Evaluating Particle Collection Efficiency in Exhaled Breath Condensate Using an Artificial Lung System

HAOXUAN CHEN, Airi Harui, Yu Feng, Michael D. Roth, Yifang Zhu, University of California, Los Angeles

     Abstract Number: 288
     Working Group: Aerosol Science of Infectious Diseases: Lessons and Open Questions on Models, Transmission and Mitigation

Abstract
The COVID-19 pandemic has renewed the interest in utilizing exhaled breath condensate (EBC) as a non-invasive sample for infection diagnosis and studying the virus-laden particles emitted through breathing. Current sampling methods prioritize condensation by rapidly cooling exhaled breath onto surfaces at very low temperatures to obtain maximal condensate volume. However, particle collection and related aerodynamics have long been overlooked. As a result, compared to reference samples (e.g., blood and urine), the low level and high variability of the analytes in EBC samples greatly impede its further application in clinical medicine.

To better understand particle collection efficiency and affecting factors in the EBC sampling process, we developed an artificial lung system that consists of a 6-L lung chamber fitted with a 3D-printed human airway structure. It can continuously breathe (i.e., inhale and exhale) with the temperature and humidity independently controlled to approximate human lungs. Additionally, the system integrates aerosolization of lung fluid surrogate, enabling exhalation of breath-borne particles to mimic human breath. We studied the particle collection efficiency of the RTube, a commonly used commercial EBC collector, in a 10-min simulated sampling process. Our results show a temperature-dependent curve for exhaled particle collection efficiency, with collection efficiency decreasing from 50% to 20% as the sampling temperature increases from -40 to -20 ℃. Ongoing studies will characterize the size-resolved particle collection curves under different sampling temperatures and examine whether implementing particle capture mechanisms such as impaction can enhance particle collection efficiency and thus improve the analyte levels in the EBC samples.

This study provides novel insights into the collection of exhaled particles during the EBC sampling process and generates valuable information for improving the EBC sampling method toward standardization for further clinical applications.