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Measurements of Exhaled SARS-CoV-2 and Human Respiratory Droplets Using an Infectious Aerosol Capture Mask
JOSHUA SANTARPIA, Nicholas Markin, Steven Lisco, Gabriel Lucero, Danielle Rivera, Vicki Herrera, Sarah Stein, University of Nebraska Medical Center
Abstract Number: 631
Working Group: Infectious Aerosols in the Age of COVID-19
Abstract
There are several remaining unanswered knowledge gaps regarding the details of the mechanisms of aerosol transmission of SARS-CoV-2, the virus that caused the COVID-19 pandemic. One of these gaps is an understanding the range of infectious virus that are emitted by an infected individual as an aerosol. The present work focuses on the utilization of an Infectious Aerosol Capture Mask (IACM), originally employed as system to isolate COVID-19 patients, and in the present study repurposed to collect exhaled aerosols from infected individuals. The system consists of an oxygen delivery mask and filter cartridge attached to either hospital suction or an independent vacuum pump. The efficacy of the mask in capturing exhaled breath aerosols was evaluated using a mannequin attached to a nebulizer and simulated using computational fluid dynamics. To quantify the viral content of exhaled breath from COVID-19 patients, a gelatin filter was used to capture aerosol particles from the mask and the interior surface was swabbed and subsequently assayed by PCR. Test with inert aerosols indicated that at vacuum flow rates of at least 1 SCFM the mask captured at least 99% of the aerosol generated through the mouth and nose of the mannequin. CFD simulations were run with the mask vacuum flow rate at 1 SCFM and initial aerosol velocities representative of breathing, speaking, and coughing. During breathing and speaking, all particles between 0.5 and 20 µm were captured either on the surface of the mask (0-1% for breathing, 71-84% for speaking) or in the filter (99-100% for breathing, 16-29% for speaking). During coughing, a small fraction of particles (1-8%) may escape the mask, but the remaining are either impacted on the mask surface (81-91%) or collected at the filter (8-11%). Exhaled aerosol samples from eight patients, previously diagnosed with COVID-19, were collected using the IACM. Total exhaled virus concentrations ranged from below the limit of detection to 1.1x106 RNA copies/hr of the viral E gene of SARS-CoV-2. No SARS-CoV-2 aerosol was detected in air samples collected adjacent to the patient when the mask was being worn. These data indicate that the IACM is both useful for containing the exhaled aerosol of infected individuals and can be used to quantify the viral aerosol production rates during respiratory activities.