Isoprene and acetone concentration profiles during exercise on an ergometer

A real-time recording setup combining exhaled breath 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. [1] and Karl et al. [2]. 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, 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 one minute. 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.Comment: 35 page

Analiza wydechu - oznaczanie zawartości związków lipofilowych w organizmie człowieka

Real-time analysis of exhaled breath is a promising new method to get quantitative information on lipophilic compounds stored in the human body. Some pilot results are presented on isoprene, which is produced as a by-product of the cholesterol synthesis and appears in exhaled breath at concentrations of about 100 parts-per-billion (ppb). The results have been obtained using proton transfer reaction mass spectrometry (PTR-MS) from healthy volunteers undergoing an ergometer challenge test (with 75 W). Peak exhalation flow of isoprene is about 400 nmol/min shortly after start of the challenge. The setup holds great potential in capturing continuous dynamics of non-polar, low-soluble VOCs over a wide measurement range with simultaneous recording of physiological parameters affecting exhalation kinetics.Przedstawiono wstępne wyniki oznaczenia stężenia izoprenu w wydechu zdrowego człowieka. Izopren jest produktem ubocznym reakcji syntezy cholesterolu. Do oznaczenia zastosowano metodę reakcji przeniesienia protonu przy wykorzystaniu spektrometrii mas (PTR-MS)