Calculation of aerosol deposition in human lung airways using Horsfield geometric model

Exploring nanoparticles in lungs under COPD conditions for nanospray drug flow and deposition: CFD simulations and AI predictions

Chronic obstructive pulmonary disease (COPD) plays a heavy burden on individuals and the social health system, not only causing direct medical costs but also economic losses. Today, treatments for COPD include drugs, bronchodilators, and oxygen therapies. In these treatments, depositing drug particles within the bronchioles is quite critical. This study utilizes the Weibel five-generation lung model (G5-G9) and the out-of-plane modeling method to improve the three-dimensional characterization of the airways. COPD's impact on nanoparticle deposition at different stages is evaluated under the actual respiratory condition with a respiratory rate of about 30 L‧min-1. In addition, the deposition of medicine nanoparticles at three typical nanoparticle densities (i.e., 1000, 1100, and 1550 kg m-3) is also studied by considering the nanoparticle sizes ranging from 10 to 100 nm. The predictions illustrate the airflow patterns of streamlines. The characteristics of nanoparticle deposition and the correlations between Stokes number and total deposition are further explored. It is found that COPD significantly affects airflow patterns and causes disturbances at airway bifurcations, which leads to higher flow velocities, more collisions of nanoparticles on the walls, and subsequent nanoparticle deposition. Remarkable hot spots occur in some airway segments due to airflow deflection and secondary flow appearance. Furthermore, the impact of various nanoparticle sizes can be predicted at each stage by employing artificial neural networks based on computational fluid dynamics data of flow patterns and deposition of drug nanoparticles. The results benefit the reduction of drug waste, thereby lowering the escalating global public health burden associated with COPD.

Ultrafine organic aerosol particles inhaled by mice at low doses remain in lungs more than half a year

Experimental results of the second series of experiments on the penetration of monodisperse polymeric particles, inhaled at low dose by mice, to different organs using direct way of particle registration, based on the ultra-sensitive accelerator mass spectrometer (AMS), are presented. Polystyrene (PS) beads, composed of radiocarbon-labeled styrene, were produced for testing them as model organic aerosols. Mice inhaled ¹⁴ C-PS aerosol of 3·10⁵ ultrafine particles per 1 cm³ for 30 minutes every day during 5 days. Long-term investigation showed that PS ultrafine particles have been effectively accumulated in lungs with the maximum content in the fifth day of postexposure, and have also appeared in liver on the fifth day of exposure and in the brain on the 30th day of experiments. No particles have been detected in kidneys, spleen, and excrements. Thirty-five millions of particles remained in the lungs after half a year of postexposure showing extremely slow removal of such particles from the organ.

Ultrasensitive detection of inhaled organic aerosol particles by accelerator mass spectrometry

Accelerator mass spectrometry (AMS) was shown to be applicable for studying the penetration of organic aerosols, inhaled by laboratory mice at ultra-low concentration ca. 10(3) cm(-3). We synthesized polystyrene (PS) beads, composed of radiocarbon-labeled styrene, for testing them as model organic aerosols. As a source of radiocarbon we used methyl alcohol with radioactivity. Radiolabeled polystyrene beads were obtained by emulsifier-free emulsion polymerization of synthesized (14)C-styrene initiated by K2S2O8 in aqueous media. Aerosol particles were produced by pneumatic spraying of diluted (14)C-PS latex. Mice inhaled (14)C-PS aerosol consisting of the mix of 10(3) 225-nm particles per 1 cm(3) and 5·10(3) 25-nm particles per 1 cm(3) for 30 min every day during five days. Several millions of 225-nm particles deposited in the lungs and slowly excreted from them during two weeks of postexposure. Penetration of particles matter was also observed for liver, kidneys and brain, but not for a heart.

Effects of breath holding at low and high lung volumes on amount of exhaled particles

Exhaled breath contains particles originating from the respiratory tract lining fluid. The particles are thought to be generated during inhalation, by reopening of airways closed in the preceding expiration. The aim here was to explore processes that control exhaled particle concentrations. The results show that 5 and 10s breath holding at residual volume increased the median concentration of particles in exhaled air by 63% and 110%, respectively, averaged over 10 subjects. An increasing number of closed airways, developing on a timescale of seconds explains this behaviour. Breath holds of 5, 10 and 20s at total lung capacity decreased the concentration to 63%, 45% and 28% respectively, of the directly exhaled concentration. The decrease in particle concentration after breath holding at total lung capacity is caused by gravitational settling in the alveoli and associated bronchioles. The geometry employed here when modelling the deposition is however not satisfactory and ways of improving the description are discussed.