Exploring the mechanisms of respiratory droplet generation during coughing

Many infectious respiratory diseases, such as influenza and SARS-CoV-2, are transmitted via respiratory droplets. These droplets can be generated from coughing, sneezing, talking, or breathing, and can remain airborne for an extended period. Understanding how these droplets are formed, how they are expelled into the environment, and their size and number can aid in creating policies to reduce the spread of these diseases.

Khoa et al. employed a numerical analysis to explore how droplets are generated during coughing. They developed an oral airway model complete with teeth features and the respiratory tract, employed an Eulerian Wall Film model to produce droplets, and tracked them with a Discrete Phase model.

With this unique approach, the team could follow the generated droplets from their formation to their expulsion during coughing. Their results highlight the importance of including a detailed oral cavity and tooth structure when designing respiratory droplet models.

“The results showed that the largest droplet concentration was generated at the start of coughing, peaking with the cough flow rate,” said author Nguyen Dang Khoa. “Most generated and exhaled droplets originate in the oral cavity and teeth surface, followed by the caudal region of the respiratory system.”

Following this success, the team plans to continue expanding their model to encompass more aspects of respiratory disease infection.

“Our research team’s primary goal is to create a seamless analysis that includes the entire process, starting from the exposure phase, the production of RNA viral copies in the mucous membrane, and their re-emission from the infected host during coughs,” said Khoa. “The findings from this study represent just one piece of the overall process.”

Source: “Coupled eulerian wall film-discrete phase model for predicting the respiratory droplets generation during the coughing event,” by Nguyen Dang Khoa, Kazuki Kuga, Kiao Inthavong, and Kazuhide Ito, Physics of Fluids (2023). The article can be accessed at https://doi.org/10.1063/5.0174014 .

This paper is part of the Flow and the Virus Collection, learn more here .