- Email: [email protected]
Upper airway function: objective measures and computer simulation
Track 13. Respiratory Mechanics
13.6. Transport in the Upper Airways
wall mass flux and tissue phase dosimeters can be made. In this approach, nasal extraction (NE) data was obtained in hydrogen sulfide-exposed rats and an air-tissue PBPK model was developed to simulate hydrogen sulfide extraction by the rat nasal cavity. Kinetic parameters for the elimination of hydrogen sulfide in nasal tissue by first-order and saturable metabolism were estimated by fitting the PBPK model to the NE data. These parameters were then implemented in a mass transfer boundary condition in a CFD model of hydrogen sulfide transport in the rat nasal passages. Predicted NE values obtained using this PBPK-informed CFD approach were in good agreement with the experimental measurements. This approach can be extended to predict localized levels of tissue-phase dosimeters that may be linked to inhalantinduced damage. These predictions will allow the extrapolation of tissue damage induced in laboratory animals to humans on the basis of relevant tissue dose metrics that incorporate species-specific anatomy, physiology, and tissue-phase biochemistry. 5624 We, 12:00-12:15 (P31) Impact o f the g e o m e t r y on the nose flow I. H6rschler, W. Schr6der. Aeredynamisches Institut, RWTH Aachen, Germany The human nasal cavity covers a variety of different functions. Besides respiration and the sense of smell it is responsible for moistening, tempering and cleaning the air. These functions are expected to strongly depend on the complex internal geometry of the nasal cavity. Impaired nasal respiration is a common and widespread disease, which makes nose surgery one of the most often performed operations in the western world. Unfortunately, the success rate of such surgery is not satisfactory. To enhance this situation, it is desired to numerically predict the flow inside the nose and its relation to geometric changes. The presentation covers a detailed analysis of the flow through different variations of an anatomic correct replica model of the human nasal cavity with and without turbinates and/or spurs. The flow is investigated for inspiration and expiration at Reynolds numbers based on the throat diameter of Re =500, 1000 for inspiration and Re = 400, 790 for expiration. The numerical method is second order accurate on a multi-block structured grid. Flow measurements are based on the method of Digital Particle-Image Velocimetry (DPIV) in transparent nose models. The experimental results corroborate the numerical flow structure thereby evidencing that the nose flow can be considered laminar in the Reynolds number range investigated. Moreover, the analysis of the flow field indicates overall, the higher susceptibility to geometric changes at inspiration and in particular, the lower turbinate to have the major impact on the flow structure especially when air is inhaled. In the presentation, the grid generation is described first, followed by a concise presentation of the numerical method of solution and the boundary conditions. Subsequently, the experimental setup is explained. Finally, the results are discussed using for instance streamline patterns, pressure and skin friction contours. 7738 Computational modelling o f nasal aerodynamics
We, 12:15-12:30 (P31)
M. Kleven 1, M.C. Melaaen 1, M. Reimers 2, P.G. Djupesland 3. 1Telemark University College and Telemark R&D Centre (TeI-Tek), Porsgrunn, Norway, 2 CMA, University of Oslo, Oslo, Norway, 3 0ptiNose AS, Oslo, Norway Computational fluid dynamics (CFD) is used as a tool in the development and optimization of the patented bi-directional concept for efficient nasal delivery of drugs and vaccines (OptiNose AS, Oslo, Norway). The bi-directional delivery concept is thoroughly described in Djupesland et al. (2004). Traditionally, the CFD technology has a wide application in industrial processes. Transferring and implementing already developed theories on the relatively new field namely nasal aerodynamics - can be used to further optimize the design and performance of OptiNose's delivery devices. The nose is a complex organ with several important physiological functions. Its narrow flow passages and its physiological roles offer considerable challenges in the modelling process. Earlier publications from the research group, see e.g. Kleven et al. (2005), describe the modelling process of the first CFD model we developed. In this paper, an enhanced model is presented. The numerical accuracy is considerable increased by doubling of the number of grid cells, with focus on the narrowest passages in the nose. We present simulations of fluid flow and particle deposition performed with the commercial CFD code Fluent (www.fluent.com). References Djupesland P.G., Skretting A., Vinderen M., Holand T. (2004). Bi-directional nasal delivery of aerosols can prevent lung deposition. J Aerosol Med 17(3): 249-259. Kleven M., Melaaen M.C., Reimers M., R~tnes J.S., Aurdal L., Djupesland, P.G. (2005). Using computational fluid dynamics (CFD) to improve the bi-directional
$271
nasal drug delivery concept. J Food and Bioproducts Processing 83(C2): 107117. 4351 Th, 11:00-11:30 (P41) Upper airway function: objective measures and computer simulation T. Keck, A. Rozsasi. Dept. of Otorhinolaryngology, University of UIm, UIm, Germany Besides olfaction, gas exchange, air conditioning, and cleansing, unspecific and specific defense mechanisms belong also to the main function of the nasal airways. The nasal function depends on several known and unknown factors, e.g. the nasal geometry and the nasal mucosa, the airflow within the nasal cavity, and environmental factors of the air such as the amount of particles, the content of pollutants, allergens, bacteria, and toxins. Knowledge on nasal function and the availability of objective measures of nasal functionality is important for several specialities, e.g. for the rhinologist in planning rhinosurgical procedures to estimate future benefit of rhinosurgery and to objectively diagnose nasal discomfort, for the allergologist in diagnosing nasal hyperreactivity and nasal allergy, for several specialists diagnosing, treating, and researching on the impact of the environment on the nose. Besides commercially available setups for e.g. measurement of nasal patency, nasal geometry, olfactory activity, and mucosal blood flow, numerous experimental systems are used to further examine special nasal functions such as conditioning in the nasal airways, gas exchange, alteration of blood flow after nasal provocation and others. Experimental systems have to fulfill several criteria for reliable in vive measurements: simplicity, accuracy and reproducibility, high response speed for realtime registration, adaptability to biological systems without impairment of nasal function, suitability for clinical application, minimal discomfort for the volunteer. Due to these criteria, only limited setups with still more or less tolerable detection errors are currently used for experimental measurement of nasal function. When in vive measurements are not feasible or cannot reliably be performed within the small upper respiratory tract, additional information may be obtained by computer simulation. Nowadays computer simulation enables the scientist to accurately simulate for example airflow, airway temperature, and distribution of particle deposition within the upper respiratoy tract. This presentation provides an overview on the current measures of nasal function, its value in clinical practice and experimental research, and the need for additional computer simulation. 6394 Th, 11:30-11:45 (P41) Numerical and experimental study on nasal airflow B. Louis 1, C. Croce 1, J.-F. Papon 1,2, J.-R. Blondeau 2, G. Caillibotte 3, A. Coste 1,2, G. Sbirlea-Apiou 3, D. Isabey 1, R. Fodil 1. 1Fonctions Cellulaires et Mel6culaires de I'Appareil Respiratoire et des Vaisseaux INSERM U651, Cr6teil, France, 2Services de Radiologie, d'ORL et de Chirurgie Cervico-Faciale, CHIC et HOpital Henri Mender (AP-HP), Cr~teil, France, 3 Centre de Recherche Claude Delorme, Air Liquide, Jouy-en-Josas, France Nasal inspiratory airflow simulations in numerical 3D reconstruction issued from CT scans were performed. A complete plastinated specimen issued from a cadaver, a healthy subject and a subject with an obstructive septal deviation were tested. The inspiratory air flows were supposed to be incompressible, quasi-steady and laminar. We tested the validity of our complete process (3D reconstruction + CFD computation) by comparing the pressure-flow relationships measured in the plastinated specimen with the numerically computed pressure drop. A good agreement between measured and numerical data was observed up to a flow rate of 250 ml/s. Computed velocity fields found in this study are globally in agreement with the results of the literature [1,2,3,4]. During inspiration air entering the nostrils undergoes a sudden acceleration due to the narrowed nasal valve and then a slow deceleration when entering the vestibule. The spatial evolution of the mean total pressure in the nose sections when we go from the nostrils to the nasopharynx showed that the main total pressure drop arises in the anterior part of the nose. In the tested cases the total pressure variations induced by the variation of kinetic energy, estimated from the computed 3D velocity profile, does not seem to be preponderant probably because the tested flow was relatively small (250 ml/s). However, in the living subjects the kinetic energy coefficient associated with the various sections reached the value of 5 at the level of the middle meatus region. This relatively high value suggests that the role of kinetic energy may be significant during period of hyperventilation. References [1] Hahn et al. J. Applied Physiol. 1993; 75: 2273-2287. [2] Hopkins et al. Experiments in Fluids 2000; 29: 91-95. [3] Keyhani et al. J. Biomech Eng. 1995; 117: 429-441.
13.6. Transport in the Upper Airways
wall mass flux and tissue phase dosimeters can be made. In this approach, nasal extraction (NE) data was obtained in hydrogen sulfide-exposed rats and an air-tissue PBPK model was developed to simulate hydrogen sulfide extraction by the rat nasal cavity. Kinetic parameters for the elimination of hydrogen sulfide in nasal tissue by first-order and saturable metabolism were estimated by fitting the PBPK model to the NE data. These parameters were then implemented in a mass transfer boundary condition in a CFD model of hydrogen sulfide transport in the rat nasal passages. Predicted NE values obtained using this PBPK-informed CFD approach were in good agreement with the experimental measurements. This approach can be extended to predict localized levels of tissue-phase dosimeters that may be linked to inhalantinduced damage. These predictions will allow the extrapolation of tissue damage induced in laboratory animals to humans on the basis of relevant tissue dose metrics that incorporate species-specific anatomy, physiology, and tissue-phase biochemistry. 5624 We, 12:00-12:15 (P31) Impact o f the g e o m e t r y on the nose flow I. H6rschler, W. Schr6der. Aeredynamisches Institut, RWTH Aachen, Germany The human nasal cavity covers a variety of different functions. Besides respiration and the sense of smell it is responsible for moistening, tempering and cleaning the air. These functions are expected to strongly depend on the complex internal geometry of the nasal cavity. Impaired nasal respiration is a common and widespread disease, which makes nose surgery one of the most often performed operations in the western world. Unfortunately, the success rate of such surgery is not satisfactory. To enhance this situation, it is desired to numerically predict the flow inside the nose and its relation to geometric changes. The presentation covers a detailed analysis of the flow through different variations of an anatomic correct replica model of the human nasal cavity with and without turbinates and/or spurs. The flow is investigated for inspiration and expiration at Reynolds numbers based on the throat diameter of Re =500, 1000 for inspiration and Re = 400, 790 for expiration. The numerical method is second order accurate on a multi-block structured grid. Flow measurements are based on the method of Digital Particle-Image Velocimetry (DPIV) in transparent nose models. The experimental results corroborate the numerical flow structure thereby evidencing that the nose flow can be considered laminar in the Reynolds number range investigated. Moreover, the analysis of the flow field indicates overall, the higher susceptibility to geometric changes at inspiration and in particular, the lower turbinate to have the major impact on the flow structure especially when air is inhaled. In the presentation, the grid generation is described first, followed by a concise presentation of the numerical method of solution and the boundary conditions. Subsequently, the experimental setup is explained. Finally, the results are discussed using for instance streamline patterns, pressure and skin friction contours. 7738 Computational modelling o f nasal aerodynamics
We, 12:15-12:30 (P31)
M. Kleven 1, M.C. Melaaen 1, M. Reimers 2, P.G. Djupesland 3. 1Telemark University College and Telemark R&D Centre (TeI-Tek), Porsgrunn, Norway, 2 CMA, University of Oslo, Oslo, Norway, 3 0ptiNose AS, Oslo, Norway Computational fluid dynamics (CFD) is used as a tool in the development and optimization of the patented bi-directional concept for efficient nasal delivery of drugs and vaccines (OptiNose AS, Oslo, Norway). The bi-directional delivery concept is thoroughly described in Djupesland et al. (2004). Traditionally, the CFD technology has a wide application in industrial processes. Transferring and implementing already developed theories on the relatively new field namely nasal aerodynamics - can be used to further optimize the design and performance of OptiNose's delivery devices. The nose is a complex organ with several important physiological functions. Its narrow flow passages and its physiological roles offer considerable challenges in the modelling process. Earlier publications from the research group, see e.g. Kleven et al. (2005), describe the modelling process of the first CFD model we developed. In this paper, an enhanced model is presented. The numerical accuracy is considerable increased by doubling of the number of grid cells, with focus on the narrowest passages in the nose. We present simulations of fluid flow and particle deposition performed with the commercial CFD code Fluent (www.fluent.com). References Djupesland P.G., Skretting A., Vinderen M., Holand T. (2004). Bi-directional nasal delivery of aerosols can prevent lung deposition. J Aerosol Med 17(3): 249-259. Kleven M., Melaaen M.C., Reimers M., R~tnes J.S., Aurdal L., Djupesland, P.G. (2005). Using computational fluid dynamics (CFD) to improve the bi-directional
$271
nasal drug delivery concept. J Food and Bioproducts Processing 83(C2): 107117. 4351 Th, 11:00-11:30 (P41) Upper airway function: objective measures and computer simulation T. Keck, A. Rozsasi. Dept. of Otorhinolaryngology, University of UIm, UIm, Germany Besides olfaction, gas exchange, air conditioning, and cleansing, unspecific and specific defense mechanisms belong also to the main function of the nasal airways. The nasal function depends on several known and unknown factors, e.g. the nasal geometry and the nasal mucosa, the airflow within the nasal cavity, and environmental factors of the air such as the amount of particles, the content of pollutants, allergens, bacteria, and toxins. Knowledge on nasal function and the availability of objective measures of nasal functionality is important for several specialities, e.g. for the rhinologist in planning rhinosurgical procedures to estimate future benefit of rhinosurgery and to objectively diagnose nasal discomfort, for the allergologist in diagnosing nasal hyperreactivity and nasal allergy, for several specialists diagnosing, treating, and researching on the impact of the environment on the nose. Besides commercially available setups for e.g. measurement of nasal patency, nasal geometry, olfactory activity, and mucosal blood flow, numerous experimental systems are used to further examine special nasal functions such as conditioning in the nasal airways, gas exchange, alteration of blood flow after nasal provocation and others. Experimental systems have to fulfill several criteria for reliable in vive measurements: simplicity, accuracy and reproducibility, high response speed for realtime registration, adaptability to biological systems without impairment of nasal function, suitability for clinical application, minimal discomfort for the volunteer. Due to these criteria, only limited setups with still more or less tolerable detection errors are currently used for experimental measurement of nasal function. When in vive measurements are not feasible or cannot reliably be performed within the small upper respiratory tract, additional information may be obtained by computer simulation. Nowadays computer simulation enables the scientist to accurately simulate for example airflow, airway temperature, and distribution of particle deposition within the upper respiratoy tract. This presentation provides an overview on the current measures of nasal function, its value in clinical practice and experimental research, and the need for additional computer simulation. 6394 Th, 11:30-11:45 (P41) Numerical and experimental study on nasal airflow B. Louis 1, C. Croce 1, J.-F. Papon 1,2, J.-R. Blondeau 2, G. Caillibotte 3, A. Coste 1,2, G. Sbirlea-Apiou 3, D. Isabey 1, R. Fodil 1. 1Fonctions Cellulaires et Mel6culaires de I'Appareil Respiratoire et des Vaisseaux INSERM U651, Cr6teil, France, 2Services de Radiologie, d'ORL et de Chirurgie Cervico-Faciale, CHIC et HOpital Henri Mender (AP-HP), Cr~teil, France, 3 Centre de Recherche Claude Delorme, Air Liquide, Jouy-en-Josas, France Nasal inspiratory airflow simulations in numerical 3D reconstruction issued from CT scans were performed. A complete plastinated specimen issued from a cadaver, a healthy subject and a subject with an obstructive septal deviation were tested. The inspiratory air flows were supposed to be incompressible, quasi-steady and laminar. We tested the validity of our complete process (3D reconstruction + CFD computation) by comparing the pressure-flow relationships measured in the plastinated specimen with the numerically computed pressure drop. A good agreement between measured and numerical data was observed up to a flow rate of 250 ml/s. Computed velocity fields found in this study are globally in agreement with the results of the literature [1,2,3,4]. During inspiration air entering the nostrils undergoes a sudden acceleration due to the narrowed nasal valve and then a slow deceleration when entering the vestibule. The spatial evolution of the mean total pressure in the nose sections when we go from the nostrils to the nasopharynx showed that the main total pressure drop arises in the anterior part of the nose. In the tested cases the total pressure variations induced by the variation of kinetic energy, estimated from the computed 3D velocity profile, does not seem to be preponderant probably because the tested flow was relatively small (250 ml/s). However, in the living subjects the kinetic energy coefficient associated with the various sections reached the value of 5 at the level of the middle meatus region. This relatively high value suggests that the role of kinetic energy may be significant during period of hyperventilation. References [1] Hahn et al. J. Applied Physiol. 1993; 75: 2273-2287. [2] Hopkins et al. Experiments in Fluids 2000; 29: 91-95. [3] Keyhani et al. J. Biomech Eng. 1995; 117: 429-441.