Fluid dynamic insights into virus deposition and transport in the deep lung

Chakravarty, Aranyak; Panchagnula, Mahesh V.; Patankar, Neelesh A.

The primary mode of respiratory virus transmission is by means of virus-laden aerosols. The aerosols are inhaled into the respiratory tract and deposited in the mucosa, where the virus may interact with the epithelial tissue causing infection. Transport of virus within the respiratory tract and clearance from the lungs, as such, becomes extremely important. This phenomena is mathematically modelled using a coupled model of aerosol transport and virus transport within a Weibel-like idealisation of the lung geometry. The analysis is carried out in a dimensionless manner and the results are presented in terms of various dimensionless parameters. It is observed that the main factor determining virus transport and clearance from the lungs is the region where the virus-laden aerosols are deposited within the lungs. Viruses deposited in the upper respiratory tract are cleared out of the lung relatively faster due to the impact of mucociliary clearance. Viruses deposited in the deep lung are cleared much slowly due to absence of mucociliary clearance. Deep lung deposition is observed to take place for a specific range of aerosol sizes. Slower breathing and deep breaths is observed to promote deep lung deposition. Slower breathing and larger mucus clearance is also observed to enhance virus clearance from the upper respiratory tract. It is further observed that virus clearance from the deep lung can only be enhanced by increasing virus diffusivity. This enhancement is, however, not substantial. It is, thus, essential to eliminate the situations which promote deep lung deposition of the viruses.