Impact of Age-Related Anatomical and Physiological Changes on Airflow and Particle Transport Characteristics in Human Nasal Airways

The human nasal cavity plays a crucial role for respiratory health, acting as the first line of defense by filtering, warming, and humidifying inhaled air. Throughout an individual’s life, the nasal cavity undergoes changes in geometry and structure during growth, maturation, and aging. These changes can be accompanied by anatomical disorders such as septal deviation and adenoid hypertrophy, which may influence nasal physiology. Though conventional respiratory assessment methods, such as rhinomanometry, and medical imaging techniques like MRI provide valuable information, neither fully captures the complexities of airflow dynamics within the nasal airways. This thesis employs Computational Fluid Dynamics (CFD) to delve deeply into nasal airflow dynamics and particle transport in subjects across different age groups, providing a comprehensive assessment of health risks from inhalation exposure to airborne particles and evaluating the performance of medicinal aerosol delivery. Structured in four main sections, the dissertation deepens the research scope narrative progressively. The early chapters (Chapter 2-3) lay the foundation with an extensive literature review on nasal anatomy, pathologies, and prior experimental and numerical studies, highlighting the gaps in current research. Subsequently, Chapter 4 and 5 investigate the impact of age-related anatomical variations on nasal patency and nanoparticle exposure risks, categorizing subjects into children, adults, and the elderly. This section systematically compares anatomical features, airflow parameters with an emphasis on fractional flow in the olfactory region, where correlations of deposition efficiency is developed incorporating characteristic geometrical parameters of nasal airway. Given the rapid anatomical and physiological changes experienced by children, the subsequent chapters (Chapter 6 and 7) are dedicated to children subjects. Unlike previous studies, this research (Chapter 6) includes a significant sample size of 13 subjects, predominantly aged between 7 to 12 years old. With a comprehensive investigation based on these subjects, significant insights are provided into pediatric nasal airflow dynamics and airborne particle deposition behaviors in specific functional regions. Chapter 7 focuses on Adenoid Hypertrophy (AH), a prevalent nasopharyngeal condition in children’s group. Through virtual surgery on a diseased nasal cavity, the research examines the restoration of healthy airflow features, contributing to the understanding of surgical treatments and associated drug delivery mechanism. In conclusion, this research establishes a systematic platform for evaluating the impact of age-related anatomical and physiological changes on human nasal airflow and particle transport. In addition to current treatment methods based on images and experience, informative and critical results on fluid field, wall shear stress distribution, and spatial particle distributions are offered. The research outcomes are poised to assist physicians in making informed decisions regarding nasal obstruction assessments, the anticipated outcomes of planned surgeries, and inhalation therapy efficacy across diverse settings. The developed method, applicable to a wide range of demographic age groups, represents a valuable advancement in respiratory health care and management.<p></p>