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Abstract: A real-time recording setup combining exhaled breath VOC measurements byproton transfer reaction mass spectrometry PTR-MS with hemodynamic andrespiratory data is presented. Continuous automatic sampling of exhaled breathis implemented on the basis of measured respiratory flow: a flow-controlledshutter mechanism guarantees that only end-tidal exhalation segments are drawninto the mass spectrometer for analysis.Exhaled breath concentration profiles of two prototypic compounds, isopreneand acetone, during several exercise regimes were acquired, reaffirming andcomplementing earlier experimental findings regarding the dynamic response ofthese compounds reported by Senthilmohan et al. 1 and Karl et al. 2. Whileisoprene tends to react very sensitively to changes in pulmonary ventilationand perfusion due to its lipophilic behavior and low Henry constant,hydrophilic acetone shows a rather stable behavior. Characteristic medianvalues for breath isoprene concentration and molar flow, i.e., the amount ofisoprene exhaled per minute are 100 ppb and 29 nmol-min, respectively, withsome intra-individual day-to-day variation. At the onset of exercise breathisoprene concentration increases drastically, usually by a factor of ~3-4within about one minute. Due to a simultaneous increase in ventilation, theassociated rise in molar flow is even more pronounced, leading to a ratiobetween peak molar flow and molar flow at rest of ~11.Our setup holds great potential in capturing continuous dynamics ofnon-polar, low-soluble VOCs over a wide measurement range with simultaneousappraisal of decisive physiological factors affecting exhalation kinetics.



Autor: J. King, A. Kupferthaler, K. Unterkofler, H. Koc, S. Teschl, G. Teschl, W. Miekisch, J. Schubert, H. Hinterhuber, A. Amann

Fuente: https://arxiv.org/







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