Minimizing Exposure to Respiratory Droplets, 'Jet Riders' and Aerosols in Air-Conditioned Hospital Rooms by a 'Shield-And-Sink' Strategy

Abstract

Objectives: In COVID-19, transfer of respiratory materials transmits disease but the interplay of droplet and aerosol physics, physiology and environment is not fully understood. To advance understanding of disease transmission mechanisms and to find novel exposure minimization strategies, we studied cough-driven material transport modes and the efficacy of control strategies.Design and methods: Computer simulations and real-world experiments were used for integrating an intensive care setting, multi-physics, and physiology. Patient-focused airflow management and air purification strategies were examined computationally and validated by submicron particle exhalation imaging in volunteers.Results Respiratory materials ejected by cough exhibited four transport modes: long-distance ballistic, short-distance ballistic, “jet rider”, and aerosol modes. Interaction with air conditioning driven flow contaminated a hospital room rapidly. Different than large droplets or aerosols, “jet rider” droplets travelled with the turbulent air jet initially, but fell out at a distance, were not well eliminated by air conditioning and exposed bystanders at larger distance and longer time; their size predisposes them to preferential capture in the nasal mucosa, the primordial COVID-19 infection site. “Cough shields” captured large droplets but induced lateral dispersion of aerosols and jet riders. An air purification device alone had limited efficacy. A “Shield and Sink” approach combining “cough shields” with “virus sinks” miminized exposure to all secretions in modeling and real-life experiments.Conclusions “Jet riders” have characteristics of highly efficient respiratory infection vectors and may play a role in COVID-19 transmission. Exposure to all droplet types can be minimized through an easily implemented “Shield and Sink” strategy.