Age does not affect airway pH and ammonia as determined by exhaled breath measurements

Reference Ranges of 8-Isoprostane Concentrations in Exhaled Breath Condensate (EBC): A Systematic Review and Meta-Analysis

Isoprostanes are physiopathologic mediators of oxidative stress, resulting in lipid peroxidation. 8-isoprostane seems particularly useful for measuring oxidative stress damage. However, no reference range values are available for 8-isoprosante in exhaled breath condensate (EBC) of healthy adults, enabling its meaningful interpretation as a biomarker. We conducted this systematic review and meta-analysis according to the protocol following PROSPERO (CRD42020146623). After searching and analyzing the literature, we included 86 studies. After their qualitative synthesis and risk of bias assessment, 52 studies were included in meta-analysis. The latter focused on studies using immunological analytical methods and investigated how the concentrations of 8-isoprostane differ based on gender. We found that gender had no significant effect in 8-isoprostane concentration. Among other studied factors, such as individual characteristics and factors related to EBC collection, only the device used for EBC collection significantly affected measured 8-isoprostane concentrations. However, adjustment for the factors related to EBC collection, yielded uncertainty whether this effect is due to the device itself or to the other factors. Given this uncertainty, we estimated the reference range values of 8-isoprostane stratified by gender and EBC collection device. A better standardization of EBC collection seems necessary; as well more studies using chemical analytical methods to extend this investigation.

Sr-Doped Cubic In2O3/Rhombohedral In2O3 Homojunction Nanowires for Highly Sensitive and Selective Breath Ethanol Sensing: Experiment and DFT Simulation Studies

In recent years, it is urgent and challenging to fabricate highly sensitive and selective gas sensors for breath analyses. In this work, Sr-doped cubic In₂O₃/rhombohedral In₂O₃ homojunction nanowires (NWs) are synthesized by one-step electrospun technology. The Sr doping alters the cubic phase of pure In₂O₃ into the rhombohedral phase, which is verified by the high-resolution transmittance electron microscopy, X-ray diffraction, and Raman spectroscopy, and is attributable to the low cohesive energy as calculated by the density functional theory (DFT). As a proof-of-concept of fatty liver biomarker sensing, ethanol sensors are fabricated using the electrospun In₂O₃ NWs. The results show that 8 wt % Sr-doped In₂O₃ shows the highest ethanol sensing performance with a high response of 21-1 ppm, a high selectivity over other interfering gases such as methanol, acetone, formaldehyde, toluene, xylene, and benzene, a high stability measured in 6 weeks, and also a high resistance to high humidity of 80%. The outstanding ethanol sensing performance is attributable to the enhanced ethanol adsorption by Sr doping as calculated by DFT, the stable rhombohedral phase and the preferred (104) facet exposure, and the formed homojunctions favoring the electron transfer. All these results show the effective structural modification of In₂O₃ by Sr doping, and also the great potency of the homojunction Sr-doped In₂O₃ NWs for highly sensitive, selective, and stable breath ethanol sensing.

NOx in exhaled breath condensate is related to allergic sensitization in young and middle-aged adults

BACKGROUND

Asthma and allergic diseases are heterogeneous. Measurement of biomarkers in exhaled breath condensate (EBC) may help to discriminate between different phenotypes and may assist with clinical prognostication.

OBJECTIVES

We aimed to assess associations between total nitric oxide products (NO_x ) in EBC and different allergic phenotypes and lung function in young and middle-aged adults.

METHODS

Cross-sectional analyses were nested within two Australian longitudinal studies, the Melbourne Atopy Cohort Study (MACS, mean age 17.8 years) and the Tasmanian Longitudinal Health Study (TAHS, mean age 49.4 years). Levels of EBC NO_x were determined by Griess-reaction fluorescent method. Associations were assessed between EBC NO_x and different allergic phenotypes, lung function and airway reactivity.

RESULTS

Atopy, with or without asthma or rhinitis, was associated with increased EBC NO_x levels particularly in individuals with poly-aero-sensitization. These findings were generally consistent across the two age groups. In the older cohort, use of ICS in the previous 12 months masked the association between sensitization and EBC NO_x (OR = 0.64, 95% CI = 0.21-1.96, p for interaction = 0.05).

CONCLUSIONS AND CLINICAL RELEVANCE

In these population-based samples, EBC NO_x was most strongly associated with atopic sensitization, rather than either current asthma or rhinitis, possibly indicating underlying increased airway inflammation associated with atopy. Therefore, EBC NO_x could be a key predictor of atopy in both young and middle-aged adults, regardless of the presence of concomitant asthma or rhinitis.

Performance of a whole-body human dust inhalation challenge exposure chamber

Background

Evaluation of the performance of a whole-body human dust exposure chamber is presented in this report.

Methods

The volume of the chamber is 2.13 m³ and it is operated at a flow rate of 1.0 m³/min. Makeup and exhaust air were filtered. A Wright Dust Feeder was used to generate fly ash, the testing agent. An elutriator was used to maintain particles in the respirable range. A Rupprecht and Patashnick PM-10 TEOM, a direct reading instrument, was used to monitor particle concentration. Particle size distributions were determined by a QCM cascade impactor. The evenness of dust concentrations in the chamber was determined gravimetrically.

Results

Dust concentrations measured at different points within the chamber were associated with variability less than 10%. Dust concentrations measured by the TEOM, in μg/m³, at 0.2, 0.4, 0.8 and 1.6 RPMs of the Wright Dust Feeder, were 110 ± 2.8, 173 ± 8.5, 398 ± 20 and 550 ± 17, respectively. Particle size distributions (MMD and GSD) were 1.27 μm and 2.35, 1.39 and 2.22, 1.46 and 2.08, 1.15 and 2.2, respectively. Total dust concentrations measured gravimetrically in μg/m³, were 135 ± 21, 200 ± 35, 333 ± 18 and 891 ± 27, respectively.

Conclusion

The whole-body human exposure chamber offers several advantages and has better performance than most of the inhalation challenge systems previously described.

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.

The analysis of volatile organic compounds in exhaled breath and biomarkers in exhaled breath condensate in children - clinical tools or scientific toys?

Current monitoring strategies for respiratory diseases are mainly based on clinical features, lung function and imaging. As airway inflammation is the hallmark of many respiratory diseases in childhood, noninvasive methods to assess the presence and severity of airway inflammation might be helpful in both diagnosing and monitoring paediatric respiratory diseases. At present, the measurement of fractional exhaled nitric oxide is the only noninvasive method available to assess eosinophilic airway inflammation in clinical practice. We aimed to evaluate whether the analysis of volatile organic compounds (VOCs) in exhaled breath (EB) and biomarkers in exhaled breath condensate (EBC) is helpful in diagnosing and monitoring respiratory diseases in children. An extensive literature search was conducted in Medline, Embase and PubMed on the analysis and applications of VOCs in EB and EBC in children. We retrieved 1165 papers, of which nine contained original data on VOCs in EB and 84 on biomarkers in EBC. These were included in this review. We give an overview of the clinical applications in childhood and summarize the methodological issues. Several VOCs in EB and biomarkers in EBC have the potential to distinguish patients from healthy controls and to monitor treatment responses. Lack of standardization of collection methods and analysis techniques hampers the introduction in clinical practice. The measurement of metabolomic profiles may have important advantages over detecting single markers. There is a lack of longitudinal studies and external validation to reveal whether EB and EBC analysis have added value in the diagnostic process and follow-up of children with respiratory diseases. In conclusion, the use of VOCs in EB and biomarkers in EBC as markers of inflammatory airway diseases in children is still a research tool and not validated for clinical use.

Noninvasive effects measurements for air pollution human studies: methods, analysis, and implications

Human exposure studies, compared with cell and animal models, are heavily relied upon to study the associations between health effects in humans and air pollutant inhalation. Human studies vary in exposure methodology, with some work conducted in controlled settings, whereas other studies are conducted in ambient environments. Human studies can also vary in the health metrics explored, as there exists a myriad of health effect end points commonly measured. In this review, we compiled mini reviews of the most commonly used noninvasive health effect end points that are suitable for panel studies of air pollution, broken into cardiovascular end points, respiratory end points, and biomarkers of effect from biological specimens. Pertinent information regarding each health end point and the suggested methods for mobile collection in the field are assessed. In addition, the clinical implications for each health end point are summarized, along with the factors identified that can modify each measurement. Finally, the important research findings regarding each health end point and air pollutant exposures were reviewed. It appeared that most of the adverse health effects end points explored were found to positively correlate with pollutant levels, although differences in study design, pollutants measured, and study population were found to influence the magnitude of these effects. Thus, this review is intended to act as a guide for researchers interested in conducting human exposure studies of air pollutants while in the field, although there can be a wider application for using these end points in many epidemiological study designs.

Aging and airway inflammation

BACKGROUND

Since little is known of airways inflammation in the elderly, we have carried out a study to explore the presence of some inflammatory markers in the airways of healthy subjects of different ages using a non-invasive method which is particularly suitable for aged people.

OBJECTIVE

The aim of this work was to investigate whether parameters, including (1) pH, IL-8 and TNF-α in exhaled breath condensate (EBC), (2) exhaled nitric oxide levels (NO), and (3) inflammatory cell profile in induced sputum, are age-related.

MATERIALS AND METHODS

Thirty healthy adults (10 subjects below the age of 30 [A], 10 subjects between 30 and 60 years [B], and 10 subjects over 60 years of age [C]), were enrolled in the study. IL-8 and TNF-α levels were measured in breath condensate. Exhaled pH was measured after deaeration/decarbonation by means of a pH-meter. A rapid-response chemiluminescence NO analyzer was used to quantify NO. Induced sputum was collected, homogenized with dithiothreitol, and cytospins for differential cell were produced.

RESULTS

The levels of IL-8 and TNF-α in EBC, the levels of exhaled NO, and the percentage of neutrophils in induced sputum were significantly elevated in C and B compared with A; the EBC pH level was significantly reduced in C and B compared with A. The EBC levels of IL-8, TNF-α, pH, the level of exhaled NO, and the percentage of neutrophils correlated significantly with age.

CONCLUSION

This study has shown the presence of age-related airways inflammation in healthy subjects.

Respiratory health and breath condensate acidity in sawmill workers

PURPOSE

The aim of the study was to evaluate exhaled breath condensate acidity (EBC pH) as a biomarker of airway response to occupational respiratory hazards present in sawmill.

METHODS

Sixty-one sawmill workers in total (26 from Sawmill 1 and 35 from Sawmill 2) provided EBC samples at the beginning and at the end of the working week. Respiratory symptoms, lung function, bronchodilator test and atopy status were assessed. Occupational environment was checked for the levels of respiratory hazards.

RESULTS

Airborne dust concentrations were below threshold limit value. Endotoxin in Sawmill 1 and Sawmill 2, and moulds in Sawmill 1 were at the levels able to induce inflammatory response in the airways. Mould levels were 2.5 times higher in Sawmill 1 than in Sawmill 2. Compared to Sawmill 2 workers, lower spirometry values, higher prevalence of dry cough and positive bronchodilator test were found in Sawmill 1 workers. Monday EBC pH values did not differ between sawmills, but declined after one working week in Sawmill 1 workers (from 7.88 to 7.49, P = 0.012) and not in Sawmill 2 workers. Similar results were obtained when only respiratory healthy non-smokers were analysed. Monday-to-Friday change of other respiratory parameters was not observed.

CONCLUSION

The results suggest EBC pH as a biomarker of acute respiratory effects related to occupational exposure to respiratory hazards in sawmills, presumably increased mould levels. The effect was present even at subclinical level, namely in respiratory healthy subjects. The long-term health implications remain unclear and should be evaluated in a follow-up study.

Breath-ammonia testing of healthy subjects and patients with cirrhosis

BACKGROUND

Hepatic encephalopathy (HE) is a serious neuropsychiatric complication in both acute and chronic liver disease.

AIMS

To establish the utility of a portable noninvasive method to measure ammonia in the breath of healthy subjects and patients with HE.

METHODS

The study included 106 subjects: 44 women and 62 men, 51 healthy and 55 cirrhotic. The breath ammonia was measured with an electrochemical sensor and expressed in parts/billion (ppb).

RESULTS

The breath ammonia in healthy subjects had an average value of 151.4 ppb (95% confidence interval [CI]: 149.4-153.4) and the average value in cirrhotic patients was 169.9 ppb (95% CI: 163.5-176.2) (P < 0.0001). In cirrhotic patients with and without HE, the corresponding values were 184.1 ppb (95% CI: 167.7-200.6) and 162.9 ppb (95% CI: 158.8-167.0), respectively (P = 0.0011). Ammonia levels ≥ 165 ppb permitted a differentiation between healthy and cirrhotic subjects; the area under the receiver operating characteristic (ROC) curve for the ammonia-level values in cirrhotic versus control patients was 0.86 (95% CI: 0.79-0.93). In cirrhotic patients, ammonia levels ≥ 175 ppb permitted the distinction between patients with and without HE; the area under the ROC curve in cirrhotic patients with versus without HE was 0.83 (95% CI: 0.73-0.94).

CONCLUSION

A portable sensor for measuring breath ammonia can be developed. If the results of the present study are confirmed, breath-ammonia determinations could produce a significant impact on the care of patients with cirrhosis and could even include the possibility of self-monitoring.

Breath ammonia levels in a normal human population study as determined by photoacoustic laser spectroscopy

Photoacoustic laser spectroscopy was used as a technique to measure real-time levels of ammonia in exhaled human breath in a small, locally recruited, normal healthy population (n = 30). This yielded an average level of breath ammonia of 265 ppb, ranging from 29 to 688 ppb. Although average levels were marginally higher in male volunteers, this was not statistically significant. In addition, no correlation could be found between age, body mass index, or breath carbon dioxide levels. Monitoring of the daily routine of two individuals showed a consistent decrease in oral breath ammonia concentrations by the early afternoon (post-prandial), but was followed by a gradual increase towards late afternoon. However, in a comparison of oral and nasal breath in two volunteers, nasal breath ammonia levels were found to be significantly lower than oral levels. In addition, the daily variation was only seen in oral rather than nasal measurements which may indicate that significant background levels are predominantly of oral origin and that nasal sampling is the preferred route to eradicate this background in future studies. These results provide a healthy human breath ammonia baseline upon which other studies may be compared.

Exhaled breath condensate: lessons learned from veterinary medicine

Exhaled breath condensate (EBC) describes any sample collected by cooling exhaled breath. Because the method of condensate collection is simple, non-invasive, repeatable and does not necessarily require patient cooperation, EBC is not only an interesting, but also challenging, biological sample. Despite a period of EBC research lasting for more than 15 years, there are still many open questions with respect to EBC collection and analysis, and many biomarkers are still awaiting careful validation. In veterinary research, EBC collection has been described in conscious animals including calves, pigs, horses, cats and dogs. Numerous studies performed in these domestic animals not only contributed substantially to the current knowledge about the potentials of EBC-based diagnoses but also demonstrated pitfalls in EBC collection, analysis and interpretation. This review summarizes information about the collection of EBC and the interpretation of EBC results, particularly with respect to proteins, leukotrienes, hydrogen peroxide, urea, ammonia and pH. Published data emphasize the need to standardize approaches to produce reproducible EBC data. Quantifying the concentration of the EBC component of interest exhaled in a defined volume of exhaled breath (instead of comparing concentrations of this component analysed in liquid EBC) is an important step of standardization that might help to overcome methodological limitations deriving from the EBC collection process. Although information is based on domestic animal studies, it contributes to the general understanding in EBC research-independent of any particular mammalian species-and opens new perspectives for further studies.

Expression of the gas-transporting proteins, Rh B glycoprotein and Rh C glycoprotein, in the murine lung

A family of gas-transporting proteins, the Mep/Amt/Rh glycoprotein family, has been identified recently. These are integral membrane proteins, are widely expressed in sites of gas transport, and are known to transport the gaseous molecule, NH(3), and recent evidence indicates they can transport CO(2). Because the mammalian lung is a critical site for gas transport, the current studies examine the expression of the nonerythroid members of this extended family, Rh B glycoprotein (Rhbg) and Rh C glycoprotein (Rhcg), in the normal mouse lung. Real-time RT-PCR and immunoblot analysis demonstrated both Rhbg and Rhcg mRNA and protein expression, respectively. Immunohistochemistry demonstrated both Rhbg and Rhcg were expressed in bronchial and bronchiolar epithelial cells. Rhbg was expressed by Clara cells, specifically, whereas all bronchial/bronchiolar epithelial cells, with the exception of goblet cells, expressed Rhcg. Rhbg expression was basolateral, whereas Rhcg exhibited apical and intracellular immunolabel, polarized expression similar to that observed in Rhbg- and Rhcg-expressing epithelial cells in other organs. There was no detectable expression of either Rhbg or Rhcg in alveolar endothelial or epithelial cells, in pneumocytes or in vascular tissue. In vitro studies using cultured bronchial epithelial cells confirm Rhbg and Rhcg expression, demonstrate that saturable, not diffusive, transport is the primary mechanism of ammonia/methylammonia transport, and show that the saturable transport mechanism has kinetics similar to those demonstrated previously for Rhbg and Rhcg. These findings suggest Rhbg and Rhcg may contribute to bronchial epithelial cell ammonia metabolism and suggest that they do not contribute to pulmonary CO(2) transport.

Impact of age on pH, 8-isoprostane, and nitrogen oxides in exhaled breath condensate

BACKGROUND

Few studies have addressed the effects of aging on levels of inflammatory markers in exhaled breath condensate (EBC). The aim of this study was to determine whether there are significant age-associated differences in pH, 8-isoprostane, and nitrogen oxide values in EBC from a population of healthy adults.

MATERIAL AND METHODS

EBC samples were obtained from 75 healthy volunteers aged 18 to 80 years and stratified into five groups according to age (n = 15): 18 to 29, 30 to 39 years, 40 to 49 years, 50 to 59 years, and 60 to 80 years. The following were measured in the samples collected: pH before and after deaeration, nitrite, nitrate, and 8-isoprostane. Differences between the groups were assessed by the Kruskal-Wallis test.

RESULTS

Significant differences in deaerated pH (p < 0.0001) were found in the group of individuals 60 to 80 years of age as compared to the remaining groups. Significant differences were also found in 8-isoprostane levels between the younger and older groups (18 to 29 years and 30 to 39 years of age; p = 0.006 and p = 0.034, respectively). There were no significant differences in nitrite or nitrate values between younger and older individuals.

CONCLUSION

The results of this study indicate that pH and 8-isoprostane levels in EBC show a relationship with age. Thus, values obtained in studies with control groups may require adjustment for these factors.

Drinking influences exhaled breath condensate acidity

Exhaled breath condensate analysis is a developing method for investigating airway pathology. Impact of food and drink on breath condensate composition has not been systematically addressed. The aim of the study was to follow exhaled breath condensate pH after drinking an acidic and a neutral beverage. Breath condensate, capillary blood, and urine of 12 healthy volunteers were collected before and after drinking either 1 l of coke or 1 l of mineral water. The pH of each sample was determined with a blood gas analyzer. The mean difference between the pH of two breath condensate samples collected within 15 min before drinking was 0.13+/-0.03. Condensate pH decreased significantly from 6.29+/-0.02 to 6.24+/-0.02 (p<0.03) after drinking coke and from 6.37+/-0.03 to 6.22+/-0.04 (p<0.003) after drinking water. Drinking coke induced significant changes in blood and urine pH as well. Drinking influences exhaled breath condensate composition and may contribute to the variability of exhaled breath condensate pH.