A review of the USEPA's single breath canister (SBC) method for exhaled volatile organic biomarkers

Influence of ventilatory parameters on the concentration of exhaled volatile organic compounds in mechanically ventilated patients

Analysis of volatile organic compounds (VOC) within exhaled breath is subject to numerous sources of methodological and physiological variability. Whilst breathing pattern is expected to influence the concentrations of selected exhaled VOCs, it remains challenging to investigate respiratory rate and depth accurately in awake subjects. Online breath sampling was performed in 20 mechanically ventilated patients using proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS). The effect of variation in respiratory rate (RR) and tidal volume (TV) on the VOC release profiles was examined. A panel of nineteen VOCs were selected, including isoprene, acetone, propofol, volatile aldehydes, acids and phenols. Variation in RR had the greatest influence on exhaled isoprene levels, with maximum and average concentrations being inversely correlated with RR. Variations in RR had a statistically significant impact on acetone, C3-C7 linear aldehydes and acetic acid. In comparison, phenols (including propofol), C8-C10 aldehydes and C3-C6 carboxylic acids were not influenced by RR. Isoprene was the only compound to be influenced by variation in TV. These findings, obtained under controlled conditions, provide useful guidelines for the optimisation of breath sampling protocols to be applied on awake patients.

Breath analysis combined with cardiopulmonary exercise testing and echocardiography for monitoring heart failure patients: the AEOLUS protocol

This paper describes the AEOLUS pilot study which combines breath analysis with cardiopulmonary exercise testing (CPET) and an echocardiographic examination for monitoring heart failure (HF) patients. Ten consecutive patients with a prior clinical diagnosis of HF with reduced left ventricular ejection fraction were prospectively enrolled together with 15 control patients with cardiovascular risk factors, including hypertension, type II diabetes or chronic ischemic heart disease. Breath samples were collected at rest and during CPET coupled with exercise stress echocardiography (CPET-ESE) protocol by means of needle trap micro-extraction and were analyzed through gas-chromatography coupled with mass spectrometry. The protocol also involved using of a selected ion flow tube mass spectrometer for a breath-by-breath isoprene and acetone analysis during exercise. At rest, HF patients showed increased breath levels of acetone and pentane, which are related to altered oxidation of fatty acids and oxidative stress, respectively. A significant positive correlation was observed between acetone and the gold standard biomarker NT-proBNP in plasma (r= 0.646,p< 0.001), both measured at rest. During exercise, some exhaled volatiles (e.g., isoprene) mirrored ventilatory and/or hemodynamic adaptation, whereas others (e.g., sulfide compounds and 3-hydroxy-2-butanone) depended on their origin. At peak effort, acetone levels in HF patients differed significantly from those of the control group, suggesting an altered myocardial and systemic metabolic adaptation to exercise for HF patients. These preliminary data suggest that concomitant acquisition of CPET-ESE and breath analysis is feasible and might provide additional clinical information on the metabolic maladaptation of HF patients to exercise. Such information may refine the identification of patients at higher risk of disease worsening.

Effects of long-term vegan diet on breath composition

The composition of exhaled breath derives from an intricate combination of normal and abnormal physiological processes that are modified by the consumption of food and beverages, circadian rhythms, bacterial infections, and genetics as well as exposure to xenobiotics. This complexity, which results wide intra- and inter-individual variability and is further influenced by sampling conditions, hinders the identification of specific biomarkers and makes it difficult to differentiate between pathological and nominally healthy subjects. The identification of a "normal" breath composition and the relative influence of the aforementioned parameters would make breath analyses much faster for diagnostic applications. We thus compared, for the first time, the breath composition of age-matched volunteers following a vegan and a Mediterranean omnivorous diet in order to evaluate the impact of diet on breath composition. Mixed breath was collected from 38 nominally healthy volunteers who were asked to breathe into a two-liter handmade Nalophan bag. Exhalation flow rate and carbon dioxide values were monitored during breath sampling. An aliquot (100 mL) of breath was loaded into a sorbent tube (250 mg of Tenax GR, 60/80 mesh) before being analyzed by thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). Breath profiling using TD-GC-MS analysis identified five compounds (methanol, 1-propanol, pentane, hexane, and hexanal), thus enabling differentiation between samples collected from the different group members . Principal component analysis showed a clear separation between groups, suggesting that breath analysis could be used to study the influence of dietary habits in the fields of nutrition and metabolism. Surprisingly, one Italian woman and her brother showed extremely low breath isoprene levels (about 5 ppbv), despite their normal lipidic profile and respiratory data, such as flow rate and pCO2. Further investigations to reveal the reasons behind low isoprene levels in breath would help reveal the origin of isoprene in breath.

Pilot Studies of VOC Exposure Profiles during Surgical Operations

Volatile organic chemical exposure resulting from surgical operations is common in operating room personnel. The potential risk of long-term exposure to these low-level chemicals is always a concern. This study was conducted in an area hospital located in northern Taiwan to investigate the internal exposure scenario for operating room personnel. Breath samples were collected before and after surgery, whereas area samples were collected during the surgeries in process. There were 18 volatile organic compounds identified in the samples with gas chromatography-mass spectrometry. The average concentrations of sevoflurane (P = 0.0082), dimethyl sulfide (P = 0.0550), and methyl methacrylate (P = 0.0606) in breath samples collected after surgical operations were significantly higher compared to those obtained before surgical operations, whereas only slight elevations were present for benzene and hexamethyldisiloxane (P < 0.100). In addition, electrosurgical smoke-related chemicals, such as benzene, toluene, ethylbenzene, and m/p-xylene, also presented higher levels in operating room samples compared to the control area. Specifically, the findings in this preliminary study suggested the associations of elevated exposure to sevoflurane across various surgeries to methyl methacrylate with orthopedic surgery and to hexamethyldisiloxane with conventional electrosurgical units. Future study is warranted to explore the short-term high-level chemical exposure in operating rooms and to propose effective preventive measures accordingly to keep any exposure to chemicals at the lowest practical level.

Evolution of clinical and environmental health applications of exhaled breath research: Review of methods and instrumentation for gas-phase, condensate, and aerosols

Human breath, along with urine and blood, has long been one of the three major biological media for assessing human health and environmental exposure. In fact, the detection of odor on human breath, as described by Hippocrates in 400 BC, is considered the first analytical health assessment tool. Although less common in comparison to contemporary bio-fluids analyses, breath has become an attractive diagnostic medium as sampling is non-invasive, unlimited in timing and volume, and does not require clinical personnel. Exhaled breath, exhaled breath condensate (EBC), and exhaled breath aerosol (EBA) are different types of breath matrices used to assess human health and disease state. Over the past 20 years, breath research has made many advances in assessing health state, overcoming many of its initial challenges related to sampling and analysis. The wide variety of sampling techniques and collection devices that have been developed for these media are discussed herein. The different types of sensors and mass spectrometry instruments currently available for breath analysis are evaluated as well as emerging breath research topics, such as cytokines, security and airport surveillance, cellular respiration, and canine olfaction.

Techniques and issues in breath and clinical sample headspace analysis for disease diagnosis

Analysis of volatile organic compounds (VOCs) from breath or clinical samples for disease diagnosis is an attractive proposition because it is noninvasive and rapid. There are numerous studies showing its potential, yet there are barriers to its development. Sampling and sample handling is difficult, and when coupled with a variety of analytical instrumentation, the same samples can give different results. Background air and the environment a person has been exposed to can greatly affect the VOCs emitted by the body; however, this is not an easy problem to solve. This review investigates the use of VOCs in disease diagnosis, the analytical techniques employed and the problems associated with sample handling and standardization. It then suggests the barriers to future development.

Estimating central tendency from a single spot measure: A closed-form solution for lognormally distributed biomarker data for risk assessment at the individual level

Exposure-based risk assessment employs large cross-sectional data sets of environmental and biomarker measurements to predict population statistics for adverse health outcomes. The underlying assumption is that long-term (many years) latency health problems including cancer, autoimmune and cardiovascular disease, diabetes, and asthma are triggered by lifetime exposures to environmental stressors that interact with the genome. The aim of this study was to develop a specific predictive method that provides the statistical parameters for chronic exposure at the individual level based upon a single spot measurement and knowledge of global summary statistics as derived from large data sets. This is a profound shift in exposure and health statistics in that it begins to answer the question "How large is my personal risk?" rather than just providing an overall population-based estimate. This approach also holds value for interpreting exposure-based risks for small groups of individuals within a community in comparison to random individuals from the general population.

A dual mode breath sampler for the collection of the end-tidal and dead space fractions

This work presents a breath sampler prototype automatically collecting end-tidal (single and multiple breaths) or dead space air fractions (multiple breaths). This result is achieved by real time measurements of the CO2 partial pressure and airflow during the expiratory and inspiratory phases. Suitable algorithms, used to control a solenoid valve, guarantee that a Nalophan(®) bag is filled with the selected breath fraction even if the subject under test hyperventilates. The breath sampler has low pressure drop (<0.5 kPa) and uses inert or disposable components to avoid bacteriological risk for the patients and contamination of the breath samples. A fully customisable software interface allows a real time control of the hardware and software status. The performances of the breath sampler were evaluated by comparing (a) the CO2 partial pressure calculated during the sampling with the CO2 pressure measured off-line within the Nalophan(®) bag; (b) the concentrations of four selected volatile organic compounds in dead space, end-tidal and mixed breath fractions. Results showed negligible deviations between calculated and off-line CO2 pressure values and the distributions of the selected compounds into dead space, end-tidal and mixed breath fractions were in agreement with their chemical-physical properties.

Chemical analysis of whale breath volatiles: a case study for non-invasive field health diagnostics of marine mammals

We explored the feasibility of collecting exhaled breath from a moribund gray whale (Eschrichtius robustus) for potential non-invasive health monitoring of marine mammals. Biogenic volatile organic compound (VOC) profiling is a relatively new field of research, in which the chemical composition of breath is used to non-invasively assess the health and physiological processes on-going within an animal or human. In this study, two telescopic sampling poles were designed and tested with the primary aim of collecting whale breath exhalations (WBEs). Once the WBEs were successfully collected, they were immediately transferred onto a stable matrix sorbent through a custom manifold system. A total of two large volume WBEs were successfully captured and pre-concentrated onto two Tenax^®-TA traps (one exhalation per trap). The samples were then returned to the laboratory where they were analyzed using solid phase micro extraction (SPME) and gas chromatography/mass spectrometry (GC/MS). A total of 70 chemicals were identified (58 positively identified) in the whale breath samples. These chemicals were also matched against a database of VOCs found in humans, and 44% of chemicals found in the whale breath are also released by healthy humans. The exhaled gray whale breath showed a rich diversity of chemicals, indicating the analysis of whale breath exhalations is a promising new field of research.

Estimating common parameters of lognormally distributed environmental and biomonitoring data: harmonizing disparate statistics from publications

The progression of science is driven by the accumulation of knowledge and builds upon published work of others. Another important feature is to place current results into the context of previous observations. The published literature, however, often does not provide sufficient direct information for the reader to interpret the results beyond the scope of that particular article. Authors tend to provide only summary statistics in various forms, such as means and standard deviations, median and range, quartiles, 95% confidence intervals, and so on, rather than providing measurement data. Second, essentially all environmental and biomonitoring measurements have an underlying lognormal distribution, so certain published statistical characterizations may be inappropriate for comparisons. The aim of this study was to review and develop direct conversions of different descriptions of data into a standard format comprised of the geometric mean (GM) and the geometric standard deviation (GSD) and then demonstrate how, under the assumption of lognormal distribution, these parameters are used to answer questions of confidence intervals, exceedance levels, and statistical differences among distributions. A wide variety of real-world measurement data sets was reviewed, and it was demonstrated that these data sets are indeed of lognormal character, thus making them amenable to these methods. Potential errors incurred from making retrospective estimates from disparate summary statistics are described. In addition to providing tools to interpret "other people's data," this review should also be seen as a cautionary tale for publishing one's own data to make it as useful as possible for other researchers.

Socioeconomic disparities in indoor air, breath, and blood perchloroethylene level among adult and child residents of buildings with or without a dry cleaner

In many cities, dry cleaners using perchloroethylene are frequently located in multifamily residential buildings and often cause elevated indoor air levels of perchloroethylene throughout the building. To assess individual perchloroethylene exposures associated with co-located dry cleaners, we measured perchloroethylene in residential indoor air, and in blood and breath of adults and children residing in buildings with a dry cleaner as part of the New York City (NYC) Perc Project. We also measured perchloroethylene in indoor air, and in blood and breath of residents of buildings without a dry cleaner for comparison. Here, we evaluate whether an environmental disparity in perchloroethylene exposures is present. Study participants are stratified by residential building type (dry cleaner or reference) and socioeconomic characteristics (race/ethnicity and income); measures of perchloroethylene exposure are examined; and, the influence of stratified variables and other factors on perchloroethylene exposure is assessed using multivariate regression. All measures of perchloroethylene exposure for residents of buildings with a dry cleaner indicated a socioeconomic disparity. Mean indoor air perchloroethylene levels were about five times higher in minority (82.5 ug/m(3)) than in non-minority (16.5 ug/m(3)) households, and about six times higher in low-income (105.5 ug/m(3)) than in high income (17.8 ug/m(3)) households. Mean blood perchloroethylene levels in minority children (0.27 ng/mL) and adults (0.46 ng/mL) were about two and three times higher than in non-minority children (0.12 ng/mL) and adults (0.15 ng/mL), respectively. Mean blood perchloroethylene levels in low income children (0.34 ng/mL) and adults (0.62 ng/mL) were about three and four times higher than in high income children (0.11 ng/mL) and adults (0.14 ng/mL), respectively. A less marked socioeconomic disparity was observed in perchloroethylene breath levels with minority and low income residents having slightly higher levels than non-minority and high income residents. Multivariate regression affirmed that indoor air perchloroethylene level in dry cleaner buildings was the single most important factor determining perchloroethylene in blood and breath. Neither age, gender, nor socioeconomic status significantly influenced perchloroethylene levels in breath or blood. We previously reported that increased indoor air, breath, and blood perchloroethylene levels among NYC Perc Project child participants were associated with an increased risk for slightly altered vision. Thus, the disproportionately elevated perchloroethylene exposures of minority and low-income child residents of buildings with a dry cleaner shown here constitutes an environmental exposure disparity with potential public health consequences. Among residents of buildings without a dry cleaner, we observed some small increases in perchloroethylene breath and blood levels among non-minority or high income residents compared to minority or low income residents. These differences were not attributable to differences in indoor air levels of perchloroethylene which did not differ across socioeconomic categories, but appear to be associated with more frequent exposures dry cleaned garments.

Overcoming the challenges of studying conservation physiology in large whales: a review of available methods

Large whales are subjected to a variety of conservation pressures that could be better monitored and managed if physiological information could be gathered readily from free-swimming whales. However, traditional approaches to studying physiology have been impractical for large whales, because there is no routine method for capture of the largest species and there is presently no practical method of obtaining blood samples from free-swimming whales. We review the currently available techniques for gathering physiological information on large whales using a variety of non-lethal and minimally invasive (or non-invasive) sample matrices. We focus on methods that should produce information relevant to conservation physiology, e.g. measures relevant to stress physiology, reproductive status, nutritional status, immune response, health, and disease. The following four types of samples are discussed: faecal samples, respiratory samples ('blow'), skin/blubber samples, and photographs. Faecal samples have historically been used for diet analysis but increasingly are also used for hormonal analyses, as well as for assessment of exposure to toxins, pollutants, and parasites. Blow samples contain many hormones as well as respiratory microbes, a diverse array of metabolites, and a variety of immune-related substances. Biopsy dart samples are widely used for genetic, contaminant, and fatty-acid analyses and are now being used for endocrine studies along with proteomic and transcriptomic approaches. Photographic analyses have benefited from recently developed quantitative techniques allowing assessment of skin condition, ectoparasite load, and nutritional status, along with wounds and scars from ship strikes and fishing gear entanglement. Field application of these techniques has the potential to improve our understanding of the physiology of large whales greatly, better enabling assessment of the relative impacts of many anthropogenic and ecological pressures.

Quantification of personal exposure concentrations to gasoline vehicle emissions in high-end exposure microenvironments: effects of fuel and season

Mobile-source air toxic (MSAT) levels increase in confining microenvironments (MEs) with numerous emission sources of vehicle exhaust or evaporative emissions or during high-load and cold-start conditions. Reformulated fuels are expected to reduce MSAT and ozone precursor emissions. This study, required under the Clean Air Act Section 211b, evaluated high-end exposures in cities using reformulated (methyl tertiary-butyl ether [MTBE] or ethanol [EtOH]) fuels and conventional gasoline blends. The study investigates 13 high-end MEs, sampling under enhanced exposure conditions expected to result in maximal fuel and exhaust component exposures to carbon monoxide (CO), carbon dioxide (CO2), BTEX (benzene, toluene, ethylbenzene, xylenes), MTBE, 1,3-butadiene (1,3-BD), EtOH,formaldehyde (HCHO), and acetaldehyde (CH3CHO). The authors found that day-to-day ME variations in high-end benzene, 1,3-BD, HCHO, and CO concentrations are substantial, but independent of gasoline composition and season, and related to the activity and emission rates of ME sources, which differ from day to day.

Categorizing biomarkers of the human exposome and developing metrics for assessing environmental sustainability

The concept of maintaining environmental sustainability broadly encompasses all human activities that impact the global environment, including the production of energy, use and management of finite resources such as petrochemicals, metals, food production (farmland, fresh and ocean waters), and potable water sources (rivers, lakes, aquifers), as well as preserving the diversity of the surrounding ecosystems. The ultimate concern is how one can manage Spaceship Earth in the long term to sustain the life, health, and welfare of the human species and the planet's flora and fauna. On a more intimate scale, one needs to consider the human interaction with the environment as expressed in the form of the exposome, which is defined as all exogenous and endogenous exposures from conception onward, including exposures from diet, lifestyle, and internal biology, as a quantity of critical interest to disease etiology. Current status and subsequent changes in the measurable components of the exposome, the human biomarkers, could thus conceivably be used to assess the sustainability of the environmental conditions with respect to human health. The basic theory is that a shift away from sustainability will be reflected in outlier measurements of human biomarkers. In this review, the philosophy of long-term environmental sustainability is explored in the context of human biomarker measurements and how empirical data can be collected and interpreted to assess if solutions to existing environmental problems might have unintended consequences. The first part discusses four conventions in the literature for categorizing environmental biomarkers and how different types of biomarker measurements might fit into the various grouping schemes. The second part lays out a sequence of data management strategies to establish statistics and patterns within the exposome that reflect human homeostasis and how changes or perturbations might be interpreted in light of external environmental stressors. The underlying concept is to identify probative outliers from the "unremarkable exposome" in individuals or subpopulations that could be used for discerning deviations from the healthy environment, much like current diagnostic medicine uses batteries of blood and urine tests to screen for preclinical disease conditions. Such empirically derived human in vivo data could subsequently be integrated into high-throughput in vitro and in silico testing of environmental and manufactured chemicals to support real-world toxicity evaluations.

A review on the practical application of human biomonitoring in integrated environmental health impact assessment

Environmental health sciences focus on the link between the presence of contaminants in the environment and their relation with possible adverse health effects. Within this context, human biomonitoring (HBM) data have proven to be a valuable addition to, or have even surpassed, estimates of exposure based on environmental measures. Probably the main achievement of HBM data is that it provides an integrated overview of the pollutant dose any constituent is exposed to and incorporates bioaccumulation, excretion, half-life, and other potentially critical toxicokinetic parameters. In an integrated environmental health impact assessment framework, HBM serves as a pivotal point between environment and health, on the one hand leaning on environmental data to provide information on sources and pathways of exposure, and on the other hand clarifying hypotheses on the relationship between internal dose and prevalence of disease clusters. This study reflects the work performed in the INTARESE project (Integrated Assessment of Health Risk of Environmental Stressors in Europe). Because it was perceived that there was an overall lack of knowledge on the general methodology and potential application of HBM data in integrated environmental health impact assessment, an extensive review of literature was performed on past and current developments, potential, and applicability of HBM within the context of integrated environmental health impact assessment. This study covers three main topics that provide guidance for improved interpretation and application of HBM data: (1) sample collection and storage, (2) sample measurement, and (3) data interpretation. These main issues were discussed for 15 of the most common or relevant (classes of) chemicals. For more detailed information, the reader is pointed to the unabridged review (INTARESE, 2007), and consultation is available through the INTARESE web site (www.intarese.org).

Exposure reconstruction for reducing uncertainty in risk assessment: example using MTBE biomarkers and a simple pharmacokinetic model

Adverse health risks from environmental agents are generally related to average (long-term) exposures. Because a given individual's contact with a pollutant is highly variable and dependent on activity patterns, local sources and exposure pathways, simple 'snapshot' measurements of surrounding environmental media may not accurately assign the exposure level. Furthermore, susceptibility to adverse effects from contaminants is considered highly variable in the population so that even similar environmental exposure levels may result in differential health outcomes in different individuals. The use of biomarker measurements coupled to knowledge of rates of uptake, metabolism and elimination has been suggested as a remedy for reducing this type of uncertainty. To demonstrate the utility of such an approach, we invoke results from a series of controlled human exposure tests and classical first-order rate kinetic calculations to estimate how well spot measurements of methyl tertiary butyl ether and the primary metabolite, tertiary butyl alcohol, can be expected to predict different hypothetical scenarios of previous exposures. We found that blood and breath biomarker measurements give similar results and that the biological damping effect of the metabolite production gives more stable estimates of previous exposure. We also explore the value of a potential urinary biomarker, 2-hydroxyisobutyrate suggested in the literature. We find that individual biomarker measurements are a valuable tool in reconstruction of previous exposures and that a simple pharmacokinetic model can identify the time frames over which an exogenous chemical and the related chemical biomarker are useful. These techniques could be applied to broader ranges of environmental contaminants to assess cumulative exposure risks if ADME (Absorption, Distribution, Metabolization and Excretion) is understood and systemic biomarkers can be measured.

Picogram measurement of volatile n-alkanes (n-hexane through n-dodecane) in blood using solid-phase microextraction to assess nonoccupational petroleum-based fuel exposure

We describe here a new method for the analysis of alkanes ( n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, and n-dodecane) in blood using headspace solid-phase microextraction gas chromatography/mass spectrometry. This method is used to measure picogram per milliliter levels of n-alkanes in blood that may result from nonoccupational exposure to alkanes and other volatile nonpolar compounds from common sources such as petroleum-based fuel. This alkane signature is useful in distinguishing typical fuel biomarkers (e.g., benzene and toluene) from other confounding exposure sources such as cigarette smoke. Development of this method required special attention to sample handling as alkanes are not highly soluble in aqueous matrixes and exist as ubiquitous compounds found in many laboratory materials and the environment. In particular, significant n-hexane contamination ( approximately 0.4 ng/mL) occurred from collecting blood samples in vacutainers. This residue was removed by boiling the vacutainer stoppers in methanol followed by vacuum baking. For all the alkanes, the calculated accuracy demonstrated for the water-based standards ranged from 3.3% to 17% as deduced from the difference of the lowest and middle standards from the curve fit. Quality control data among runs over a 10 month period were found to vary from 14% to -29%, with a few exceptions. The resulting quantification limits for n-hexane through n-decane ranged from 0.069 to 0.132 ng/mL. In the analysis of 1200 blood samples from people with no known occupational exposure, median blood levels for all n-alkanes were below these quantification limits. n-Hexane levels above the method detection limit were, however, found in 1.3% of the samples.

Sample preparation for the analysis of volatile organic compounds in air and water matrices

This review summarizes literature data from the past 5 years on new developments and/or applications of sample preparation methods for analysis of volatile organic compounds (VOC), mainly in air and water matrices. Novel trends in the optimization and application of well-established airborne VOC enrichment techniques are discussed, like the implementation of advanced cooling systems in cryogenic trapping and miniaturization in adsorptive enrichment techniques. Next, focus is put on current tendencies in integrated sampling-extraction-sample introduction methods such as solid phase microextraction (SPME) and novel in-needle trapping devices. Particular attention is paid to emerging membrane extraction techniques such as membrane inlet mass spectrometry (MIMS) and membrane extraction with a sorbent interface (MESI). For VOC enrichment out of water, recent evolutions in direct aqueous injection (DAI) and liquid-liquid extraction (LLE) are highlighted, with main focus on miniaturized solvent extraction methods such as single drop microextraction (SDME) and liquid phase microextraction (LPME). Next, solvent-free sorptive enrichment receives major attention, with particular interest for innovative techniques such as stir bar sorptive extraction (SBSE) and solid phase dynamic extraction (SPDE). Finally, recent trends in membrane extraction are reviewed. Applications in both immersion and headspace mode are discussed.

Determination of complex mixtures of volatile organic compounds in ambient air: an overview

This article reviews developments in the sampling and analysis of volatile organic compounds (VOCs) in ambient air since the 1970s, particularly in the field of environmental monitoring. Global monitoring of biogenic and anthropogenic VOC emissions is briefly described. Approaches used for environmental monitoring of VOCs and industrial hygiene VOC exposure assessments are compared. The historical development of the sampling and analytical methods used is discussed, and the relative advantages and disadvantages of sorbent and canister methods are identified. Overall, there is considerable variability in the reliability of VOC estimates and inventories. In general, canister methods provide superior precision and accuracy and are particulary useful for the analysis of complex mixtures of VOCs. Details of canister methods are reviewed in a companion paper.

Breath analysis in critically ill patients: potential and limitations

Breath tests are attractive since they are noninvasive and can be repeated frequently in the dynamically changing state of critically ill patients. Volatile organic compounds can be produced anywhere in the body and are transported via the bloodstream and exhaled through the lung. They can reflect physiologic or pathologic biochemical processes such as lipid peroxidation, liver disease, renal failure, allograft rejection, and dextrose or cholesterol metabolism. This review describes the diagnostic potential of endogenous organic volatile substances in the breath of critically ill patients. Since many of these patients require ventilatory support, aspects of breath analysis under mechanical ventilation will be addressed. Analytical procedures, problems concerning the physiologic meaning of breath markers and future developments will be discussed.

Effects of ventilation on the collection of exhaled breath in humans

A computerized system has been developed to monitor tidal volume, respiration rate, mouth pressure, and carbon dioxide during breath collection. This system was used to investigate variability in the production of breath biomarkers over an 8-h period. Hyperventilation occurred when breath was collected from spontaneously breathing study subjects ( n = 8). Therefore, breath samples were collected from study subjects whose breathing were paced at a respiration rate of 10 breaths/min and whose tidal volumes were gauged according to body mass. In this “paced breathing” group ( n = 16), end-tidal concentrations of isoprene and ethane correlated with end-tidal carbon dioxide levels [Spearman's rank correlation test ( rs) = 0.64, P = 0.008 and rs = 0.50, P = 0.05, respectively]. Ethane also correlated with heart rate ( rs = 0.52, P < 0.05). There was an inverse correlation between transcutaneous pulse oximetry and exhaled carbon monoxide ( rs = -0.64, P = 0.008). Significant differences were identified between men ( n = 8) and women ( n = 8) in the concentrations of carbon monoxide (4 parts per million in men vs. 3 parts per million in women; P = 0.01) and volatile sulfur-containing compounds (134 parts per billion in men vs. 95 parts per billion in women; P = 0.016). There was a peak in ethanol concentration directly after food consumption and a significant decrease in ethanol concentration 2 h later ( P = 0.01; n = 16). Sulfur-containing molecules increased linearly throughout the study period (β = 7.4, P < 0.003). Ventilation patterns strongly influence quantification of volatile analytes in exhaled breath and thus, accordingly, the breathing pattern should be controlled to ensure representative analyses.

Online recording of ethane traces in human breath via infrared laser spectroscopy

A method is described for rapidly measuring the ethane concentration in exhaled human breath. Ethane is considered a volatile marker for lipid peroxidation. The breath samples are analyzed in real time during single exhalations by means of infrared cavity leak-out spectroscopy. This is an ultrasensitive laser-based method for the analysis of trace gases on the sub-parts per billion level. We demonstrate that this technique is capable of online quantifying of ethane traces in exhaled human breath down to 500 parts per trillion with a time resolution of better than 800 ms. This study includes what we believe to be the first measured expirograms for trace fractions of ethane. The expirograms were recorded after a controlled inhalation exposure to 1 part per million of ethane. The normalized slope of the alveolar plateau was determined, which shows a linear increase over the first breathing cycles and ends in a mean value between 0.21 and 0.39 liter-1. The washout process was observed for a time period of 30 min and was modelled by a threefold exponential decay function, with decay times ranging from 12 to 24, 341 to 481, and 370 to 1770 s. Our analyzer provides a promising noninvasive tool for online monitoring of the oxidative stress status.

Application of solid-phase microextraction and gas chromatography–mass spectrometry to the determination of volatile organic compounds in end-exhaled breath samples

Analysis of exhaled air is of particular interest as an indicator of health as well as a tool for the diagnosis of diseases. It is also a very attractive procedure for the biological control of the exposition to hazardous solvents. This kind of analysis presents numerous advantages over other methods, the most important being that it is not an invasive procedure and, therefore, it is well accepted and can be applied to a wide range of compounds. Furthermore, the analysis is simplified since the matrix is less complex that in the case of blood or urine. In spite of these obvious advantages and the good results obtained, analysis of exhaled air is not in daily use, probably due to the fact that there are no normalized systems of sampling, thus making the interpretation of the results difficult. In this paper, a method for the determination of tetrachloroethylene in exhaled air using solid-phase microextraction is presented. This method, which can be applied to other volatile organic compounds, was developed with special emphasis of end-exhaled breath sampling. The sample is collected in a glass tube whose ends are closed once the exhalation is finished. The tube has an orifice sealed with a septum through which the fiber is inserted. Then, the fiber is desorbed in the injector of a gas chromatograph and the analysis is accomplished using mass spectrometry for the identification and quantification of the components. The proposed system avoids the need of complex sampling equipment and allows analysis of the alveolar fraction. Additionally, the system is economical and easy to handle, thus facilitating the development of normalized methods and its routine use in field studies.