Article
J. Breath Res. 3, 027006, 16pp (2009)
[DOI: 10.1088/1752-7155/3/2/027006]
Isoprene and acetone concentration profiles during exercise on an ergometer
Julian King, Alexander Kupferthaler, Karl Unterkofler, Helin Koc, Susanne Teschl, Gerald Teschl, Wolfram Miekisch, Jochen Schubert, Hartmann Hinterhuber, and Anton Amann
A real-time recording setup combining exhaled breath volatile organic compound (VOC) measurements by
proton transfer reaction-mass spectrometry (PTR-MS) with hemodynamic and respiratory data is presented.
Continuous automatic sampling of exhaled breath is implemented on the basis of measured respiratory
flow: a flow-controlled shutter mechanism guarantees that only end-tidal exhalation segments are drawn
into the mass spectrometer for analysis. Exhaled breath concentration profiles of two prototypic
compounds, isoprene and acetone, during several exercise regimes were acquired, reaffirming and
complementing earlier experimental findings regarding the dynamic response of these compounds
reported by Senthilmohan et al (2000 Redox Rep. 5 151-3) and Karl
et al (2001 J. Appl. Physiol. 91 762-70). While isoprene tends to react
very sensitively to changes in pulmonary ventilation and perfusion due to its lipophilic behavior
and low Henry constant, hydrophilic acetone shows a rather stable behavior. Characteristic (median)
values for breath isoprene concentration and molar flow, i.e., the amount of isoprene exhaled per
minute are 100 ppb and 29 nmol min-1, respectively, with some intra-individual
day-to-day variation. At the onset of exercise breath isoprene concentration increases drastically,
usually by a factor of ~3-4 within about 1 min. Due to a simultaneous increase in ventilation,
the associated rise in molar flow is even more pronounced, leading to a ratio between peak molar
flow and molar flow at rest of ~11. Our setup holds great potential in capturing continuous dynamics
of non-polar, low-soluble VOCs over a wide measurement range with simultaneous appraisal of decisive
physiological factors affecting exhalation kinetics. In particular, data appear to favor the
hypothesis that short-term effects visible in breath isoprene levels are mainly caused by
changes in pulmonary gas exchange patterns rather than fluctuations in endogenous synthesis.
Keywords: exhaled breath analysis, isoprene, acetone, volatile organic compounds (VOCs), proton transfer reaction mass spectrometry (PTR-MS)
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