Direct numerical simulation of expiratory crackles: Relationship between airway closure dynamics and acoustic fluctuations |
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| Institution: | 1. Department of Biomedical Engineering, Tel Aviv University and Stony Brook University;2. Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY 11794, USA;3. Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY 11794, USA;1. Biomedical Imaging Center, Pontificia Universidad Catolica de Chile, Santiago, Chile;2. Electrical Engineering Department, Pontificia Universidad Catolica de Chile, Santiago, Chile;3. Structural and Geotechnical Engineering Department, Pontificia Universidad Catolica de Chile, Santiago, Chile;4. Radiology Department, School of Medicine, Pontificia Universidad Catolica de Chile, Santiago, Chile;5. Pediatric Cardiology Unit, Hospital Virgen del Rocío, Seville, Spain;6. Laboratory of Cardiovascular Pathophysiology, Seville Biomedicine Institute, Hospital Virgen del Rocío, Seville, Spain;7. Biological and Medical Engineering Institute, Schools of Engineering, Medicine and Biological Sciences, Pontificia Universidad Catolica de Chile, Santiago, Chile;1. Department of Mechanical Engineering, The University of Hong Kong, Hong Kong;2. HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI), Shenzhen, Guangdong, China;3. Department of Engineering Mechanics, Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Zhejiang University, Hangzhou, Zhejiang, China;1. Unitat Biofísica i Bioenginyeria, Facultat de Medicina, Universitat de Barcelona, Barcelona, Spain;2. Master׳s and Doctoral Degree Programs in Rehabilitation Sciences, Nove de Julho University, Sao Paulo, Brazil;3. Institut de Bioenginyeria de Catalunya, Barcelona, Spain;4. CIBER Enfermedades Respiratorias, Madrid, Spain;5. Institut Investigacions Biomediques August PiSunyer, Barcelona, Spain;1. Neurosurgical Unit A, P.-Wertheimer Hospital, Bron, France;2. Hormone Laboratory, Centre of Nuclear Medicine, Department of Chronobiology, Stem Cell and Brain Research Institute, Groupement Hospitalier Est, 59, boulevard Pinel, 69677 Bron, France;3. Neurosurgical Unit B, P.-Wertheimer Hospital, Bron, France;4. Inserm, U846, Department of Chronobiology, Stem Cell and Brain Research Institute, Bron, France;1. Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, 98 Brett Rd, Piscataway, NJ, 08854, USA;2. Skolkovo Institute of Technology, Moscow,143005, Russia;1. School of Engineering, Computer and Mathematical Sciences, Auckland University of Technology, Auckland, New Zealand;2. Department of Otolaryngology – Head and Neck Surgery, Counties District Health Board, Manukau, Auckland, New Zealand;3. Department of Surgery, University of Auckland, Auckland, New Zealand |
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| Abstract: | This paper investigates the relationship between airway closure dynamics and acoustic fluctuations in expiratory crackles using direct numerical simulation. A unified mathematical model is proposed to deal with flow in an airway, elastic deformation of the airway wall, surface tension driven motion of the liquid film that lines the airway, and their acoustic fluctuations because of material compressibility. Airway closure is induced by increasing the surrounding pressure, then the source of the pressure fluctuations is measured over time. Our results show that the airway closure occurs suddenly because of a bridge formation of the liquid film, and high energy transfer occurs between the kinetic energy, the surface energy of the liquid interface, and the elastic energy of the airway wall, invoking a large acoustic fluctuation that causes the expiratory crackles. Nonlinear behavior is observed in terms of the airway wall stiffness; the dynamic motion of the airway closure becomes moderate and both the energy transfer and acoustic fluctuations are dramatically reduced with an increase in airway wall stiffness. |
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| Keywords: | Expiratory crackles Airway closure Acoustic fluctuation Fluid–solid–acoustic interactions Direct numerical simulation |
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