Clinical and Forensic Characterization of Exhaled Breath—Multiscale Computational Studies for the Metrics of Aerosol Particle Capture

Exhaled breath research consists of the study of gases, water vapor, volatile organic compounds, as well as aerosol particles. This research field typically involves the implementation of state-of-art methodologies for both novel technology and metric test analysis. This is particularly the case when collecting, detecting, and measuring exhaled submicrometer aerosol particles. Particle matter is produced in the lungs due to mechanical disruption of the airway lining fluid, which consists of water, lipids, proteins, and non-volatile compounds. Drugs of abuse, for instance: amphetamines, cocaine, and tetrahydrocannabinol (THC), have been detected in exhaled aerosol particles in conjunction with potential biomarkers of health or disease. Particles can be deposited in surgical masks, electret filter devices, and impaction filter devices; however, the absorptive properties of masks and some filters can hinder recovery for instrumental laboratory analysis. <i>Future development and adoption of exhaled breath sample tests and aerosol particle collection based on the particle fraction of breath require a deeper understanding of how human factors interact with device design, as a collector method, to influence particle deposition</i>. Robust multiscale computational methods, such as computational fluid dynamics (CFD) in conjunction with computational fluid particle dynamics (CFPD) numerical models, can support the design, optimization, and prototype development of these breath devices while aiding the interpretation of human subject exhaled breath studies that are not yet fully comprehended. In this work, the development and application of a three dimensional (3D) multiscale CFD-CFPD model of a single impact filter is carried out to aid <i>understanding of the complexity phenomena of the dynamics, transport, and deposition of submicrometer particles in exhaled breath</i>, the macroscale domain. The focus is on numerical simulations informing about the exhaled breath velocity profile as well as the local transportation, deposition, and distribution of submicrometer polydisperse particles in exhaled flow in a single-impact filter of a commercial breath aerosol capture device. This fluid dynamics and discrete phase computational approach is novel in terms of how depicting (a) exhaled breath and particle deposition within an aerosol collection device and (b) fluid breath dynamics of submicrometer polydisperse particles deposited in a filter by means of impaction. This study highlights needed decoupling strategies to characterize the influence of the size of particle as well as their concentration distribution and human (e.g.: flowrate and breath volume) and device factors. The goal of this study is to aid reproducibility and laboratory analysis of particle collection when human subject breath analysis is involved. This work will contribute to developing crucial standardized metrics that will promote pathways to advance public health and safety while offering a mean for a deeper comprehension of exhaled breath particle research.