sections of the ide-alized nasopharynx were approximated as ellipses with cross‐sectional areas and aspect ratios equal to the average in the actual patient‐specific models. CFD simulations were performed to investigate whether nasal airflow patterns were affected when the CT‐based nasopharynx was replaced by the idealized nasopharynx in 10 nasal airway obstruction patients. Despite the simple form of the idealized geometry, all biophysical variables (nasal resistance, airflow rate, and heat fluxes) were very similar in the idealized vs patient‐specific models. The results confirmed the expectation that the nasopharynx geometry has a minimal effect in the nasal airflow patterns during inspiration. The idealized nasopharynx geometry will be useful in future CFD studies of nasal airflow based on medical images that exclude the nasopharynx.

Research paper thumbnail of Investigation of the adjoint method in aerodynamic optimization using various shape parameterization techniques

Journal of the Brazilian Society …, 2010

This paper studies the effect of design variables vector on automatic aerodynamic shape optimizat... more This paper studies the effect of design variables vector on automatic aerodynamic shape optimization in the adjoint method. Three shape techniques are studied: surface points, relations of the NACA 4-digit airfoil series and Hicks-Henne "Bump" Functions. First, this paper presents the ...

Research paper thumbnail of Correlation between subjective nasal patency

Objectives. (1) Analyze the relationship between intranasal airflow distribution and subjective n... more Objectives. (1) Analyze the relationship between intranasal airflow distribution and subjective nasal patency in healthy and nasal airway obstruction (NAO) cohorts using computational fluid dynamics (CFD). (2) Determine whether intranasal airflow distribution is an important objective measure of airflow sensation that should be considered in future NAO virtual surgery planning.