Defining adult asthma endotypes by clinical features and patterns of volatile organic compounds in exhaled air

Background

Several classifications of adult asthma patients using cluster analyses based on clinical and demographic information has resulted in clinical phenotypic clusters that do not address molecular mechanisms. Volatile organic compounds (VOC) in exhaled air are released during inflammation in response to oxidative stress as a result of activated leukocytes. VOC profiles in exhaled air could distinguish between asthma patients and healthy subjects. In this study, we aimed to classify new asthma endotypes by combining inflammatory mechanisms investigated by VOC profiles in exhaled air and clinical information of asthma patients.

Methods

Breath samples were analyzed for VOC profiles by gas chromatography–mass spectrometry from asthma patients (n = 195) and healthy controls (n = 40). A total of 945 determined compounds were subjected to discriminant analysis to find those that could discriminate healthy from asthmatic subjects. 2-step cluster analysis based on clinical information and VOCs in exhaled air were used to form asthma endotypes.

Results

We identified 16 VOCs, which could distinguish between healthy and asthma subjects with a sensitivity of 100% and a specificity of 91.1%. Cluster analysis based on VOCs in exhaled air and the clinical parameters FEV1, FEV1 change after 3 weeks of hospitalization, allergic sensitization, Junipers symptoms score and asthma medications resulted in the formation of 7 different asthma endotype clusters. We identified asthma clusters with different VOC profiles but similar clinical characteristics and endotypes with similar VOC profiles, but distinct clinical characteristics.

Conclusion

This study demonstrates that both, clinical presentation of asthma and inflammatory mechanisms in the airways should be considered for classification of asthma subtypes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-014-0136-8) contains supplementary material, which is available to authorized users.     

Preliminary investigation of using volatile organic compounds from human expired air, blood and urine for locating entrapped people in earthquakes

A preliminary investigation on the possibility of using volatile organic compounds (VOCs) determination of expired air, blood and urine, for the early location of entrapped people in earthquakes, has been carried out. A group of 15 healthy subjects has been sampled. The identification of a common "core" of substances might provide indications of human presence that can be used for the development of a real time field analytical method for the on site detection of entrapped people. Expired air samples have been analyzed by thermal desorption GC/MS and VOCs from blood and urine by headspace SPME-GC/MS. Acetone was the only compound found common in all three matrices. Isoprene was found in both expired air and blood samples. Acetone and isoprene along with a number of saturated hydrocarbons were among the major constituents identified in expired air analysis. Various ketones (2-pentanone, 4-heptanone, 2-butanone) were also determined over urine specimens. Using the techniques and methods of field analytical chemistry and technology appears to be the proper approach for applying the results of the present study in real situations.     

The volatile organic compounds from the mycelium of Tuber borchii Vitt

The mycelium of T. borchii (characterized by DNA analysis) grown in sterile liquid medium produced some VOCs. The VOCs were retained on carbographs by passing a flow of helium, isolated and characterized in a GC-MS equipment after a thermal desorption. The compounds present in the VOCs from the mycelium cultures, but not in the VOCs from the control cultures, contained 29 compounds. The main compounds were 1,3-ditertbutylbenzene (16.1 ng/l), 3-methylheptane (9.2 ng/l), butan-2-one (8.8 ng/l), ethynylbenzene (5.6 ng/l), and octan-3-one (4.9 ng/l).     

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

Exhaled alveolar breath can provide a great deal of information about an individual's health and previous exposure to potentially harmful xenobiotic materials. Because breath can be obtained non-invasively and its constituents directly reflect concentrations in the blood, its use has many potential applications in the field of biomarker research. This paper reviews the utility and application of the single breath canister (SBC) method of alveolar breath collection and analysis first developed by the US Environmental Protection Agency (USEPA) in the 1990s. This review covers the development of the SBC technique in the laboratory and its application in a range of field studies. Together these studies specifically show how the SBC method (and exhaled breath analysis in general) can be used to clearly demonstrate recent exposure to volatile organic compounds, to link particular activities to specific exposures, to determine compoundspecific uptake and elimination kinetics, and to assess the relative importance of various routes of exposure (i.e. dermal, ingestion, inhalation) in multipathway scenarios. Specific investigations covered in this overview include an assessment of exposures related to the residential use of contaminated groundwater, exposures to gasoline and fuel additives at self-service gas stations, swimmers' exposures to trihalomethanes, and occupational exposures to jet fuel.     

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

Exhaled alveolar breath can provide a great deal of information about an individual's health and previous exposure to potentially harmful xenobiotic materials. Because breath can be obtained non-invasively and its constituents directly reflect concentrations in the blood, its use has many potential applications in the field of biomarker research. This paper reviews the utility and application of the single breath canister (SBC) method of alveolar breath collection and analysis first developed by the US Environmental Protection Agency (USEPA) in the 1990s. This review covers the development of the SBC technique in the laboratory and its application in a range of field studies. Together these studies specifically show how the SBC method (and exhaled breath analysis in general) can be used to clearly demonstrate recent exposure to volatile organic compounds, to link particular activities to specific exposures, to determine compoundspecific uptake and elimination kinetics, and to assess the relative importance of various routes of exposure (i.e. dermal, ingestion, inhalation) in multipathway scenarios. Specific investigations covered in this overview include an assessment of exposures related to the residential use of contaminated groundwater, exposures to gasoline and fuel additives at self-service gas stations, swimmers' exposures to trihalomethanes, and occupational exposures to jet fuel.     

Abatement of volatile organic sulfur compounds in odorous emissions from the bio-industry

Compounds of interest in this work are methanethiol (MeSH), dimethyl sulfide (Me₂S), dimethyl polysulfides (Me₂S_x) and carbon disulfide (CS₂) since these volatiles have been identified as predominant odorants in the emission of a wide range of activities in the bio-industry (e.g. aerobic waste water treatment plants, composting plants, rendering plants). In these processes, the occurrence of volatile organic sulfur compounds is mainly related to the presence of anaerobic microsites with consecutive fermentation of sulfur containing organic material and/or to the breakdown of the latter due to thermal heating. Due to the chemical complexity of these low-concentrated waste gas streams and the high flow rates to be handled, mainly biotechnological techniques and scrubbers can be used to control the odour emission. When using biofilters or trickling filters, inoculation with specific micro-organisms and pH-control strategies should be implemented to optimise the removal of volatile organic sulfur compounds. In scrubbers, chemical oxidation of the volatile organic sulfur compounds can be obtained by dosing hypochlorite, ozone or hydrogen peroxide to the scrubbing liquid. However, optimal operational conditions for each of these abatement techniques requires a further research in order to guarantee a long-term and efficient overall odour abatement.     

Production of volatile organic compounds by mycobacteria

The need for improved rapid diagnostic tests for tuberculosis disease has prompted interest in the volatile organic compounds (VOCs) emitted by Mycobacterium tuberculosis complex bacteria. We have investigated VOCs emitted by Mycobacterium bovis BCG grown on Lowenstein-Jensen media using selected ion flow tube mass spectrometry and thermal desorption-gas chromatography-mass spectrometry. Compounds observed included dimethyl sulphide, 3-methyl-1-butanol, 2-methyl-1-propanol, butanone, 2-methyl-1-butanol, methyl 2-methylbutanoate, 2-phenylethanol and hydrogen sulphide. Changes in levels of acetaldehyde, methanol and ammonia were also observed. The compounds identified are not unique to M.?bovis BCG, and further studies are needed to validate their diagnostic value. Investigations using an ultra-rapid gas chromatograph with a surface acoustic wave sensor (zNose) demonstrated the presence of 2-phenylethanol (PEA) in the headspace of cultures of M.?bovis BCG and Mycobacterium smegmatis, when grown on Lowenstein-Jensen supplemented with glycerol. PEA is a reversible inhibitor of DNA synthesis. It is used during selective isolation of gram-positive bacteria and may also be used to inhibit mycobacterial growth. PEA production was observed to be dependent on growth of mycobacteria. Further study is required to elucidate the metabolic pathways involved and assess whether this compound is produced during in vivo growth of mycobacteria.     

Elimination of volatile compounds of leaf tobacco from air emissions using biofiltration

The composition of the volatile organic compounds (VOCs) of various leaf tobacco brands and their blends has been studied. The differences in the content of nicotine, solanone, tetramethyl hexadecenol, megastigmatrienones, and other compounds, determining the specific tobacco smell, have been revealed. A microbial consortium, which is able to deodorize simulated tobacco emissions and decompose nicotine, has been formed by long-term adaptation to the VOCs of tobacco leaves in a laboratory reactor, functioning as a trickle-bed biofilter. Such a biofilter eliminates 90% of the basic toxic compound (nicotine) and odor-active compounds; the filtration efficiency does not change for tobacco brands with different VOC concentrations or in the presence of foreign substances. The main strains, isolated from the formed consortium and participating in the nicotine decomposition process, belong to the genera Pseudomonas, Bacillus, and Rhodococcus. An examination of the biofilter trickling fluid has shown full decomposition of nicotine and odor-active VOCs. The compounds, revealed in the trickling fluid, did not have any odor and were nontoxic. The obtained results make it possible to conduct scaling of the biofiltration process to eliminate odor from air emissions in the tobacco industry.     

白色麝香霉挥发性有机化合物的抗菌活性和组成分析

采用核糖体RNA转录间隔区(internal transcribed spacer of ribosomal RNA,ITS r RNA)、RNA聚合酶II(RNA polymerase II,rpb2)和β-维管蛋白(beta-tubulin,tub1)基因系统发育分析法,鉴定了一株分离自浙江庆元的麝香霉ZJQY709,鉴定结果表明该菌为白色麝香霉Muscodor albus。生长速率法测定结果显示该菌株最适生长温度为22–28℃。二分格培养皿对峙培养法测定该菌挥发性有机化合物的抑菌活性,结果表明其挥发性有机化合物对灰葡萄孢菌和立枯丝核菌的生长抑制作用较强,而对尖孢镰刀菌和终极腐霉的抑制作用较弱。固相微萃取/气质联用法分析该菌产生的挥发性有机化合物,结果显示其挥发性有机化合物成分复杂,主要气体成分为2-甲基丙酸、乙酸-2-甲基丙酯和1-丁醇-2-甲基乙酸。     

Determination of volatile organic compounds by solid-phase microextraction

The parameters of the process of isolation, concentration, and gas chromatographic analysis of volatile organic compounds by solid-phase microextraction were optimized. With different amounts of a mixture of essential oils, the conditions of reproducibility of their determination were established based on the absolute values of the squares of chromatographic peaks obtained by capillary gas chromatography. It was found that the efficiency of the extraction of volatile compounds from gas phase by sorption on mixed polymer (consisting of polydimethylsiloxane and divinylbenzene) was significantly influenced by the structure of their molecules, while the sorption time and their content in the liquid phase influenced the significance of determination.     

Consumption of volatile organic compounds by alcaliphilic microorganisms

It has been shown that various microbial species used in bioreactors for purification of air from volatile organic compounds can grow at alkaline pH values consuming the xenobiotics as sole carbon sources. The alkali tolerance depends on the carbon source. The alkaline pH of the medium reduces the foreign microbial population restricting the potential of the bioreactor.     

Consumption of volatile organic compounds by alcaliphilic microorganisms

It has been shown that various microbial species used in bioreactors for purification of air from volatile organic impurities can grow at alkaline pH values consuming the xenobiotics as sole carbon sources. The alkali tolerance depends on the carbon source. The alkaline pH of the medium reduces the foreign microbial population restricting the potential of the bioreactor.     

Identification of volatile organic compounds secreted from cancer tissues and bacterial cultures

The early cancer diagnosis increases the possibility of total recovery. The infection of Helicobacter pylori is associated with gastric cancer, the second most common cancer in the world. The determination of volatile organic compounds (VOCs) excreted by stomach tissue and bacteria culture has been investigated. Solid-phase microextraction (SPME) was used for preconcentration and the determination was accomplished by gas chromatography coupled with mass spectrometry (GC/MS). The samples of tissue were taken from five patients (ten samples) with stomach cancer and normal (non-cancerous) segments from other parts of the stomach were used as a control. Eighteen compounds were identified in stomach tissue and seven of them were present both in healthy and cancer tissue. These compounds assumed to be endogenous and acetone ratio (AR) was calculated for ethanol, butane, carbon disulfide, 1-propanol, 2-butanone and 2-pentanone. The data shows that amount of 1-propanol and carbon disulfide in the gaseous composition is higher in cancer tissue than in normal tissue. Eight compounds were identified both in bacteria and tissue. These data suggest that bacteria present in the stomach might cause the increase in the concentration of 1-propanol and carbon disulfide in emission from cancer tissue.     

Gas chromatography-mass spectrometry with headspace for the analysis of volatile organic compounds in waste water

Headspace analysis combined with high-resolution gas chromatography and detection by mass spectrometry was evaluated for the analysis of 53 volatile organic compounds (VOCs) in river waters, waste waters and treated water samples down to 0.1 microgl(-1) concentration levels. The conditions optimised included sample thermostatting time and temperature, autosampler parameters and the nature of salt, added to the sample. The pollutions origin and their seasonal rippling have been done. It was shown that the content of VOCs in river water mainly correlates to the content of these compounds in waste waters, which shows the anthropogenic character of the pollutions.     

Morphogenetic effects of some volatile,organic compounds on Pestalotia rhododendri

Summary Some volatile alcohols, acids, esters, aldehydes and ketones influenced the morphogenesis of Pestalotia rhododendri when added through the gas phase. Linear growth, formation of aerial hyphae and production of conidial spores were determined. Mostly, increasing amounts of test substance inhibited linear growth and only one case of stimulation was noticed, viz. by nonenal.Many substances stimulated formation of aerial hyphae, particularly allyl alcohol, acetaldehyde and nonanal, but inhibitions were more common.Spore production was promoted by compounds from all the chemical classes investigated. The activity decreased as follows; alcohols > esters > acids, aldehydes > ketones. Inhibitions of spore production were also observed.The effects were reproducible on two different media.Pestalotia sydowiana exhibited the same main responses as the other Pestalotia species, but only two substances, furfural and n-propanol, were observed to promote spore formation of this species.     

A mathematical model for breath gas analysis of volatile organic compounds with special emphasis on acetone

Recommended standardized procedures for determining exhaled lower respiratory nitric oxide and nasal nitric oxide (NO) have been developed by task forces of the European Respiratory Society and the American Thoracic Society. These recommendations have paved the way for the measurement of nitric oxide to become a diagnostic tool for specific clinical applications. It would be desirable to develop similar guidelines for the sampling of other trace gases in exhaled breath, especially volatile organic compounds (VOCs) which may reflect ongoing metabolism. The concentrations of water-soluble, blood-borne substances in exhaled breath are influenced by: (i) breathing patterns affecting gas exchange in the conducting airways, (ii) the concentrations in the tracheo-bronchial lining fluid, (iii) the alveolar and systemic concentrations of the compound. The classical Farhi equation takes only the alveolar concentrations into account. Real-time measurements of acetone in end-tidal breath under an ergometer challenge show characteristics which cannot be explained within the Farhi setting. Here we develop a compartment model that reliably captures these profiles and is capable of relating breath to the systemic concentrations of acetone. By comparison with experimental data it is inferred that the major part of variability in breath acetone concentrations (e.g., in response to moderate exercise or altered breathing patterns) can be attributed to airway gas exchange, with minimal changes of the underlying blood and tissue concentrations. Moreover, the model illuminates the discrepancies between observed and theoretically predicted blood-breath ratios of acetone during resting conditions, i.e., in steady state. Particularly, the current formulation includes the classical Farhi and the Scheid series inhomogeneity model as special limiting cases and thus is expected to have general relevance for a wider range of blood-borne inert gases. The chief intention of the present modeling study is to provide mechanistic relationships for further investigating the exhalation kinetics of acetone and other water-soluble species. This quantitative approach is a first step towards new guidelines for breath gas analyses of volatile organic compounds, similar to those for nitric oxide.