When they modelled breathing frequency in a laboratory to understand how the rate of flow of droplet with virus determines its deposition in the lungs, it was found that low breathing frequency rises the time of residence of the virus and thus increase chances of deposition and consequently the infection. Also, the multiscale lung structure has a significant effect on a person’s susceptibility to COVID-19. 

“COVID-19 has opened a gap in our understanding of deep pulmonological systemic diseases. Our study demonstrates the physical process by which aerosol particles are transported into the deep generations of the lung,” said Mahesh Panchagnula, Professor, Department of Applied Mechanics, IIT-M. 

The study was conducted to pave way for developing better therapies and drugs for respiratory infections. The other members of the team included research scholars Arnab Kumar Mallik and Soumalya Mukherjee. 

Airborne infections like COVID spread through sneezing and coughing, which instantly releases a lot of tiny droplets. The team imitated the droplet dynamics in the lung by studying the movement of droplets in the small capillaries which were of a diameter similar to bronchioles. They took water mixed with fluorescent particles and generated aerosols from this liquid using a nebuliser, explained the professor. 

“These fluorescent aerosols were used to track the movement and deposition of particles in the capillaries. They found that the deposition is inversely proportional to the aspect ratio of capillaries, which suggests that the droplets are likely to deposit in longer bronchioles,” Panchagnula said. 

The researchers also studied how the ‘Reynolds Number’ a parameter that quantifies the nature of flow steady or turbulent and determines the deposition in the capillaries. 

“They found that when the flow of aerosol movement is steady then the particles deposit via the process of diffusion, however, if the flow is turbulent then the particles deposit via the process of impaction,” he said. 

The team is planning to continue studying the process by which the virus is transported from the nasal cavity to the deep lung, which is still unknown, he said.