Nasal architecture: form and flow

Effects of Hypoglossal Nerve Stimulation on Upper Airway Structure and Function Using Moving Wall Computational Fluid Dynamics Simulations: A Pilot Study

Hypoglossal nerve stimulation (HGNS) is an innovative alternative treatment option for obstructive sleep apnoea (OSA) in patients unable to tolerate continuous positive airway pressure. However, the success rate of HGNS is variable, but the reasons underlying variation in treatment efficacy are not well understood. In this pilot study of three male subjects, we propose an innovative, non-invasive method to quantify the structural and functional changes to the upper airway that occur with HGNS. We used four-dimensional computed tomography (4DCT) and computational fluid dynamics (CFD) simulations of respiratory airflow to quantify how HGNS changes: (1) airway cross-sectional area (CSA), (2) work done by muscles and air pressure in dilating and collapsing the airway and (3) airway resistance. Subjects underwent 4DCT under natural stage non-REM 2 (N2) sleep with and without HGNS. Each patient had concurrent electroencephalograms and airflow measurements. CFD simulations were performed based on anatomy and airway motion from 4DCT images and airflow data. HGNS was associated with an increase in neuromuscular work done in dilating the airway (up to 490%); airway CSA increased by up to 300%. Most motion with HGNS occurred in the oropharynx; changes in the nasopharynx and hypopharynx varied between subjects. Minute ventilation increased in all subjects (15%-36%). Airway resistance decreased across the three subjects (73%-97%). Quantifying the parameters measured in this study may help explain variable responses to HGNS as a treatment for OSA. These procedures may, in future, help predict non-responders to HGNS, isolate reasons for poor responses, or inform device titration.

Nasal Model Experiments Show That a Collimated Fluid Delivers Precise Doses to the Human Olfactory Cavity in the Side-Laying Position

The nasal administration of therapeutic fluids and vaccines is used to treat allergic rhinitis, sinusitis, congestion, coronaviruses and even Alzheimer's disease. In the latter, the drug must reach the olfactory region, so it finds its way into the central nervous system. Effective administration techniques able to reach the olfactory region are challenging due to the tortuous anatomy of the nasal cavity, and are frequently evaluated in vitro using transparent anatomical models. Here, the liquid distribution inside a 3D printed human nasal cavity is quantified for model fluids resulting from the discharge of a 1-mL syringe with either a spray-generating nozzle, and a straight tip emitting a collimated fluid stream. Experiments using two model fluids with different viscosities suggest that a simple, correctly positioned straight tip attached to a syringe is able to efficiently deliver most of a therapeutic fluid in the human olfactory region in the side-laying position, avoiding the adoption of head-back and head-down positions that can be difficult for patients in the age range typical of Alzheimer's disease. Furthermore, we demonstrate by computer simulations that the conclusion is valid within a wide range of parameters.

Assessing nasal airway resistance and symmetry: An approach to global perspective through computational fluid dynamics

This study aimed to explore the variability in nasal airflow patterns among different sexes and populations using computational fluid dynamics (CFD). We focused on evaluating the universality and applicability of dimensionless parameters R (bilateral nasal resistance) and ϕ (nasal flow asymmetry), initially established in a Caucasian Spanish cohort, across a broader spectrum of human populations to assess normal breathing function in healthy airways. In this retrospective study, CT scans from Cambodia (20 males, 20 females), Russia (20 males, 18 females), and Spain (19 males, 19 females) were analyzed. A standardized CFD workflow was implemented to calculate R-ϕ parameters from these scans. Statistical analyses were conducted to assess and compare these parameters across different sexes and populations, emphasizing their distribution and variances. Our results indicated no significant sex-based differences in the R parameter across the populations. However, moderate sexual dimorphism in the ϕ parameter was observed in the Cambodian group. Notably, no geographical differences were found in either R or ϕ parameters, suggesting consistent nasal airflow characteristics across the diverse human groups studied. The study also emphasized the importance of using dimensionless variables to effectively analyze the relationships between form and function in nasal airflow. The observed consistency of R-ϕ parameters across various populations highlights their potential as reliable indicators in both medical practice and further CFD research, particularly in diverse human populations. Our findings suggest the potential applicability of dimensionless CFD parameters in analyzing nasal airflow, highlighting their utility across diverse demographic and geographic contexts. This research advances our understanding of nasal airflow dynamics and underscores the need for additional studies to validate these parameters in broader population cohorts. The approach of employing dimensionless parameters paves the way for future research that eliminates confounding size effects, enabling more accurate comparisons across different populations and sexes. The implications of this study are significant for the advancement of personalized medicine and the development of diagnostic tools that accommodate individual variations in nasal airflow.

Effects of decongestion on nasal cavity air conditioning efficiency: a CFD cohort study

Decongestion reduces blood flow in the nasal turbinates, enlarging the airway lumen. Although the enlarged airspace reduces the trans-nasal inspiratory pressure drop, symptoms of nasal obstruction may relate to nasal cavity air-conditioning. Thus, it is necessary to quantify the efficiency of nasal cavity conditioning of the inhaled air. This study quantifies both overall and regional nasal air-conditioning in a cohort of 10 healthy subjects using computational fluid dynamics simulations before and after nasal decongestion. The 3D virtual geometry model was segmented from magnetic resonance images (MRI). Each subject was under two MRI acquisitions before and after the decongestion condition. The effects of decongestion on nasal cavity air conditioning efficiency were modelled at two inspiratory flowrates: 15 and 30 L min-1 to represent restful and light exercise conditions. Results show inhaled air was both heated and humidified up to 90% of alveolar conditions at the posterior septum. The air-conditioning efficiency of the nasal cavity remained nearly constant between nostril and posterior septum but dropped significantly after posterior septum. In summary, nasal cavity decongestion not only reduces inhaled air added heat by 23% and added moisture content by 19%, but also reduces the air-conditioning efficiency by 35% on average.

Changes in nasolabial angle may alter nasal valve morphology and airflow: a computational fluid dynamics study

Aim: Nasal valve (NV) dysfunctions are a significant cause of nasal obstruction. Changes in the nasolabial angle (NLA) may also cause changes in NV morphology. The effect of changes in the 3D structure of the nasal valve region (NVR) on nasal airflow has yet to be studied sufficiently. The accuracy of computational fluid dynamics (CFD) simulation results of nasal airflow has been confirmed by in vitro tests. Therefore, this study aimed to evaluate the effect of changes in NV structure and volume on nasal airflow based on the CFD method. Material and Method: We used CT images to create a 3D structural model of the NVR. First, CT images were transferred to MIMICS® software, and the nasal air passage was modeled. A solid reference model of the NVR was then created using SolidWorks software. Five different solid 3D nasal valve models were created with nasolabial angles of 85˚ in Model 1, 90˚ in Model 2, 95˚ in Model 3, 100˚ in Model 4, and 105˚ in Model 5. To simulate breathing during rest and exercise using the CFD method, the unilateral nasal airflow rates were set at 150 ml/s and 500 ml/s, respectively. The CFD method was then used to calculate each model’s airflow properties. Finally, the volumes of the models, pressure at the NV outlet, and airflow velocity were evaluated and calculated to investigate each model’s NV airflow characteristics. Results: Our study found a significant correlation between the nasolabial angle (NLA) and NVR volume (r=-0.998, p=0.000), flow rate and velocity (r=0.984, p=0.000), velocity and maximum pressure (r=0.920, p=0.000), velocity and minimum pressure (r=-0.969, p=0.000), flow rate and maximum pressure (r=0.974, p=0.000), and flow rate and minimum pressure (r=-0.950, p=0.000). There was no correlation between NLA increase and nasal airflow velocity. We determined that the highest pressure and lowest airflow velocity values were in the upper angle region and that the lowest pressure and highest airflow velocity values were at the bottom of the NVR in all models. Conclusion: Using the CFD method, we found a decrease in NVR volume and an increase in airflow velocity with an increase in NLA. In addition, we found that the pressure values in the NVR did not change significantly with the increase in NLA.

New insights into the variability of upper airway morphology in modern humans

The biological adaptation of the human lineage to its environment is a recurring question in paleoanthropology. Particularly, how eco-geographic factors (e.g., environmental temperature and humidity) have shaped upper airway morphology in hominins have been subject to continuing debate. Nasal shape is the result of many intertwined factors that include, but are not limited to, genetic drift, sexual selection, or adaptation to climate. A quantification of nasal airway (NA) morphological variation in modern human populations is crucial to better understand these multiple factors. In the present research, we study 195 in vivo CT scans of adult individuals collected in five different geographic areas (Chile, France, Cambodia, Russia, and South Africa). After segmentation of the nasal airway, we reconstruct 3D meshes that are analyzed with a landmark-free geometric morphometrics method based on surface deformation. Our results highlight subtle but statistically significant morphological differences between our five samples. The two morphologically closest groups are France and Russia, whose NAs are longer and narrower, with an important protrusion of the supero-anterior part. The Cambodian sample is the most morphologically distinct and clustered sample, with a mean NA that is wider and shorter. On the contrary, the Chilean sample form the most scattered cluster with the greatest intra-population variation. The South African sample is morphologically close to the Cambodian sample, but also partially overlaps the French and Russian variation. Interestingly, we record no correlation between NA volume and geographic groups, which raises the question of climate-related metabolic demands for oxygen consumption. The other factors of variation (sex and age) have no influence on the NA shape in our samples. However, NA volume varies significantly according both to sex and age: it is higher in males than in females and tends to increase with age. In contrast, we observe no effect of temperature or humidity on NA volume. Finally, we highlight the important influence of asymmetries related to nasal septum deviations in NA shape variation.

Flow Patterns and Particle Residence Times in the Oral Cavity during Inhaled Drug Delivery

Pulmonary drug delivery aims to deliver particles deep into the lungs, bypassing the mouth−throat airway geometry. However, micron particles under high flow rates are susceptible to inertial impaction on anatomical sites that serve as a defense system to filter and prevent foreign particles from entering the lungs. The aim of this study was to understand particle aerodynamics and its possible deposition in the mouth−throat airway that inhibits pulmonary drug delivery. In this study, we present an analysis of the aerodynamics of inhaled particles inside a patient-specific mouth−throat model generated from MRI scans. Computational Fluid Dynamics with a Discrete Phase Model for tracking particles was used to characterize the airflow patterns for a constant inhalation flow rate of 30 L/min. Monodisperse particles with diameters of 7 μm to 26 μm were introduced to the domain within a 3 cm-diameter sphere in front of the oral cavity. The main outcomes of this study showed that the time taken for particle deposition to occur was 0.5 s; a narrow stream of particles (medially and superiorly) were transported by the flow field; larger particles > 20 μm deposited onto the oropharnyx, while smaller particles < 12 μm were more disperse throughout the oral cavity and navigated the curved geometry and laryngeal jet to escape through the tracheal outlet. It was concluded that at a flow rate of 30 L/min the particle diameters depositing on the larynx and trachea in this specific patient model are likely to be in the range of 7 μm to 16 μm. Particles larger than 16 μm primarily deposited on the oropharynx.

MATHEMATICAL MODELS OF HUMAN RESPIRATORY AND BLOOD CIRCULATORY SYSTEMS

Aim. To analyze modern approaches to mathematical modeling of human respiratory and blood circulatory systems. Methods. Comprehensive review of scientific literature sources extracted from domestic and international resources databases. Results. Historical information and modern data concerning mathematical modeling of human functional respiratory and blood circulatory systems were summarized and analyzed in present ¬review; current trends in approaches to the construction of these models were revealed. Conclusions. Currently, two main approaches to the mathematical modeling of respiratory and blood circulatory systems exist. One of them is the construction of models of the mechanics of respiration and blood circulation. They are based on the models of mechanics of solid deformable body, thermomechanics, hydromechanics, and continuum mechanics. This approach uses complex mathematical apparatus, including Navier-Stokes equation, which makes it possible to obtain a number of theoretical results, but it is hardly usable for real problems solutions at present time. The second approach is based on the model of F. Grodins, who represented the process of breathing as a controlled dynamic system, described by ordinary differential equations, in which the process control is carried out according to the feedback principle. There is a significant number of modifications of this model, which made it possible to simulate various disturbing influences, such as physical activity, hypoxia and hyperemia, and to predict parameters characterizing functional respiratory system under these disturbing influences.

The effect of decongestion on nasal airway patency and airflow

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

A dynamical overview of droplets in the transmission of respiratory infectious diseases

The outbreak of the coronavirus disease has drawn public attention to the transmission of infectious pathogens, and as major carriers of those pathogens, respiratory droplets play an important role in the process of transmission. This Review describes respiratory droplets from a physical and mechanical perspective, especially their correlation with the transmission of infectious pathogens. It covers the important aspects of (i) the generation and expulsion of droplets during respiratory activities, (ii) the transport and evolution of respiratory droplets in the ambient environment, and (iii) the inhalation and deposition of droplets in the human respiratory tract. State-of-the-art experimental, computational, and theoretical models and results are presented, and the corresponding knowledge gaps are identified. This Review stresses the multidisciplinary nature of its subject and appeals for collaboration among different fields to fight the present pandemic.

A numerical simulation of air flow in the human respiratory system for various environmental conditions

The functions of the nasal cavity are very important for maintaining the internal environment of the lungs since the inner walls of the nasal cavity control the temperature and saturation of the inhaled air with water vapor until the nasopharynx is reached. In this paper, three-dimensional computational studies of airflow transport in the models of the nasal cavity were carried out for the usual inspiratory velocity in various environmental conditions. Three-dimensional numerical results are compared with experimental data and calculations of other authors. Numerical results show that during normal breathing, the human nose copes with heat and relative moisture metabolism in order to balance the intra-alveolar conditions. It is also shown in this paper that a normal nose can maintain balance even in extreme conditions, for example, in cold and hot weather. The nasal cavity accelerates heat transfer by narrowing the air passages and swirls from the nasal concha walls of the inner cavity.

Voxel-based simulation of flow and temperature in the human nasal cavity

The nasal airway is an extremely complex structure, therefore grid generation for numerical prediction of airflow in the nasal cavity is time-consuming. This paper describes the development of a voxel-based model with a Cartesian structured grid, which is characterized by robust and automatic grid generation, and the simulation of the airflow and air-conditioning in an individual human nasal airway. Computed tomography images of a healthy adult nose were used to reconstruct a virtual three-dimensional model of the nasal airway. Simulations of quiet restful inspiratory flow were then performed using a Neumann boundary condition for the energy equation to adequately resolve the flow and heat transfer. General agreements of airflow patterns, which were a high-speed jet posterior to the nasal valve and recirculating flow that occupied the anterior part of the upper cavity, and temperature distributions of the airflow and septum wall were confirmed by comparing in-vivo measurements with numerical simulation results.

Investigation of inhalation and exhalation flow pattern in a realistic human upper airway model by PIV experiments and CFD simulations

In this study, flow field characteristics in the trachea region in a realistic human upper airway model were firstly measured by particle image velocimetry (PIV) in the air under three constant inhalation and exhalation conditions: 36 L/min, 64 L/min and 90 L/min, representing flow rates of 18 L/min, 32 L/min and 45 L/min in real human airway (the model was twice the size of a human airway). Computational fluid dynamics (CFD) analyses were performed on four turbulence models, with boundary conditions corresponding to the PIV experiments. The effects of flow rates and breathing modes on the airflow patterns were investigated. The CFD prediction results were compared with the PIV measurements and showed relatively good agreement in all cases. During inhalation, the higher the flow rates, the less significant the "glottal jet" phenomenon, and the smaller the area of the separation zone. The air in the nasal inhalation condition accelerated more dramatically after glottis. The SST-Transition model was the best choice for predicting inhalation velocity profiles. For exhalation condition, the maximum velocity was much smaller than that during inhalation due to the more uniform flow field. The exhalation flow rates and breathing modes had little effect on the flow characteristics in the trachea region. The RNG k - ε model and SST k - ω model were recommended to simulate the flow field in the respiratory tract during exhalation.

Direct visualizations of air flow in the human upper airway using in-vitro models

A better understanding of airflow characteristics in the upper airway (UA) is crucial in investigating obstructive sleep apnea (OSA), particle sedimentation, drug delivery, and many biomedical problems. Direct visualization of air flow patterns in in-vitro models with realistic anatomical structures is a big challenge. In this study, we constructed unique half-side transparent physical models of normal UA based on realistic anatomical structures. A smoke-wire method was developed to visualize the air flow in UA models directly. The results revealed that the airflow through the pharynx was laminar but not turbulent under normal inspiration, which suggested that compared with turbulent models, a laminar model should be more suitable in numerical simulations. The flow predicted numerically using the laminar model was consistent with the observations in the physical models. The comparison of the velocity fields predicted numerically using the half-side and complete models confirmed that it was reasonable to investigate the flow behaviors in UA using the half-side model. Using the laminar model, we simulated the flow and evaluated the effects of UA narrowing caused by rostral fluid shift on pharyngeal resistance. The results suggested that fluid shift could play an important role in the formation of hypopnea or OSA during sleep.

Computer simulations show that Neanderthal facial morphology represents adaptation to cold and high energy demands, but not heavy biting

Three adaptive hypotheses have been forwarded to explain the distinctive Neanderthal face: (i) an improved ability to accommodate high anterior bite forces, (ii) more effective conditioning of cold and/or dry air and, (iii) adaptation to facilitate greater ventilatory demands. We test these hypotheses using three-dimensional models of Neanderthals, modern humans, and a close outgroup (Homo heidelbergensis), applying finite-element analysis (FEA) and computational fluid dynamics (CFD). This is the most comprehensive application of either approach applied to date and the first to include both. FEA reveals few differences between H. heidelbergensis, modern humans, and Neanderthals in their capacities to sustain high anterior tooth loadings. CFD shows that the nasal cavities of Neanderthals and especially modern humans condition air more efficiently than does that of H. heidelbergensis, suggesting that both evolved to better withstand cold and/or dry climates than less derived Homo We further find that Neanderthals could move considerably more air through the nasal pathway than could H. heidelbergensis or modern humans, consistent with the propositions that, relative to our outgroup Homo, Neanderthal facial morphology evolved to reflect improved capacities to better condition cold, dry air, and, to move greater air volumes in response to higher energetic requirements.

What Does Nasal Cavity Size Tell us about Functional Nasal Airways?

Studies on dry human skulls have shown that nasal cavity (NC) morphology varies with eco-geographic factors. These findings have been used by some authors to interpret the facial morphology of Neanderthals. However, respiratory and air-conditioning functions are primarily carried out by the nasal airways (NA), which are delimited by mucosa. The aims of this study were to test whether: (1) NC volume (V) and surface-area-to-volume ratio (SA/ V) are proportional to NA counterparts; (2) measurements for male NC and NA are larger than in females; (3) the centroid size (CS) of a set of landmarks measured on NC provides a reliable proxy for NC V. Head CT (computed tomography) images of adult patients (N = 30) at the University Hospital of Bordeaux were selected retrospectively. NA were defined by segmenting the lumen corresponding to the functional volume. NC was defined by adding to NA the soft tissues delimited by the bones forming the NC. The coordinates of 16 landmarks measured on NC bones were recorded. A rather low correlation was found between NA and NC V while NA SA/V and NC SA/V were not correlated. No significant differences were found between male and female NA and NC measurements. A rather low correlation was found between NC Vand NC CS. If these preliminary results were to be confirmed by future studies, results using NC as a proxy for NA focusing on air-conditioning and respiratory energetics might need to be re-interpreted.

Numerical simulation of two consecutive nasal respiratory cycles: toward a better understanding of nasal physiology

BACKGROUND

Computational fluid dynamic (CFD) simulations have greatly improved the understanding of nasal physiology. We postulate that simulating the entire and repeated respiratory nasal cycles, within the whole sinonasal cavities, is mandatory to gather more accurate observations and better understand airflow patterns.

METHODS

A 3-dimensional (3D) sinonasal model was constructed from a healthy adult computed tomography (CT) scan which discretized in 6.6 million cells (mean volume, 0.008 mm³ ). CFD simulations were performed with ANSYS©FluentTMv16.0.0 software with transient and turbulent airflow (k-ω model). Two respiratory cycles (8 seconds) were simulated to assess pressure, velocity, wall shear stress, and particle residence time.

RESULTS

The pressure gradients within the sinus cavities varied according to their place of connection to the main passage. Alternations in pressure gradients induced a slight pumping phenomenon close to the ostia but no movement of air was observed within the sinus cavities. Strong movements were observed within the inferior meatus during expiration contrary to the inspiration, as in the olfactory cleft at the same time. Particle residence time was longer during expiration than inspiration due to nasal valve resistance, as if the expiratory phase was preparing the next inspiratory phase. Throughout expiration, some particles remained in contact with the lower turbinates. The posterior part of the olfactory cleft was gradually filled with particles that did not leave the nose at the next respiratory cycle. This pattern increased as the respiratory cycle was repeated.

CONCLUSION

CFD is more efficient and reliable when the entire respiratory cycle is simulated and repeated to avoid losing information.

Numerical Comparison of Nasal Aerosol Administration Systems for Efficient Nose-to-Brain Drug Delivery

PURPOSE

Nose-to-brain drug administration along the olfactory and trigeminal nerve pathways offers an alternative route for the treatment of central nervous system (CNS) disorders. The characterization of particle deposition remains difficult to achieve in experiments. Alternative numerical approach is applied to identify suitable aerosol particle size with maximized inhaled doses.

METHODS

This study numerically compared the drug delivery efficiency in a realistic human nasal cavity between two aerosol drug administration systems targeting the olfactory region: the aerosol mask system and the breath-powered bi-directional system. Steady inhalation and exhalation flow rates were applied to both delivery systems. The discrete phase particle tracking method was employed to capture the aerosol drug transport and deposition behaviours in the nasal cavity. Both overall and regional deposition characteristics were analysed in detail.

RESULTS

The results demonstrated the breath-powered drug delivery approach can produce superior olfactory deposition with peaking olfactory deposition fractions for diffusive 1 nm particles and inertial 10 μm. While for particles in the range of 10 nm to 2 μm, no significant olfactory deposition can be found, indicating the therapeutic agents should avoid this size range when targeting the olfactory deposition.

CONCLUSIONS

The breath-powered bi-directional aerosol delivery approach shows better drug delivery performance globally and locally, and improved drug administration doses can be achieved in targeted olfactory region.

Computational modeling and validation of human nasal airflow under various breathing conditions

The human nose serves vital physiological functions, including warming, filtration, humidification, and olfaction. These functions are based on transport phenomena that depend on nasal airflow patterns and turbulence. Accurate prediction of these airflow properties requires careful selection of computational fluid dynamics models and rigorous validation. The validation studies in the past have been limited by poor representations of the complex nasal geometry, lack of detailed airflow comparisons, and restricted ranges of flow rate. The objective of this study is to validate various numerical methods based on an anatomically accurate nasal model against published experimentally measured data under breathing flow rates from 180 to 1100ml/s. The numerical results of velocity profiles and turbulence intensities were obtained using the laminar model, four widely used Reynolds-averaged Navier-Stokes (RANS) turbulence models (i.e., k-ε, standard k-ω, Shear Stress Transport k-ω, and Reynolds Stress Model), large eddy simulation (LES) model, and direct numerical simulation (DNS). It was found that, despite certain irregularity in the flow field, the laminar model achieved good agreement with experimental results under restful breathing condition (180ml/s) and performed better than the RANS models. As the breathing flow rate increased, the RANS models achieved more accurate predictions but still performed worse than LES and DNS. As expected, LES and DNS can provide accurate predictions of the nasal airflow under all flow conditions but have an approximately 100-fold higher computational cost. Among all the RANS models tested, the standard k-ω model agrees most closely with the experimental values in terms of velocity profile and turbulence intensity.

The association between mid-facial morphology and climate in northeast Europe differs from that in north Asia: Implications for understanding the morphology of Late Pleistocene Homo sapiens

The climate of northeastern Europe is likely to resemble in many ways Late Pleistocene periglacial conditions in Europe, but there have been relatively few studies exploring the association between climate and morphology in the mid-face of modern northeastern European populations. To fill this gap, we sampled 540 male skulls from 22 European and Near Eastern groups, including 314 skulls from 11 populations from northeastern Europe, to test for possible climate-morphology association at the continental scale. Our results found a moderate and highly significant association (R = 0.48, p = 0.0013, Mantel test) between sets of 23 mid-facial measurements and eight climatic variables. A partial least squares analysis revealed this association to be mostly driven by differences between groups from northeastern Europe and populations from the Mediterranean and the Caucasus. Matrices of between-group genetic distances based on Y-chromosome and mtDNA markers, as well as cranial non-metric and geographic distance matrices, were used to control for the possible influence of shared population history. Irrespective of which measure of neutral between-population distances is taken into account, the association between cranial variables and climate remains significant. The pattern of association between climate and morphology of the mid-face in western Eurasia was then compared to that in east and north Asia. Although differences between the two were found, there were also similarities that support existing functional interpretations of morphology for the bony parts of the upper airways. Last, in a preliminary analysis using a reduced set of measurements, mid-facial morphology of several Upper Paleolithic European Homo sapiens specimens was found to be more similar to groups from northern and northeastern Europe than to southern European populations. Thus, the population of northeastern Europe rather than east and north Asian groups should be used as a model when studying climate-mediated mid-facial morphology of Upper Paleolithic European H. sapiens.

The Landscape Ecology and Microbiota of the Human Nose, Mouth, and Throat

Landscape ecology examines the relationships between the spatial arrangement of different landforms and the processes that give rise to spatial and temporal patterns in local community structure. The spatial ecology of the microbial communities that inhabit the human body-in particular, those of the nose, mouth, and throat-deserves greater attention. Important questions include what defines the size of a population (i.e., "patch") in a given body site, what defines the boundaries of distinct patches within a single body site, and where and over what spatial scales within a body site are gradients detected. This Review looks at the landscape ecology of the upper respiratory tract and mouth and seeks greater clarity about the physiological factors-whether immunological, chemical, or physical-that govern microbial community composition and function and the ecological traits that underlie health and disease.

[Numerical flow simulation : A new method for assessing nasal breathing]

The current options for objective assessment of nasal breathing are limited. The maximum they can determine is the total nasal resistance. Possibilities to analyze the endonasal airstream are lacking. In contrast, numerical flow simulation is able to provide detailed information of the flow field within the nasal cavity. Thus, it has the potential to analyze the nasal airstream of an individual patient in a comprehensive manner and only a computed tomography (CT) scan of the paranasal sinuses is required. The clinical application is still limited due to the necessary technical and personnel resources. In particular, a statistically based referential characterization of normal nasal breathing does not yet exist in order to be able to compare and classify the simulation results.

Non-invasive Assessment and Symptomatic Improvement of the Obstructed Nose (NASION): a physiology-based patient-centred approach to treatment selection and outcomes assessment in nasal obstruction

OBJECTIVES

To evaluate the impact of selecting treatment for nasal obstruction on the basis of a structured physiology-based assessment protocol on patient outcomes.

DESIGN

Prospective longitudinal study.

SETTING

District general hospital.

PARTICIPANTS

A population of 71 patients with a mean age of 33 years, containing 36 males, presented with nasal obstruction for consideration of nasal surgery. All patients underwent a structured clinical assessment, skin prick allergy testing and oral-nasal flow-volume loop examination. Fifty-one patients completed the follow-up, and mean follow-up was 11 months.

MAIN OUTCOME MEASURES

NOSE, SNOT-22 and NASION scales.

RESULTS

Of the 51 patients who completed follow-up, six had conservative treatment, 28 had septal/turbinate surgery, and 17 underwent nasal valve surgery. Mean NOSE score fell from 68 ± 18 to 39 ± 31 following the treatment. Mean SNOT-22 score fell from 47 ± 20 to 29 ± 26 following the treatment. The difference between pre-treatment and post-treatment NOSE and SNOT-22 scores were statistically significant. Success rate of septal/turbinate surgery in patients without nasal allergy was 88%, and this fell to 42% in patients undergoing septal/turbinate surgery who also had nasal allergy. Presence of nasal allergy was the only independent predictor of treatment failure. Patients with nasal valve surgery reported significantly greater symptomatic improvement following surgery. The newly formed NASION scale demonstrated internal consistency with a Cronbach α of 0.9 and excellent change-responsiveness and convergent validity with correlation coefficients of 0.64 and 0.77 against treatment-related changes in SNOT-22 and NOSE scales, respectively.

CONCLUSIONS

Successful surgical outcomes can be achieved with the use of a structured history, clinical evaluation and physiological testing. Flow-volume loops can help elucidate the cause of nasal obstruction. The newly formed NASION scale is a validated retrospective single time-point patient outcome measure.

A computational analysis of nasal vestibule morphologic variabilities on nasal function

Although advances in computational modeling have led to increased understanding of nasal airflow, not much is known about the effects of normal sinonasal anatomic variabilities on nasal function. In this study, three distinct variations in the human nasal vestibule airspace that have not been previously described were identified. Computational fluid dynamics modeling of nasal airflow profile in each identified variation of nasal vestibule phenotype was conducted to assess the role of these phenotypes on nasal physiology. Three-dimensional reconstructions of the nasal geometry in sixteen subjects with normal radiographic sinonasal images were created and each respective unilateral nasal cavity was classified as Notched, Standard, or Elongated phenotype based nasal vestibule morphology. Steady state, laminar and incompressible flow simulations were performed in the nasal geometries under physiological, pressure-driven conditions with constant inspiratory pressure. Results showed that at localized regions of the unilateral nasal cavity, average resistance was significantly different among nasal vestibule phenotypes. However, global comparison from nostril to choana showed that average resistance was not significantly different across phenotypes; suggesting that with normal anatomic variations, the nose has a natural compensatory mechanism that modulates localized airflow in order to achieve a desired amount of global airflow.

Large-scale CFD simulations of the transitional and turbulent regime for the large human airways during rapid inhalation

The dynamics of unsteady flow in the human large airways during a rapid inhalation were investigated using highly detailed large-scale computational fluid dynamics on a subject-specific geometry. The simulations were performed to resolve all the spatial and temporal scales of the flow, thanks to the use of massive computational resources. A highly parallel finite element code was used, running on two supercomputers, solving the transient incompressible Navier-Stokes equations on unstructured meshes. Given that the finest mesh contained 350 million elements, the study sets a precedent for large-scale simulations of the respiratory system, proposing an analysis strategy for mean flow, fluctuations and wall shear stresses on a rapid and short inhalation (a so-called sniff). The geometry used encompasses the exterior face and the airways from the nasal cavity, through the trachea and up to the third lung bifurcation; it was derived from a contrast-enhanced computed tomography (CT) scan of a 48-year-old male. The transient inflow produces complex flows over a wide range of Reynolds numbers (Re). Thanks to the high fidelity simulations, many features involving the flow transition were observed, with the level of turbulence clearly higher in the throat than in the nose. Spectral analysis revealed turbulent characteristics persisting downstream of the glottis, and were captured even with a medium mesh resolution. However a fine mesh resolution was found necessary in the nasal cavity to observe transitional features. This work indicates the potential of large-scale simulations to further understanding of airway physiological mechanics, which is essential to guide clinical diagnosis; better understanding of the flow also has implications for the design of interventions such as aerosol drug delivery.

Differential Scaling Patterns in Maxillary Sinus Volume and Nasal Cavity Breadth Among Modern Humans

Among modern humans, nasal cavity size and shape reflect its vital role in air conditioning processes. The ability for the nasal cavity to augment its shape, particularly in inferior breadth, likely relates to the surrounding maxillary sinuses acting as zones of accommodation. However, much is still unknown regarding how nasal and sinus morphology relate to each other and to overall craniofacial form, particularly across diverse populations with varying respiratory demands. As such, this study uses computed tomographic (CT) scans of modern human crania (N = 171) from nine different localities to investigate ecogeographic differences in (1) the interaction between maxillary sinus volume (MSV) and nasal cavity breadth (NCB) and (2) scaling patterns of MSV and NCB in relation to craniofacial size. Reduced major axis (RMA) regression reveals that all samples exhibit an inverse relationship between MSV and NCB, but statistical significance and the strength of that relationship is sample dependent. Individuals from cold-dry climates have larger MSVs with narrower NCBs, while smaller MSVs are associated with wider NCBs in hot-humid climates. MSV and NCB each scale with positive allometry relative to overall craniofacial size. However, sample differences are evident in the both the interaction between MSV and NCB, as well as their correlation with craniofacial size. While these results provide further support that the maxillary sinus and nasal cavity are integrated among populations from opposite ends of the climatic spectrum, additional epigenetic factors are needed to explain variation of these structures among populations from more intermediate climates.

Dynamics of airflow in a short inhalation

During a rapid inhalation, such as a sniff, the flow in the airways accelerates and decays quickly. The consequences for flow development and convective transport of an inhaled gas were investigated in a subject geometry extending from the nose to the bronchi. The progress of flow transition and the advance of an inhaled non-absorbed gas were determined using highly resolved simulations of a sniff 0.5 s long, 1 l s⁻¹ peak flow, 364 ml inhaled volume. In the nose, the distribution of airflow evolved through three phases: (i) an initial transient of about 50 ms, roughly the filling time for a nasal volume, (ii) quasi-equilibrium over the majority of the inhalation, and (iii) a terminating phase. Flow transition commenced in the supraglottic region within 20 ms, resulting in large-amplitude fluctuations persisting throughout the inhalation; in the nose, fluctuations that arose nearer peak flow were of much reduced intensity and diminished in the flow decay phase. Measures of gas concentration showed non-uniform build-up and wash-out of the inhaled gas in the nose. At the carina, the form of the temporal concentration profile reflected both shear dispersion and airway filling defects owing to recirculation regions.

Effects of CT resolution and radiodensity threshold on the CFD evaluation of nasal airflow

The article focuses on the robustness of a CFD-based procedure for the quantitative evaluation of the nasal airflow. CFD ability to yield robust results with respect to the unavoidable procedural and modeling inaccuracies must be demonstrated to allow this tool to become part of the clinical practice in this field. The present article specifically addresses the sensitivity of the CFD procedure to the spatial resolution of the available CT scans, as well as to the choice of the segmentation level of the CT images. We found no critical problems concerning these issues; nevertheless, the choice of the segmentation level is potentially delicate if carried out by an untrained operator.

Localization of Transcranial Targets for Photoacoustic-Guided Endonasal Surgeries

Neurosurgeries to remove pituitary tumors using the endonasal, transsphenoidal approach often incur the risk of patient death caused by injury to the carotid arteries hidden by surrounding sphenoid bone. To avoid this risk, we propose intraoperative photoacoustic vessel visualization with an optical fiber attached to the surgical tool and an external ultrasound transducer placed on the temple. Vessel detection accuracy is limited by acoustic propagation properties, which were investigated with k-Wave simulations. In a two-layer model of temporal bone (3200 m/s sound speed, 1-4 mm thickness) and surrounding tissues, the localization error was ≤2 mm in the tranducer's axial dimension, while temporal bone curvature further degraded target localization. Phantom experiments revealed that multiple image targets (e.g. sphenoid bone and vessels) can be visualized, particularly with coherence-based beamforming, to determine tool-to-vessel proximity despite expected localization errors. In addition, the potential flexibility of the fiber position relative to the transducer and vessel was elucidated.

Processing the image gradient field using a topographic primal sketch approach

The spatial derivatives of the image intensity provide topographic information that may be used to identify and segment objects. The accurate computation of the derivatives is often hampered in medical images by the presence of noise and a limited resolution. This paper focuses on accurate computation of spatial derivatives and their subsequent use to process an image gradient field directly, from which an image with improved characteristics can be reconstructed. The improvements include noise reduction, contrast enhancement, thinning object contours and the preservation of edges. Processing the gradient field directly instead of the image is shown to have numerous benefits. The approach is developed such that the steps are modular, allowing the overall method to be improved and possibly tailored to different applications. As presented, the approach relies on a topographic representation and primal sketch of an image. Comparisons with existing image processing methods on a synthetic image and different medical images show improved results and accuracy in segmentation. Here, the focus is on objects with low spatial resolution, which is often the case in medical images. The methods developed show the importance of improved accuracy in derivative calculation and the potential in processing the image gradient field directly. Copyright © 2015 John Wiley & Sons, Ltd.

[The paranasal sinuses as the nitric oxide depot]

This paper was designed to report the currently available data on physiology of the nasal cavity and paranasal sinuses together with the results of national and international investigations on the computer modeling of the air flow in these structures. Also discussed are the gas composition in the paranasal sinuses and the potential factors responsible for the changes in the concentration of nitric oxide with the chemical formula of NO in the nasal cavity and paranasal sinuses.

Nasal region dimensions in children: a CT study and clinical implications

Atresias of nasal cavity, especially in young children, pose an essential problem in children's otolaryngology. Only a few morphometric studies of nasal cavity concerning healthy neonates and young infants without nasal stenosis are available. Multislice computed tomography is a perfect tool enabling a precise evaluation of anatomic structures. The aim of this study was a complex morphometric evaluation of clinically important bone and mucosal structures of nasal cavity and examination of their dependence on age and sex in children up to 3 years of age. 180 children, age range 0–3 years, were divided into 5 age groups, and measurements of 18 distances between skeletal structures and between mucosal structures of nasal cavity were performed on their CT scans. A correlation between the widths of selected bone structures was examined. There were no statistically significant differences in analyzed morphometric parameters between adjacent age groups. The differences were statistically significant only between extreme age groups. There was a correlation between evaluated structures and age. Our results are a valuable supplement of nasal cavity morphometric data of young children. They may be useful in setting reference values of evaluated parameters in children and in diagnosis and planning of surgical treatment in children's otolaryngology.

Computational model of particle deposition in the nasal cavity under steady and dynamic flow

A computational model for flow and particle deposition in a three-dimensional representation of the human nasal cavity is developed. Simulations of steady state and dynamic airflow during inhalation are performed at flow rates of 9-60 l/min. Depositions for particles of size 0.5-20 μm are determined and compared with experimental and simulation results from the literature in terms of deposition efficiencies. The nasal model is validated by comparison with experimental and simulation results from the literature for particle deposition under steady-state flow. The distribution of deposited particles in the nasal cavity is presented in terms of an axial deposition distribution as well as a bivariate axial deposition and particle size distribution. Simulations of dynamic airflow and particle deposition during an inhalation cycle are performed for different nasal cavity outlet pressure variations and different particle injections. The total particle deposition efficiency under dynamic flow is found to depend strongly on the dynamics of airflow as well as the type of particle injection.

Standardization of Malaysian adult female nasal cavity

This research focuses on creating a standardized nasal cavity model of adult Malaysian females. The methodology implemented in this research is a new approach compared to other methods used by previous researchers. This study involves 26 females who represent the test subjects for this preliminary study. Computational fluid dynamic (CFD) analysis was carried out to better understand the characteristics of the standardized model and to compare it to the available standardized Caucasian model. This comparison includes cross-sectional areas for both half-models as well as velocity contours along the nasal cavities. The Malaysian female standardized model is larger in cross-sectional area compared to the standardized Caucasian model thus leading to lower average velocity magnitudes. The standardized model was further evaluated with four more Malaysian female test subjects based on its cross-sectional areas and average velocity magnitudes along the nasal cavities. This evaluation shows that the generated model represents an averaged and standardized model of adult Malaysian females.

Hygroscopic aerosol deposition in the human upper respiratory tract under various thermo-humidity conditions

The deposition of hygroscopic aerosols is highly complex in nature, which results from a cumulative effect of dynamic particle growth and the real-time size-specific deposition mechanisms. The objective of this study is to evaluate hygroscopic effects on the particle growth, transport, and deposition of nasally inhaled aerosols across a range of 0.2-2.5 μm in an adult image-based nose-throat model. Temperature and relative humidity fields were simulated using the LRN k-ω turbulence model and species transport model under a spectrum of thermo-humidity conditions. Particle growth and transport were simulated using a well validated Lagrangian tracking model coupled with a user-defined hygroscopic growth module. Results of this study indicate that the saturation level and initial particle size are the two major factors that determine the particle growth rate (d/d0), while the effect of inhalation flow rate is found to be not significant. An empirical correlation of condensation growth of nasally inhaled hygroscopic aerosols in adults has been developed based on a variety of thermo-humidity inhalation conditions. Significant elevated nasal depositions of hygroscopic aerosols could be induced by condensation growth for both sub-micrometer and small micrometer particulates. In particular, the deposition of initially 2.5 μm hygroscopic aerosols was observed to be 5-8 times that of inert particles under warm to hot saturated conditions. Results of this study have important implications in exposure assessment in hot humid environments, where much higher risks may be expected compared to normal conditions.

Dynamic growth and deposition of hygroscopic aerosols in the nasal airway of a 5-year-old child

Hygroscopic growth within the human respiratory tract can be significant, which may notably alter the behavior and fate of the inhaled aerosols. The objective of this study is to evaluate the hygroscopic effects upon the transport and deposition of nasally inhaled fine-regime aerosols in children. A physiologically realistic nasal-laryngeal airway model was developed based on magnetic resonance imaging of a 5-year-old boy. Temperature and relative humidity field were simulated using the low Reynolds number k - ε turbulence model and chemical specie transport model under a spectrum of four thermo-humidity conditions. Particle growth and transport were simulated using a well validated Lagrangian tracking model coupled with a user-defined hygroscopic growth module. The subsequent aerosol depositions for the four inhalation scenarios were evaluated on a multiscale basis such as total, subregional, and cellular-level depositions. Results of this study show that a supersaturated humid environment is possible in the nasal turbinate region and can lead to significant condensation growth (d / d(0)  > 10) of nasally inhaled aerosols. Depositions in the nasal airway can also be greatly enhanced by condensation growth with appropriate inhalation temperature and humidity. For subsaturated and mild inhalation conditions, the hygroscopic effects were found to be nonsignificant for total depositions, while exerting a large impact upon localized depositions.

Patient specific CFD models of nasal airflow: overview of methods and challenges

Respiratory physiology and pathology are strongly dependent on the airflow inside the nasal cavity. However, the nasal anatomy, which is characterized by complex airway channels and significant individual differences, is difficult to analyze. Thus, commonly adopted diagnostic tools have yielded limited success. Nevertheless, with the rapid advances in computer resources, there have been more elaborate attempts to correlate airflow characteristics in human nasal airways with the symptoms and functions of the nose by computational fluid dynamics study. Furthermore, the computed nasal geometry can be virtually modified to reflect predicted results of the proposed surgical technique. In this article, several computational fluid mechanics (CFD) issues on patient-specific three dimensional (3D) modeling of nasal cavity and clinical applications were reviewed in relation to the cases of deviated nasal septum (decision for surgery), turbinectomy, and maxillary sinus ventilation (simulated- and post-surgery). Clinical relevance of fluid mechanical parameters, such as nasal resistance, flow allocation, wall shear stress, heat/humidity/NO gas distributions, to the symptoms and surgical outcome were discussed. Absolute values of such parameters reported by many research groups were different each other due to individual difference of nasal anatomy, the methodology for 3D modeling and numerical grid, laminar/turbulent flow model in CFD code. But, the correlation of these parameters to symptoms and surgery outcome seems to be obvious in each research group with subject-specific models and its variations (virtual- and post-surgery models). For the more reliable, patient-specific, and objective tools for diagnosis and outcomes of nasal surgery by using CFD, the future challenges will be the standardizations on the methodology for creating 3D airway models and the CFD procedures.

Local deposition fractions of ultrafine particles in a human nasal-sinus cavity CFD model

Ultrafine particle deposition studies in the human nasal cavity regions often omit the paranasal sinus regions. Because of the highly diffusive nature of nanoparticles, it is conjectured that deposition by diffusion may occur in the paranasal sinuses, which may affect the residual deposition fraction that leaves the nasal cavity. Two identical CFD models of a human nasal cavity, one with sinuses and one without, were reconstructed from CT-scans to determine the uptake of ultrafine particles. In general, there was little flow passing through the paranasal sinuses. However, flow patterns revealed that some streamlines reached the upper nasal cavity near the olfactory regions. These flow paths promote particle deposition in the sphenoid and ethmoid sinuses. It was found that there were some differences in the deposition fractions and patterns for 5 and 10 nm particles between the nasal-sinus and the nasal cavity models. This difference is amplified when the flow rate is decreased and at a flow rate of 4 L/min the maximum difference was 17%. It is suggested that evaluations of nanoparticle deposition should consider some deposition occurring in the paranasal sinuses especially if flow rates are of concern.

Nasal inspiratory flow: at rest and sniffing

BACKGROUND

This study quantifies the time-varying flow rate during inspiration at rest and in sniffing, both predecongestion and postdecongestion. It aims to provide a better understanding of nasal airflow mechanics, for application to the physiological modeling of nasal respiration and to therapeutic drug delivery.

METHODS

The temporal profiles of nasal inspiration were measured at high fidelity in 14 healthy individuals using simultaneous bilateral hot-wire anemometry. Peak nasal inspiratory flow (PNIF) rate, acoustic rhinometry (AR), and the sinonasal outcome test (SNOT) provided complementary clinical measurements. The impact of decongestion was also investigated.

RESULTS

In the initial phase of inspiration, a rapid rise in flow rate was observed. Flow first exceeded 150 mL/second in either passage within a median time of approximately 120 ms for inspiration at rest and approximately 60 ms in sniffing (∼20 ms in the fastest sniffs). The mean sustained flow rate attained and the overall period of each measured inspiratory profile were analyzed. AR showed a significant change in nasal volume with decongestion, although these change were not manifest in the temporal profiles of inspiratory flow (barring a weak effect associated with the most vigorous sniffs).

CONCLUSION

Novel methods were applied to investigate the temporal profiles of nasal inspiration. Characteristic features of the profile were identified and found to be significantly different between inspiration at rest and sniffing. Decongestion was found to have little effect on the temporal profiles for the flow regimes studied.

Assessment of nasal septoplasty using NOSE and RhinoQoL questionnaires

The objective was to assess outcomes of nasal septoplasty without turbinectomy using validated subjective instruments and to correlate results with patient satisfaction. The prospective observational study was conducted in a tertiary referral center. The method included the use of NOSE and RhinoQoL questionnaires to assess patients before and 6 months after Cottle septoplasty without turbinectomy. Patient satisfaction was measured on a visual analog scale. Data were compared by the non-parametric Wilcoxon test. Minimal Clinically Important Differences (MCIDs) were calculated. Correlations between post-operative scores and patient satisfaction were assessed using the Spearman test. Univariate analysis was performed to assess predictors of improvement. One hundred patients were enrolled. Their mean age was 43.4 years and 28% had allergic rhinitis. There was a highly significant improvement in each score at 6 months (p < 0.00001). The MCID for the NOSE was comprised between 5 and 7.5, whereas the mean change was 35.2 points. They ranged from 3.8 to 6.1 for RhinoQoL scores, whereas mean changes were comprised between 12.6 and 20.9. Allergic rhinitis was a predictive factor of less improvement (NOSE p = 0.04-RhinoQoL p = 0.0001). Mean patient satisfaction was 8.2 ± 1.8. Post-operative NOSE and RhinoQoL frequency scores were moderately correlated (r = 0.380; r = 0.356, respectively) whereas bothersomeness and impact scores were highly correlated with patient satisfaction (r = 0.459; r = 0.443, p < 0.00001, respectively). This study shows that the NOSE and RhinoQoL questionnaires can be used in English- and French-speaking populations to perform pre- and post-therapeutic assessment. These validated instruments show that septoplasty without turbinectomy allows management of nasal obstruction and its burden.

Decomposition and description of the nasal cavity form

Patient-specific studies of physiological flows rely on anatomically realistic or idealized models. Objective comparison of datasets or the relation of specific to idealized geometries has largely been performed in an ad hoc manner. Here, two rational procedures (based respectively on Fourier descriptors and medial axis (MA) transforms) are presented; each provides a compact representation of a complex anatomical region, specifically the nasal airways. The techniques are extended to furnish average geometries. These retain a sensible anatomical form, facilitating the identification of a specific anatomy as a set of weighted perturbations about the average. Both representations enable a rapid translation of the surface description into a virtual model for computation of airflow, enabling future work to comprehensively investigate the relation between anatomic form and flow-associated function, for the airways or for other complex biological conduits. The methodology based on MA transforms is shown to allow flexible geometric modeling, as illustrated by a local alteration in airway patency. Computational simulations of steady inspiratory flow are used to explore the relation between the flow in individual vs. averaged anatomical geometries. Results show characteristic flow measures of the averaged geometries to be within the range obtained from the original three subjects, irrespective of averaging procedure. However the effective regularization of anatomic form resulting from the shape averaging was found to significantly reduce trans-nasal pressure loss and the mean shear stress in the cavity. It is suggested that this may have implications in attempts to relate model geometries and flow patterns that are broadly representative.

Physical and computational modeling of ventilation of the maxillary sinus

Objective. Sinus ventilation is often associated with sinusitis, a common condition causing significant pain and reduced quality of life. Clinical implications of the diverse anatomy of ostia connecting sinus to nose and the efficacy of surgical intervention in chronic sinusitis are poorly understood. This study aimed to measure sinus ventilation and explore variables in physical and mathematical models.

Study Design. γ-Scintigraphy of krypton 81m (81mKr) was carried out in a stylized physical model of a human maxillary sinus. Computational simulations matched this model for validation and extrapolated to combinations of variables not possible experimentally for evaluation of transport mechanisms.

Setting. Research laboratory in Department of Aeronautics. Imperial College London, and Department of Nuclear Medicine, Hammersmith Hospital, London.

Methods. 81mKr distribution was measured with both single- and double-ostia sinuses. Computational simulations matched and extended the physical measurements and enabled separate identification and evaluation of transport mechanisms.

Results. The presence of an additional ostium resulted in a 50-fold increase in the effective volume flow rate of gas replacement in the sinus. In the case of a single ostium, doubling the ostial diameter doubled the effective volume flow rate of gas exchange.

Conclusion. γ-Scintigraphy of 81mKr enables quantitative assessment of effective volume flow rate in physical model sinuses. These flow rates obtained experimentally for single- and double-ostium sinuses match the computational predictions of matching geometries. The increased ventilation seen with an additional ostium or increased ostial diameters may not be clinically beneficial, because it could reduce nitric oxide concentration in the sinus.

[Nasal-air conditioning]

INTRODUCTION

We present a review of nasal-air conditioning, a process essential to undisturbed gas exchange and cleansing of the respiratory mucosa in the nose.

METHODS

A selective literature review was made on the basis of in vivo measurements and computer simulation of the upper airways as well as the authors' own clinical and experimental data.

RESULTS AND DISCUSSION

Healthy subjects normally breathe through the nose, although the nasal airways have significantly higher airway resistance compared to the oral cavity, which is opened for breathing during exercise, in the case of nasal airway blockage, or in allergic rhinitis. In addition to olfaction, the main tasks of nasal breathing include: cleansing, defense, and conditioning (i.e., humidification and heating). The current knowledge of nasal conditioning processes will be discussed. In addition, research activities of particular relevance for diagnosis and intervention in various pathologies of the upper airways will be presented.

Numerical investigation of septal deviation effect on deposition of nano/microparticles in human nasal passage

Three dimensional computational models of both sides of human nasal passages were developed to investigate the effect of septal deviation on the flow patterns and deposition of micro/nano-particles in the realistic human nasal airways before and after septoplasty. A series of coronal CT scan images from a live 25-year old nonsmoking male with septal deviation in his right nasal passage was used to construct the model. For low to moderate activities, the steady airflows through the nasal passages were simulated. Eulerian and Lagrangian approaches were used, respectively, for nano- and micro-particles. The results show that the flow field and particle deposition strongly depend on the passage geometry especially for micro particles. In particular, the deposition rate in the passage with septal deviation was much higher compared with those in the normal (left) passage and the postoperative passage. Despite the similarity of total micro-particle deposition in the postoperative and the normal cavities, the regional deposition patterns were quite different in these passages. The deposition of nano-particles, however, showed similar trends in the postoperative right nasal passage and the normal left passage. The simulation results showed that in addition to the major alteration of the airflow pattern after the septoplasty operation, there are significant changes in the deposition pattern of nano- and micro-particles. Despite the anatomical differences between the available experimental configuration and the present computer model, the simulation results for the deposition efficiency of particles of different sizes are in qualitative agreement with the available data.