Construction and Evaluation of a Versatile ${\hbox {CO}}_{2}$ Controlled Breath Collection Device

Breath gas analysis offers fascinating new opportunities as it is completely noninvasive and provides a unique window to various biochemical processes in the organism. Requirements for clinical application of this innovative technique include on site and point of care applicability. As most analytical methods like sensors are often not fast enough to realize breath-to-breath sampling additional effort is necessary to provide breath samples of well defined and reproducible composition. For that purpose, we built an automatic CO₂ controlled device from standard industrial components that enables adjustable breath sampling in any phase of expiration. Control of sampling was realized by fast responding infrared CO₂ sensors. The electrical signal of these sensors was used to trigger a micro pump and a valve. In order to render the device as versatile as possible direct coupling with sensors as well as continuous or discrete sampling via a sample loop or traps was possible. CO₂ concentrations, gas flow, and sample volumes were continuously recorded. Reliability and reproducibility of the device were evaluated and compared with an already established and validated manual sampling method. Alveolar concentrations of selected volatile organic compounds (VOCs) were determined in the corresponding samples taken in rest and during treadmill exercise. Substance concentrations of breath biomarkers in the automatically and manually collected alveolar samples were identical. Reliable sampling was possible with the automatic device up to respiratory rates of 40/min. Controlled and versatile alveolar sampling represents an indispensable requirement of application of most analytical methods and sensor technology in breath analysis.