Hypoxia-like incidents in-flight have increased over the past decade causing severe safety concerns across the aviation community. As a result, the need to monitor flight crews in real-time for the onset of hypoxic conditions is paramount for continued aeronautical safety. Here, hypoxic events were simulated in the laboratory via a reduced
oxygen-breathing device to determine the effect of recovery gas
oxygen concentration (21% and 100%) on exhaled breath
volatile organic compound composition. Data from samples collected both serially (throughout the exposure), prior to, and following exposures yielded 326 statistically significant features, 203 of which were unique. Of those, 72 features were tentatively identified while 51 were verified with authentic standards. A comparison of samples collected serially between recovery and
hypoxia time points shows a statistically significant reduction in exhaled breath
isoprene (2-methyl-1,3-
butadiene, log2 FC -0.399, p = 0.005, FDR = 0.034, q = 0.033), however no significant difference in
isoprene abundance was observed when comparing recovery
gases (21% or 100% O2, p = 0.152). Furthermore, examination of pre-/post-exposure 1 l bag breath samples illustrate an overall increase in exhaled
isoprene abundance post-exposure (log2 FC 0.393, p = 0.005, FDR = 0.094, q = 0.033) but again no significant difference between recovery gas (21% and 100%, p = 0.798) was observed. A statistically significant difference in trend was observed between
isoprene abundance and recovery
gases O2 concentration when plotted against minimum oxygen saturation (p = 0.0419 100% O2, p = 0.7034 21% O2). Collectively, these results suggest exhaled
isoprene is dynamic in the laboratory ROBD setup and additional experimentation will be required to fully understand the dynamics of
isoprene in response to acute hypoxic stress.