A Cough Aerosol Simulator for the Study of Disease Transmission by Human Cough-Generated Aerosols

Abstract

Aerosol particles expelled during human coughs are a potential pathway for infectious disease transmission. However, the importance of airborne transmission is unclear for many diseases. To better understand the role of cough aerosol particles in the spread of disease and the efficacy of different types of protective measures, we constructed a cough aerosol simulator that produces a humanlike cough in a controlled environment. The simulated cough has a 4.2 l volume and is based on coughs recorded from influenza patients. In one configuration, the simulator produces a cough aerosol containing particles from 0.1 to 100 µm in diameter with a volume median diameter (VMD) of 8.5 µm and a geometric standard deviation (GSD) of 2.9. In a second configuration, the cough aerosol has a size range of 0.1-30 µm, a VMD of 3.4 µm, and a GSD of 2.3. The total aerosol volume expelled during each cough is 68 µl. By generating a controlled and reproducible artificial cough, the simulator allows us to test different ventilation, disinfection, and personal protection scenarios. The system can be used with live pathogens, including influenza virus, which allows isolation precautions used in the healthcare field to be tested without risk of exposure for workers or patients. The information gained from tests with the simulator will help to better understand the transmission of infectious diseases, develop improved techniques for infection control, and improve safety for healthcare workers and patients.

Quantifying the size-resolved dynamics of indoor bioaerosol transport and control

“…Results are averaged over a combination of both constant low‐flow “breathing” and periodic high‐flow “coughing.” The size distributions with both organisms had peak number concentrations between 40 and 70 nm, but peak volume concentrations were between 5 and 10 μm. The resulting size‐resolved number and volume distributions are reasonably well aligned with recently developed cough simulators and with the small number of studies that have investigated particle size distributions resulting from human respiratory emissions using aerosol monitoring equipment that can measure below ~0.3 μm . Given that the mass fraction of nonvolatile components is approximately 1%, the fully desiccated particle diameter would be expected to be only ~22% of the original emitted particle diameter .…”

“…The mean (±SD) volumetric airflow rate was estimated to be ~10 (±1) L/s by multiplying the cross‐sectional area of the tube by the measured air velocity. Both flow rates are considered to be reasonably in range with previous measurements of average flow rates during breathing and coughing by adult human subjects and are similar to those used in a recently developed cough simulator . However, the concentration of model organisms loaded into the nebulizer did not vary with flow rate and the simulated breathing flow rate was somewhat lower than the 0.17‐0.18 L/s recommended in ISO/TS Standard 16976‐1 .…”

“…Measurements were made ~0.3 m and ~3 m away from the outlet orifice and were repeated twice with each of the two model organisms loaded in the nebulizer separately. Results were compared to those from human expiratory emissions measurements in the literature using similar instrumentation and methods …”

The coronavirus pandemic and aerosols: Does COVID-19 transmit via expiratory particles?

“…It is unclear which of these mechanisms plays a key role in transmission of COVID-19. Much airborne disease research prior to the current pandemic has focused on 'violent' expiratory events like sneezing and coughing (e.g., Lindsley et al 2013;Bourouiba, Dehandschoewercker, and Bush 2014). There is strong evidence now, however, that many infected individuals who transmit COVID-19 are either minimally symptomatic or not symptomatic at all.…”

Efficacy of Face Shields Against Cough Aerosol Droplets from a Cough Simulator

“…The cough aerosol simulator used in these experiments has been described in detail previously. (21) The test aerosol was generated by aerosolizing CDMEM alone for the aerosol particle measurement experiments, and CDMEM containing influenza virus for the influenza virus experiments. For some experiments, an air brush (Model 200, Badger Air-Brush Co., Franklin, Ill.) was used to produce a cough aerosol with a volume median diameter (VMD) of 8.5 μm and a geometric standard deviation (GSD) of 2.9 (referred to here as the "largeparticle cough aerosol").…”