SARS CoV-2 aerosol: How far it can travel to the lower airways?

Abstract

The recent outbreak of the SARS CoV-2 virus has had a significant effect on human respiratory health around the world. The contagious disease infected a large proportion of the world population, resulting in long-term health issues and an excessive mortality rate. The SARS CoV-2 virus can spread as small aerosols and enters the respiratory systems through the oral (nose or mouth) airway. The SARS CoV-2 particle transport to the mouth-throat and upper airways is analyzed by the available literature. Due to the tiny size, the virus can travel to the terminal airways of the respiratory system and form a severe health hazard. There is a gap in the understanding of the SARS CoV-2 particle transport to the terminal airways. The present study investigated the SARS CoV-2 virus particle transport and deposition to the terminal airways in a complex 17-generation lung model. This first-ever study demonstrates how far SARS CoV-2 particles can travel in the respiratory system. ANSYS Fluent solver was used to simulate the virus particle transport during sleep and light and heavy activity conditions. Numerical results demonstrate that a higher percentage of the virus particles are trapped at the upper airways when sleeping and in a light activity condition. More virus particles have lung contact in the right lung than the left lung. A comprehensive lobe specific deposition and deposition concentration study was performed. The results of this study provide a precise knowledge of the SARs CoV-2 particle transport to the lower branches and could help the lung health risk assessment system.

FIG. 1.

Highly asymmetric five-lobes 17-generation human lung model.

FIG. 2.

Numerical results validation with available literature at 10 l/min inlet airflow.

FIG. 3.

Numerical results validation with available literature at 20 l/min inlet flow (Cheng et al., 1993, 1995; Longest and Xi, 2007; Xi et al., 2012).

FIG. 4.

Air velocity profiles at the randomly chosen location of the airway, (a) random location definition, (b) trachea, (c) right upper (RU) lobe, (d) right middle (RM) lobe, (e) right lower (RL) lobe, (f) left upper (LU) lobe, and (g) left lower (LL) lobe.

FIG. 5.

Velocity streamline at different airflow rates, (a) 7.5, (b) 15, and (c) 30 l/min.

FIG. 6.

Pressure contour throughout the lung airways, (a) 7.5, (b) 15, and (c) 30 l/min.

FIG. 7.

SARS CoV-2 Aerosol deposition (120 nm) at different physical conditions (a) 7.5, (b) 15, and (c) 30 l/min flow rate. (Sphere size is increased during post-processing for visualization purpose.)

FIG. 8.

DE comparison at right and left lung for different airflow rate conditions.

FIG. 9.

Local deposition of SARS CoV-2 aerosol at different inlet conditions. LU, left upper lobe; LL, left lower lobe; RU, right upper lobe; RM, right middle lobe; and RL, right lower lobe.

FIG. 10.

SARS CoV-2 aerosol deposition concentration from trachea to the terminal airways for various airflow rate conditions, (a) 7.5 l/min at right lung, (b) 7.5 l/min at left lung, (c) right lung, and (d) left lung.