Human breath metabolomics using an optimized non-invasive exhaled breath condensate sampler

Abstract

Exhaled breath condensate (EBC) analysis is a developing field with tremendous promise to advance personalized, non-invasive health diagnostics as new analytical instrumentation platforms and detection methods are developed. Multiple commercially-available and researcher-built experimental samplers are reported in the literature. However, there is very limited information available to determine an effective breath sampling approach, especially regarding the dependence of breath sample metabolomic content on the collection device design and sampling methodology. This lack of an optimal standard procedure results in a range of reported results that are sometimes contradictory. Here, we present a design of a portable human EBC sampler optimized for collection and preservation of the rich metabolomic content of breath. The performance of the engineered device is compared to two commercially available breath collection devices: the RTube™ and TurboDECCS. A number of design and performance parameters are considered, including: condenser temperature stability during sampling, collection efficiency, condenser material choice, and saliva contamination in the collected breath samples. The significance of the biological content of breath samples, collected with each device, is evaluated with a set of mass spectrometry methods and was the primary factor for evaluating device performance. The design includes an adjustable mass-size threshold for aerodynamic filtering of saliva droplets from the breath flow. Engineering an inexpensive device that allows efficient collection of metalomic-rich breath samples is intended to aid further advancement in the field of breath analysis for non-invasive health diagnostic. EBC sampling from human volunteers was performed under UC Davis IRB protocol 63701-3 (09/30/2014-07/07/2017).

Analytical methodologies for broad metabolite coverage of exhaled breath condensate

“…The engineering design and operational principle of the EBC collection device employed for the EBC collection was recently described elsewhere [31]. The device is portable, suitable for a wide-spread use similar to the RTube®, a common commercially available device for EBC collection: the exhaled breath is passed through a chilled tube where it is condensed and then physically removed.…”

“…Unlike the RTube®, the employed device uses a glass condenser surface to enhance measurement of metabolites in exhaled breath condensate [32], a flow-controlled saliva filter to reduce sample dilution and contamination with saliva microdroplets originating in the mouth cavity [33–35], and an active thermal mass cooling mechanism to maintain low condenser temperature to avoid physical change of the sample and preserve greater concentrations of VOCs [36]. These design factors contribute to reduced variability in the metabolomic content caused by the collection device [31]. …”

“…The samples are stored in glass cap-sealed vials at −80 °C until further analysis. For a healthy subject of ~80 kg, the described device can typically collect 1.2 ± 0.3 gram of ice-frozen EBC in 10 min [31]. …”

“…To eliminate sample bias at the sampling step, an “averaged” EBC sample aliquoted from individual EBC samples collected from a group of six volunteers, spanning both genders and a range of ages, was used to represent a “typical” breath sample. The individual EBC samples were collected with a collection device that demonstrated metabolite capture [31]. A systematic metabolite survey is presented in this paper.…”

Answer to: “Biomarkers in allergic asthma: Which matrix should we use?”

“…Up to date, the exploration and use of EBC had seemed to be limited by the lack of an optimal standard procedure for breath sampling. Sample variability, effect of pH over some metabolites and high dilution are mostly the challenges that EBC sampling is facing, where currently great efforts are being made . Despite EBC is not a sample used in the daily clinic routine compared to blood and urine, it has showed recently its potential into the clinical setting .…”