Nitric Oxide and Exhaled Breath Nitrite/Nitrates in Chronic Obstructive Pulmonary Disease Patients

SARS CoV-2 infection screening via the exhaled breath fingerprint obtained by FTIR spectroscopic gas-phase analysis. A proof of concept

The COVID-19 pandemic remains a global challenge now with the long-COVID arising. Mitigation measures focused on case counting, assessment and determination of variants and their likely targets of infection and transmission, the pursuit of drug treatments, use and enhancement of masks, social distancing, vaccination, post-infection rehabilitation, and mass screening. The latter is of utmost importance given the current scenario of infections, reinfections, and long-term health effects. Research on screening platforms has been developed to provide more sensitive, specific, and reliable tests that are accessible to the entire population and can be used to assess the prognosis of the disease as well as the subsequent health follow-up of patients with sequelae of COVID-19. Therefore, the aim of the present study was the simulation of exhaled breath of COVID-19 patients by evaluation of three identified COVID-19 indicator breath biomarkers (acetone (ACE), acetaldehyde (ACH) and nitric oxide (NO)) by gas-phase infrared spectroscopy as a proof-of-concept principle for the detection of infected patients' exhaled breath fingerprint and subsequent follow-up. The specific fingerprints of each of the compounds and the overall fingerprint were obtained. The synthetic exhaled breath evaluation concept revealed a linearity of r = 0.99 for all compounds, and LODs of 6.42, 13.81, 9.22 ppm, and LOQs of 42.26, 52.57, 69.23 ppm for NO, ACE, and ACH, respectively. This study proves the fundamental feasibility of gas-phase infrared spectroscopy for fingerprinting lung damage biomarkers in exhaled breath of patients with COVID-19. This analysis would allow faster and cheaper screening and follow-up of infected individuals, which could improve mass screening in POC settings.

NOx Sensor Constructed from Conductive Metal-Organic Framework and Graphene for Airway Inflammation Screening

The detection of nitric oxide in human exhaled breath (EB) has received wide attention due to its close relationship with respiratory tract inflammation. Herein, a ppb-level NOx chemiresistive sensor was prepared by assembling graphene oxide (GO) with a conductive π-d conjugated metal-organic framework Co3(HITP)2 (HITP = 2,3,6,7,10,11-hexaiminotriphenylene) in the presence of poly(dimethyldiallylammonium chloride) (PDDA). The construction of a gas sensor chip was achieved by drop-casting the GO/PDDA/Co3(HITP)2 composite onto ITO-PET interdigital electrodes, followed by in situ reduction of GO to reduced graphene oxide (rGO) in hydrazine hydrate vapor. Compared with bare rGO, the nanocomposite shows significantly improved sensitivity and selectivity for NOx among various gas analytes owing to its folded and porous structure as well as its numerous active sites. The limit of detection (LOD) for NO and NO2 can reach as low as 11.2 and 6.8 ppb, respectively, and the response/recovery time to 200 ppb NO is 24/41 s. These results indicate that rGO/PDDA/Co3(HITP)2 can achieve a sensitive and fast response toward NOx at room temperature (RT). Additionally, good repeatability and long-term stability were observed. Furthermore, the sensor shows improved humidity tolerance owing to the presence of hydrophobic benzene rings in Co3(HITP)2. To demonstrate its ability in EB detection, EB samples collected from healthy individuals were spiked with a certain amount of NO to simulate the EB of respiratory inflammatory patients. The sensor can successfully distinguish healthy people from the simulated patients. Furthermore, in real clinical sample detection, the sensor can further differentiate acute respiratory inflammatory patients from the chronic ones.

Exhaled Biomarkers for Point-of-Care Diagnosis: Recent Advances and New Challenges in Breathomics

Cancers, chronic diseases and respiratory infections are major causes of mortality and present diagnostic and therapeutic challenges for health care. There is an unmet medical need for non-invasive, easy-to-use biomarkers for the early diagnosis, phenotyping, predicting and monitoring of the therapeutic responses of these disorders. Exhaled breath sampling is an attractive choice that has gained attention in recent years. Exhaled nitric oxide measurement used as a predictive biomarker of the response to anti-eosinophil therapy in severe asthma has paved the way for other exhaled breath biomarkers. Advances in laser and nanosensor technologies and spectrometry together with widespread use of algorithms and artificial intelligence have facilitated research on volatile organic compounds and artificial olfaction systems to develop new exhaled biomarkers. We aim to provide an overview of the recent advances in and challenges of exhaled biomarker measurements with an emphasis on the applicability of their measurement as a non-invasive, point-of-care diagnostic and monitoring tool.

Blood Eosinophils and Exhaled Nitric Oxide: Surrogate Biomarkers of Airway Eosinophilia in Stable COPD and Exacerbation

In recent years, tremendous efforts have been devoted to characterizing the inflammatory processes in chronic obstructive pulmonary disease (COPD) in order to provide more personalized treatment for COPD patients. While it has proved difficult to identify COPD-specific inflammatory pathways, the distinction between eosinophilic and non-eosinophilic airway inflammation has gained clinical relevance. Evidence has shown that sputum eosinophil counts are increased in a subset of COPD patients and that these patients are more responsive to oral or inhaled corticosteroid therapy. Due to feasibility issues associated with sputum cell profiling in daily clinical practice, peripheral blood eosinophil counts and fractional exhaled nitric oxide levels have been evaluated as surrogate biomarkers for assessing the extent of airway eosinophilia in COPD patients, both in stable disease and acute exacerbations. The diagnostic value of these markers is not equivalent and depends heavily on the patient’s condition at the time of sample collection. Additionally, the sensitivity and specificity of these tests may be influenced by the patient’s maintenance treatment. Overall, eosinophilic COPD may represent a distinct disease phenotype that needs to be further investigated in terms of prognosis and treatment outcomes.

Predictive Value of Exhaled Nitric Oxide and Blood Eosinophil Count in the Assessment of Airway Eosinophilia in COPD

Purpose

Fractional exhaled nitric oxide (FENO50) level and peripheral blood eosinophil count may serve as indicators of airway eosinophilia. The aim of this study was to estimate the diagnostic value of these markers for detecting airway eosinophilia in patients with stable chronic obstructive pulmonary disease (COPD) and those experiencing an acute exacerbation (AECOPD).

Patients and Methods

FENO50 levels, sputum and blood eosinophil counts were assessed in 53 clinically stable ex-smoker COPD patients and 67 ex-smoker COPD patients experiencing a severe exacerbation. In AECOPD, clinical variables were measured at the time of hospital admission and discharge following treatment.

Results

In stable COPD, blood eosinophil count but not FENO50 level was found to be a good predictor of airway eosinophilia (area under the receiver operating characteristic curve [ROC AUC]: ≥0.82). The sensitivity and the specificity of the test ranged between 75% and 98%, the negative predictive value (NPV) was high (>90%). In AECOPD, FENO50 was predictive for airway eosinophilia (ROC AUC: >0.8) with high NPV (>88%), but with lower sensitivity and specificity (64-70%). In contrast, the predictive accuracy of blood eosinophil count for airway eosinophilia in AECOPD was modest (ROC AUC: 0.54-0.63). The combined use of the two markers provided only limited additional benefit. Correlation analyses supported ROC curve findings.

Conclusion

In stable COPD the peripheral blood eosinophil count, while in AECOPD the FENO50 level is a good surrogate marker of airway eosinophilia.

Interaction of Staphylococcus aureus and Host Cells upon Infection of Bronchial Epithelium during Different Stages of Regeneration

The primary barrier that protects our lungs against infection by pathogens is a tightly sealed layer of epithelial cells. When the integrity of this barrier is disrupted as a consequence of chronic pulmonary diseases or viral insults, bacterial pathogens will gain access to underlying tissues. A major pathogen that can take advantage of such conditions is Staphylococcus aureus, thereby causing severe pneumonia. In this study, we investigated how S. aureus responds to different conditions of the human epithelium, especially nonpolarization and fibrogenesis during regeneration using an in vitro infection model. The infective process was monitored by quantification of the epithelial cell and bacterial populations, fluorescence microscopy, and mass spectrometry. The results uncover differences in bacterial internalization and population dynamics that correlate with the outcome of infection. Protein profiling reveals that, irrespective of the polarization state of the epithelial cells, the invading bacteria mount similar responses to adapt to the intracellular milieu. Remarkably, a bacterial adaptation that was associated with the regeneration state of the epithelial cells concerned the early upregulation of proteins controlled by the redox-responsive regulator Rex when bacteria were confronted with a polarized cell layer. This is indicative of the modulation of the bacterial cytoplasmic redox state to maintain homeostasis early during infection even before internalization. Our present observations provide a deeper insight into how S. aureus can take advantage of a breached epithelial barrier and show that infected epithelial cells have limited ability to respond adequately to staphylococcal insults.

The anti-sigma factor MucA of Pseudomonas aeruginosa: Dramatic differences of a mucA22 vs. a ΔmucA mutant in anaerobic acidified nitrite sensitivity of planktonic and biofilm bacteria in vitro and during chronic murine lung infection

Mucoid mucA22 Pseudomonas aeruginosa (PA) is an opportunistic lung pathogen of cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD) patients that is highly sensitive to acidified nitrite (A-NO₂^-). In this study, we first screened PA mutant strains for sensitivity or resistance to 20 mM A-NO₂^- under anaerobic conditions that represent the chronic stages of the aforementioned diseases. Mutants found to be sensitive to A-NO₂^- included PA0964 (pmpR, PQS biosynthesis), PA4455 (probable ABC transporter permease), katA (major catalase, KatA) and rhlR (quorum sensing regulator). In contrast, mutants lacking PA0450 (a putative phosphate transporter) and PA1505 (moaA2) were A-NO₂^- resistant. However, we were puzzled when we discovered that mucA22 mutant bacteria, a frequently isolated mucA allele in CF and to a lesser extent COPD, were more sensitive to A-NO₂^- than a truncated ΔmucA deletion (Δ157–194) mutant in planktonic and biofilm culture, as well as during a chronic murine lung infection. Subsequent transcriptional profiling of anaerobic, A-NO₂^--treated bacteria revealed restoration of near wild-type transcript levels of protective NO₂^- and nitric oxide (NO) reductase (nirS and norCB, respectively) in the ΔmucA mutant in contrast to extremely low levels in the A-NO₂^--sensitive mucA22 mutant. Proteins that were S-nitrosylated by NO derived from A-NO₂^- reduction in the sensitive mucA22 strain were those involved in anaerobic respiration (NirQ, NirS), pyruvate fermentation (UspK), global gene regulation (Vfr), the TCA cycle (succinate dehydrogenase, SdhB) and several double mutants were even more sensitive to A-NO₂^-. Bioinformatic-based data point to future studies designed to elucidate potential cellular binding partners for MucA and MucA22. Given that A-NO₂^- is a potentially viable treatment strategy to combat PA and other infections, this study offers novel developments as to how clinicians might better treat problematic PA infections in COPD and CF airway diseases.

Exhaled nitric oxide in patients with chronic obstructive pulmonary disease: a systematic review and meta-analysis

Background

Fractional exhaled nitric oxide (FENO) is a useful and noninvasive biomarker for eosinophilic airway inflammation, particularly in asthma. However, its utility in chronic obstructive pulmonary disease (COPD) remains controversial. In this study, we performed a systematic review and meta-analysis to evaluate FENO levels in COPD.

Methods

A search of PubMed, Embase, Cochrane Library, and clinical trial registry was conducted from inception to January 2018. Studies were included if they reported FENO levels in patients with COPD and healthy controls. We then extracted relevant information and analyzed data. Standard mean difference (SMD) with 95% confidence interval (CI) was applied in this meta-analysis.

Results

A total of 2,073 studies were reviewed for eligibility, with 24 studies pooled for analysis. The FENO levels in patients with COPD were elevated mildly compared with healthy controls (SMD 1.28, 95% CI 0.60-1.96). A similar result was also observed in stable COPD, with an SMD of 1.21 (95% CI 0.47-1.96). On the other hand, we found no association between FENO levels and exacerbated COPD. Additionally, for patients with COPD, ex-smokers had higher levels of FENO than current smokers (SMD 2.05, 95% CI 1.13-2.97).

Conclusion

Our studies demonstrated a mild elevation of FENO in COPD, and the association between exacerbated COPD and FENO levels needs to be further explored. The potential mechanism is still unknown and conflicting.

Investigating Fractional Exhaled Nitric Oxide in Chronic Obstructive Pulmonary Disease (COPD) and Asthma-COPD Overlap (ACO): A Scoping Review

Chronic obstructive pulmonary disease (COPD) is the most common fixed airflow limitation. Individuals may present with the features of both asthma and COPD called asthma-COPD overlap (ACO) with more severity and worse health-related quality of life than COPD or asthma. One of the promising biomarkers that could be used in clinical practice to differentiate ACO from COPD is fractional exhaled nitric oxide (F_ENO). The role of Fractional exhaled nitric oxide (F_ENO) in COPD/ACO remains unknown. This scoping review aims to investigate the role of F_ENO measurement to differentiate COPD from ACO, to anticipate disease severity/progression and treatment response. A structured comprehensive literature search was performed in major databases including Medline, EMBASE, CINAHL, Cochrane Library, Web of Science, and BIOSIS from 2005 onwards. Thirty-eight studies were retrieved. Based on the synthesis of the reviewed literature, six themes emerged. Thirty-four articles covered more than one theme. From which, 24 articles were on modifying factors in F_ENO measurement, 18 on F_ENO in COPD compared with healthy subjects, and seven on F_ENO in ACO compared with COPD, 22 on F_ENO and disease severity/progression,12 on F_ENO and biomarkers, and eight on F_ENO and treatment response. F_ENO measurement cannot be used alone in the clinical settings of COPD patients. Although F_ENO level is higher in ACO patients than COPD-only, it is still unclear if there is a F_ENO cut-off that can be used to make the diagnosis of ACO and/or to guide therapy with inhaled corticosteroids/glucocorticoids in COPD patients.

Relationships between adult asthma and oxidative stress markers and pH in exhaled breath condensate: a systematic review

Oxidative stress has a recognized role in the pathophysiology of asthma. Recently, interest has increased in the assessment of pH and airway oxidative stress markers. Collection of exhaled breath condensate (EBC) and quantification of biomarkers in breath samples can potentially indicate lung disease activity and help in the study of airway inflammation, and asthma severity. Levels of oxidative stress markers in the EBC have been systematically evaluated in children with asthma; however, there is no such systematic review conducted for adult asthma. A systematic review of oxidative stress markers measured in EBC of adult asthma was conducted, and studies were identified by searching MEDLINE and SCOPUS databases. Sixteen papers met the inclusion criteria. Concentrations of exhaled hydrogen ions, nitric oxide products, hydrogen peroxide and 8-isoprostanes were generally elevated and related to lower lung function tests in adults with asthma compared to healthy subjects. Assessment of EBC markers may be a noninvasive approach to evaluate airway inflammation, exacerbations, and disease severity of asthma, and to monitor the effectiveness of anti-inflammatory treatment regimens. Longitudinal studies, using standardized analytical techniques for EBC collection, are required to establish reference values for the interpretation of EBC markers in the context of asthma.

Effect of naturally occurring ozone air pollution episodes on pulmonary oxidative stress and inflammation

This study aimed to determine if naturally occurring episodes of ozone air pollution in the Salt Lake Valley in Utah, USA, during the summer are associated with increased pulmonary inflammation and oxidative stress, increased respiratory symptoms, and decreased lung function in individuals with chronic obstructive pulmonary disease (COPD) compared to controls. We measured biomarkers (nitrite/nitrate (NO_x), 8-isoprostane) in exhaled breath condensate (EBC), spirometry, and respiratory symptoms in 11 former smokers with moderate-to-severe COPD and nine former smokers without airflow obstruction during periods of low and high ozone air pollution. High ozone levels were associated with increased NO_x in EBC in both COPD (8.7 (±8.5) vs. 28.6 (±17.6) μmol/L on clean air vs. pollution days, respectively, p < 0.01) and control participants (7.6 (±16.5) vs. 28.5 (±15.6) μmol/L on clean air vs. pollution days, respectively, p = 0.02). There was no difference in pollution effect between COPD and control groups, and no difference in EBC 8-isoprostane, pulmonary function, or respiratory symptoms between clean air and pollution days in either group. Former smokers both with and without airflow obstruction developed airway oxidative stress and inflammation in association with ozone air pollution episodes.

Predicting sputum eosinophilia in exacerbations of COPD using exhaled nitric oxide

Fractional exhaled nitric oxide (FENO) may be a pulmonary biomarker in chronic obstructive pulmonary disease (COPD). In this prospective study, the relationship between FENO and airway inflammation was assessed in COPD exacerbations. FENO and lung function were measured, and sputum was collected from 49 ex-smoking COPD patients, first at the time of hospital admission and again at discharge following treatment. There was a significant positive correlation between the percentage of sputum eosinophils and FENO concentrations, both at exacerbation (r = 0.593, p < 0.001) and discharge (r = 0.337, p = 0.044). The increase in forced expiratory volume in one second (FEV(1)) after treatment was greater in patients with sputum eosinophilia (ΔFEV(1) 0.35 ± 0.12 vs. 0.13 ± 0.04 L, p = 0.046), and FENO was a strong predictor of sputum eosinophilia (area under the receiver operating characteristic curve, 0.89). The optimum cut point was 19 parts per billion (sensitivity: 90 %; specificity: 74 %). Our data suggest that FENO is a good surrogate marker of eosinophilic inflammation in COPD patients with exacerbations.

Air pollution and subclinical airway inflammation in the SALIA cohort study

Background

The association between long-term exposure to air pollution and local inflammation in the lung has rarely been investigated in the general population of elderly subjects before. We investigated this association in a population-based cohort of elderly women from Germany.

Methods

In a follow-up examination of the SALIA cohort study in 2008/2009, 402 women aged 68 to 79 years from the Ruhr Area and Borken (Germany) were clinically examined. Inflammatory markers were determined in exhaled breath condensate (EBC) and in induced sputum (IS). We used traffic indicators and measured air pollutants at single monitoring stations in the study area to assess individual traffic exposure and long-term air pollution background exposure. Additionally long-term residential exposure to air pollution was estimated using land-use regression (LUR) models. We applied multiple logistic and linear regression analyses adjusted for age, indoor mould, smoking, passive smoking and socio-economic status and additionally conducted sensitivity analyses.

Results

Inflammatory markers showed a high variability between the individuals and were higher with higher exposure to air pollution. NO derivatives, leukotriene (LT) B₄ and tumour necrosis factor-α (TNF-α) showed the strongest associations. An increase of 9.42 μg/m³ (interquartile range) in LUR modelled NO₂ was associated with measureable LTB₄ level (level with values above the detection limit) in EBC (odds ratio: 1.38, 95% CI: 1.02 -1.86) as well as with LTB₄ in IS (%-change: 19%, 95% CI: 7% - 32%). The results remained consistent after exclusion of subpopulations with risk factors for inflammation (smoking, respiratory diseases, mould infestation) and after extension of models with additional adjustment for season of examination, mass of IS and urban/rural living as sensitivity analyses.

Conclusions

In this analysis of the SALIA study we found that long-term exposure to air pollutants from traffic and industrial sources was associated with an increase of several inflammatory markers in EBC and in IS. We conclude that long-term exposure to air pollution might lead to changes in the inflammatory marker profile in the lower airways in an elderly female population.

Biomarkers in Exhaled Breath Condensate and Serum of Chronic Obstructive Pulmonary Disease and Non-Small-Cell Lung Cancer

Chronic obstructive pulmonary disease (COPD) and lung cancer are leading causes of deaths worldwide which are associated with chronic inflammation and oxidative stress. Lung cancer, in particular, has a very high mortality rate due to the characteristically late diagnosis. As such, identification of novel biomarkers which allow for early diagnosis of these diseases could improve outcome and survival rate. Markers of oxidative stress in exhaled breath condensate (EBC) are examples of potential diagnostic markers for both COPD and non-small-cell lung cancer (NSCLC). They may even be useful in monitoring treatment response. In the serum, S100A8, S100A9, and S100A12 of the S100 proteins are proinflammatory markers. They have been indicated in several inflammatory diseases and cancers including secondary metastasis into the lung. It is highly likely that they not only have the potential to be diagnostic biomarkers for NSCLC but also prognostic indicators and therapeutic targets.

Breath biomarkers in diagnosis of pulmonary diseases

Breath analysis provides a convenient and simple alternative to traditional specimen testing in clinical laboratory diagnosis. As such, substantial research has been devoted to the analysis and identification of breath biomarkers. Development of new analytes enhances the desirability of breath analysis especially for patients who monitor daily biochemical parameters. Elucidating the physiologic significance of volatile substances in breath is essential for clinical use. This review describes the use of breath biomarkers in diagnosis of asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), lung cancer, as well as other pulmonary diseases. A number of breath biomarkers in lung pathophysiology will be described including nitric oxide (NO), carbon monoxide (CO), hydrogen peroxide (H₂O₂) and other hydrocarbons.

Rapid flu diagnosis using silicon nanowire sensor

Influenza epidemics worldwide result in substantial economic and human costs annually. However, rapid and reliable flu diagnosis methods are significantly lacking. Here we have demonstrated the selective detection of influenza A viruses down to 29 viruses/μL in clinical exhaled breath condensate (EBC) samples (diluted by 100-fold) within minutes using silicon nanowire (SiNW) sensor devices. For 90% of the cases, we have observed that EBC samples tested positive or negative by gold standard method RT-qPCR generated corresponding positive or negative SiNW sensor responses. High selectivity of SiNW sensing was also demonstrated using H1N1 viruses, 8 iso PGF 2a, and inert nanoparticles. Finally, magnetic beads were shown capable of enhancing SiNW sensing directly for low level viruses and 8 iso PGF 2a. When calibrated by virus standards and EBC controls, our work suggests that the SiNW sensor device can be reliably applied to the diagnosis of flu in a clinical setting with 2 orders of magnitude less time compared to the gold standard method RT-qPCR.

Plasma and exhaled breath condensate nitrite-nitrate level in relation to environmental exposures in adults in the EGEA study

This study evaluated the associations between biological markers in the nitrate-nitrite-NO pathway and four environmental exposures among subjects examined in the second survey (2003-2007) of the French Epidemiological study on Genetics and Environment of Asthma (EGEA). Total nitrite and nitrate (NO(2)(-) /NO(3)(-)) levels were measured both in plasma and in exhaled breath condensate (EBC) in 949 adults. Smoking, diet and exposure to chlorine products were assessed using standardized questionnaires. Exposure to air pollutants was estimated by using geostatistical models. All estimates were obtained with generalized estimating equations for linear regression models. Median levels of NO(2)(-)/NO(3)(-) were 36.3 μM (1st-3rd quartile: 25.7, 51.1) in plasma and 2.0 μmol/mg proteins (1st-3rd quartile 0.9, 3.9) in EBC. After adjustment for asthma, age, sex and menopausal status, plasma NO(2)(-)/NO(3)(-) level increased with leafy vegetable consumption (above versus below median=0.04 (95%CI: 0.001, 0.07)) and decreased in smokers (versus non/ex-smokers=-0.08 (95%CI: -0.11, -0.04). EBC NO(2)(-)/NO(3)(-) level decreased in smokers (-0.08 (95%CI: -0.16, -0.001)) and with exposure to ambient O(3) concentration (above versus below median=-0.10 (95%CI: -0.17, -0.03)). Cured meat, chlorine products, PM(10) and NO(2) concentrations were not associated with NO(2)(-)/NO(3)(-) levels. Results suggest that potential modifiable environmental and behavioral risk factors may modify NO(2)(-)/NO(3)(-) levels in plasma and EBC according to the route of exposure.

Spirometric maneuvers and inhaled salbutamol do not affect exhaled nitric oxide measurements among patients with allergic asthma

BACKGROUND

Exhaled nitric oxide (ENO) is used as a marker of airway inflammation. Factors such as spirometric maneuvers (SPM), β(2)-agonists, or tobacco smoking have been postulated to affect ENO measurements. Guidelines on measurement techniques have been published based on expert opinions. Nevertheless, there is no strong clinical evidence of many aspects because they have not been supported by research data.

OBJECTIVES

The aim of this study was to evaluate the influence of performing a spirometry or receiving inhaled salbutamol on ENO readings.

METHODS

One hundred forty-five adults and 62 children with allergic asthma were included with a mean age of 36 ± 13 years for adults and 13 ± 2 years for children. A control group comprised 30 healthy adults and 30 children with a mean age of 37 ± 14 years and 13 ± 2 years, respectively. ENO measurements were performed with a NIOX-MINO® electrochemical device. In 179 patients ENO was measured before and after performing SPM and in 88 patients before and 15 min after SPM plus 2 puffs of salbutamol (100 μg/puff).

RESULTS

There were no significant differences in mean ENO levels before and after SPM or before and after SPM plus 2 puffs of inhaled salbutamol in adults or children (asthmatic or healthy).

CONCLUSIONS

Levels of ENO are not significantly affected by SPM or salbutamol inhalation.

Nitrite in exhaled breath condensate as a marker of nitrossative stress in the airways of patients with asthma, COPD, and idiopathic pulmonary fibrosis

BACKGROUND

Nitrite and nitrate are exhaled in droplets of an aerosol during breathing and can be assayed in the exhaled breath condensate (EBC) as markers of nitrossative stress in the airways of patients with asthma, COPD, and idiopathic pulmonary fibrosis (IPF).

SUBJECTS AND METHODS

Using HPLC with fluorescence detection, nitrite and nitrate were assayed in EBC of 14 atopic patients with mild-to-moderate stable asthma, 18 atopic asthmatics with exacerbation, 14 COPD patients without exacerbation, 18 patients with exacerbated COPD, 13 patients with active IPF, and in 29 healthy subjects.

RESULTS

The geometric mean [exp(mean±SD)] EBC concentrations of nitrite (micromol/l) in patients with asthma [5.1(2.1-12.3)], exacerbation of asthma [5.1(2.8-9.6)], exacerbation of COPD [5.3(3.2-8.7)], and with IPF [5.5(2.9-10.2)] were higher (P<0.05) compared with those of healthy subjects [2.9(1.6-5.3)] and patients with stable COPD [3.0(1.3-6.7)]. Nitrite concentration increased with decreased lung function of patients with asthma (r(s)=-0.31, P<0.02). Presumably owing to the contamination of the EBC sample with nitrate during collection, nitrate levels were highly variable among healthy subjects and higher compared with all groups of patients.

CONCLUSION

EBC nitrite is a suitable marker of nitrossative stress in adult patients with lung diseases but cannot differentiate controlled and exacerbated asthma. Further improvements to the methods of EBC collection and sample handling are warranted.

Oxidative stress in COPD and its measurement through exhaled breath condensate

Oxidative stress and airway inflammation together form a vicious cycle, which is responsible for the disease progression in chronic pulmonary obstructive disease (COPD). The damaging effects of oxidative stress accumulate over the years, causing increased bronchial hyperresponsiveness and inflammation and destruction of airway epithelial cells and impairing the functions of antiproteases and surfactant. Although the lung expresses a number of antioxidants, cigarette smoking and recurrent infections associated with this disease overwhelm this protective mechanism. Studies of antioxidants in COPD have yielded conflicting results, probably due to the compartmentalization of these mediators, and because of the fact that the lung is a difficult organ to sample. Chronic exposure to oxidants upregulates the production of antioxidants, which become depleted during acute exacerbations. Future studies of the pathogenesis of COPD require a noninvasive yet accurate sampling procedure, of which exhaled breath condensate (EBC) is a good candidate. EBC samples the epithelial lining fluid, which contains the local oxidative stress markers in the lung. Oxidative stress markers such as hydrogen ions, hydrogen peroxide, 8-isoprostanes, thiobarbituric acid reactive products, nitrosothiols, and nitrite/nitrate have been identified in EBC of COPD patients, whereas many other markers of the oxidative-antioxidative balance have yet to be investigated.

Relationship between exhaled nitric oxide and treatment response in COPD patients with exacerbations

BACKGROUND AND OBJECTIVE

Fractional exhaled nitric oxide (FENO) has been implicated as a pulmonary biomarker in various respiratory diseases, including COPD. In this longitudinal study, the benefit of measuring FENO in a routine clinical setting was assessed in COPD patients hospitalized with an exacerbation of the disease.

METHODS

FENO, lung function and blood gases were measured in 58 COPD patients at hospital admission due to an exacerbation, and at discharge following treatment with corticosteroids and bronchodilators.

RESULTS

FENO levels were significantly decreased at discharge, compared with those at admission (geometric mean 25.3 ppb (95% CI: 21.2-30.1) vs 19.7 ppb (95% CI: 17.2-22.6); P = 0.002). There was a significant positive correlation between FENO concentrations at admission and the increase in FEV(1) after treatment (r = 0.441, P < 0.001), and a significant inverse correlation between FENO values at admission and the mean length of hospital stay (r = -0.297, P = 0.016). Using receiver operating characteristic curve analysis, the optimum cut point for FENO as a predictor for significant increase in FEV(1) was 26.8 ppb (sensitivity: 74%, specificity: 75%). There were no correlations between FENO levels and absolute values for lung function variables at admission or discharge.

CONCLUSIONS

These data suggest that FENO levels determined at hospital admission may predict the overall response to treatment in COPD patients with acute exacerbations.

Exhaled breath condensate and airway inflammation

PURPOSE OF REVIEW

The collection of exhaled breath condensate (EBC) is a noninvasive method for evaluation of airway inflammation. This article reviews recent data concerning the ability of EBC markers to reflect alterations in asthma and chronic obstructive pulmonary disease or environment and occupation-induced changes.

RECENT FINDINGS

The recovery of biomarkers in EBC is affected by physical characteristics of the condensing device and collecting circumstances as well as environmental conditions or exercise. The complexities of nitrogen oxide chemistry make assessment of nitric oxide metabolites in EBC and exhaled nitric oxide complementary. Analysing of EBC markers is valuable in asthma, as changes were reported irrespective of current anti-inflammatory treatment or atopic status as well as in monitoring cigarette smoking-related airway inflammation in chronic obstructive pulmonary disease patients. Hyperinflation in chronic obstructive pulmonary disease might be a potential confounder for the level of inflammation markers in EBC. In general, patterns of markers are likely to more accurately reflect the complex pathophysiological processes and therefore should be evaluated rather than a single marker.

SUMMARY

EBC might be of particular interest in preventive medicine as inflammatory processes triggered may precede changes in lung function. Robust and easy-to-handle condensing devices and analytical methods are warranted to spread the use of EBC.

Bibliography. Current world literature

This bibliography is compiled by clinicians from the journals listed at the end of this publication. It is based on literature entered into our database between 1 November 2007 and 31 October 2008 (articles are generally added to the database about two and a half months after publication). In addition, the bibliography contains every paper annotated by reviewers; these references were obtained from a variety of bibliographic databases and published between the beginning of the review period and the time of going to press. The bibliography has been grouped into topics that relate to the reviews in this issue.

Fractional exhaled nitric oxide in asthma: an update

In asthma, clinical symptoms and lung function are insensitive in reflecting the underlying airway inflammation, and monitoring of this process has only recently become available. Fractional exhaled nitric oxide (Fe(NO)) is now recognized as a reliable surrogate marker of eosinophilic airway inflammation and offers the advantage of being completely non-invasive and very easy to obtain. This review summarizes the clinical use of Fe(NO) in asthma. It covers the relationship between Fe(NO) and the underlying eosinophilic inflammation, the pathophysiology and production of Fe(NO), technical aspects of Fe(NO) measurement and potential confounding factors in interpreting levels. Fe(NO) reference values and the role of Fe(NO) in asthma assessment, diagnosis and management are also discussed.

Biomarkers in exhaled breath condensate: a review of collection, processing and analysis

Exhaled breath condensate (EBC) is a potential rich source for countless biomarkers that can provide valuable information about respiratory as well as systemic diseases. EBC has been studied in a variety of diseases including allergic rhinitis, asthma, chronic obstructive lung disease, cystic fibrosis, lung cancer, and obstructive sleep apnea syndrome. Although numerous biomarkers have been discovered and studied in EBC, the methods of collection and biomarker detection have not been fully standardized. While leaving standardization methods up to individual labs for the present time is optimal for the continued discovery of new biomarkers in EBC, this decreases the reproducibility and generalizability of the findings. In this review we will discuss specific biomarkers studied in specific diseases as well as some of the related technical issues including collection, processing and analysis.

Exhaled breath analysis: novel approach for early detection of lung cancer

Lung cancer is a leading cause of cancer death, with the prognosis adversely affected by late diagnosis. Early diagnosis of lung cancer is desirable, but current evidence does not support the application of screening with techniques such as chest radiography, sputum cytology or computed tomography. Breath analysis, which includes gaseous phase analysis that measures volatile organic compounds using electronic noses, exhaled nitric oxide, and exhaled breath condensate (EBC), has been proposed as a non-invasive and simple technique to investigate neoplastic processes in the airways. EBC can be easily collected by breathing into a cooling system that condenses the water vapour in the breath. EBC has already been demonstrated to be useful in investigating inflammatory and oxidative stress changes in various respiratory conditions as it contains measurable mediators of airway inflammation and oxidative stress markers. Furthermore, EBC has also been shown to be a useful method to monitor severity of diseases such as asthma and to act as a surrogate measure of compliance to medical therapy. Presently, there still remains a relative paucity of lung cancer research involving EBC. However, since EBC is a simple, non-invasive technique that can be easily performed, even in ill patients, it has the potential to be validated for use in screening for the early diagnosis of lung cancer.