The identification of hypoxia biomarkers from exhaled breath under normobaric conditions.

Pilots have reported experiencing in-flight hypoxic-like symptoms since the inception of high-altitude aviation. As a result, the need to monitor pilots, in-flight, for the onset of hypoxic conditions is of great interest to the aviation community. We propose that exhaled breath is an appropriate non-invasive medium for monitoring pilot hypoxic risk through volatile organic compound (VOC) analysis. To identify changes in the exhaled breath VOCs produced during periods of reduced O2 levels, volunteers were exposed to simulated flight profiles, i.e. sea level for 5 min, O2 levels found at elevated altitudes for 5 min or placebo and 5 min at 100% O2 recovery gas, using a modified flight mask interfaced with a reduced O2 breathing device. During the course of these test events, time series breath samples from the flight mask and pre/post bag samples were collected and analyzed by gas chromatography/mass spectrometry (GC/MS). Seven compounds (pentanal, 4-butyrolactone, 2-pentanone, 2-hexanone, 2-cyclopenten-1-one, 3-methylheptane and 2-heptanone) were found to significantly change in response to hypoxic conditions. Additionally, the isoprene, 2-methyl-1,3-butadiene, was found to increase following the overall exposure profile. This study establishes an experimental means for monitoring changes in VOCs in response to hypoxic conditions, a computational workflow for compound analysis via the Metabolite Differentiation and Discovery Lab and MatLab(©) software and identifies potential volatile organic compound biomarkers of hypoxia exposure.

Detection of volatile organic compounds indicative of human presence in the air.

Volatile organic compounds were collected and analyzed from a variety of indoor and outdoor air samples to test whether human-derived compounds can be readily detected in the air and if they can be associated with human occupancy or presence. Compounds were captured with thermal desorption tubes and then analyzed by gas chromatography with mass spectrometry. Isoprene, a major volatile organic compound in exhaled breath, was shown to be the best indicator of human presence. Acetone, another major breath-borne compound, was higher in unoccupied or minimally occupied areas than in human-occupied areas, indicating that its majority may be derived from exogenous sources. The association of endogenous skin-derived compounds with human occupancy was not significant. In contrast, numerous compounds that are found in foods and consumer products were detected at elevated levels in the occupied areas. Our results revealed that isoprene and many exogenous volatile organic compounds consumed by humans are emitted at levels sufficient for detection in the air, which may be indicative of human presence.