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Flow of aerosol in a 3D alveolated bend: experimental measurements by Particle Image Velocimetry (PIV) and Particle Tracking Velocimetry (PTV)
$594
Journal o f Biomechanics 2006, Vol. 39 (Suppl 1)
loss tangent in dexamethasone treated cells was 'q =0.312±0.005) (p =0.52 vs. control). Therefore, dexamethasone stiffens A549 alveolar epithelial cells by inducing a parallel increase in both the elastic and loss moduli. Cell stiffening results in increased elastic centripetal forces during the cell stretching associated with breathing or mechanical ventilation. Cell-cell and cell-matrix adhesion forces should counterbalance the increased elastic forces to maintain monolayer integrity. Supported in part by: SAF 2005q30110 and FIS-PI040929. 6244 We-Th, no. 6 (P64) Computer-aided segmentation and quantification of the human airway tree on the basis o f multi CT images T. Miki 1, S. Wada 1, M. Nakamura 1, K.-i. Tsubota 1, T. Yamaguchi 1, '~ Suda 2, G. Tamura 3 . 1Department of Bioengineering and Robotics, Tohoku University,
Sendal, Japan, 2Sendal Open Hospital, Sendal, Japan, 3 Tohoku University Hospital, Sendal, Japan Morphological structure of the airways is related to a respiratory function. To improve the diagnosis of pulmonary diseases such as asthma, we developed an algorithm for automated segmentation and quantification of the human airway tree on the basis of multi CT images of the lung. The algorithm consists of segmentation of the airway tree, its skeletonization, identification of the airway generation, and measurement of volume, length and diameter of each airway. CT images were acquired with the up-to-date multi slice CT scanner, Aquillion64 (Toshiba Medical Systems Corp., Japan). The airway lumen was extracted from CT images with the region growing method; a grayscale intensity specific to a tissue of the airway wall was determined in the CT images at the entrance of trachea and it was handed to subsequent CT images to trace and construct a 3-D airway model of the airway tree. For morphometric identification of airways' branching, the 3-D airway model was skeletonized. Although the current skeletonization algorithm yielded some pseudo branches, those were deleted manually. Given the skeletonized model, the generation number was defined to each branch of the airway model. A diameter of a branch was calculated under the assumption that the branch was truly cylindrical. The results showed it was possible to extract up to the 14th generation of the airway tree whose diameter was 1.7 mm. The airway diameters obtained were in good agreement with those reported in autopsy study (Weibel et al., 1963), although the diameters on and after 8th generation were all larger than those in Weibel et al. (1963) due probably to an insufficient resolution of CT images. These results addressed the validity of the algorithm developed in this study in quantification of the airway tree. References Weibel et al. (1963). Morphometry of the Human Lung. Academic Press Inc., New York, p. 139.
6162 We-Th, no. 7 (P64) Relationship between ozone absorption and uric acid concentration in the human nasal cavities J.S. Ultman 1, A. Fassih 1, L.Y. Santiago 2, A. Ben-Jebria 1. 1Department ef
Chemical Engineering, Penn State University, University Park, Pennsylvania, USA, 2Department of Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA The nose protects the lower respiratory tract by extracting oxidative air pollutants such as ozone (03) from inhaled air by chemical reaction with nasal antioxidants such as uric acid (UA). The purpose of this study was to quantify the relationship between the fractional uptake of 03 in the nasal cavities (Ao3) and the corresponding concentration of UA in nasal lavage samples (CuA). Measurements of Ao3 were performed in triplicate using an apparatus that supplied a 3 - 5 Lpm stream of air containing 0.36 ppm 03 to one nostril and monitored 03 concentration in air exiting the second nostril while a subject kept their glottis in a closed position. Nasal lavage samples were processed by HPLC to determine CUA. Three different experiments were performed on healthy adult nonsmokers: in a day-to-day variability study, 15 subjects reported to the laboratory on three separate days during which Ao3 measurement was made immediately before a single nasal lavage sample was taken; in a sequential washing study, a series of three sets of Ao3 measurements, each immediately followed by nasal lavage, were made on 11 subjects during a single visit to the lab; and in an 03 exposure study, performed on 11 subjects during a single lab visit, an initial Ao3 measurement and nasal lavage was following by a 30-minute continuous exposure to 0.36 ppm 03 before a final Ao3 measurement and nasal lavage were performed. The natural day-to-day variations of Ao3 in the first study were not correlated with CUA (P >0.4). On the other hand, the systematic changes in Ao3 that were induced either by sequential washings or by continuous 03 exposure were both significantly correlated with CUA (P <0.05). The combination of a onedimensional convection-diffusion model of gas transport in the nasal airways with a reaction-diffusion model of gas uptake into the surrounding mucous
Poster Presentations
layer allowed us to estimate a second-order rate constant of 6x10 s L/mol-s for the chemical reaction between 03 and UA. Supported in part by a research grant from the Philip Morris External Research Program. 6328 We-Th, no. 8 (P64) Theoretical study of gas exchange in total liquid ventilation H. Fujioka 1, S. Tredici 2, R.B. Hirschl 2, R.H. Bartlett 2, J.B. Grotberg 1,2.
1Biomedical Engineering Department, University of Michigan, Ann Arbor, USA, 2Department of General Surgery, University of Michigan, Ann Arbor, USA Diseases such as adult respiratory distress syndrome and neonatal respiratory distress syndrome (hyaline membrane disease) are characterized by less compliant lungs, a result of insufficient surfactant production or effectiveness. Total liquid ventilation (TLV) is an artificial ventilation system which uses perfluorocarbon (PFC) liquid to eliminate the air-liquid interface. PFC has high solubilities of oxygen and carbon-dioxide. In TLV, the convective transport in PFC is an important factor for gas exchange in the alveolar region because the diffusivities of oxygen and carbon dioxide in PFC are four orders of magnitude lower than in air. In this study, a computational model for gas exchange in the lung is developed: a conducting airways branching network is modeled as a trumpet-shaped tube; the terminal alveolar sac is modeled as an oscillating spherical shell; a tissue and capillary blood are modeled as wellmixed compartments; and mixed-venous gas partial pressures are calculated assuming a constant oxygen consumption and carbon dioxide production. Since the convection dominates the transport in the sac as well as in the conducting airways, steep partial pressure gradients in the sac exist from the middle of inspiration to the beginning of expiration. End-inspiratory dwell-time enhances gas exchange rate. Our computational results for the arterial gas partial pressures were agreed well with the experimental results of TLV for rabbits. This work is supported by NIH grant HL64373. 6370 We-Th, no. 9 (P64) Flow o f aerosol in a 3D alveolated bend: experimental measurements by Particle Image Velocimetry (PIV) and Particle Tracking Velocimetry (PTV) P. Corieri 1, R. Theunissen 1, N. Buchmann 1, C. van Ertbruggen 2, C. Darquenne 2, M.L. Riethmuller 1. l v o n Karman Institute for Fluid Dynamics,
Rhode-St-Genese, Belgium, 2Dept. Medicine, University of California San Diego, La Jolla, USA Understanding the transport of inhaled particles in the alveolar region of the lung is important whether particle exposure results from pollution or inhaled drug therapy. Aerosol transport mechanisms are however not yet fully understood despite their investigation in numerous computational studies. Furthermore, because of the absence of in-vivo measurements, these computational studies lack experimental validation. We built a 3D scaled-up model of a curved pipe with circular cavities representative of the alveolar region of the lung in which both flow velocities and aerosol trajectories were measured by PIV and PTV, respectively. Measurements provided a comprehensive dataset for validation of numerical simulations performed in a similar model. Silicone oil was used as carrier fluid and 1.2 mmdiameter iron particles were used. Flow rate was 0.84 ml/s (Re = 0.07). These experimental conditions were representative of transport of 12.8 ~tm-diameter aerosol in the acinus. Flow field was characterised by a curvilinear separation streamline at the alveolar openings, indicating little convective exchange between the alveoli and the lumen. In the lumen, velocity profiles agreed with Poiseuille flow. In each alveolar cavity, slow rotating fluid elements could be identified with the advanced interrogation methodology. Velocities inside these cavities were about two orders of magnitude smaller than the mean lumen velocity. These data validate numerical simulations presented in a separate paper. PTV data showed that particles did not follow the streamlines. Because Stokes number along the particle trajectories was - 1 0 -4 , inertial forces were negligible and particles behaviour was mainly affected by viscous forces suggesting that deviation from the streamlines resulted from gravity. In conclusion, we showed that both PIV and PTV can be successfully used to track particle trajectories under Stokes flow conditions present in the alveolar region of the lung. These techniques can therefore reliably be used in future investigations of aerosol behaviour in more complex acinar models.
Journal o f Biomechanics 2006, Vol. 39 (Suppl 1)
loss tangent in dexamethasone treated cells was 'q =0.312±0.005) (p =0.52 vs. control). Therefore, dexamethasone stiffens A549 alveolar epithelial cells by inducing a parallel increase in both the elastic and loss moduli. Cell stiffening results in increased elastic centripetal forces during the cell stretching associated with breathing or mechanical ventilation. Cell-cell and cell-matrix adhesion forces should counterbalance the increased elastic forces to maintain monolayer integrity. Supported in part by: SAF 2005q30110 and FIS-PI040929. 6244 We-Th, no. 6 (P64) Computer-aided segmentation and quantification of the human airway tree on the basis o f multi CT images T. Miki 1, S. Wada 1, M. Nakamura 1, K.-i. Tsubota 1, T. Yamaguchi 1, '~ Suda 2, G. Tamura 3 . 1Department of Bioengineering and Robotics, Tohoku University,
Sendal, Japan, 2Sendal Open Hospital, Sendal, Japan, 3 Tohoku University Hospital, Sendal, Japan Morphological structure of the airways is related to a respiratory function. To improve the diagnosis of pulmonary diseases such as asthma, we developed an algorithm for automated segmentation and quantification of the human airway tree on the basis of multi CT images of the lung. The algorithm consists of segmentation of the airway tree, its skeletonization, identification of the airway generation, and measurement of volume, length and diameter of each airway. CT images were acquired with the up-to-date multi slice CT scanner, Aquillion64 (Toshiba Medical Systems Corp., Japan). The airway lumen was extracted from CT images with the region growing method; a grayscale intensity specific to a tissue of the airway wall was determined in the CT images at the entrance of trachea and it was handed to subsequent CT images to trace and construct a 3-D airway model of the airway tree. For morphometric identification of airways' branching, the 3-D airway model was skeletonized. Although the current skeletonization algorithm yielded some pseudo branches, those were deleted manually. Given the skeletonized model, the generation number was defined to each branch of the airway model. A diameter of a branch was calculated under the assumption that the branch was truly cylindrical. The results showed it was possible to extract up to the 14th generation of the airway tree whose diameter was 1.7 mm. The airway diameters obtained were in good agreement with those reported in autopsy study (Weibel et al., 1963), although the diameters on and after 8th generation were all larger than those in Weibel et al. (1963) due probably to an insufficient resolution of CT images. These results addressed the validity of the algorithm developed in this study in quantification of the airway tree. References Weibel et al. (1963). Morphometry of the Human Lung. Academic Press Inc., New York, p. 139.
6162 We-Th, no. 7 (P64) Relationship between ozone absorption and uric acid concentration in the human nasal cavities J.S. Ultman 1, A. Fassih 1, L.Y. Santiago 2, A. Ben-Jebria 1. 1Department ef
Chemical Engineering, Penn State University, University Park, Pennsylvania, USA, 2Department of Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA The nose protects the lower respiratory tract by extracting oxidative air pollutants such as ozone (03) from inhaled air by chemical reaction with nasal antioxidants such as uric acid (UA). The purpose of this study was to quantify the relationship between the fractional uptake of 03 in the nasal cavities (Ao3) and the corresponding concentration of UA in nasal lavage samples (CuA). Measurements of Ao3 were performed in triplicate using an apparatus that supplied a 3 - 5 Lpm stream of air containing 0.36 ppm 03 to one nostril and monitored 03 concentration in air exiting the second nostril while a subject kept their glottis in a closed position. Nasal lavage samples were processed by HPLC to determine CUA. Three different experiments were performed on healthy adult nonsmokers: in a day-to-day variability study, 15 subjects reported to the laboratory on three separate days during which Ao3 measurement was made immediately before a single nasal lavage sample was taken; in a sequential washing study, a series of three sets of Ao3 measurements, each immediately followed by nasal lavage, were made on 11 subjects during a single visit to the lab; and in an 03 exposure study, performed on 11 subjects during a single lab visit, an initial Ao3 measurement and nasal lavage was following by a 30-minute continuous exposure to 0.36 ppm 03 before a final Ao3 measurement and nasal lavage were performed. The natural day-to-day variations of Ao3 in the first study were not correlated with CUA (P >0.4). On the other hand, the systematic changes in Ao3 that were induced either by sequential washings or by continuous 03 exposure were both significantly correlated with CUA (P <0.05). The combination of a onedimensional convection-diffusion model of gas transport in the nasal airways with a reaction-diffusion model of gas uptake into the surrounding mucous
Poster Presentations
layer allowed us to estimate a second-order rate constant of 6x10 s L/mol-s for the chemical reaction between 03 and UA. Supported in part by a research grant from the Philip Morris External Research Program. 6328 We-Th, no. 8 (P64) Theoretical study of gas exchange in total liquid ventilation H. Fujioka 1, S. Tredici 2, R.B. Hirschl 2, R.H. Bartlett 2, J.B. Grotberg 1,2.
1Biomedical Engineering Department, University of Michigan, Ann Arbor, USA, 2Department of General Surgery, University of Michigan, Ann Arbor, USA Diseases such as adult respiratory distress syndrome and neonatal respiratory distress syndrome (hyaline membrane disease) are characterized by less compliant lungs, a result of insufficient surfactant production or effectiveness. Total liquid ventilation (TLV) is an artificial ventilation system which uses perfluorocarbon (PFC) liquid to eliminate the air-liquid interface. PFC has high solubilities of oxygen and carbon-dioxide. In TLV, the convective transport in PFC is an important factor for gas exchange in the alveolar region because the diffusivities of oxygen and carbon dioxide in PFC are four orders of magnitude lower than in air. In this study, a computational model for gas exchange in the lung is developed: a conducting airways branching network is modeled as a trumpet-shaped tube; the terminal alveolar sac is modeled as an oscillating spherical shell; a tissue and capillary blood are modeled as wellmixed compartments; and mixed-venous gas partial pressures are calculated assuming a constant oxygen consumption and carbon dioxide production. Since the convection dominates the transport in the sac as well as in the conducting airways, steep partial pressure gradients in the sac exist from the middle of inspiration to the beginning of expiration. End-inspiratory dwell-time enhances gas exchange rate. Our computational results for the arterial gas partial pressures were agreed well with the experimental results of TLV for rabbits. This work is supported by NIH grant HL64373. 6370 We-Th, no. 9 (P64) Flow o f aerosol in a 3D alveolated bend: experimental measurements by Particle Image Velocimetry (PIV) and Particle Tracking Velocimetry (PTV) P. Corieri 1, R. Theunissen 1, N. Buchmann 1, C. van Ertbruggen 2, C. Darquenne 2, M.L. Riethmuller 1. l v o n Karman Institute for Fluid Dynamics,
Rhode-St-Genese, Belgium, 2Dept. Medicine, University of California San Diego, La Jolla, USA Understanding the transport of inhaled particles in the alveolar region of the lung is important whether particle exposure results from pollution or inhaled drug therapy. Aerosol transport mechanisms are however not yet fully understood despite their investigation in numerous computational studies. Furthermore, because of the absence of in-vivo measurements, these computational studies lack experimental validation. We built a 3D scaled-up model of a curved pipe with circular cavities representative of the alveolar region of the lung in which both flow velocities and aerosol trajectories were measured by PIV and PTV, respectively. Measurements provided a comprehensive dataset for validation of numerical simulations performed in a similar model. Silicone oil was used as carrier fluid and 1.2 mmdiameter iron particles were used. Flow rate was 0.84 ml/s (Re = 0.07). These experimental conditions were representative of transport of 12.8 ~tm-diameter aerosol in the acinus. Flow field was characterised by a curvilinear separation streamline at the alveolar openings, indicating little convective exchange between the alveoli and the lumen. In the lumen, velocity profiles agreed with Poiseuille flow. In each alveolar cavity, slow rotating fluid elements could be identified with the advanced interrogation methodology. Velocities inside these cavities were about two orders of magnitude smaller than the mean lumen velocity. These data validate numerical simulations presented in a separate paper. PTV data showed that particles did not follow the streamlines. Because Stokes number along the particle trajectories was - 1 0 -4 , inertial forces were negligible and particles behaviour was mainly affected by viscous forces suggesting that deviation from the streamlines resulted from gravity. In conclusion, we showed that both PIV and PTV can be successfully used to track particle trajectories under Stokes flow conditions present in the alveolar region of the lung. These techniques can therefore reliably be used in future investigations of aerosol behaviour in more complex acinar models.