Versatile breath sampler for online gas sensor analysis

Abstract

Breath analysis is an emerging field in gas sensor technology aiming for the next generation of hand-held and non-invasive medical diagnostic and monitoring devices. Often unrecognized, however, remains the importance of correct and standardized breath sampling, a prerequisite for meaningful breath analysis. Here, a simple and modular sampler design is presented that enables monitored breath extraction for reproducible and online gas sensor analysis. It consists of an inlet to monitor airway pressure and CO2 concentration online during exhalation and a tube to capture and buffer (20–40 s) end-tidal breath to meet prolonged exposure requirements of some gas sensors. Demonstrated on the example of acetone, a breath marker for fat burn, this sampler is suitable for continuous (refreshment ∼100 s) and reproducible online breath analysis, as validated by state-of-the-art proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS). Most interestingly, even short breath pulses down to 1 s result in reliable determination of end-tidal acetone concentrations while it is severely underestimated when sampling is not done properly. Finally, this sampler is applied to detect breath acetone with solid-state Si-doped WO3 sensors in humans. The proposed sampler can be connected to various types of gas sensors and applied flexibly for other breath markers (including isoprene, ethanol and methanol).