Breath sulfides and pulmonary function in cystic fibrosis

Identification of Exhaled Metabolites Correlated with Respiratory Function and Clinical Features in Adult Patients with Cystic Fibrosis by Real-Time Proton Mass Spectrometry

Cystic fibrosis (CF) is a hereditary disease characterized by the progression of respiratory disorders, especially in adult patients. The purpose of the study was to identify volatile organic compounds (VOCs) as predictors of respiratory dysfunction, chronic respiratory infections of Staphylococcus aureus, Pseudomonas aeruginosa, Burkholderia cepacia, and VOCs associated with severe genotype and highly effective modulator treatment (HEMT). Exhaled breath samples from 102 adults with CF were analyzed using PTR-TOF-MS, obtained during a forced expiratory maneuver and normal quiet breathing. Using cross-validation and building gradient boosting classifiers (XGBoost), the importance of VOCs for functional and clinical outcomes was determined. The presence of the previously identified VOCs indole, phenol, and dimethyl sulfide were metabolic outcomes associated with impaired respiratory function. New VOCs associated with respiratory disorders were methyl acetate, carbamic acid, 1,3-Pentadiene, and 2,3-dimethyl-2-butene; VOCs associated with the above mentioned respiratory pathogens were non-differentiable nitrogen-containing organic compounds m/z = 47.041 (CH5NO)+ and m/z = 44.044 (C2H5NH+), hydrocarbons (cyclopropane, propene) and methanethiol; and VOCs associated with severe CFTR genotype were non-differentiable VOC m/z = 281.053. No significant features associated with the use of HEMT were identified. Early non-invasive determination of VOCs as biomarkers of the severity of CF and specific pathogenic respiratory flora could make it possible to prescribe adequate therapy and assess the prognosis of the disease. However, further larger standardized studies are needed for clinical use.

Early Detection of Ventilator-associated Pneumonia From Exhaled Breath in Intensive Care Unit Patients

OBJECTIVE

Evaluate associations between volatile organic compounds (VOCs) in heat and moisture exchange (HME) filters and the presence of ventilator-associated pneumonia (VAP).

BACKGROUND

Clinical diagnostic criteria for VAP have poor interobserver reliability, and cultures are slow to result. Exhaled breath contains VOCs related to gram-negative bacterial proliferation, the most identified organisms in VAP. We hypothesized that exhaled VOCs on HME filters can predict nascent VAP in mechanically ventilated intensive care unit patients.

METHODS

Gas chromatography-mass spectrometry was used to analyze 111 HME filters from 12 intubated patients who developed VAP. Identities and relative amounts of VOCs were associated with dates of clinical suspicion and culture confirmation of VAP. Matched pairs t tests were performed to compare VOC abundances in HME filters collected within 3 days pre and postclinical suspicion of VAP (pneumonia days), versus outside of these days (non-pneumonia days). A receiver operating characteristic curve was generated to determine the diagnostic potential of VOCs.

RESULTS

Carbon disulfide, associated with the proliferation of certain gram-negative bacteria, was found in samples collected during pneumonia days for 11 of 12 patients. Carbon disulfide levels were significantly greater ( P = 0.0163) for filters on pneumonia days. The Area Under the Curve of the Reciever Operating Characteristic curve (AUC ROC) for carbon disulfide was 0.649 (95% CI: 0.419-0.88).

CONCLUSIONS

Carbon disulfide associated with gram-negative VAP can be identified on HME filters up to 3 days before the initial clinical suspicion, and approximately a week before culture confirmation. This suggests VOC sensors may have potential as an adjunctive method for early detection of VAP.

Exhaled breath analysis in adult patients with cystic fibrosis by real-time proton mass spectrometry

BACKGROUND

Proton-transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS) is a promising tool for a rapid online determination of exhaled volatile organic compounds (eVOCs) profiles in patients with cystic fibrosis (CF).

OBJECTIVE

To detect VOC breath signatures specific to adult patients with CF compared with controls using PTR-TOF-MS.

METHODS

102 CF patients (54 M/48, mean age 25.6 ± 7.8 yrs) and 97 healthy controls (56 M/41F, mean age 25.8 ± 6.0 yrs) were examined. Samples from normal quiet breathing and forced expiratory maneuvers were analyzed with PTR-TOF-MS (Ionicon, Austria) to obtain VOC profiles listed as ions at various mass-to-charge ratios (m/z).

RESULTS

PTR-TOF-MS analysis was able to detect 167 features in exhaled breath from CF patients and healthy controls. According to cluster analysis and LASSO regression, patients with CF and controls were separated. The most significant VOCs for CF were indole, phenol, dimethyl sulfide, and not indicated: m/z = 297.0720 ([C12H13N2O7 and C17H13O5]H + ), m/z = 281.0534 ([C19H7NO2, C12H11NO7 and C16H9O5]H + ) during five-fold cross-validation both in forced expiratory maneuver and in normal quiet breathing.

CONCLUSION

PTR-TOF-MS is a promising method for determining the molecular composition of exhaled air specific to CF.

Thiol-Activated 1,2,4-Thiadiazolidin-3,5-diones Release Hydrogen Sulfide through a Carbonyl-Sulfide-Dependent Pathway

Recent efforts have expanded the development of small molecule donors that release the important biological signaling molecule hydrogen sulfide (H₂S). Previous work on 1,2,4-thiadiazolidin-3,5-diones (TDZNs) reported that these compounds release H₂S directly, albeit inefficiently. However, TDZNs showed promising efficacy in H₂S-mediated relaxation in ex vivo aortic ring relaxation models. Here, we show that TDZNs release carbonyl sulfide (COS) efficiently, which can be converted to H₂S by the enzyme carbonic anhydrase (CA) rather than releasing H₂S directly as previously reported.

Volatolomics in healthcare and its advanced detection technology

Various diseases increasingly challenge the health status and life quality of human beings. Volatolome emitted from patients has been considered as a potential family of markers, volatolomics, for diagnosis/screening. There are two fundamental issues of volatolomics in healthcare. On one hand, the solid relationship between the volatolome and specific diseases needs to be clarified and verified. On the other hand, effective methods should be explored for the precise detection of volatolome. Several comprehensive review articles had been published in this field. However, a timely and systematical summary and elaboration is still desired. In this review article, the research methodology of volatolomics in healthcare is critically considered and given out, at first. Then, the sets of volatolome according to specific diseases through different body sources and the analytical instruments for their identifications are systematically summarized. Thirdly, the advanced electronic nose and photonic nose technologies for volatile organic compounds (VOCs) detection are well introduced. The existed obstacles and future perspectives are deeply thought and discussed. This article could give a good guidance to researchers in this interdisciplinary field, not only understanding the cutting-edge detection technologies for doctors (medicinal background), but also making reference to clarify the choice of aimed VOCs during the sensor research for chemists, materials scientists, electronics engineers, etc.

Breath-Taking Perspectives and Preliminary Data toward Early Detection of Chronic Liver Diseases

The gold standard method for chronic liver diseases diagnosis and staging remains liver biopsy, despite the spread of less invasive surrogate modalities based on imaging and blood biomarkers. Still, more than 50% of chronic liver disease cases are detected at later stages when patients exhibit episodes of liver decompensation. Breath analysis represents an attractive means for the development of non-invasive tests for several pathologies, including chronic liver diseases. In this perspective review, we summarize the main findings of studies that compared the breath of patients with chronic liver diseases against that of control subjects and found candidate biomarkers for a potential breath test. Interestingly, identified compounds with best classification performance are of exogenous origin and used as flavoring agents in food. Therefore, random dietary exposure of the general population to these compounds prevents the establishment of threshold levels for the identification of disease subjects. To overcome this limitation, we propose the exogenous volatile organic compounds (EVOCs) probe approach, where one or multiple of these flavoring agent(s) are administered at a standard dose and liver dysfunction associated with chronic liver diseases is evaluated as a washout of ingested compound(s). We report preliminary results in healthy subjects in support of the potential of the EVOC Probe approach.

Metabolic Phenotypes in Asthmatic Adults: Relationship with Inflammatory and Clinical Phenotypes and Prognostic Implications

Bronchial asthma is a chronic disease that affects individuals of all ages. It has a high prevalence and is associated with high morbidity and considerable levels of mortality. However, asthma is not a single disease, and multiple subtypes or phenotypes (clinical, inflammatory or combinations thereof) can be detected, namely in aggregated clusters. Most studies have characterised asthma phenotypes and clusters of phenotypes using mainly clinical and inflammatory parameters. These studies are important because they may have clinical and prognostic implications and may also help to tailor personalised treatment approaches. In addition, various metabolomics studies have helped to further define the metabolic features of asthma, using electronic noses or targeted and untargeted approaches. Besides discriminating between asthma and a healthy state, metabolomics can detect the metabolic signatures associated with some asthma subtypes, namely eosinophilic and non-eosinophilic phenotypes or the obese asthma phenotype, and this may prove very useful in point-of-care application. Furthermore, metabolomics also discriminates between asthma and other “phenotypes” of chronic obstructive airway diseases, such as chronic obstructive pulmonary disease (COPD) or Asthma–COPD Overlap (ACO). However, there are still various aspects that need to be more thoroughly investigated in the context of asthma phenotypes in adequately designed, homogeneous, multicentre studies, using adequate tools and integrating metabolomics into a multiple-level approach.

Measurement Device for Ambient Carbonyl Sulfide by Means of Catalytic Reduction Followed by Wet Scrubbing/Fluorescence Detection

A portable chemical analysis system for monitoring ambient carbonyl sulfide (COS) was investigated for the first time. COS is paid attention to from the perspectives of photosynthesis tracer, breath diagnosis marker, and new process-use in the manufacture of semiconductors. Recently, the threshold level value of COS was settled at 5 ppm in volume ratio (ppmv) for workplace safety management. In this work, COS was converted to H₂S by a small column packed with alumina catalyzer at 65 °C. Then, the H₂S produced was collected in a small channel scrubber to react with fluorescein mercuric acetate (FMA), and the resulting fluorescence quenching was monitored using an LED/photodiode-based miniature detector. The miniature channel scrubber was re-examined to determine its robustness and easy fabrication, and conditions of the catalyzer were optimized. When the FMA concentration used was 1 μM, the limit of detection and dynamic range, which were both proportional to the FMA concentration, were 0.07 and 25 ppbv, respectively. Ambient COS in the background level and even contaminated COS in the nitrogen gas cylinder could be detected. If necessary, H₂S was removed selectively by reproducible adsorbent columns. COS concentrations of engine exhaust were measured by the proposed method and by cryo-trap-gas chromatography-flame photometric detection, and the results obtained (0.5-5.9 ppbv) by the two methods agreed well (R ² = 0.945, n = 19). COS in ambient air and exhaust gases was successfully measured without any batchwise pretreatment.

Progress toward colorimetric and fluorescent detection of carbonyl sulfide

We report here that a fluorescent benzobisimidazolium salt (TBBI) can be used for the fluorescent and colorimetric detection of carbonyl sulfide (COS) over related heterocumulenes including CO2 and CS2 in wet MeCN. The reaction between TBBI and COS in the presence of fluoride yields a highly fluorescent (λem = 354 nm) and colored product (λmax = 321, 621 nm), that is readily observed by the naked eye. We view these results as a first step toward developing activity-based probes for COS detection.

Absorption lines measurements of carbon disulfide at 4.6 μm with quantum cascade laser absorption spectroscopy

We report measured line intensities and air- and self-broadening coefficients for fifty-one carbon disulfide transitions in the ν1 + ν3 band near 4.6 μm. This spectral region was chosen due to the strong carbon disulfide absorption strength and in the range of the mid-infrared atmospheric window for laser-based sensing applications. Spectroscopic parameters were determined by spectra measuring with quantum cascade laser direct absorption spectroscopy and multi-line fitting with Voigt lineshape. These measured results would facilitate the development of calibrated-free mid-infrared carbon disulfide sensors.

Esterase-Triggered Self-Immolative Thiocarbamates Provide Insights into COS Cytotoxicity

Hydrogen sulfide (H₂S) is an important gasotransmitter and biomolecule, and many synthetic small-molecule H₂S donors have been developed for H₂S-related research. One important class of triggerable H₂S donors is self-immolative thiocarbamates, which function by releasing carbonyl sulfide (COS), which is rapidly converted to H₂S by the ubiquitous enzyme carbonic anhydrase (CA). Prior studies of esterase-triggered thiocarbamate donors reported significant inhibition of mitochondrial bioenergetics and toxicity when compared to direct sulfide donors, suggesting that COS may function differently than H₂S. Here, we report a suite of modular esterase-triggered self-immolative COS donors and include the synthesis, H₂S release profiles, and cytotoxicity of the developed donors. We demonstrate that the rate of ester hydrolysis correlates directly with the observed cytotoxicity in cell culture, which further supports the hypothesis that COS functions as more than a simple H₂S shuttle in certain biological systems.

Breath analysis in respiratory diseases: state-of-the-art and future perspectives

INTRODUCTION

The vast majority of respiratory diseases are associated with the production of volatile organic compounds (VOCs), the analysis of which might improve our knowledge about these disorders and their clinical management. The aim of this narrative review is to provide a comprehensive summary of current evidence supporting the application of breath analysis in the field of respiratory diseases, as well as suggesting potential applications available in the near future. Areas covered: A computerized literature search was performed to identify relevant articles reporting original data on the clinical use of breath analysis in respiratory diseases. Papers focusing on diseases other than respiratory, technical issues of VOC sampling and analysis, in vitro experiments or exogenous compounds were excluded. Expert commentary: Currently available evidence on the application of breath analysis in respiratory diseases is encouraging; however, it is mostly based on single-center studies without external validation. The standardization of the technique, together with multicenter clinical trials with external validation, will ensure it is ready for clinical use. Current and new applications in respiratory diseases may represent a major breakthrough in the field, so much so as to deserve further efforts in outlining the most effective way to apply VOC analysis for clinical purposes.

Emerging Roles of Carbonyl Sulfide in Chemical Biology: Sulfide Transporter or Gasotransmitter?

SIGNIFICANCE

Carbonyl sulfide (COS) is the most prevalent sulfur-containing gas in the Earth's atmosphere, and it plays important roles in the global sulfur cycle. COS has been implicated in origin of life peptide ligation, is the primary energy source for certain bacteria, and has been detected in mammalian systems. Despite this long and intertwined history with terrestrial biology, limited attention has focused on potential roles of COS as a biological mediator. Recent Advances: Although bacterial COS production is well documented, definitive sources of mammalian COS production have not been confirmed. Enzymatic COS consumption in mammals, however, is well documented and occurs primarily by carbonic anhydrase (CA)-mediated conversion to hydrogen sulfide (H2S). COS has been detected in ex vivo mammalian tissue culture, as well as in exhaled breath as a potential biomarker for different disease pathologies, including cystic fibrosis and organ rejection. Recently, chemical tools for COS delivery have emerged and are poised to advance future investigations into the role of COS in different biological contexts.

CRITICAL ISSUES

Possible roles of COS as an important biomolecule, gasotransmitter, or sulfide transport intermediate remain to be determined. Key advances in both biological and chemical tools for COS research are needed to further investigate these questions.

FUTURE DIRECTIONS

Further evaluation of the biological roles of COS and disentangling the chemical biology of COS from that of H2S are needed to further elucidate these interactions. Chemical tools for COS delivery and modulation may provide a first avenue of investigative tools to answer many of these questions. Antioxid. Redox Signal. 28, 1516-1532.

H2S and polysulfide metabolism: Conventional and unconventional pathways

It is now well established that hydrogen sulfide (H₂S) is an effector of a wide variety of physiological processes. It is also clear that many of the effects of H₂S are mediated through reactions with cysteine sulfur on regulatory proteins and most of these are not mediated directly by H₂S but require prior oxidation of H₂S and the formation of per- and polysulfides (H₂S_n, n = 2-8). Attendant with understanding the regulatory functions of H₂S and H₂S_n is an appreciation of the mechanisms that control, i.e., both increase and decrease, their production and catabolism. Although a number of standard "conventional" pathways have been described and well characterized, novel "unconventional" pathways are continuously being identified. This review summarizes our current knowledge of both the conventional and unconventional.

Exhaled Volatile Organic Compounds of Infection: A Systematic Review

With heightened global concern of microbial drug resistance, advanced methods for early and accurate diagnosis of infection are urgently needed. Analysis of exhaled breath volatile organic compounds (VOCs) toward detecting microbial infection potentially allows a highly informative and noninvasive alternative to current genomics and culture-based methods. We performed a systematic review of research literature reporting human and animal exhaled breath VOCs related to microbial infections. In this Review, we find that a wide range of breath sampling and analysis methods are used by researchers, which significantly affects interstudy method comparability. Studies either perform targeted analysis of known VOCs relating to an infection, or non-targeted analysis to obtain a global profile of volatile metabolites. In general, the field of breath analysis is still relatively immature, and there is much to be understood about the metabolic production of breath VOCs, particularly in a host where both commensal microflora as well as pathogenic microorganisms may be manifested in the airways. We anticipate that measures to standardize high throughput sampling and analysis, together with an increase in large scale collaborative international trials, will bring routine breath VOC analysis to improve diagnosis of infection closer to reality.

Inhibition of Mitochondrial Bioenergetics by Esterase-Triggered COS/H2S Donors

Hydrogen sulfide (H2S) is an important biological mediator, and synthetic H2S donating molecules provide an important class of investigative tools for H2S research. Here, we report esterase-activated H2S donors that function by first releasing carbonyl sulfide (COS), which is rapidly converted to H2S by the ubiquitous enzyme carbonic anhydrase (CA). We report the synthesis, self-immolative decomposition, and H2S release profiles of the developed scaffolds. In addition, the developed esterase-triggered COS/H2S donors exhibit higher levels of cytotoxicity than equivalent levels of Na2S or the common H2S donors GYY4137 and AP39. Using cellular bioenergetics measurements, we establish that the developed donors reduce cellular respiration and ATP synthesis in BEAS 2B human lung epithelial cells, which is consistent with COS/H2S inhibition of cytochrome c oxidase in the mitochondrial respiratory chain although not observed with common H2S donors at the same concentrations. Taken together, these results may suggest that COS functions differently than H2S in certain biological contexts or that the developed donors are more efficient at delivering H2S than other common H2S-releasing motifs.

A European Respiratory Society technical standard: exhaled biomarkers in lung disease

Breath tests cover the fraction of nitric oxide in expired gas (F_eNO), volatile organic compounds (VOCs), variables in exhaled breath condensate (EBC) and other measurements. For EBC and for F_eNO, official recommendations for standardised procedures are more than 10 years old and there is none for exhaled VOCs and particles. The aim of this document is to provide technical standards and recommendations for sample collection and analytic approaches and to highlight future research priorities in the field. For EBC and F_eNO, new developments and advances in technology have been evaluated in the current document. This report is not intended to provide clinical guidance on disease diagnosis and management.Clinicians and researchers with expertise in exhaled biomarkers were invited to participate. Published studies regarding methodology of breath tests were selected, discussed and evaluated in a consensus-based manner by the Task Force members.Recommendations for standardisation of sampling, analysing and reporting of data and suggestions for research to cover gaps in the evidence have been created and summarised.Application of breath biomarker measurement in a standardised manner will provide comparable results, thereby facilitating the potential use of these biomarkers in clinical practice.

Stable isotope profiles reveal active production of VOCs from human-associated microbes

Volatile organic compounds (VOCs) measured from exhaled breath have great promise for the diagnosis of bacterial infections. However, determining human or microbial origin of VOCs detected in breath remains a great challenge. For example, the microbial fermentation product 2,3-butanedione was recently found in the breath of Cystic Fibrosis (CF) patients; parallel culture-independent metagenomic sequencing of the same samples revealed that Streptococcus and Rothia spp. have the genetic capacity to produce 2,3-butanedione. To investigate whether the genetic capacity found in metagenomes translates to bacterial production of a VOC of interest such as 2,3-butanedione, we fed stable isotopes to three bacterial strains isolated from patients: two gram-positive bacteria, Rothia mucilaginosa and Streptococcus salivarius, and a dominant opportunistic gram-negative pathogen, Pseudomonas aeruginosa. Culture headspaces were collected and analyzed using a gas chromatographic system to quantify the abundance of VOCs of interest; mass spectroscopy was used to determine whether the stable isotope label had been incorporated. Our results show that R. mucilaginosa and S. salivarius consumed D-Glucose-¹³C₆ to produce labeled 2,3-butanedione. R. mucilaginosa and S. salivarius also produced labeled acetaldehyde and ethanol when grown with ²H₂O. Additionally, we find that P. aeruginosa growth and dimethyl sulfide production are increased when exposed to lactic acid in culture. These results highlight the importance VOCs produced by P. aeruginosa, R. mucilaginosa, and S. salivarius as nutrients and signals in microbial communities, and as potential biomarkers in a CF infection.

In vitro volatile organic compound profiling using GC×GC-TOFMS to differentiate bacteria associated with lung infections: a proof-of-concept study

Chronic pulmonary infections are the principal cause of morbidity and mortality in individuals with cystic fibrosis (CF). Due to the polymicrobial nature of these infections, the identification of the particular bacterial species responsible is an essential step in diagnosis and treatment. Current diagnostic procedures are time-consuming, and can also be expensive, invasive and unpleasant in the absence of spontaneously expectorated sputum. The development of a rapid, non-invasive methodology capable of diagnosing and monitoring early bacterial infection is desired. Future visions of real-time, in situ diagnosis via exhaled breath testing rely on the differentiation of bacteria based on their volatile metabolites. The objective of this proof-of-concept study was to investigate whether a range of CF-associated bacterial species (i.e. Pseudomonas aeruginosa, Burkholderia cenocepacia, Haemophilus influenzae, Stenotrophomonas maltophilia, Streptococcus pneumoniae and Streptococcus milleri) could be differentiated based on their in vitro volatile metabolomic profiles. Headspace samples were collected using solid phase microextraction (SPME), analyzed using comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS) and evaluated using principal component analysis (PCA) in order to assess the multivariate structure of the data. Although it was not possible to effectively differentiate all six bacteria using this method, the results revealed that the presence of a particular pattern of VOCs (rather than a single VOC biomarker) is necessary for bacterial species identification. The particular pattern of VOCs was found to be dependent upon the bacterial growth phase (e.g. logarithmic versus stationary) and sample storage conditions (e.g. short-term versus long-term storage at  -18 °C). Future studies of CF-associated bacteria and exhaled breath condensate will benefit from the approaches presented in this study and further facilitate the production of diagnostic tools for the early detection of bacterial lung infections.

Compact quantum cascade laser based quartz-enhanced photoacoustic spectroscopy sensor system for detection of carbon disulfide

A compact gas sensor system based on quartz-enhanced photoacoustic spectroscopy (QEPAS) employing a continuous wave (CW) distributed feedback quantum cascade laser (DFB-QCL) operating at 4.59 µm was developed for detection of carbon disulfide (CS₂) in air at trace concentration. The influence of water vapor on monitored QEPAS signal was investigated to enable compensation of this dependence by independent moisture sensing. A 1 σ limit of detection of 28 parts per billion by volume (ppbv) for a 1 s lock-in amplifier time constant was obtained for the CS₂ line centered at 2178.69 cm^-1 when the gas sample was moisturized with 2.3 vol% H₂O. The work reports the suitability of the system for monitoring CS₂ with high selectivity and sensitivity, as well as low sample gas volume requirements and fast sensor response for applications such as workplace air and process monitoring at industry.

Pediatric Cystic Fibrosis Sputum Can Be Chemically Dynamic, Anoxic, and Extremely Reduced Due to Hydrogen Sulfide Formation

Severe and persistent bacterial lung infections characterize cystic fibrosis (CF). While several studies have documented the microbial diversity within CF lung mucus, we know much less about the inorganic chemistry that constrains microbial metabolic processes and their distribution. We hypothesized that sputum is chemically heterogeneous both within and between patients. To test this, we measured microprofiles of oxygen and sulfide concentrations as well as pH and oxidation-reduction potentials in 48 sputum samples from 22 pediatric patients with CF. Inorganic ions were measured in 20 samples from 12 patients. In all cases, oxygen was depleted within the first few millimeters below the sputum-air interface. Apart from this steep oxycline, anoxia dominated the sputum environment. Different sputum samples exhibited a broad range of redox conditions, with either oxidizing (16 mV to 355 mV) or reducing (-300 to -107 mV) potentials. The majority of reduced samples contained hydrogen sulfide and had a low pH (2.9 to 6.5). Sulfide concentrations increased at a rate of 0.30 µM H2S/min. Nitrous oxide was detected in only one sample that also contained sulfide. Microenvironmental variability was observed both within a single patient over time and between patients. Modeling oxygen dynamics within CF mucus plugs indicates that anoxic zones vary as a function of bacterial load and mucus thickness and can occupy a significant portion of the mucus volume. Thus, aerobic respiration accounts only partially for pathogen survival in CF sputum, motivating research to identify mechanisms of survival under conditions that span fluctuating redox states, including sulfidic environments.

IMPORTANCE

Microbial infections are the major cause of morbidity and mortality in people living with CF, and yet microbial growth and survival in CF airways are not well understood. Insufficient information about the chemistry of the in vivo environment contributes to this knowledge gap. Our documentation of variable redox states corresponding to the presence or absence of sulfide begins to fill this void and motivates understanding of how different opportunistic pathogens adapt in these dynamic environments. Given the changing chemical state of CF sputum over time, it is important to consider a spectrum of aerobic and anaerobic lifestyles when studying CF pathogens in the laboratory. This work not only provides relevant constraints that can shape the design of laboratory experiments, it also suggests that sulfide might be a useful proxy for assessing the redox state of sputum in the clinic.

A Winogradsky-based culture system shows an association between microbial fermentation and cystic fibrosis exacerbation

There is a poor understanding of how the physiology of polymicrobial communities in cystic fibrosis (CF) lungs contributes to pulmonary exacerbations and lung function decline. In this study, a microbial culture system based on the principles of the Winogradsky column (WinCF system) was developed to study the physiology of CF microbes. The system used glass capillary tubes filled with artificial sputum medium to mimic a clogged airway bronchiole. Chemical indicators were added to observe microbial physiology within the tubes. Characterization of sputum samples from seven patients showed variation in pH, respiration, biofilm formation and gas production, indicating that the physiology of CF microbial communities varied among patients. Incubation of homogenized tissues from an explant CF lung mirrored responses of a Pseudomonas aeruginosa pure culture, supporting evidence that end-stage lungs are dominated by this pathogen. Longitudinal sputum samples taken through two exacerbation events in a single patient showed that a two-unit drop in pH and a 30% increase in gas production occurred in the tubes prior to exacerbation, which was reversed with antibiotic treatment. Microbial community profiles obtained through amplification and sequencing of the 16S rRNA gene showed that fermentative anaerobes became more abundant during exacerbation and were then reduced during treatment where P. aeruginosa became the dominant bacterium. Results from the WinCF experiments support the model where two functionally different CF microbial communities exist, the persistent Climax Community and the acute Attack Community. Fermentative anaerobes are hypothesized to be the core members of the Attack Community and production of acidic and gaseous products from fermentation may drive developing exacerbations. Treatment targeting the Attack Community may better resolve exacerbations and resulting lung damage.

Advances in electronic-nose technologies for the detection of volatile biomarker metabolites in the human breath

Recent advancements in the use of electronic-nose (e-nose) devices to analyze human breath profiles for the presence of specific volatile metabolites, known as biomarkers or chemical bio-indicators of specific human diseases, metabolic disorders and the overall health status of individuals, are providing the potential for new noninvasive tools and techniques useful to point-of-care clinical disease diagnoses. This exciting new area of electronic disease detection and diagnosis promises to yield much faster and earlier detection of human diseases and disorders, allowing earlier, more effective treatments, resulting in more rapid patient recovery from various afflictions. E-nose devices are particularly suited for the field of disease diagnostics, because they are sensitive to a wide range of volatile organic compounds (VOCs) and can effectively distinguish between different complex gaseous mixtures via analysis of electronic aroma sensor-array output profiles of volatile metabolites present in the human breath. This review provides a summary of some recent developments of electronic-nose technologies, particularly involving breath analysis, with the potential for providing many new diagnostic applications for the detection of specific human diseases associated with different organs in the body, detectable from e-nose analyses of aberrant disease-associated VOCs present in air expired from the lungs.

Breath analysis as a potential and non-invasive frontier in disease diagnosis: an overview

Currently, a small number of diseases, particularly cardiovascular (CVDs), oncologic (ODs), neurodegenerative (NDDs), chronic respiratory diseases, as well as diabetes, form a severe burden to most of the countries worldwide. Hence, there is an urgent need for development of efficient diagnostic tools, particularly those enabling reliable detection of diseases, at their early stages, preferably using non-invasive approaches. Breath analysis is a non-invasive approach relying only on the characterisation of volatile composition of the exhaled breath (EB) that in turn reflects the volatile composition of the bloodstream and airways and therefore the status and condition of the whole organism metabolism. Advanced sampling procedures (solid-phase and needle traps microextraction) coupled with modern analytical technologies (proton transfer reaction mass spectrometry, selected ion flow tube mass spectrometry, ion mobility spectrometry, e-noses, etc.) allow the characterisation of EB composition to an unprecedented level. However, a key challenge in EB analysis is the proper statistical analysis and interpretation of the large and heterogeneous datasets obtained from EB research. There is no standard statistical framework/protocol yet available in literature that can be used for EB data analysis towards discovery of biomarkers for use in a typical clinical setup. Nevertheless, EB analysis has immense potential towards development of biomarkers for the early disease diagnosis of diseases.

Carbon disulfide mediates socially-acquired nicotine self-administration

The social environment plays a critical role in smoking initiation as well as relapse. We previously reported that rats acquired nicotine self-administration with an olfactogustatory cue only when another rat consuming the same cue was present during self-administration. Because carbon disulfide (CS₂) mediates social learning of food preference in rodents, we hypothesized that socially acquired nicotine self-administration is also mediated by CS₂. We tested this hypothesis by placing female adolescent Sprague-Dawley rats in operant chambers equipped with two lickometers. Licking on the active spout meeting a fixed-ratio 10 schedule triggered the concurrent delivery of an i.v. infusion (saline, or 30 µg/kg nicotine, free base) and an appetitive olfactogustatory cue containing CS₂ (0–500 ppm). Rats that self-administered nicotine with the olfactogustatory cue alone licked less on the active spout than on the inactive spout. Adding CS₂ to the olfactogustatory cue reversed the preference for the spouts. The group that received 500 ppm CS₂ and the olfactogustatory cue obtained a significantly greater number of nicotine infusions than other groups. After extinction training, the original self-administration context reinstated nicotine-seeking behavior in all nicotine groups. In addition, in rats that received the olfactogustatory cue and 500 ppm CS₂ during SA, a social environment where the nicotine-associated olfactory cue is present, induced much stronger drug-seeking behavior compared to a social environment lacking the olfactogustatory cue. These data established that CS₂ is a critical signal that mediates social learning of nicotine self-administration with olfactogustatory cues in rodents. Additionally, these data showed that the social context can further enhance the drug-seeking behavior induced by the drug-taking environment.

Breath gas metabolites and bacterial metagenomes from cystic fibrosis airways indicate active pH neutral 2,3-butanedione fermentation

The airways of cystic fibrosis (CF) patients are chronically colonized by patient-specific polymicrobial communities. The conditions and nutrients available in CF lungs affect the physiology and composition of the colonizing microbes. Recent work in bioreactors has shown that the fermentation product 2,3-butanediol mediates cross-feeding between some fermenting bacteria and Pseudomonas aeruginosa, and that this mechanism increases bacterial current production. To examine bacterial fermentation in the respiratory tract, breath gas metabolites were measured and several metagenomes were sequenced from CF and non-CF volunteers. 2,3-butanedione was produced in nearly all respiratory tracts. Elevated levels in one patient decreased during antibiotic treatment, and breath concentrations varied between CF patients at the same time point. Some patients had high enough levels of 2,3-butanedione to irreversibly damage lung tissue. Antibiotic therapy likely dictates the activities of 2,3-butanedione-producing microbes, which suggests a need for further study with larger sample size. Sputum microbiomes were dominated by P. aeruginosa, Streptococcus spp. and Rothia mucilaginosa, and revealed the potential for 2,3-butanedione biosynthesis. Genes encoding 2,3-butanedione biosynthesis were disproportionately abundant in Streptococcus spp, whereas genes for consumption of butanedione pathway products were encoded by P. aeruginosa and R. mucilaginosa. We propose a model where low oxygen conditions in CF lung lead to fermentation and a decrease in pH, triggering 2,3-butanedione fermentation to avoid lethal acidification. We hypothesize that this may also increase phenazine production by P. aeruginosa, increasing reactive oxygen species and providing additional electron acceptors to CF microbes.

Hydrogen sulfide as a potential biomarker of asthma

Hydrogen sulfide (H2S), a gas characterized by the odor of rotten eggs, is produced by many cells in the airways and lungs, and may regulate physiologic and pathophysiologic processes. It plays a role in cellular signaling, and represents the third gasotransmitter after nitric oxide and carbon monoxide. Endogenous and exogenous H₂S have anti-inflammatory and anti-proliferative effects, with inhibitory effects in models of lung inflammation and fibrosis. Under certain conditions, H₂S may also be proinflammatory. It is generally a vasodilator and relaxant of airway and vascular smooth muscle cells. It acts as a reducing agent, being able to scavenge superoxide and peroxynitrite. H₂S is detectable in serum and in sputum supernatants with raised levels observed in asthmatics. The sputum levels correlated inversely with lung function. H₂S may play a role in the pathogenesis of asthma.

Relations between isoprene and nitric oxide in exhaled breath and the potential influence of outdoor ozone: a pilot study

The role of endogenous isoprene in the human body, if any, is unclear because previous research is inconsistent and mechanistic evidence for the biologic function of isoprene is lacking. Given previous evidence that exhaled isoprene is elevated in systemic inflammatory states, we hypothesized that exhaled isoprene would be positively associated with a breath biomarker of airway inflammation, the fractional concentration of exhaled nitric oxide (FENO). We examined relationships of exhaled breath isoprene with FENO and with outdoor ozone given that ozone chemically reacts with isoprene and has been positively associated with FENO in past studies. Sixteen elderly subjects were followed with ≤12 weekly exhaled hydrocarbon and FENO collections at the subjects' retirement community. Outdoor ozone concentrations were measured continuously on site. Mixed-effects regression analyses tested relations of FENO with isoprene, and FENO and isoprene with ozone, adjusted for temperature. We found FENO was inversely associated with isoprene, and this was not confounded by ozone. Isoprene was inversely related to ozone. FENO was positively related to ozone and this relation was not confounded by isoprene. In contrast to hypothesized relations, we conclude that exhaled isoprene is inversely associated with FENO as well as outdoor ozone, which suggests possible protective ozone-scavenging functions of endogenous isoprene. Findings may indicate chemical reactions of isoprene oxidation by ozone and by hydroxyl radicals in the presence of O2 that is dependent on NO concentration. These preliminary results need to be confirmed in additional studies of human subjects, particularly as they apply to FENO monitoring in asthma.

Elevated carbon monoxide in the exhaled breath of mice during a systemic bacterial infection

Blood is the specimen of choice for most laboratory tests for diagnosis and disease monitoring. Sampling exhaled breath is a noninvasive alternative to phlebotomy and has the potential for real-time monitoring at the bedside. Improved instrumentation has advanced breath analysis for several gaseous compounds from humans. However, application to small animal models of diseases and physiology has been limited. To extend breath analysis to mice, we crafted a means for collecting nose-only breath samples from groups and individual animals who were awake. Samples were subjected to gas chromatography and mass spectrometry procedures developed for highly sensitive analysis of trace volatile organic compounds (VOCs) in the atmosphere. We evaluated the system with experimental systemic infections of severe combined immunodeficiency Mus musculus with the bacterium Borrelia hermsii. Infected mice developed bacterial densities of ∼10⁷ per ml of blood by day 4 or 5 and in comparison to uninfected controls had hepatosplenomegaly and elevations of both inflammatory and anti-inflammatory cytokines. While 12 samples from individual infected mice on days 4 and 5 and 6 samples from uninfected mice did not significantly differ for 72 different VOCs, carbon monoxide (CO) was elevated in samples from infected mice, with a mean (95% confidence limits) effect size of 4.2 (2.8–5.6), when differences in CO₂ in the breath were taken into account. Normalized CO values declined to the uninfected range after one day of treatment with the antibiotic ceftriaxone. Strongly correlated with CO in the breath were levels of heme oxygenase-1 protein in serum and HMOX1 transcripts in whole blood. These results (i) provide further evidence of the informativeness of CO concentration in the exhaled breath during systemic infection and inflammation, and (ii) encourage evaluation of this noninvasive analytic approach in other various other rodent models of infection and for utility in clinical management.

Gas signatures from Escherichia coli and Escherichia coli-inoculated human whole blood

BACKGROUND

The gaseous headspace above naïve Escherichia Coli (E. coli) cultures and whole human blood inoculated with E. coli were collected and analyzed for the presence of trace gases that may have the potential to be used as novel, non-invasive markers of infectious disease.

METHODS

The naïve E. coli culture, LB broth, and human whole blood or E. coli inoculated whole blood were incubated in hermetically sealable glass bioreactors at 37°C for 24 hrs. LB broth and whole human blood were used as controls for background volatile organic compounds (VOCs). The headspace gases were collected after incubation and analyzed using a gas chromatographic system with multiple column/detector combinations.

RESULTS

Six VOCs were observed to be produced by E. coli-infected whole blood while there existed nearly zero to relatively negligible amounts of these gases in the whole blood alone, LB broth, or E. coli-inoculated LB broth. These VOCs included dimethyl sulfide (DMS), carbon disulfide (CS2), ethanol, acetaldehyde, methyl butanoate, and an unidentified gas S. In contrast, there were several VOCs significantly elevated in the headspace above the E. coli in LB broth, but not present in the E. coli/blood mixture. These VOCs included dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), methyl propanoate, 1-propanol, methylcyclohexane, and unidentified gases R2 and Q.

CONCLUSIONS

This study demonstrates 1) that cultivated E. coli in LB broth produce distinct gas profiles, 2) for the first time, the ability to modify E. coli-specific gas profiles by the addition of whole human blood, and 3) that E. coli-human whole blood interactions present different gas emission profiles that have the potential to be used as non-invasive volatile biomarkers of E. coli infection.

Clinical use of exhaled volatile organic compounds in pulmonary diseases: a systematic review

There is an increasing interest in the potential of exhaled biomarkers, such as volatile organic compounds (VOCs), to improve accurate diagnoses and management decisions in pulmonary diseases. The objective of this manuscript is to systematically review the current knowledge on exhaled VOCs with respect to their potential clinical use in asthma, lung cancer, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), and respiratory tract infections. A systematic literature search was performed in PubMed, EMBASE, Cochrane database, and reference lists of retrieved studies. Controlled, clinical, English-language studies exploring the diagnostic and monitoring value of VOCs in asthma, COPD, CF, lung cancer and respiratory tract infections were included. Data on study design, setting, participant characteristics, VOCs techniques, and outcome measures were extracted. Seventy-three studies were included, counting in total 3,952 patients and 2,973 healthy controls. The collection and analysis of exhaled VOCs is non-invasive and could be easily applied in the broad range of patients, including subjects with severe disease and children. Various research groups demonstrated that VOCs profiles could accurately distinguish patients with a pulmonary disease from healthy controls. Pulmonary diseases seem to be characterized by a disease specific breath-print, as distinct profiles were found in patients with dissimilar diseases. The heterogeneity of studies challenged the inter-laboratory comparability. In conclusion, profiles of VOCs are potentially able to accurately diagnose various pulmonary diseases. Despite these promising findings, multiple challenges such as further standardization and validation of the diverse techniques need to be mastered before VOCs can be applied into clinical practice.

The clinical potential of exhaled breath analysis for diabetes mellitus

Various compounds in present human breath have long been loosely associated with pathological states (including acetone smell in uncontrolled diabetes). Only recently, however, the precise measurement of exhaled volatile organic compounds (VOCs) and aerosolized particles was made possible at extremely low concentrations by advances in several analytical methodologies, described in detail in the international literature and each suitable for specific subsets of exhaled compounds. Exhaled gases may be generated endogenously (in the pulmonary tract, blood, or peripheral tissues), as metabolic by-products of human cells or colonizing micro-organisms, or may be inhaled as atmospheric pollutants; growing evidence indicates that several of these molecules have distinct cell-to-cell signaling functions. Independent of origin and physiological role, exhaled VOCs are attractive candidates as biomarkers of cellular activity/metabolism, and could be incorporated in future non-invasive clinical testing devices. Indeed, several recent studies reported altered exhaled gas profiles in dysmetabolic conditions and relatively accurate predictions of glucose concentrations, at least in controlled experimental conditions, for healthy and diabetic subjects over a broad range of glycemic values. Optimization of this methodology and validation in large-scale trials under a wider range of conditions is needed to determine its true potential to transition into practical clinical use.

Mitochondrial adaptations to utilize hydrogen sulfide for energy and signaling

Sulfur is a versatile molecule with oxidation states ranging from -2 to +6. From the beginning, sulfur has been inexorably entwined with the evolution of organisms. Reduced sulfur, prevalent in the prebiotic Earth and supplied from interstellar sources, was an integral component of early life as it could provide energy through oxidization, even in a weakly oxidizing environment, and it spontaneously reacted with iron to form iron-sulfur clusters that became the earliest biological catalysts and structural components of cells. The ability to cycle sulfur between reduced and oxidized states may have been key in the great endosymbiotic event that incorporated a sulfide-oxidizing α-protobacteria into a host sulfide-reducing Archea, resulting in the eukaryotic cell. As eukaryotes slowly adapted from a sulfidic and anoxic (euxinic) world to one that was highly oxidizing, numerous mechanisms developed to deal with increasing oxidants; namely, oxygen, and decreasing sulfide. Because there is rarely any reduced sulfur in the present-day environment, sulfur was historically ignored by biologists, except for an occasional report of sulfide toxicity. Twenty-five years ago, it became evident that the organisms in sulfide-rich environments could synthesize ATP from sulfide, 10 years later came the realization that animals might use sulfide as a signaling molecule, and only within the last 4 years did it become apparent that even mammals could derive energy from sulfide generated in the gastrointestinal tract. It has also become evident that, even in the present-day oxic environment, cells can exploit the redox chemistry of sulfide, most notably as a physiological transducer of oxygen availability. This review will examine how the legacy of sulfide metabolism has shaped natural selection and how some of these ancient biochemical pathways are still employed by modern-day eukaryotes.

The message in the air: hydrogen sulfide metabolism in chronic respiratory diseases

Hydrogen sulfide (H(2)S) is an important gasotransmitter in the mammalian respiratory system. The enzymes that produce H(2)S - mainly cystathionine-β-synthase and cystathionine-γ-lyase - are expressed in pulmonary and airway tissues. Endogenous H(2)S participates in the regulation of the respiratory system's physiological functions and pathophysiological alterations, such as chronic obstructive pulmonary disease, asthma, pulmonary fibrosis and hypoxia-induced pulmonary hypertension, to name a few. The cellular targets of H(2)S in the respiratory system are diverse, including airway smooth muscle cells, epithelial cells, fibroblasts, and pulmonary artery smooth muscle cells. H(2)S also regulates respiratory functions such as airway constriction, pulmonary circulation, cell proliferation or apoptosis, fibrosis, oxidative stress, and neurogenic inflammation. Cross-talk between H(2)S and other gasotransmitters also affects the net outcome of lung function. The metabolism of H(2)S in the lungs and airway may serve as a biomarker for specific respiratory diseases. It is expected that strategies targeted at the metabolism and function of H(2)S will prove useful for the prevention and treatment of selective chronic respiratory diseases.

Noninvasive measurement of plasma triglycerides and free fatty acids from exhaled breath

BACKGROUND

Although altered metabolism has long been known to affect human breath, generating clinically usable metabolic tests from exhaled compounds has proven challenging. If developed, a breath-based lipid test would greatly simplify management of diabetes and serious pathological conditions (e.g., obesity, familial hyperlipidemia, and coronary artery disease), in which systemic lipid levels are a critical risk factor for onset and development of future cardiovascular events.

METHODS

We, therefore, induced controlled fluctuations of plasma lipids (insulin-induced lipid suppression or intravenous infusion of Intralipid) during 4-h in vivo experiments on 23 healthy volunteers (12 males/11 females, 28.0 ± 0.3 years) to find correlations between exhaled volatile organic compounds and plasma lipids. In each subject, plasma triglycerides (TG) and free fatty acids (FFA) concentrations were both directly measured and calculated via individualized prediction equations based on the multiple linear regression analysis of a cluster of 4 gases. In the lipid infusion protocol, we also generated common prediction equations using a maximum of 10 gases.

RESULTS

This analysis yielded strong correlations between measured and predicted values during both lipid suppression (r = 0.97 for TG; r = 0.90 for FFA) and lipid infusion (r = 0.97 for TG; r = 0.94 for FFA) studies. In our most accurate common prediction model, measured and predicted TG and FFA values also displayed very strong statistical agreement (r = 0.86 and r = 0.81, respectively).

CONCLUSIONS

Our results demonstrate the feasibility of measuring plasma lipids through breath analysis. Optimization of this technology may ultimately lead to the development of portable breath analyzers for plasma lipids, replacing blood-based bioassays.

Laser spectroscopy on volatile sulfur compounds: possibilities for breath analysis

There is an emerging interest in the detection of volatile sulfur compounds (VSCs) in the breath environment, given their biological relevance as potential signatures of several pathological conditions. Particularly, laser-based spectroscopic sensors are candidates for conducting accurate breath diagnostics in clinical settings. With these aims in mind, the current status of VSC sensing via laser absorption spectroscopy is reviewed in this paper. Attention has been focused on the most promising exhaled markers of pathological conditions, namely hydrogen sulfide, carbonyl sulfide, methanethiol, carbon disulfide and dimethyl sulfide. Details of the most relevant spectroscopic studies conducted on such molecules are presented, together with suggestions on the future direction of this challenging analytical field.

The therapeutic potential of hydrogen sulfide: separating hype from hope

Hydrogen sulfide (H(2)S) has become the hot new signaling molecule that seemingly affects all organ systems and biological processes in which it has been investigated. It has also been shown to have both proinflammatory and anti-inflammatory actions and proapoptotic and anti-apoptotic effects and has even been reported to induce a hypometabolic state (suspended animation) in a few vertebrates. The exuberance over potential clinical applications of natural and synthetic H(2)S-"donating" compounds is understandable and a number of these function-targeted drugs have been developed and show clinical promise. However, the concentration of H(2)S in tissues and blood, as well as the intrinsic factors that affect these levels, has not been resolved, and it is imperative to address these points to distinguish between the physiological, pharmacological, and toxicological effects of this molecule. This review will provide an overview of H(2)S metabolism, a summary of many of its reported "physiological" actions, and it will discuss the recent development of a number of H(2)S-donating drugs that show clinical potential. It will also examine some of the misconceptions of H(2)S chemistry that have appeared in the literature and attempt to realign the definition of "physiological" H(2)S concentrations upon which much of this exuberance has been established.

Detection of exhaled hydrogen sulphide gas in healthy human volunteers during intravenous administration of sodium sulphide

INTRODUCTION

Hydrogen sulphide (H(2)S) is an endogenous gaseous signaling molecule and potential therapeutic agent. Emerging studies indicate its therapeutic potential in a variety of cardiovascular diseases and in critical illness. Augmentation of endogenous sulphide concentrations by intravenous administration of sodium sulphide can be used for the delivery of H(2)S to the tissues. In the current study, we have measured H(2)S concentrations in the exhaled breath of healthy human volunteers subjected to increasing doses sodium sulphide in a human phase I safety and tolerability study.

METHODS

We have measured reactive sulphide in the blood via ex vivo derivatization of sulphide with monobromobimane to form sulphide-dibimane and blood concentrations of thiosulfate (major oxidative metabolite of sulphide) via ion chromatography. We have measured exhaled H(2)S concentrations using a custom-made device based on a sulphide gas detector (Interscan).

RESULTS

Administration of IK-1001, a parenteral formulation of Na(2)S (0.005-0.20 mg kg(-1), i.v., infused over 1 min) induced an elevation of blood sulphide and thiosulfate concentrations over baseline, which was observed within the first 1-5 min following administration of IK-1001 at 0.10 mg kg(-1) dose and higher. In all subjects, basal exhaled H(2)S was observed to be higher than the ambient concentration of H(2)S gas in room air, indicative of on-going endogenous H(2)S production in human subjects. Upon intravenous administration of Na(2)S, a rapid elevation of exhaled H(2)S concentrations was observed. The amount of exhaled H(2)S rapidly decreased after discontinuation of the infusion of Na(2)S.

CONCLUSION

Exhaled H(2)S represents a detectable route of elimination after parenteral administration of Na(2)S.

Multicomponent Breath Analysis With Infrared Absorption Using Room-Temperature Quantum Cascade Lasers

Breath analysis is a powerful noninvasive technique for the diagnosis and monitoring of respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD). Nitric oxide (NO) and carbon monoxide (CO) are markers of airway inflammation and can indicate the extent of respiratory diseases. We have developed a compact fast response laser system for analysis of multiple gases by infrared absorption. The instrument uses room temperature quantum cascade lasers to simultaneously measure NO, CO, carbon dioxide (CO(2)) and nitrous oxide (N(2)O) in exhaled breath. Four breath flow rates are employed to explore their exchange dynamics in the lungs and airways. We obtain 1-s detection precisions of 0.5-0.8 parts-per-billion (ppb) for NO, CO, and N(2)O with an instrument response time of less than 1 s. The breath analysis system has been demonstrated in a preliminary study of volunteers. It is currently deployed in a trial clinical study.

Ethane and n-pentane in exhaled breath are biomarkers of exposure not effect

The relationship of exhaled ethane and n-pentane to exhaled NO, carbonylated proteins, and indoor/outdoor atmospheric pollutants were examined in order to evaluate ethane and n-pentane as potential markers of airway inflammation and/or oxidative stress. Exhaled NO and carbonylated proteins were found to have no significant associations with either ethane (p = 0.96 and p = 0.81, respectively) or n-pentane (p = 0.44 and 0.28, respectively) when outliers were included. In the case where outliers were removed n-pentane was found to be inversely associated with carbonylated proteins. Exhaled hydrocarbons adjusted for indoor hydrocarbon concentrations were instead found to be positively associated with air pollutants (NO, NO(2) and CO), suggesting pollutant exposure is driving exhaled hydrocarbon concentrations. Given these findings, ethane and n-pentane do not appear to be markers of airway inflammation or oxidative stress.

Improved pre-concentration and detection methods for volatile sulphur breath constituents

Suitability of different types of pre-concentration (solid phase microextraction and sorbent trapping) and detection (flame photometric detector (FPD) and mass selective detector (MSD)) for gas chromatographic determination of sulphur-containing compounds (H2S, MeSH, EtSH, DMS, COS and CS2) in breath-gas was assessed in this study. Several factors like influence of humidity, influence of oxygen, or stability of target compounds in extraction vessels (SPME vials and sorbent tubes) were investigated. Despite poor stability of VSCs in SPME vials and matrix effects (unfavorable influence of humidity), SPME was found to be a fast and reliable enrichment method, which coupled with mass selective detector provided satisfactory LODs of target compounds at the ppt level (from 0.15 ppb for CS2 to 2.3 ppb for H2S). Application of sorbent trapping with two-bed sorbent tubes containing Tenax TA and Carboxen 1000 gave excellent LODs (0.03-0.3 ppb for 200 ml sample and MSD). Stability of investigated VSCs in sorbents was found to be very poor (30-40% losses after 2 h). FPD showed satisfactory sensitivity only when it was coupled with sorbent trapping. Breath samples were collected into Tedlar bags in a CO2-controlled manner. Humidity was removed during sampling (permeation dryer--Nafion) to avoid unfavorable water dependent effects during analysis.

Acetaldehyde and hexanaldehyde from cultured white cells

BACKGROUND

Noninvasive detection of innate immune function such as the accumulation of neutrophils remains a challenge in many areas of clinical medicine. We hypothesized that granulocytes could generate volatile organic compounds.

METHODS

To begin to test this, we developed a bioreactor and analytical GC-MS system to accurately identify and quantify gases in trace concentrations (parts per billion) emitted solely from cell/media culture. A human promyelocytic leukemia cell line, HL60, frequently used to assess neutrophil function, was grown in serum-free medium.

RESULTS

HL60 cells released acetaldehyde and hexanaldehyde in a time-dependent manner. The mean +/- SD concentration of acetaldehyde in the headspace above the cultured cells following 4-, 24- and 48-h incubation was 157 +/- 13 ppbv, 490 +/- 99 ppbv, 698 +/- 87 ppbv. For hexanaldehyde these values were 1 +/- 0.3 ppbv, 8 +/- 2 ppbv, and 11 +/- 2 ppbv. In addition, our experimental system permitted us to identify confounding trace gas contaminants such as styrene.

CONCLUSION

This study demonstrates that human immune cells known to mimic the function of innate immune cells, like neutrophils, produce volatile gases that can be measured in vitro in trace amounts.

Exhaled methyl nitrate as a noninvasive marker of hyperglycemia in type 1 diabetes

Recent technical advances allow detection of several hundred volatile organic compounds (VOCs) in human exhaled air, many of which reflect unidentified endogenous pathways. Our group has previously estimated plasma glucose levels in healthy adults during a standard oral glucose tolerance test via exhaled VOC analysis. As a result of the metabolic characteristics of hyperglycemia in the diabetic (low insulin and increased free fatty acids and ketones), we hypothesized that different exhaled VOC profiles may be present in children with type 1 diabetes mellitus (T1DM) during spontaneous hyperglycemia. Exhaled methyl nitrate strongly correlated specifically with the acute, spontaneous hyperglycemia of T1DM children. Eighteen experiments were conducted among 10 T1DM children. Plasma glucose and exhaled gases were monitored during either constant euglycemia (n = 5) or initial hyperglycemia with gradual correction (n = 13); all subjects received i.v. insulin and glucose as needed. Gas analysis was performed on 1.9-liter breath samples via gas chromatography using electron capture, flame ionization, and mass selective detection. Among the approximately 100 measured exhaled gases, the kinetic profile of exhaled methyl nitrate, commonly present in room air in the range of 5-10 parts per trillion, was most strongly statistically correlated with that of plasma glucose (P = 0.003-0.001). Indeed, the kinetic profiles of the two variables paralleled each other in 16 of 18 experiments, including repeat subjects who at different times displayed either euglycemia or hyperglycemia.