1
|
Lauria M, Singhrao K, Stiehl B, Low D, Goldin J, Barjaktarevic I, Santhanam A. Automatic triangulated mesh generation of pulmonary airways from segmented lung 3DCTs for computational fluid dynamics. Int J Comput Assist Radiol Surg 2021; 17:185-197. [PMID: 34328596 DOI: 10.1007/s11548-021-02465-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 07/15/2021] [Indexed: 10/20/2022]
Abstract
PURPOSE Computational fluid dynamics (CFD) of lung airflow during normal and pathophysiological breathing provides insight into regional pulmonary ventilation. By integrating CFD methods with 4D lung imaging workflows, regions of normal pulmonary function can be spared during treatment planning. To facilitate the use of CFD simulations in a clinical setup, a robust, automated, and CFD-compliant airway mesh generation technique is necessary. METHODS We define a CFD-compliant airway mesh to be devoid of blockages of airflow and leaks in the airway path, both of which are caused by airway meshing errors that occur when using conventional meshing techniques. We present an algorithm to create a CFD-compliant airway mesh in an automated manner. Beginning with a medial skeleton of the airway segmentation, the branches were tracked, and 3D points at which bifurcations occur were identified. Airway branches and bifurcation features were isolated to allow for automated and careful meshing that considered their anatomical nature. RESULTS We present the meshing results from three state-of-the-art tools and compare them with the meshes generated by our algorithm. The results show that fully CFD-compliant meshes were automatically generated for an ideal geometry and patient-specific CT scans. Using an open-source smoothed-particle hydrodynamics CFD implementation, we compared the airflow using our approach and conventionally generated airway meshes. CONCLUSION Our meshing algorithm was able to successfully generate a CFD-compliant mesh from pre-segmented lung CT scans, providing an automatic meshing approach that enables interventional CFD simulations to guide lung procedures such as radiotherapy or lung volume reduction surgery.
Collapse
Affiliation(s)
| | | | | | - Daniel Low
- University of California, Los Angeles, CA, 90095, USA
| | | | | | | |
Collapse
|
2
|
Polak AG, Obojski A, Mroczka J. Quantitative Assessment of the Airway Response to Bronchial Tests Based on a Spirometric Curve Shift. IEEE Trans Biomed Eng 2021; 68:739-746. [PMID: 32746039 DOI: 10.1109/tbme.2020.3004907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
OBJECTIVE Although spirometry is the most common pulmonary function test, there is no method to quantitatively infer about airway resistance or other properties from the flow-volume curves. Recently, an identifiable inverse model for forced expiration was proposed, as well as the idea to deduce changes in airway resistances and compliances from spirometric curve evolution. The aim of this work was to combine the above advances in a method for assessing the airway response to bronchial tests from a spirometric curve shift. METHODS The approach is based on the differential measurement of the degree, site of maximal effect and width of changes, further recalculated into relative changes in the distribution of airway resistances (δRg) and compliances (δCg) along the bronchial tree. To this end, appropriate models were identified using the pre- and post-test spirometry data. The accuracy was validated using sets of data simulated by the anatomy and physiology based models. Finally, the method was used to analyze the bronchodilation tests of three asthmatic subjects. RESULTS The expected errors in assessing the degree, site and width of changes in the zone of conducting airways were 6.3%, 2.4 generations and 22%, respectively, and for δRg and δCg were 5-10% and 13-16%, respectively. The analyses of clinical data indicated a significant reduction in resistances and an increase in compliances of airway generations 8-12, consistent with clinical knowledge. CONCLUSION An unprecedented method to plausibly transforming the spirometry data into the site and degree of changes in airway properties has been proposed. SIGNIFICANCE The method can be used to deduce about the effects of bronchial tests, as well as to monitor changes in the airways between visits or to investigate how inhaled pharmaceuticals affect the bronchi.
Collapse
|
3
|
Gu Q, Qi S, Yue Y, Shen J, Zhang B, Sun W, Qian W, Islam MS, Saha SC, Wu J. Structural and functional alterations of the tracheobronchial tree after left upper pulmonary lobectomy for lung cancer. Biomed Eng Online 2019; 18:105. [PMID: 31653252 PMCID: PMC6815003 DOI: 10.1186/s12938-019-0722-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 10/15/2019] [Indexed: 12/18/2022] Open
Abstract
Background Pulmonary lobectomy has been a well-established curative treatment method for localized lung cancer. After left upper pulmonary lobectomy, the upward displacement of remaining lower lobe causes the distortion or kink of bronchus, which is associated with intractable cough and breathless. However, the quantitative study on structural and functional alterations of the tracheobronchial tree after lobectomy has not been reported. We sought to investigate these alterations using CT imaging analysis and computational fluid dynamics (CFD) method. Methods Both preoperative and postoperative CT images of 18 patients who underwent left upper pulmonary lobectomy are collected. After the tracheobronchial tree models are extracted, the angles between trachea and bronchi, the surface area and volume of the tree, and the cross-sectional area of left lower lobar bronchus are investigated. CFD method is further used to describe the airflow characteristics by the wall pressure, airflow velocity, lobar flow rate, etc. Results It is found that the angle between the trachea and the right main bronchus increases after operation, but the angle with the left main bronchus decreases. No significant alteration is observed for the surface area or volume of the tree between pre-operation and post-operation. After left upper pulmonary lobectomy, the cross-sectional area of left lower lobar bronchus is reduced for most of the patients (15/18) by 15–75%, especially for 4 patients by more than 50%. The wall pressure, airflow velocity and pressure drop significantly increase after the operation. The flow rate to the right lung increases significantly by 2–30% (but there is no significant difference between each lobe), and the flow rate to the left lung drops accordingly. Many vortices are found in various places with severe distortions. Conclusions The favorable and unfavorable adaptive alterations of tracheobronchial tree will occur after left upper pulmonary lobectomy, and these alterations can be clarified through CT imaging and CFD analysis. The severe distortions at left lower lobar bronchus might exacerbate postoperative shortness of breath.
Collapse
Affiliation(s)
- Qingtao Gu
- Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang, China.,Key Laboratory of Medical Image Computing of Northeastern University (Ministry of Education), Shenyang, China
| | - Shouliang Qi
- Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang, China. .,Key Laboratory of Medical Image Computing of Northeastern University (Ministry of Education), Shenyang, China.
| | - Yong Yue
- Department of Radiology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Jing Shen
- Department of Radiology, Affiliated Zhongshan Hospital of Dalian University, Dalian, China
| | - Baihua Zhang
- Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang, China
| | - Wei Sun
- The Graduate School, Dalian Medical University, Dalian, China
| | - Wei Qian
- Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang, China.,College of Engineering, University of Texas at El Paso, El Paso, USA
| | - Mohammad Saidul Islam
- School of Mechanical and Mechatronic Engineering, Faculty of Engineering and Information Technology, University of Technology Sydney, Brisbane, Australia
| | - Suvash C Saha
- School of Mechanical and Mechatronic Engineering, Faculty of Engineering and Information Technology, University of Technology Sydney, Brisbane, Australia
| | - Jianlin Wu
- Department of Radiology, Affiliated Zhongshan Hospital of Dalian University, Dalian, China.
| |
Collapse
|
4
|
Qi S, Zhang B, Yue Y, Shen J, Teng Y, Qian W, Wu J. Airflow in Tracheobronchial Tree of Subjects with Tracheal Bronchus Simulated Using CT Image Based Models and CFD Method. J Med Syst 2018; 42:65. [PMID: 29497841 DOI: 10.1007/s10916-017-0879-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 12/13/2017] [Indexed: 12/13/2022]
Abstract
Tracheal Bronchus (TB) is a rare congenital anomaly characterized by the presence of an abnormal bronchus originating from the trachea or main bronchi and directed toward the upper lobe. The airflow pattern in tracheobronchial trees of TB subjects is critical, but has not been systemically studied. This study proposes to simulate the airflow using CT image based models and the computational fluid dynamics (CFD) method. Six TB subjects and three health controls (HC) are included. After the geometric model of tracheobronchial tree is extracted from CT images, the spatial distribution of velocity, wall pressure, wall shear stress (WSS) is obtained through CFD simulation, and the lobar distribution of air, flow pattern and global pressure drop are investigated. Compared with HC subjects, the main bronchus angle of TB subjects and the variation of volume are large, while the cross-sectional growth rate is small. High airflow velocity, wall pressure, and WSS are observed locally at the tracheal bronchus, but the global patterns of these measures are still similar to those of HC. The ratio of airflow into the tracheal bronchus accounts for 6.6-15.6% of the inhaled airflow, decreasing the ratio to the right upper lobe from 15.7-21.4% (HC) to 4.9-13.6%. The air into tracheal bronchus originates from the right dorsal near-wall region of the trachea. Tracheal bronchus does not change the global pressure drop which is dependent on multiple variables. Though the tracheobronchial trees of TB subjects present individualized features, several commonalities on the structural and airflow characteristics can be revealed. The observed local alternations might provide new insight into the reason of recurrent local infections, cough and acute respiratory distress related to TB.
Collapse
Affiliation(s)
- Shouliang Qi
- Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang, China. .,Key Laboratory of Medical Image Computing of Northeastern University (Ministry of Education), Shenyang, China.
| | - Baihua Zhang
- Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang, China.,Key Laboratory of Medical Image Computing of Northeastern University (Ministry of Education), Shenyang, China
| | - Yong Yue
- Department of Radiology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Jing Shen
- Department of Radiology, Affiliated Zhongshan Hospital of Dalian University, Dalian, China
| | - Yueyang Teng
- Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang, China.,Key Laboratory of Medical Image Computing of Northeastern University (Ministry of Education), Shenyang, China
| | - Wei Qian
- Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang, China.,College of Engineering, University of Texas at El Paso, El Paso, TX, USA
| | - Jianlin Wu
- Department of Radiology, Affiliated Zhongshan Hospital of Dalian University, Dalian, China
| |
Collapse
|
5
|
Qi S, Zhang B, Teng Y, Li J, Yue Y, Kang Y, Qian W. Transient Dynamics Simulation of Airflow in a CT-Scanned Human Airway Tree: More or Fewer Terminal Bronchi? COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2017; 2017:1969023. [PMID: 29333194 PMCID: PMC5733160 DOI: 10.1155/2017/1969023] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 08/29/2017] [Accepted: 11/05/2017] [Indexed: 01/09/2023]
Abstract
Using computational fluid dynamics (CFD) method, the feasibility of simulating transient airflow in a CT-based airway tree with more than 100 outlets for a whole respiratory period is studied, and the influence of truncations of terminal bronchi on CFD characteristics is investigated. After an airway model with 122 outlets is extracted from CT images, the transient airflow is simulated. Spatial and temporal variations of flow velocity, wall pressure, and wall shear stress are presented; the flow pattern and lobar distribution of air are gotten as well. All results are compared with those of a truncated model with 22 outlets. It is found that the flow pattern shows lobar heterogeneity that the near-wall air in the trachea is inhaled into the upper lobe while the center flow enters the other lobes, and the lobar distribution of air is significantly correlated with the outlet area ratio. The truncation decreases airflow to right and left upper lobes and increases the deviation of airflow distributions between inspiration and expiration. Simulating the transient airflow in an airway tree model with 122 bronchi using CFD is feasible. The model with more terminal bronchi decreases the difference between the lobar distributions at inspiration and at expiration.
Collapse
Affiliation(s)
- Shouliang Qi
- Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang, China
- Key Laboratory of Medical Image Computing, Northeastern University, Ministry of Education, Shenyang, China
| | - Baihua Zhang
- Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang, China
- Key Laboratory of Medical Image Computing, Northeastern University, Ministry of Education, Shenyang, China
| | - Yueyang Teng
- Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang, China
- Key Laboratory of Medical Image Computing, Northeastern University, Ministry of Education, Shenyang, China
| | - Jianhua Li
- Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang, China
- Key Laboratory of Medical Image Computing, Northeastern University, Ministry of Education, Shenyang, China
| | - Yong Yue
- Department of Radiology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Yan Kang
- Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang, China
- Key Laboratory of Medical Image Computing, Northeastern University, Ministry of Education, Shenyang, China
| | - Wei Qian
- Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang, China
- College of Engineering, University of Texas, El Paso, TX, USA
| |
Collapse
|
6
|
Tena AF, Fernández J, Álvarez E, Casan P, Walters DK. Design of a numerical model of lung by means of a special boundary condition in the truncated branches. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2017; 33:e2830. [PMID: 27595502 DOI: 10.1002/cnm.2830] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 08/25/2016] [Accepted: 09/01/2016] [Indexed: 06/06/2023]
Abstract
BACKGROUND The need for a better understanding of pulmonary diseases has led to increased interest in the development of realistic computational models of the human lung. METHODS To minimize computational cost, a reduced geometry model is used for a model lung airway geometry up to generation 16. Truncated airway branches require physiologically realistic boundary conditions to accurately represent the effect of the removed airway sections. A user-defined function has been developed, which applies velocities mapped from similar locations in fully resolved airway sections. The methodology can be applied in any general purpose computational fluid dynamics code, with the only limitation that the lung model must be symmetrical in each truncated branch. RESULTS Unsteady simulations have been performed to verify the operation of the model. The test case simulates a spirometry because the lung is obliged to rapidly perform both inspiration and expiration. Once the simulation was completed, the obtained pressure in the lower level of the lung was used as a boundary condition. The output velocity, which is a numerical spirometry, was compared with the experimental spirometry for validation purposes. CONCLUSIONS This model can be applied for a wide range of patient-specific resolution levels. If the upper airway generations have been constructed from a computed tomography scan, it would be possible to quickly obtain a complete reconstruction of the lung specific to a specific person, which would allow individualized therapies.
Collapse
Affiliation(s)
- Ana F Tena
- University of Oviedo. Hospital Universitario Central de Asturias (HUCA), Avda de Roma s/n, 33011, Oviedo, Spain
| | - Joaquín Fernández
- University of Oviedo, Department of Energy, Campus de Barredo, 33600, Mieres, Spain
| | - Eduardo Álvarez
- University of Oviedo, Department of Energy, Campus de Barredo, 33600, Mieres, Spain
| | - Pere Casan
- University of Oviedo. Hospital Universitario Central de Asturias (HUCA), Avda de Roma s/n, 33011, Oviedo, Spain
| | - D Keith Walters
- University of Oklahoma, School of Aerospace and Mechanical Engineering, Norman, OK, 73019, USA
| |
Collapse
|
7
|
Miyawaki S, Hoffman EA, Lin CL. Numerical simulations of aerosol delivery to the human lung with an idealized laryngeal model, image-based airway model, and automatic meshing algorithm. COMPUTERS & FLUIDS 2017; 148:1-9. [PMID: 28959080 PMCID: PMC5612319 DOI: 10.1016/j.compfluid.2017.02.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The authors proposed a new method to automatically mesh computed tomography (CT)-based three-dimensional human airway geometry for computational fluid dynamics (CFD)-based simulations of pulmonary gas-flow and aerosol delivery. Traditional methods to construct and mesh realistic geometry were time-consuming, because they were done manually using image-processing and mesh-generating programs. Furthermore, most of CT thoracic image data sets do not include the upper airway structures. To overcome these issues, the proposed method consists of CFD grid-size distribution, an automatic meshing algorithm, and the addition of a laryngeal model along with turbulent velocity inflow boundary condition attached to the proximal end of the trachea. The method is based on our previously developed geometric model with irregular centerlines and cross-sections fitted to CT segmented airway surfaces, dubbed the "fitted-surface model." The new method utilizes anatomical information obtained from the one-dimensional tree, e.g., skeleton connectivity and branch diameters, to efficiently generate optimal CFD mesh, automatically impose boundary conditions, and systematically reduce simulation results. The aerosol deposition predicted by the proposed method agreed well with the prediction by a traditional CT-based model, and the laryngeal model generated a realistic level of turbulence in the trachea. Furthermore, the computational time was reduced by factor of two without losing accuracy by using the proposed grid-size distribution. The new method is well suited for branch-by-branch analyses of gas-flow and aerosol distribution in multiple subjects due to embedded anatomical information.
Collapse
Affiliation(s)
- Shinjiro Miyawaki
- IIHR-Hydroscience & Engineering, University of Iowa, Iowa City, Iowa 52242
| | - Eric A. Hoffman
- Department of Biomedical Engineering, University of Iowa, Iowa City, Iowa 52242
- Medicine, University of Iowa, Iowa City, Iowa 52242
- Radiology, University of Iowa, Iowa City, Iowa 52242
| | - Ching-Long Lin
- IIHR-Hydroscience & Engineering, University of Iowa, Iowa City, Iowa 52242
- Radiology, University of Iowa, Iowa City, Iowa 52242
- Mechanical and Industrial Engineering, University of Iowa, Iowa City, Iowa 52242
- Corresponding author: (Ching-Long Lin)
| |
Collapse
|
8
|
Miyawaki S, Tawhai MH, Hoffman EA, Wenzel SE, Lin CL. Automatic construction of subject-specific human airway geometry including trifurcations based on a CT-segmented airway skeleton and surface. Biomech Model Mechanobiol 2016; 16:583-596. [PMID: 27704229 DOI: 10.1007/s10237-016-0838-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 09/21/2016] [Indexed: 11/27/2022]
Abstract
We propose a method to construct three-dimensional airway geometric models based on airway skeletons, or centerlines (CLs). Given a CT-segmented airway skeleton and surface, the proposed CL-based method automatically constructs subject-specific models that contain anatomical information regarding branches, include bifurcations and trifurcations, and extend from the trachea to terminal bronchioles. The resulting model can be anatomically realistic with the assistance of an image-based surface; alternatively a model with an idealized skeleton and/or branch diameters is also possible. This method systematically identifies and classifies trifurcations to successfully construct the models, which also provides the number and type of trifurcations for the analysis of the airways from an anatomical point of view. We applied this method to 16 normal and 16 severe asthmatic subjects using their computed tomography images. The average distance between the surface of the model and the image-based surface was 11 % of the average voxel size of the image. The four most frequent locations of trifurcations were the left upper division bronchus, left lower lobar bronchus, right upper lobar bronchus, and right intermediate bronchus. The proposed method automatically constructed accurate subject-specific three-dimensional airway geometric models that contain anatomical information regarding branches using airway skeleton, diameters, and image-based surface geometry. The proposed method can construct (i) geometry automatically for population-based studies, (ii) trifurcations to retain the original airway topology, (iii) geometry that can be used for automatic generation of computational fluid dynamics meshes, and (iv) geometry based only on a skeleton and diameters for idealized branches.
Collapse
Affiliation(s)
- Shinjiro Miyawaki
- IIHR-Hydroscience and Engineering, University of Iowa, Iowa City, IA, 52242, USA
- CH2M, 1100 NE Circle Blvd., Suite 300, Corvallis, OR, 97330, USA
| | - Merryn H Tawhai
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Eric A Hoffman
- The Department of Biomedical Engineering, Medicine, and Radiology, University of Iowa, Iowa City, IA, 52242, USA
| | - Sally E Wenzel
- The Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA, 15213, USA
| | - Ching-Long Lin
- IIHR-Hydroscience and Engineering and the Department of Mechanical and Industrial Engineering, University of Iowa, 3131 Seamans Center, Iowa City, IA, 52242, USA.
| |
Collapse
|
9
|
Christley S, Emr B, Ghosh A, Satalin J, Gatto L, Vodovotz Y, Nieman GF, An G. Bayesian inference of the lung alveolar spatial model for the identification of alveolar mechanics associated with acute respiratory distress syndrome. Phys Biol 2013; 10:036008. [PMID: 23598859 DOI: 10.1088/1478-3975/10/3/036008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Acute respiratory distress syndrome (ARDS) is acute lung failure secondary to severe systemic inflammation, resulting in a derangement of alveolar mechanics (i.e. the dynamic change in alveolar size and shape during tidal ventilation), leading to alveolar instability that can cause further damage to the pulmonary parenchyma. Mechanical ventilation is a mainstay in the treatment of ARDS, but may induce mechano-physical stresses on unstable alveoli, which can paradoxically propagate the cellular and molecular processes exacerbating ARDS pathology. This phenomenon is called ventilator induced lung injury (VILI), and plays a significant role in morbidity and mortality associated with ARDS. In order to identify optimal ventilation strategies to limit VILI and treat ARDS, it is necessary to understand the complex interplay between biological and physical mechanisms of VILI, first at the alveolar level, and then in aggregate at the whole-lung level. Since there is no current consensus about the underlying dynamics of alveolar mechanics, as an initial step we investigate the ventilatory dynamics of an alveolar sac (AS) with the lung alveolar spatial model (LASM), a 3D spatial biomechanical representation of the AS and its interaction with airflow pressure and the surface tension effects of pulmonary surfactant. We use the LASM to identify the mechanical ramifications of alveolar dynamics associated with ARDS. Using graphical processing unit parallel algorithms, we perform Bayesian inference on the model parameters using experimental data from rat lung under control and Tween-induced ARDS conditions. Our results provide two plausible models that recapitulate two fundamental hypotheses about volume change at the alveolar level: (1) increase in alveolar size through isotropic volume change, or (2) minimal change in AS radius with primary expansion of the mouth of the AS, with the implication that the majority of change in lung volume during the respiratory cycle occurs in the alveolar ducts. These two model solutions correspond to significantly different mechanical properties of the tissue, and we discuss the implications of these different properties and the requirements for new experimental data to discriminate between the hypotheses.
Collapse
Affiliation(s)
- Scott Christley
- Department of Surgery, University of Chicago, Chicago, IL 60637, USA
| | | | | | | | | | | | | | | |
Collapse
|