Helium–oxygen mixtures (HeliOx) have been proposed to enhance aerosol drug delivery by reducing airflow turbulence and facilitating deeper penetration of medications into the respiratory tract. However, previous studies on HeliOx efficacy have yielded mixed results, often limited by unrealistic anatomical models and steady-state assumptions, and focus on restricted sections of the airway. This study aims to address these limitations by investigating the transport and deposition of pharmaceutical aerosols in HeliOx compared to atmospheric air using a realistic, computed tomography-based nose-to-lung respiratory tract model that extends from a face mask to the 13th generation of tracheobronchial airways. Experimentally measured, dynamic breathing profiles were incorporated to simulate realistic inhalation conditions. Pharmaceutical aerosols with diameters ranging from 1 to 100 μm were released under two conditions: ambient air and HeliOx. Computational fluid–particle dynamics simulations were performed to model and visualize the transport and deposition patterns of aerosols throughout the respiratory tract during inhalation. The simulation results indicate that HeliOx promotes more steady airflow with reduced turbulence, facilitating a deeper delivery of drug aerosols compared to ambient air. Specifically, HeliOx reduced turbulence intensity in the nasal cavity, larynx, and upper trachea regions, and enhanced aerosol penetration to the lower respiratory tract, increasing the deposition fraction in the deeper lung regions. These findings suggest that utilizing HeliOx as a carrier gas can improve deep lung-targeted drug delivery, potentially enhancing therapeutic outcomes for pulmonary diseases.

Recent research has raised significant concerns regarding microplastic (MP) exposure through cigarette smoking. This study investigates the inhalation dynamics and deposition patterns of four types of cigarette smoke MPs, ranging in diameter from 1 to 100 μm, during cigarette smoking. A computed tomography-based respiratory tract model extending from the nasal cavity to the 13th bronchial generation was implemented to ensure anatomical accuracy. To advance the understanding of MP behavior in the respiratory system, computational fluid–particle dynamics modeling was conducted. Specifically, the study utilized the finite volume method, integrating the k–ω shear–stress transport turbulence model and discrete phase model to accurately capture the complexities of airflow turbulence and particle dynamics. Three instantaneous puffing (breathing) profiles (fast, intermediate, and slow) were employed to simulate typical airflow variations encountered during smoking. Additionally, a novel modeling approach for nonspherical, elongated MPs was introduced, incorporating experimentally measured circularity and eccentricity. The results revealed insights into how particle shape, size, and puffing profiles influence transport and deposition within the respiratory tract during smoking. Through the analysis of the deposition patterns and risk contribution fraction of cigarette smoke MPs, this study significantly enhances the understanding of MP inhalation risks, providing valuable information for public  health interventions and regulatory frameworks.