Volatile metabolites in the exhaled breath of healthy volunteers: their levels and distributions.
ABSTRACT The data obtained for the concentration distributions of the most abundant volatile metabolites in exhaled breath determined in two independent studies are reviewed, the first limited study involving five healthy volunteers providing daily breath samples over a month, and the subsequent study involving 30 healthy volunteers providing breath samples weekly over six months. Both studies were carried out using selected ion flow tube mass spectrometry, SIFT-MS, to obtain on-line, real-time analyses of single breath exhalations, avoiding the complications associated with sample collection. The distributions of the metabolites from the larger more comprehensive study are mostly seen to be log normal with the median values (in parts per billion, ppb) being ammonia (833), acetone (477), methanol (461), ethanol (112), propanol (18), acetaldehyde (22), isoprene (106) with the geometric standard deviation being typically 1.6, except for ethanol which was larger (3.24) due to the obvious increase of breath ethanol following the ingestion of sugar. These were the first well-defined concentration distributions of breath metabolites obtained and they are the essential requirement for recognizing abnormally high levels that are associated with particular diseases. The associations of each metabolite with known diseased states are alluded to. These SIFT-MS studies reveal the promise of breath analysis as a valuable addition to the tools for clinical diagnosis and therapeutic monitoring.
Article: Breath isoprene--aspects of normal physiology related to age, gender and cholesterol profile as determined in a proton transfer reaction mass spectrometry study.[show abstract] [hide abstract]
ABSTRACT: This study was performed to clarify variations in breath isoprene concentrations with age, gender, body mass index (BMI) and total serum cholesterol. Our cohort consisted of 205 adult volunteers of different smoking background without health complaints. Total cholesterol in blood serum was measured in 79 of these volunteers. Mixed expiratory exhaled breath was sampled using Tedlar bags. Concentrations of isoprene were then determined using proton transfer reaction-mass spectrometry. Isoprene concentrations ranged from 5.8 to 274.9 ppb, with an overall geometric mean (GM) of 99.3 ppb. There was no statistically significant difference in mean isoprene in breath between males and females (GM 105.4 and 95.5 ppb, respectively). Ageing led to a decrease in concentration in men, with an estimated slope of the regression line for log-transformed isoprene concentrations of -0.0049, but did not influence isoprene levels in women. We did not observe any significant correlation between isoprene breath content and cholesterol level in blood, even after adjusting for the possible influence of age. Similarly, no correlation was found between isoprene levels and BMI. Isoprene concentrations in exhaled breath showed gender-specific correlations with respect to age. Further investigations are necessary to clarify the relation between isoprene concentrations in exhaled breath and cholesterol levels and synthesis rates in blood.Clinical Chemistry and Laboratory Medicine 02/2008; 46(7):1011-8. · 2.15 Impact Factor
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ABSTRACT: Exhaled breath contains more than 1000 constituents at trace level concentrations, with a wide variety of these compounds potentially serving as biomarkers for specific diseases, physiologic status, or therapeutic progress. Some of the compounds in exhaled breath (EB) are well studied, and their relationship with disease pathologies is well established. However, molecularly specific analysis of such biomarkers in EB at clinically relevant levels remains an analytical and practical challenge due to the low levels of such biomarkers frequently below the ppb (v/v) range in EB. In this contribution, mid-infrared (MIR) spectroscopic sensing techniques are reviewed for potential application in breath diagnostics. While the spectral regime from 3-20 Â¿m has already been utilized for fundamental studies on breath analysis, significant further improvements are in demand for substantiating MIR spectroscopy and sensing techniques as a suitable candidate for clinically deployable breath analyzers. Several advantageous features including inherent molecular selectivity, real-time monitoring capability, comparable ease of operation, potentially low costs, and a compact device footprint promise reliable optical diagnostics in the MIR. Hence, while the application of MIR spectroscopy and sensing systems to breath analysis yet appear in their infancy, recent progress on advanced MIR light sources, waveguides, and device concepts forecasts next-generation optical sensing platforms suitable for addressing the challenges of in situ breath diagnostics.IEEE Sensors Journal 02/2010; · 1.52 Impact Factor
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ABSTRACT: This paper deals with variability issues connected with the proton transfer reaction-mass spectrometry (PTR-MS) measurements of isoprene concentration. We focus on isoprene as an abundant and widely studied compound in human breath. The variability caused by the measurement process is described by the within-sample distribution. Thus, based on the formula for computing isoprene concentration that reflects the principle of the PTR-MS, a theoretical model for the within-sample distribution of isoprene concentration is suggested. This model, which assumes that the distribution is proportional to a quotient of two independent Poisson-distributed random variables, is then confronted with empirical distributions obtained from 17 breath samples collected from a healthy individual within a month. (In each sample, isoprene concentration was determined 97 times.) The empirical within-sample distributions are also compared to normal and log-normal distributions. While those seem to be satisfactory approximations, the theoretical model is found suitable only in 10 out of 17 breath samples. We also comment on the stability of samples during the measurement process in the PTR-MS instrument and, for the sake of comparison, determine the within-sample and the within-subject variability of isoprene concentrations in our data. The respective geometric standard deviations are 1.01 and 1.29.Journal of Breath Research 09/2008; 2(3):037007. · 2.54 Impact Factor