Particle Deposition In Human Lungs Research Articles

Particle deposition in obstructed airways

One approach to tackle the particle deposition in human lungs in close proximity is to develop an understanding of the particle motion in bifurcation airways. Chronic obstructive pulmonary disease (COPD) is one of the most common diseases in humans. COPD always results in inflammation that leads to narrowing and obstructing of the airways. The obstructive airways can alter the respiratory flow and particle deposition significantly. In order to study the effect of obstruction on particle deposition, four three-dimensional four-generation lung models based on the 23-generation model of Weibel [1963. Morphometry of the Human Lung. New York Academic Press, Springer, Berlin.] have been generated. The fully three-dimensional incompressible laminar Navier–Stokes equations are solved using computational fluid dynamics (CFD) solver on structured hexahedral meshes. Subsequently, a symmetric four-generation airway model serves as the reference and the other three models are considered to be obstructed at each generation, respectively. The calculation results show that the obstructive airway has significant influence on the particle deposition down-stream of the obstruction. The skewed velocity profile in the bifurcation airway is modified by the throat; consequently, more particles impact on the divider which results in higher deposition efficiency.

Mathematical Analysis of Particle Deposition in Human Lungs: An Improved Single Path Transport Model

A dynamic single-path mathematical model was developed that is capable of analyzing detailed deposition patterns of inhaled particles in human lungs. Weibel's symmetric lung morphology was adopted as the basic lung structure, and detailed transport processes were evaluated numerically using the fully implicit procedure. Deposition efficiencies by specific mechanisms were individually examined for accuracy and new empirical formulas were incorporated whenever appropriate. Deposition in the alveolar region was divided into deposition fractions in the alveolar duct and alveoli, considering active transport processes between the two regions. The deposition fractions were obtained for each airway generation, serial lung volumetric compartments, and conventional three-compartment anatomic lung regions. In addition, the surface dose and cumulative deposition with time were analyzed. The results showed excellent agreement with available experimental data. The present model provides an improvement from the previously reported models and can be used as a tool in assessing internal dose of inhaled particles under various inhalation conditions.

Theoretical analysis of particle deposition in human lungs considering stochastic variations of airway morphology

Particle deposition in human lungs was investigated theoretically considering a stochastic variation of airway morphology using a Monte Carlo method. In computing the total and regional deposition each airway generation was divided into infinitesimal volume segments and each volume segment was allowed to pass through randomly selected airway branches of which morphology (e.g., airway dimensions and branching angle) was varied randomly. Deposition values obtained by the Monte Carlo method were compared with those obtained by the traditional deterministic method. It was found that the Monte Carlo method predicted deposition values generally comparable to those predicted by deterministic method for sub-micron size particles. However, for micron size particles the Monte Carlo method provided greater deposition values in the proximal airway regions where deposition occurs mainly by inertial impaction. The difference could be attributed to the non-linear relationship between deposition efficiency and airway dimensions in the inertial deposition regime. The results suggest that a Monte Carlo method may be a useful tool for evaluating deposition of inhaled particles in the lungs with a wide variation of airway dimensions.

Modeling intersubject variability of particle deposition in human lungs

The morphological variability in human lungs was simulated by 10 multiple-path lung models, generated on the basis of probability distributions and correlations of airway parameters provided by the stochastic lung model of Koblinger and Hofmann (Phys. Med. Biol. 30 (1985) 541). Total, regional and generation-per-generation deposition was computed for particle sizes in the range of 0.01– 10 μm under resting breathing conditions. Our calculations suggest that structural and volumetric differences of lung morphologies among different individuals are primarily responsible for the experimentally observed intersubject variability in total and regional deposition under controlled breathing conditions. Individual differences in deposition among single airways can be substantially larger than those in total and regional deposition. Furthermore, variations are most pronounced for small (0.01 μm) and large (10 μm) particles.

32 O 04 A comparative study of submicron particle deposition in human lungs

32 O 04 A comparative study of submicron particle deposition in human lungs

A Method of Modifying the Sensitivity Function of an Aerosol Photometer

The application of a virtual impactor to modify the overall sensitivity function of an aerosol photometer has been studied. The measurement of particles in the minor airflow of a virtual impactor results in a significant increase in the photometer's sensitivity to large particles. The increased response to large particles is considered as a change in the sensitivity function. The location of the overall sensitivity maximum can be shifted from the submicrometer-size range to the 2–3 µm region (the region where the particle deposition in human lungs is high).