Simulations of exhaled breath aerosol deposition to support laboratory breath aerosol measurements

V. Malave
National Institute of Standards and Technology (NIST),
United States

Keywords: aerosol deposition, exhaled breath, breathalyzer, computational fluid and particle dynamics, simulations, modeling, breath research


Breathalyzers for providing evidence of exhaled breath aerosols are in the infancy of development. There are cases wherein both the size and number density of aerosols per exhalation are so small that it requires concentration from multiple breaths through filtration devices. Collecting and accurately analyzing breath aerosol particles, typically in very small volume fractions (in the nm-to-µm size range) is a very difficult problem for both laboratory and computational experimentalists. In addition, aerosol particles are not transported in the breath vapor phase as other exhaled species are, e.g.: ethanol and nitrogen. The mode of aerosol cloud trajectory in a filtration device doesn’t necessarily follow the streamlines of the exhaled vapor phase. Furthermore, the deposition mechanism for particle capture is typically uncertain. Complex and detailed computational models need to be developed to handle the distinctive turbulence that exist in human breath in conjunction with particle deposition and oral fluid contamination effects on exhaled breath particulate capture and detection inside aerosol breath devices. This overall problem is too complex to be understood and guided by simple analytical theory – sophisticated computational algorithms such as computational fluid and particle dynamics (CFPD), are needed. CFPD couples the effect of fluid dynamics on particle transport and deposition mechanisms and can be implemented in breath research protocols to accurately predict whether a characteristic breath particle, considering all human and design variability factors, will be deposited on any given location in a breath device. In this talk, it will be highlighted how we are leading our laboratory experimental measurements in breath research by developing CFPD models to better understand exhaled breath fluid-particulate interaction in a commercial breathalyzer that includes the effect of possible oral fluid contamination and point the way to breath aerosol measurements in much broader health fields. Based on our computational findings, our primary goal is to improve experimental capture, detection, measurement, and repeatability while simultaneously showing experimentalists how to control for the effects of test variables such as exhaled breath flow velocity and turbulence.