Formation of respiratory aerosols: Modeling and experiments (FRAME)

It is generally established that respiratory droplets and aerosols are formed from the fluid lining the respiratory tract. However, unlike modeling of the fate of inhaled aerosols, modeling the formation of respiratory droplets and aerosols is a much less studied area. In the fall of 2024, aerosol science experts in both experimental and clinical aspects of respiratory aerosols, along with experts in mathematical and computational modelling of viscoelastic fluids, participated in a weeklong workshop to address the challenges of characterizing respiratory aerosol composition and of modeling their formation. Topics that were discussed include the mechanisms of formation, the measurement of viscoelastic and rheological properties of the lung lining fluids, the intersubject production variability, and how in-vivo/in-vitro data can be used to inform and validate modeling. This publication summarizes the current consensus on the topic as it was discussed at the workshop. It also highlights the current experimental and numerical challenges, and key gaps in the available data. The most critical needs for a more predictive understanding of respiratory aerosol generation were identified as 1) robust, high-resolution rheological and compositional measurements of lung lining fluids, 2) experimental systems that replicate dynamic airway processes under controlled conditions, 3) multiscale simulations that incorporate nonlinear constitutive behavior, complex geometries, and surface-driven instabilities with appropriate validation, and 4) integration of pathogen viability and chemical microenvironments into aerosol fate models.