Interdisciplinary Approaches to COVID-19.

The coronavirus disease 2019 (COVID-19) pandemic has been a significant concern worldwide. The pandemic has demonstrated that public health issues are not merely a health concern but also affect society as a whole. In this chapter, we address the importance of bringing together the world's scientists to find appropriate solutions for controlling and managing the COVID-19 pandemic. Interdisciplinary cooperation, through modern scientific methods, could help to handle the consequences of the pandemic and to avoid the recurrence of future pandemics.

CFD simulation of aerosol delivery to a human lung via surface acoustic wave nebulization.

Administration of drug in the form of particles through inhalation is generally preferable in the treatment of respiratory disorders. Conventional inhalation therapy devices such as inhalers and nebulizers, nevertheless, suffer from low delivery efficiencies, wherein only a small fraction of the inhaled drug reaches the lower respiratory tract. This is primarily because these devices are not able to produce a sufficiently fine drug mist that has aerodynamic diameters on the order of a few microns. This study employs computational fluid dynamics to investigate the transport and deposition of the drug particles produced by a new aerosolization technique driven by surface acoustic waves (SAWs) into an in silico lung model geometrically reconstructed using computed tomography scanning. The particles generated by the SAW are released in different locations in a spacer chamber attached to a lung model extending from the mouth to the 6th generation of the lung bronchial tree. An Eulerian approach is used to solve the Navier-Stokes equations that govern the airflow within the respiratory tract, and a Lagrangian approach is adopted to track the particles, which are assumed to be spherical and inert. Due to the complexity of the lung geometry, the airflow patterns vary as it penetrates deeper into the lung. High inertia particles tend to deposit at locations where the geometry experiences a significant reduction in cross section. Our findings, nevertheless, show that the injection location can influence the delivery efficiency: Injection points close to the spacer centerline result in deeper penetration into the lung. Additionally, we found that the ratio of drug particles entering the right lung is significantly higher than the left lung, independent of the injection location. This is in good agreement with this fact that the most of airflow enters to the right lobes.

Details of regional particle deposition and airflow structures in a realistic model of human tracheobronchial airways: two-phase flow simulation.

In the present investigation, detailed two-phase flow modeling of airflow, transport and deposition of micro-particles (1-10µm) in a realistic tracheobronchial airway geometry based on CT scan images under various breathing conditions (i.e. 10-60l/min) was considered. Lagrangian particle tracking has been used to investigate the particle deposition patterns in a model comprising mouth up to generation G6 of tracheobronchial airways. The results demonstrated that during all breathing patterns, the maximum velocity change occurred in the narrow throat region (Larynx). Due to implementing a realistic geometry for simulations, many irregularities and bending deflections exist in the airways model. Thereby, at higher inhalation rates, these areas are prone to vortical effects which tend to entrap the inhaled particles. According to the results, deposition fraction has a direct relationship with particle aerodynamic diameter (for dp=1-10µm). Enhancing inhalation flow rate and particle size will largely increase the inertial force and consequently, more particle deposition is evident suggesting that inertial impaction is the dominant deposition mechanism in tracheobronchial airways.

Magnetic drug targeting through a realistic model of human tracheobronchial airways using computational fluid and particle dynamics.

Magnetic drug targeting (MDT) is a local drug delivery system which aims to concentrate a pharmacological agent at its site of action in order to minimize undesired side effects due to systemic distribution in the organism. Using magnetic drug particles under the influence of an external magnetic field, the drug particles are navigated toward the target region. Herein, computational fluid dynamics was used to simulate the air flow and magnetic particle deposition in a realistic human airway geometry obtained by CT scan images. Using discrete phase modeling and one-way coupling of particle-fluid phases, a Lagrangian approach for particle tracking in the presence of an external non-uniform magnetic field was applied. Polystyrene (PMS40) particles were utilized as the magnetic drug carrier. A parametric study was conducted, and the influence of particle diameter, magnetic source position, magnetic field strength and inhalation condition on the particle transport pattern and deposition efficiency (DE) was reported. Overall, the results show considerable promise of MDT in deposition enhancement at the target region (i.e., left lung). However, the positive effect of increasing particle size on DE enhancement was evident at smaller magnetic field strengths (Mn [Formula: see text] 1.5 T), whereas, at higher applied magnetic field strengths, increasing particle size has a inverse effect on DE. This implies that for efficient MTD in the human respiratory system, an optimal combination of magnetic drug career characteristics and magnetic field strength has to be achieved.

Airflow, transport and regional deposition of aerosol particles during chronic bronchitis of human central airways.

In the present study, the effects of airway blockage in chronic bronchitis disease on the flow patterns and transport/deposition of micro-particles in a human symmetric triple bifurcation lung airway model, i.e., Weibel's generations G3-G6 was investigated. A computational fluid and particle dynamics model was implemented, validated and applied in order to evaluate the airflow and particle transport/deposition in central airways. Three breathing patterns, i.e., resting, light activity and moderate exercise, were considered. Using Lagrangian approach for particle tracking and random particle injection, an unsteady particle tracking method was performed to simulate the transport and deposition of micron-sized aerosol particles in human central airways. Assuming laminar, quasi-steady, three-dimensional air flow and spherical non-interacting particles in sequentially bifurcating rigid airways, airflow patterns and particle transport/deposition in healthy and chronic bronchitis (CB) affected airways were evaluated and compared. Comparison of deposition efficiency (DE) of aerosols in healthy and occluded airways showed that at the same flow rates DE values are typically larger in occluded airways. While in healthy airways, particles deposit mainly around the carinal ridges and flow dividers--due to direct inertial impaction, in CB affected airways they deposit mainly on the tubular surfaces of blocked airways because of gravitational sedimentation.