Monitoring Diurnal Changes in Exhaled Human Breath

The development of noninvasive analytical techniques
is of interest
to the field of chronobiology, in order to reveal the human metabolome
that seems to show temporal patterns and to predict internal body
time. We report on the real-time mass spectrometric analysis of human
breath as a potential method to be used in this field. The breath
of 12 subjects was analyzed during 9 days by secondary electrospray
ionization-mass spectrometry (SESI-MS). The samples were collected
during four time slots: morning (8:00–11:00), before lunch
(11:00–13:00), after lunch (13:00–15:00), and late afternoon
(15:00–18:00). A total of 203 mass spectra were statistically
analyzed. Univariate analysis revealed a number of features with a
marked temporal behavior. Principal component analysis/canonical analysis
showed a clear temporal evolution of the breath patterns. A blind
cross-validation yielded 84% of correct classifications of the time
slot at which the breath samples were collected. We conclude that
this approach seems to have potential for the investigation of biological
clocks, including the description of internal body time, which may
have important implications for the timing of pharmacotherapy.