Background Oriented Schlieren (BOS) Visualization for Evaluation of Risk in Aerosol-Generating Procedures

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Project Summary Aerosol-generating procedures (AGPs) are medical procedures that produce aerosols that can be laden with pathogens if the patient has a viral infection, such as SARS-CoV-2 or influenza. These aerosols pose a significant risk to health care workers, as they can linger in the air for extended periods of time and are small enough to bypass ordinary surgical masks. There is currently no established, unambiguous way to evaluate the risks to healthcare workers associated with a specific AGP, nor is there a rigorous method by which to assess a proposed risk-mitigation strategy. To address this gap, a flow visualization technique must be developed that can be applied in a clinical setting during actual medical procedures and is capable of detecting aerosol-laden flows produced by AGPs or potential AGPs. In this R21 proposal, we will adapt background-oriented schlieren (BOS) visualization, a method from fluid mechanics, into a technique that can be applied to study flows produced by AGPs. The R21 project is high risk with no published preliminary data, but the PIs have successfully demonstrated visualziation of aerosols produced by jet ventilation, a specific type of AGP, using BOS in a proof-of-concept experiment. The proposed work is significant and timely, as assessment of the risk associated with AGPs is extremely important in the context of the COVID-19 pandemic. We will use the novel BOS technique to assess risks and evaluate mitigation strategies for three specific AGPs in both ex vivo and in vivo conditions. Specific Aim 1: Develop a human-scale BOS system and establish a procedure for evaluating the risk of AGPs in a clinical setting. Specific Aim 2: Quantify the risk of aerosol exposure under different simulated and in-vivo conditions, and identify strategies to mitigate the risks. The significance and impact of the proposed research will be in developing a tool for unambiguously evaluat- ing the risks associated with AGPs in realistic clinical settings, and urgently-needed risk assessments for three specific AGPs and experimentally verified risk mitigation strategies for each.