[Schwarz2009] "Breath acetone-aspects of normal physiology related to age and gender as determined in a PTR-MS study.",
J Breath Res
, vol. 3, no. 2: Department of Operative Medicine, Innsbruck Medical University, Anichstrasse 35, A-6020 Innsbruck, Austria. Breath Research Unit of the Austrian Academy of Sciences, Dammstrasse 22, A-6850 Dornbirn, Austria., pp. 027003, Jun, 2009.
The present study was performed to determine the variations of breath acetone concentrations with age, gender and body-mass index (BMI). Previous investigations were based on a relatively small cohort of subjects (see Turner et al 2006 Physiol. Meas. 27 321-37). Since exhaled breath analysis is affected by considerable variation, larger studies are needed to get reliable information about the correlation of concentrations of volatiles in breath when compared with age, gender and BMI. Mixed expiratory exhaled breath was sampled using Tedlar bags. The concentrations of a mass-to-charge ratio (m/z) of 59, attributed to acetone, were then determined using proton transfer reaction-mass spectrometry. Our cohort, consisting of 243 adult volunteers not suffering from diabetes, was divided into two groups: one that fasted overnight prior to sampling (215 volunteers) and the other without a dietary control (28 volunteers). In addition, we considered a group of 44 healthy children (5-11 years old).The fasted subjects' concentrations of acetone ranged from 177 ppb to 2441 ppb, with an overall geometric mean (GM) of 628 ppb; in the group without a dietary control, the subjects' concentrations ranged from 281 ppb to 1246 ppb with an overall GM of 544 ppb. We found no statistically significant shift between the distributions of acetone levels in the breath of males and females in the fasted group (the Wilcoxon-Mann-Whitney test yielded p = 0.0923, the medians being 652 ppb and 587 ppb). Similarly, there did not seem to be a difference between the acetone levels of males and females in the group without a dietary control. Aging was associated with a slight increase of acetone in the fasted females; in males the increase was not statistically significant. Compared with the adults (a merged group), our group of children (5-11 years old) showed lower concentrations of acetone (p < 0.001), with a median of 263 ppb. No correlation was found between the acetone levels and BMI in adults. Our results extend those of Turner et al's (2006 Physiol. Meas. 27 321-37), who analyzed the breath of 30 volunteers (without a dietary control) by selected ion flow tube-mass spectrometry. They reported a positive correlation with age (but without statistical significance in their cohort, with p = 0.82 for males and p = 0.45 for females), and, unlike us, arrived at a p-value of 0.02 for the separation of males and females with respect to acetone concentrations. Our median acetone concentration for children (5-11 years) coincides with the median acetone concentration of young adults (17-19 years) reported by Spanel et al (2007 J. Breath Res. 1 026001).
[Schwarz2009a] "Determining concentration patterns of volatile compounds in exhaled breath by PTR-MS.",
J Breath Res
, vol. 3, no. 2: Department of Operative Medicine, Innsbruck Medical University, Anichstrasse 35, A-6020 Innsbruck, Austria. Breath Research Unit of the Austrian Academy of Sciences, Dammstrasse 22, A-6850 Dornbirn, Austria., pp. 027002, Jun, 2009.
Proton-transfer-reaction mass spectrometry (PTR-MS) is a convenient technique for fast analysis of exhaled breath without prior sample preparation. Since compounds are not separated prior to analysis as in gas chromatography mass spectrometry (GC-MS), and since protonated molecules may fragment, relatively complex spectra may arise, which are not easily interpreted in a quantitative way. We calibrated 21 different compounds of importance for exhaled breath analysis, based on the respective pure standards diluted with nitrogen. These calibration measurements included determination of the fragmentation pattern of each compound under dry conditions and in the absence of CO(2). Even though the fragmentation pattern may be predicted in a qualitative manner, the quantitative details may depend on water and CO(2) content. This is exemplarily shown for isoprene. Out of the selected 21 compounds, 11 compounds showed substantial fragmentation (fragments proportion > 10%). Fragmentation of several volatile organic compounds (VOCs) in the drift tube of PTR-MS has been previously observed (Buhr et al 2002 Int. J. Mass Spectrom. 221 1-7; Taipale et al 2008 Atmos. Chem. Phys. Discuss. 8 9435-75; Hewitt et al 2003 J. Environ. Monit. 51-7; Warneke et al 2003 Environ. Sci. Technol. 37 2494-501; de Gouw and Warneke 2007 Mass Spectrom. Rev. 26 223-57; Pozo-Bayon et al 2008 J. Agric. Food Chem. 56 5278-84) and calibration factors for several compounds at corresponding mass-to-charge ratios have been calculated. In this paper, besides the calibration factors, the proportions of substantial fragments are also taken into account for a correct quantification in the case of overlapping signals. The spectrum of a mixture of the considered 21 compounds may be simulated. Conversely, the determination of concentrations from the spectrum of such a mixture is a linear optimization problem, whose solution is determined here using the simplex algorithm.
[King2009] "Isoprene and acetone concentration profiles during exercise on an ergometer.",
J Breath Res
, vol. 3, no. 2: A-6850 Dornbirn, Austria. Vorarlberg University of Applied Sciences, Hochschulstr. 1, A-6850 Dornbirn, Austria., pp. 027006, Jun, 2009.
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.