Abstract Number: 87 Working Group: Instrumentation and Methods
Abstract The Exhaled Breath Collector (EBC) was developed for efficient collection of exhaled particles and proteins. The EBC system consist of six laminar-flow growth tubes (24” long) maintained at 1oC. The outcoming flow is joined in one single delivery nozzle and impacted onto ice. Particles down to 10nm contained in the vapor-saturated exhaled breath grow to above 1µm, while the excess water vapor condenses on the wick walls and is removed. Impaction on an ice surface preserves the integrity of proteins exhaled during breathing, while eliminating particle bounce. The EBC runs at a flow rate of 12 lpm and the condensationally enlarged particles are collected into approximately 2mL for a 30 min sampling time. Using analytical techniques such as PCR, immunoassays and proteomics, proteins present in the collected sample can be quickly identified, allowing diagnosis of lung infections in less than an hour.
Characterization and optimization of sampling conditions for high collection efficiency of the EBC was conducted in our laboratory, using both laboratory generated ammonium sulfate particles and ambient particles. The effect of the relative humidity (RH) of the incoming air, particle size (Dp) and number concentration (#/cc) on the collection efficiency was evaluated and the parameters optimized.
The RH of the incoming flow was the most important parameter. Collection efficiencies were <50% for low RH values, rapidly increasing after the RH reached 70%. Optimum collection efficiency (>90%) was achieved when the RH was >85%. Collection efficiency didn’t vary with particle sizes between 10nm and 250nm when run at RH >85%. For particles smaller than 10nm, collection efficiency decreased, with 80% efficiency for 8nm particles. The EBC was also tested for particle number concentrations varying between 0.5x103 and 1.2x104 particles/cc. Collection efficiencies above 95% were obtained for all sizes and concentrations.