Effects of airway deformation and alveolar pores on particle deposition in the lungs

Impact of the diseased lung microenvironment on the in vivo fate of inhaled particles

Inhalation drug delivery is superior for local lung disease therapy. However, there are several unique absorption barriers for inhaled drugs to overcome, including limited drug deposition at the target site, mucociliary clearance, pulmonary macrophage phagocytosis, and systemic exposure. Moreover, the respiratory disease state can affect or even destroy the physiology of the lung, thus influencing the in vivo fate of inhaled particles compared with that in healthy lungs. Nevertheless, limited information is available on this effect. Thus, in this review, we present pathological changes of the lung microenvironment under varied respiratory diseases and their influence on the in vivo fate of inhaled particles; such insights could provide a basis for rational inhalation particle design based on specific disease states.

Optimal Treatment of Tumor in Upper Human Respiratory Tract Using Microaerosols

Lung cancer is a frequently diagnosed respiratory disease caused by particulate matter in the environment, especially among older individuals. For its effective treatment, a promising approach involves administering drug particles through the inhalation route. Multiple studies have investigated the flow behavior of inhaled particles in the respiratory airways of healthy patients. However, the existing literature lacks studies on the precise understanding of the transportation and deposition (TD) of inhaled particles through age-specific, unhealthy respiratory tracts containing a tumor, which can potentially optimize lung cancer treatment. This study aims to investigate the TD of inhaled drug particles within a tumorous, age-specific human respiratory tract. The computational model reports that drug particles within the size range of 5-10 μm are inclined to deposit more on the tumor located in the upper airways of a 70-year-old lung. Conversely, for individuals aged 50 and 60 years, an optimal particle size range for achieving the highest degree of particle deposition onto upper airway tumor falls within the 11-20 μm range. Flow disturbances are found to be at a maximum in the airway downstream of the tumor. Additionally, the impact of varying inhalation flow rates on particle TD is examined. The obtained patterns of airflow distribution and deposition efficiency on the tumor wall for different ages and tumor locations in the upper tracheobronchial airways would be beneficial for developing an efficient and targeted drug delivery system.

Study on the flow mechanism and frequency characteristics of rales in lower respiratory tract

The frequency characteristics of lung sounds have great significance for noninvasive diagnosis of respiratory diseases. The rales in the lower respiratory tract region that can provide rich information about symptoms of respiratory diseases are not clear. In this paper, a three-dimensional idealized bifurcated lower respiratory tract geometric model, which contains 3rd to 13th generation (G3-G13) bronchi is constructed, where Re ∼ 10 1 - 10 3 , and then the large eddy simulation and volume of fluid are used to study the fluid flow characteristics. Ffowcs Williams and Hawkings model are subsequently used to study the frequency characteristics of rale of different generations of bronchi. The results showed that bronchial blockage and sputum movement will enhance the turbulence intensity and vortex shedding intensity of flow. The dominant frequency and highest value of sound pressure level (SPL) of rhonchi/moist crackles decrease with the increase of bronchial generation. The change rates of dominant frequency of rhonchi / moist crackles in adjacent generations were 5.0 ± 0.1 ~ 9.1 ± 0.2% and 3.1 ± 0.1 ~ 11.9 ± 0.3%, respectively, which is concentrated in 290 ~ 420 Hz and 200 ~ 300 Hz, respectively. The change rates of SPL of rhonchi/moist crackles were 8.8 ± 0.1 ~ 15.7 ± 0.1% and 7.1 ± 0.1 ~ 19.5 ± 0.2%, respectively, which is concentrated in 28 ~ 50 dB and 16 ~ 32 dB, respectively. In the same generation of bronchus (e.g., G8, G9) with the same degree of initial blockage, the dominant frequency and SPL of moist crackles can be 3.7 ± 0.2% and 4.5 ± 0.3% slightly higher than that of rhonchi, respectively. This research is conducive to the establishment of a rapid and accurate noninvasive diagnosis system for respiratory diseases.

Development of multi-generation lower respiratory tract model and insights into the transport and deposition characteristics of inhalable particles

Airborne particles can spread quickly and enter human respiratory system via inhalation, causing chronic diseases, even cancer. Although recent studies have informed of toxicity of various pollutants, understanding the transport and deposition characteristics of particles in lower respiratory tract is still challenging. The current study proposes a novel model to simulate flow field change from the entrance of lower respiratory tract to pulmonary acinus, while studying particle transport and deposition characteristics. This model for lower respiratory tract with several bronchial extensions containing virtual pulmonary acinus is calculated using computational fluid dynamics and dynamics mesh. The results showed that in the first 10 generations of the lower respiratory tract, vortices and gravity interfered with particles' trajectory, affecting particle deposition distribution. For the first to the tenth-generation respiratory tract, coarse particles were deposited throughout almost the whole respiratory tract model. In contrast, ultrafine particles did not deposit in the higher-generation respiratory tract. The particle enrichment ability of various lobes was uneven with three particle deposition fraction variation patterns. Virtual pulmonary acinus influenced particle deposition and distribution because of vortex ring's trapped ability during expansion and contraction. This new attempt to build a virtual pulmonary acinus model to simulate particle deposition effects in human respiratory system may provide a reference for studying the toxicities of inhalable particles in the exposed human body.