Exhaled markers of pulmonary disease

Activation of heme oxygenase and suppression of cGMP are associated with impaired endothelial function in obstructive sleep apnea with hypertension

BACKGROUND

Obstructive sleep apnea (OSA) is a highly prevalent disorder that increases the risk of systemic hypertension and cardiovascular diseases. Heme oxygenase (HO) has been shown to be upregulated in patients with OSA and its overexpression in mice causes hypertension. End products of HO are carbon monoxide (CO) and bilirubin. CO exerts a pleiotropic action on vasoregulation. Despite high prevalence and incident of hypertension in OSA, its pathophysiology is not well-understood, particularly in regard to varying susceptibility of patients to hypertension. We investigated the role of HO in endothelial dysfunction and hypertension in OSA.

METHODS

We determined flow-mediated vasodilatation (FMD) as a measure of endothelial-dependent vasodilatory capacity, exhaled CO, bilirubin, and guanosine 3',5'-cyclic monophosphate (cGMP) in 63 subjects with OSA (normotensive 27, hypertensive 36) and in 32 subjects without OSA (normotensive 19, hypertensive 13).

RESULTS

Hypertensive OSA demonstrated marked impairment in FMD (8.0 ± 0.5% vasodilatation) compared to 10.5 ± 0.8% in hypertensives non-OSA (P < 0.01) and 13.5 ± 0.5% in normotensive OSA (P < 0.001) and 16.1 ± 1.1% in normotensive non-OSA (P < 0.0001). HO was upregulated and plasma nitric oxide (NO) was significantly increased in hypertensive OSA compared to normotensive OSA and hypertensive non-OSA. Conversely, serum cGMP was markedly decreased in hypertensive OSA (12.9 ± 1.8 pmol/ml vs. 20.6 ± 3.7 in normotensive OSA, P = 0.032). There was an inverse relationship between FMD and CO and bilirubin concentrations (r = 0.43, P = 0.0001 and r = 0.28, P = 0.01, respectively).

CONCLUSIONS

These data show that increased CO in the setting of elevated NO concentrations is associated with decreased cGMP, impaired FMD, and hypertension in patient with OSA.

Allergic asthma exhaled breath metabolome: a challenge for comprehensive two-dimensional gas chromatography

Allergic asthma represents an important public health issue, most common in the paediatric population, characterized by airway inflammation that may lead to changes in volatiles secreted via the lungs. Thus, exhaled breath has potential to be a matrix with relevant metabolomic information to characterize this disease. Progress in biochemistry, health sciences and related areas depends on instrumental advances, and a high throughput and sensitive equipment such as comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC×GC-ToFMS) was considered. GC×GC-ToFMS application in the analysis of the exhaled breath of 32 children with allergic asthma, from which 10 had also allergic rhinitis, and 27 control children allowed the identification of several hundreds of compounds belonging to different chemical families. Multivariate analysis, using Partial Least Squares-Discriminant Analysis in tandem with Monte Carlo Cross Validation was performed to assess the predictive power and to help the interpretation of recovered compounds possibly linked to oxidative stress, inflammation processes or other cellular processes that may characterize asthma. The results suggest that the model is robust, considering the high classification rate, sensitivity, and specificity. A pattern of six compounds belonging to the alkanes characterized the asthmatic population: nonane, 2,2,4,6,6-pentamethylheptane, decane, 3,6-dimethyldecane, dodecane, and tetradecane. To explore future clinical applications, and considering the future role of molecular-based methodologies, a compound set was established to rapid access of information from exhaled breath, reducing the time of data processing, and thus, becoming more expedite method for the clinical purposes.

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.

Cardiovascular biomarkers in exhaled breath

With each breath that we exhale, thousands of molecules are expelled in our breath, giving individuals a "breath-print" that can tell a lot about them and their state of health. Breath analysis is rapidly evolving as the new frontier in medical testing. The end of the 20th century and the beginning of the 21st century have arguably witnessed a revolution in our understanding of the constituents of exhaled breath and the development of the field of breath analysis and testing. Thanks to major breakthroughs in new technologies (infrared, electrochemical, chemiluminescence, and others) and the availability of mass spectrometers, the field of breath analysis has made considerable advances in the 21st century. Several methods are now in clinical use or nearly ready to enter that arena. Breath analysis has the potential to offer relatively inexpensive, rapid, noninvasive methods for detecting and/or monitoring a variety of diseases. Breath analysis also has applications in fields beyond medicine, including environmental monitoring, security, and others. This review will focus on exhaled breath as a potential source of biomarkers for medical applications with specific attention to applications (and potential applications) in cardiovascular disease.

New insights into the role of oxidative stress in scleroderma fibrosis

Systemic sclerosis (Scleroderma – SSc) is a connective tissue disorder of unknown aetiology characterized by extensive fibrosis of the skin and visceral organs, by vascular abnormalities and immunological manifestations.

Recent evidence suggest that the cellular redox state may play a significant role in the progression of scleroderma fibrosis. Mechanisms involved include an autoamplification circuit linking ROS, Ras and ERK 1-2 which in turn amplifies and maintains the autocrine loop made up by cytokines, growth factors and their cognate receptors.

This review summarizes the recent progress on the role of oxidative stress in the pathophysiology of scleroderma and disorders characterised by organ fibrosis

Exhaled eicosanoids and biomarkers of oxidative stress in exacerbation of chronic obstructive pulmonary disease

INTRODUCTION

Eicosanoids and oxidants play an important role in inflammation, but their role in chronic obstructive pulmonary disease (COPD) is uncertain. In this study we hypothesized that levels of exhaled leukotrienes, prostaglandins and biomarkers of oxidative stress are increased in infectious exacerbations of COPD and that they decrease after antibiotic therapy.

MATERIAL AND METHODS

Cysteinyl-leukotrienes (LTs), leukotriene B(4) (LTB(4)), prostaglandin E(4), hydrogen peroxide (H(2)O(2)) and 8-isoprostane were measured in exhaled breath condensate (EBC) in 16 COPD patients with infectious exacerbations (mean age 64 ±12 years, 13 male) on day 1, during antibiotic therapy (days 2-4), 2-4 days after therapy and at a follow-up visit when stable (21-28 days after therapy).

RESULTS

There was a significant fall in concentration of cys-LTs, LTB(4) and 8-isoprostane at visit 3 compared to day 1 (cys-LTs: 196.5 ±38.4 pg/ml vs. 50.1 ±8.2 pg/ml, p < 0.002; LTB(4): 153.6 ±25.5 pg/ml vs. 71.9 ±11.3 pg/ml, p < 0.05; 8-isoprostane: 121.4 ±14.6 pg/ml vs. 56.1 ±5.2 pg/ml, p < 0.03, respectively). Exhaled H(2)O(2) was higher on day 1 compared to that at visits 2 and 3 (0.74 ±0.046 µM vs. 0.52 ±0.028 µM and 0.35 ±0.029 µM, p < 0.01 and p < 0.01, respectively). Exhaled PGE(2) levels did not change during exacerbations of COPD. Exhaled eicosanoids and H(2)O(2) in EBC measured at the follow-up visit (stable COPD) were significantly higher compared to those from healthy subjects.

CONCLUSIONS

We conclude that eicosanoids and oxidants are increased in infectious exacerbations of COPD. They are also elevated in the airways of stable COPD patients compared to healthy subjects.

Exhaled breath condensate collection in the mechanically ventilated patient

Collection of exhaled breath condensate (EBC) is a non-invasive means of sampling the airway-lining fluid of the lungs. EBC contains numerous measurable mediators, whose analysis could change the management of patients with certain pulmonary diseases. While initially popularized in investigations involving spontaneously breathing patients, an increasing number of studies have been performed using EBC in association with mechanical ventilation. Collection of EBC in mechanically ventilated patients follows basic principles of condensation, but is influenced by multiple factors. Effective collection requires selection of a collection device, adequate minute ventilation, low cooling temperatures, and sampling times of greater than 10 min. Condensate can be contaminated by saliva, which needs to be filtered. Dilution of samples occurs secondary to distilled water in vapors and humidification in the ventilator circuit. Dilution factors may need to be employed when investigating non-volatile biomarkers. Storage and analysis should occur promptly at -70 °C to -80 °C to prevent rapid degradation of samples. The purpose of this review is to examine and describe methodologies and problems of EBC collection in mechanically ventilated patients. A straightforward and safe framework has been established to investigate disease processes in this population, yet technical aspects of EBC collection still exist that prevent clinical practicality of this technology. These include a lack of standardization of procedure and analysis of biomarkers, and of normal reference ranges for mediators in healthy individuals. Once these procedural aspects have been addressed, EBC could serve as a non-invasive alternative to invasive evaluation of lungs in mechanically ventilated patients.

Lipoxin A(4) and 8-isoprostane in the exhaled breath condensate of children hospitalized for status asthmaticus

OBJECTIVE

To measure levels of 8-isoprostane and Lipoxin A4 in the exhaled breath condensate of children (7-17 yrs old) recovering from status asthmaticus in a pediatric intensive care unit and to compare their respective levels in the exhaled breath condensate collected from age-matched "healthy" children enrolled from an ambulatory pediatric clinic during well-child visits.

DESIGN

Prospective case-controlled study.

SETTING

Teaching hospitals and a research laboratory.

PATIENTS

Children recovering from status asthmaticus and age-matched controls.

INTERVENTIONS

Collection of exhaled breath condensate from patients recovering from status asthmaticus and controls for purpose of measurement of 8-isoprostane and Lipoxin A4.

MEASUREMENTS AND MAIN RESULTS

There was no difference in age (11.9 ± 3.0 vs. 12.0 ± 3.3 yrs, p = .9) between patients and control subjects. All participants completed the exhaled breath condensate collection without complications. There was no difference in the pulmonary index (3.3 ± 2.2 vs. 3.1 ± 1.9, p = 1.0) after collection of exhaled breath condensate compared with baseline values in patients with status asthmaticus. The level of 8-isoprostane was significantly higher (63 ± 9 vs. 41 ± 13 pg/mL, p < .001), whereas the level of Lipoxin A4 was significantly lower (5.6 ± 2.9 vs. 10.5 ± 3.1 ng/mL, p < .001) in the exhaled breath condensate from children recovering from status asthmaticus compared with control subjects.

CONCLUSIONS

8-Isoprostane was elevated and Lipoxin A4 is decreased in the exhaled breath condensate of children recovering from status asthmaticus in a pediatric intensive care unit. These data may provide new insight into the pathophysiology of asthma in children in this clinical setting.

Irritant-induced airway disorders

Thousands of persons experience accidental high-level irritant exposures each year but most recover and few die. Irritants function differently than allergens because their actions proceed nonspecifically and by nonimmunologic mechanisms. For some individuals, the consequence of a single massive exposure to an irritant, gas, vapor or fume is persistent airway hyperresponsiveness and the clinical picture of asthma, referred to as reactive airways dysfunction syndrome (RADS). Repeated irritant exposures may lead to chronic cough and continual airway hyperresponsiveness. Cases of asthma attributed to repeated irritant-exposures may be the result of genetic and/or host factors.

Hyperoxidized peroxiredoxins in peripheral blood mononuclear cells of asthma patients is associated with asthma severity

AIMS

Oxidative stress is involved in the pathogenesis of asthma, and peroxiredoxins (PRDX) may be critical in controlling intracellular oxidative stress. The aim of this study was to evaluate expressions of PRDX and their hyperoxidized forms in asthmatic individuals.

MAIN METHODS

The levels of expression of PRDX1, PRDX2, PRDX3, and PRDX6 and their hyperoxidized forms (PRDX-SO(3)) were measured in PBMCs from asthma patients and control subjects. In addition, cells from these subjects were treated with hydrogen peroxide (H(2)O(2)) and their intracellular concentrations of reactive oxygen species (ROS) were measured.

KEY FINDINGS

The ratios of hyperoxidized to total PRDX (PRDX-SO(3/)PRDX) in PBMCs were significantly higher in asthma patients than in normal subjects and were correlated with disease severity, with the highest ratio seen in patients with severe asthma. Furthermore, H(2)O(2) treatment of PBMCs, particularly lymphocytes, increased intracellular ROS concentrations with greater and more persistent increases observed in cells from asthmatic than from control subjects.

SIGNIFICANCE

Hyperoxidation of PRDX may serve as a biomarker of asthma severity and may predict enhanced susceptibility to oxidative stress load in PBMCs of asthmatics.

Exhaled breath condensate (EBC) biomarkers in pulmonary fibrosis

The diffuse parenchymal lung diseases (DPLDs) are a group of clinicopathological entities which have recently undergone reclassification. The commonest type of idiopathic DPLD is interstitial pulmonary fibrosis (PF), which is histologically characterized by usual interstitial pneumonia (UIP), with inflammatory changes in the alveoli and subsequent collagen deposition. A similar type of inflammatory change can also be seen with connective tissue disorders. Many mediators are involved, but it is difficult to study these in a non-invasive manner in patients. The aim of the study detailed in this paper was to investigate inflammatory and oxidative stress biomarkers in PF and correlate these with lung function. 20 PF patients and 20 controls participated in the study. Exhaled breath condensate (EBC) was collected over 10 min using a refrigerated condenser, after fractional exhaled nitric oxide (FeNO) and carbon monoxide (eCO) measurement. EBC total nitrogen oxides (NOx), hydrogen peroxide (H(2)O(2)), 8-isoprostane (8-iso), 3-nitrotyrosine (3-NT), pH and total protein were measured. EBC biomarkers were significantly raised in PF compared with controls: EBC 3-NT (2.5 (0.7-8.9) versus 0.3 (0.1-1.1) ng ml(-1), p = 0.02); pH (7.6 ± 0.3 versus 7.4 ± 0.2, p = 0.004); 8-isoprostane (0.2 (0.1-0.4) versus 0.08 (0.04-0.2) ng ml(-1), p = 0.04) and total protein (24.7 ± 21.1 versus 10.7 ± 7.0 µg ml(-1), p = 0.008). FeNO and eCO were also increased (8.6 (7.1-10.4) versus 6.6 (5.6-7.8) ppb, p = 0.04, and 4.5 ± 1.7 versus 2.7 ± 0.7 ppm, p = 0.001, respectively), but no significant differences were found for NOx or H(2)O(2). In conclusion, inflammatory and oxidative stress biomarkers are raised in patients with PF compared with controls. EBC may be useful for detecting and monitoring lung inflammation in PF.

Interest of exhaled biomarkers in occupational asthma to latex: a case report

New methods for exploring pulmonary inflammation might be useful: measurements of exhaled nitric oxide (NO) and hydrogen peroxide (H(2)O(2)) in exhaled breath condensate (EBC). The authors describe the application and utility of these methods in a case report of pediatric nurse presenting an occupational asthma to latex. Despite compliance with avoidance measures, respiratory discomfort had worsened during work. Classical tests (spirometry, monitoring of peak expiratory flow) were not contributing to objectify the discomfort. Exhaled NO and H(2)O(2) in EBC increased immediately after work periods, compared with rest periods. Application of these new methods, at the same time, in workplace appears useful in the objective demonstration of a temporal relation between work and respiratory problems. The results allowed the occupational physician to transfer the patient to a new work station more appropriate for her respiratory health status.

Biomarkers of therapeutic response in patients with chronic obstructive pulmonary disease: a critical review of the literature

Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality across the world. Unfortunately, none of the current therapies, except for smoking cessation and supplemental domiciliary oxygen for hypoxaemic patients, can modify its natural course or alter survival. The pipeline for new compounds is not very promising owing to repeated failures, and many large pharmaceutical companies have abandoned COPD drug discovery altogether. One major barrier to new drug discovery is the lack of modifiable biomarkers that can be used as surrogates of clinical outcomes such as exacerbation and mortality. The only accepted marker in COPD is forced expiratory volume in 1 second (FEV(1)). However, by definition, COPD is a non-reversible or poorly reversible condition with respect to FEV(1). Thus, very few drugs except for bronchodilators have been able to address this endpoint. Of many candidate molecules, sputum neutrophil counts, exhaled corrected alveolar nitric oxide and proline-glycine-proline (PGP) and N-α-PGP, which are breakdown products of collagen, are promising lung-based biomarkers. However, their clinical utility has not been validated in large clinical trials. Promising blood biomarkers include surfactant protein D, and pulmonary- and activation-regulated chemokine (PARC/CCL-18). However, the clinical data have been inconsistent. Non-specific inflammatory biomarkers such as C-reactive protein and interleukin-6 lack specificity for COPD and thus are of limited clinical usefulness.

Assessing recent smoking status by measuring exhaled carbon monoxide levels

BACKGROUND

Cigarette smoke causes both acute and chronic changes of the immune system. Excluding recent smoking is therefore important in clinical studies with chronic inflammation as primary focus. In this context, it is common to ask the study subjects to refrain from smoking within a certain time frame prior to sampling. The duration of the smoking cessation is typically from midnight the evening before, i.e. 8 hours from sampling. As it has been shown that a proportion of current smokers underestimates or denies smoking, objective assessment of recent smoking status is of great importance. Our aim was to extend the use of exhaled carbon monoxide (CO(breath)), a well-established method for separating smokers from non-smokers, to assessment of recent smoking status.

METHODS AND FINDINGS

The time course of CO(breath) decline was investigated by hourly measurements during one day on non-symptomatic smokers and non-smokers (6+7), as well as by measurements on three separate occasions on non-smokers (n = 29), smokers with normal lung function (n = 38) and smokers with chronic obstructive pulmonary disease (n = 19) participating in a clinical study. We used regression analysis to model the decay, and receiver operator characteristics analysis for evaluation of model performance. The decline was described as a mono-exponential decay (r(2) = 0.7) with a half-life of 4.5 hours. CO decline rate depends on initial CO levels, and by necessity a generic cut-off is therefore crude as initial CO(breath) varies a lot between individuals. However, a cut-off level of 12 ppm could classify recent smokers from smokers having refrained from smoking during the past 8 hours with a specificity of 94% and a sensitivity of 90%.

CONCLUSIONS

We hereby describe a method for classifying recent smokers from smokers having refrained from smoking for >8 hours that is easy to implement in a clinical setting.

The application of statistical methods using VOCs to identify patients with lung cancer

In this work, an attempt was made to determine a group of lung cancer biomarkers. For this study, breath samples collected from 137 patients with confirmed lung cancer were analyzed by the SPME-GC/MS method. As a reference group, exhaled air from 143 healthy volunteers with different smoking habits (active smokers, passive smokers and nonsmokers) was applied. Statistical methods such as discriminant analysis (DA) and the CHAID model tree were used for data processing and evaluation. In the breath of patients with lung cancer, increased concentration of ethanol, acetone, butane, dimethyl sulfide, isoprene, propanal, 1-propanol, 2-pentanone, furan, o-xylene and ethylbenzene was observed in comparison to healthy nonsmokers. Furthermore, pentanal, hexanal and nonane were identified only in the breath of people who suffered from cancer. DA confirmed the importance of these compounds and allowed us to identify patients with lung cancer from healthy volunteers. In the exhaled air of healthy smokers (passive and active), a higher concentration of acetonitrile, benzene and furan derivatives was observed than in nonsmokers. DA revealed that in order to recognize healthy volunteers with different smoking habits by breath analysis, butyrolactone, carbon disulfide and dimethyl sulfide have to be considered.

Genetic and epigenetic variations in inducible nitric oxide synthase promoter, particulate pollution, and exhaled nitric oxide levels in children

BACKGROUND

Inducible nitric oxide synthase (iNOS; encoded by nitric oxide synthase isoform 2 [NOS2]) is the major enzyme for nitric oxide synthesis in airways. As such, measurement of fractional concentration of exhaled nitric oxide (Feno) provides an in vivo assessment of iNOS activity. Short-term exposure to air pollution, haplotypes, and DNA methylation in the NOS2 promoter has been associated independently with iNOS expression, Feno levels, or both.

OBJECTIVE

We aimed to examine the effects of ambient air pollutants, NOS2 promoter haplotypes, and NOS2 promoter methylation on Feno levels in children.

METHODS

We selected 940 participants in the Children's Health Study who provided buccal samples and had undergone Feno measurement on the same day. DNA methylation was measured with a bisulfite-PCR Pyrosequencing assay. Seven single nucleotide polymorphisms captured the haplotype diversity in the NOS2 promoter. Average particulate matter with an aerodynamic diameter of 2.5 μm or less (PM(2.5)) and 10 μm (PM(10)) or less and ozone and nitrogen dioxide levels 7 days before Feno measurement were estimated based on air pollution data obtained at central monitoring sites.

RESULTS

We found interrelated effects of PM(2.5), NOS2 promoter haplotypes, and iNOS methylation on Feno levels. Increased 7-day average PM(2.5) exposure was associated with lower iNOS methylation (P = .01). NOS2 promoter haplotypes were globally associated with NOS2 promoter methylation (P = 6.2 × 10(-8)). There was interaction among 1 common promoter haplotype, iNOS methylation level, and PM(2.5) exposure on Feno levels (P(interaction) = .00007).

CONCLUSION

Promoter variants in NOS2 and short-term PM(2.5) exposure affect iNOS methylation. This is one of the first studies showing contributions of genetic and epigenetic variations in air pollution-mediated phenotype expression.

Pathophysiology of allergic inflammation

Allergic inflammation is due to a complex interplay between several inflammatory cells, including mast cells, basophils, lymphocytes, dendritic cells, eosinophils, and sometimes neutrophils. These cells produce multiple inflammatory mediators, including lipids, purines, cytokines, chemokines, and reactive oxygen species. Allergic inflammation affects target cells, such as epithelial cells, fibroblasts, vascular cells, and airway smooth muscle cells, which become an important source of inflammatory mediators. Sensory nerves are sensitized and activated during allergic inflammation and produce symptoms. Allergic inflammatory responses are orchestrated by several transcription factors, particularly NF-κB and GATA3. Inflammatory genes are also regulated by epigenetic mechanisms, including DNA methylation and histone modifications. There are several endogenous anti-inflammatory mechanisms, including anti-inflammatory lipids and cytokines, which may be defective in allergic disease, thus amplifying and perpetuating the inflammation. Better understanding of the pathophysiology of allergic inflammation has identified new therapeutic targets but developing effective novel therapies has been challenging. Corticosteroids are highly effective with a broad spectrum of anti-inflammatory effects, including epigenetic modulation of the inflammatory response and suppression of GATA3.

Validation study of asthma screening criteria based on subjective symptoms and fractional exhaled nitric oxide

BACKGROUND

In the latest Global Initiative for Asthma guideline, neither sputum eosinophilia nor fractional exhaled nitric oxide (FeNO) have been evaluated prospectively as an aid in asthma diagnosis, but these measurements are being evaluated for potential use in determining optimal treatment.

OBJECTIVE

To report criteria for screening asthma using subjective symptoms and FeNO levels and results of a prospective validation study using these criteria.

METHODS

Sixty-one outpatients with recurrent cough, wheezing, or dyspnea underwent measurements of FeNO levels, pulmonary function, methacholine airway responsiveness, and inflammatory cells in induced sputum. The sensitivity, specificity, and concordance achieved using the FeNO-based criteria (at least 1 of the following subjective symptoms: recurrent cough, wheezing, or dyspnea and/or FeNO level ≥ 40 ppb) were analyzed and compared with the values obtained using conventional asthma diagnostic criteria, which includes subjective symptoms with any 2 of the following conditions: airway hyperresponsiveness, reversible airflow limitation, and eosinophilia in induced sputum.

RESULTS

Of the 61 patients, 41 were diagnosed as having asthma by the conventional criteria, and 33 were diagnosed as having asthma by the FeNO-based criteria, which showed a sensitivity of 78.6%, a specificity of 89.5%, and a concordance rate of 0.62. Nine of 42 patients were misdiagnosed as not having asthma by FeNO-based criteria (mean [SD] FeNO level, 23.9 [8.0] ppb). Seven of 9 patients were diagnosed as having nonatopic asthma according to IgE levels.

CONCLUSIONS

Asthma may be accurately diagnosed in daily practice on the basis of subjective symptoms and FeNO levels, particularly in atopic patients.

Fractional exhaled nitric oxide measurements in rhinitis and asthma in children

Exaled nitric oxide (FeNO) is considered a good noninvasive marker to assess airway inflammation in asthma and allergic rhinitis. In asthma, exhaled NO is very useful to verify adherence to therapy, and to predict upcoming asthma exacerbations. It has been also proposed that adjusting anti-inflammatory drugs guided by the monitoring of exhaled NO, could improve overall asthma control. Other studies showed increased FeNO levels in subjects with allergic rhinitis.

The application of exhaled breath gas and exhaled breath condensate analysis in the investigation of the lower respiratory tract in veterinary medicine: A review

The analysis of biomarkers in exhaled breath (EB) and exhaled breath condensate (EBC) may allow non-invasive and repeatable assessment of respiratory health and disease in mammals. Compared to human medicine, however, research data from EB and EBC analysis in veterinary medicine are limited and more patient variables influencing concentrations of EB/EBC analytes may be present. In addition, variations in methodologies between studies may influence results. A comparison of the approaches used in veterinary research by different groups may aid in the identification of potentially reliable and repeatable biomarkers suitable for further investigation. To date, changes in acid-base status and increased concentrations of inflammatory mediators have been the main findings in studies of pulmonary disease states in animals. Whilst these biomarkers are unlikely to represent specific and sensitive diagnostic parameters, they do have potential application in monitoring disease progression and treatment response.

Clinical study of multiple breath biomarkers of asthma and COPD (NO, CO(2), CO and N(2)O) by infrared laser spectroscopy

Breath analysis is a powerful non-invasive technique for the diagnosis and monitoring of respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD). Exhaled 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 quantum cascade laser system for analysis of multiple gases by tunable infrared absorption spectroscopy. The ARI breath analysis instrument has been deployed in a study of exhaled breath from patients with asthma or COPD. A total of 173 subjects participated, including both adult and pediatric patients. Patients in asthma or COPD exacerbations were evaluated twice-during the exacerbation and at a follow-up visit-to compare variations in breath biomarkers during these events. The change in exhaled NO levels between exacerbation and 'well' visits is consistent with spirometry data collected. Respiratory models are important for understanding the exchange dynamics of nitric oxide and other species in the lungs and airways. At each patient's visit, tests were conducted at four expiratory flow rates. We have applied a trumpet model with axial diffusion to the multi-flow exhaled nitric oxide data, obtaining NO alveolar concentrations and airway fluxes. We found higher airway fluxes for those with more severe asthma and during exacerbation events. The alveolar concentrations from the model were higher in adults with asthma and COPD, but this trend was less clear among the pediatric subjects.

The effect of caffeinated coffee on airway response to methacholine and exhaled nitric oxide

BACKGROUND

The bronchoprotective effect of caffeine on histamine challenge testing (HCT) has been studied with equivocal results. Current guidelines for bronchoprovocation testing recommend exclusion of caffeine the day of testing. The effects of caffeine on methacholine challenge testing (MCT), now more commonly performed than histamine challenge, are unknown.

METHODS

Sixteen well-controlled asthmatics with a forced expiratory volume in 1 s (FEV(1)) > 65% predicted and methacholine provocation concentration causing a 20% fall in FEV(1) (PC(20)) ≤ 16 mg/ml participated in a randomized single-blind crossover study. The two treatments included 16 ounces of caffeinated and decaffeinated coffee given on two separate days. The fraction of exhaled nitric oxide (eNO) and FEV(1) were measured before and 1 h after each treatment. One hour post treatment blood was drawn for serum caffeine level and the MCT was done.

RESULTS

Fourteen subjects completed the study; there were no adverse events. No significant bronchodilation was seen between the mean FEV(1) values before and after the caffeinated treatment (3.31 ± 0.75 L and 3.36 ± 0.74 L, respectively). No significant bronchoprotection was seen between the caffeinated and decaffeinated treatment's geometric mean PC(20) values (1.35 mg/ml and 1.36 mg/ml, respectively). Mean eNO values before and after caffeinated treatment were not significantly different (31.2 ± 19.6 ppb and 31.5 ± 20.4 ppb).

CONCLUSION

The amount of caffeine in a normal dietary serving of a 16 oz cup of coffee is not enough to cause significant bronchoprotection, bronchodilation, or decrease eNO values. Registered at http://clinicaltrials.gov: NCT01057875.

Analysis of nitrogen oxides (NOx) in the exhaled breath condensate (EBC) of subjects with asthma as a complement to exhaled nitric oxide (FeNO) measurements: a cross-sectional study

Background

The study of pulmonary biomarkers with noninvasive methods, such as the analysis of exhaled breath condensate (EBC), provides a useful approach to the pathophysiology of asthma. Although many recent publications have applied such methods, numerous methodological pitfalls remain. The first stage of our study consisted of validating methods for the collection, storage and analysis of EBC; we next sought to clarify the utility of analysing nitrogen oxides (NOx) in the EBC of asthmatics, as a complement to measuring exhaled nitric oxide (FeNO).

Methods

This hospital-based cross-sectional study included 23 controls matched with 23 asthmatics. EBC and FeNO were performed and respiratory function measured. Intra-assay and intra-subject reproducibility were assessed for the analysis of NOx in the EBC of 10 healthy subjects.

Results

The intraclass correlation coefficient (ICC) was excellent for intra-assay reproducibility and was moderate for intra-subject reproducibility (Fermanian's classification). NOx was significantly higher in asthmatics (geometric mean [IQR] 14.4 μM [10.4 - 19.7] vs controls 9.9 μM [7.5 - 15.0]), as was FeNO (29.9 ppb [17.9 - 52.4] vs controls 9.6 ppb [8.4 - 14.2]). FeNO also increased significantly with asthma severity.

Conclusions

We validated the procedures for NOx analysis in EBC and confirmed the need for assays of other biomarkers to further our knowledge of the pathophysiologic processes of asthma and improve its treatment and control.

Nitrative stress in inflammatory lung diseases

Since the discovery of nitric oxide (NO), an intracellular signal transmitter, the role of NO has been investigated in various organs. In the respiratory system, NO derived from the constitutive type of NO synthase (cNOS, NOS1, NOS3) induces bronchodilation and pulmonary vasodilatation to maintain homeostasis. In contrast, the roles of excessive NO derived from the inducible type of NOS (iNOS, NOS2) in airway and lung inflammation in inflammatory lung diseases including bronchial asthma and chronic obstructive pulmonary disease (COPD) are controversial. In these inflammatory lung diseases, excessive nitrosative stress has also been observed. In asthma, some reports have shown that nitrosative stress causes airway inflammation, airway hyperresponsiveness, and airway remodeling, which are the features of asthma, whereas others have demonstrated the anti-inflammatory role of NO derived from NOS2. In the case of refractory asthma, more nitrosative stress has been reported to be observed in such airways compared with that in well-controlled asthmatics. In COPD, reactive nitrogen species (RNS), which are NO and NO-related molecules including nitrogen dioxide and peroxynitrite, cause lung inflammation, oxidative stress, activation of matrix metalloproteinase, and inactivation of antiprotease, which are involved in the pathophysiology of the disease. In the present paper, we review the physiological and pathophysiological effects of NO and NO-related molecules in the respiratory system and in inflammatory lung diseases.

Ambient analysis of trace compounds in gaseous media by SIFT-MS

The topic of ambient gas analysis has been rapidly developed in the last few years with the evolution of the exciting new techniques such as DESI, DART and EESI. The essential feature of all is that analysis of trace gases can be accomplished either in the gas phase or those released from surfaces, crucially avoiding sample collection or modification. In this regard, selected ion flow tube mass spectrometry, SIFT-MS, also performs ambient analyses both accurately and rapidly. In this focused review we describe the underlying ion chemistry underpinning SIFT-MS through a discourse on the reactions of different classes of organic and inorganic molecules with H(3)O(+), NO(+) and O(2)(+)˙ studied using the SIFT technique. Rate coefficients and ion products of these reactions facilitate absolute SIFT-MS analyses and can also be useful for the interpretation of data obtained by the other ambient analysis methods mentioned above. The essential physics and flow dynamics of SIFT-MS are described that, together with the reaction kinetics, allow SIFT-MS to perform absolute ambient analyses of trace compounds in humid atmospheric air, exhaled breath and the headspace of aqueous liquids. Several areas of research that, through pilot experiments, are seen to benefit from ambient gas analysis using SIFT-MS are briefly reviewed. Special attention is given to exhaled breath and urine headspace analysis directed towards clinical diagnosis and therapeutic monitoring, and some other areas researched using SIFT-MS are summarised. Finally, extensions to current areas of application and indications of other directions in which SIFT-MS can be exploited for ambient analysis are alluded to.

Exploring airway diseases by NMR-based metabonomics: a review of application to exhaled breath condensate

There is increasing evidence that biomarkers of exhaled gases or exhaled breath condensate (EBC) may help in detecting abnormalities in respiratory diseases mirroring increased, oxidative stress, airways inflammation and endothelial dysfunction. Beside the traditional techniques to investigate biomarker profiles, "omics" sciences have raised interest in the clinical field as potentially improving disease phenotyping. In particular, metabonomics appears to be an important tool to gain qualitative and quantitative information on low-molecular weight metabolites present in cells, tissues, and fluids. Here, we review the potential use of EBC as a suitable matrix for metabonomic studies using nuclear magnetic resonance (NMR) spectroscopy. By using this approach in airway diseases, it is now possible to separate specific EBC profiles, with implication in disease phenotyping and personalized therapy.

Progress in SIFT-MS: breath analysis and other applications

The development of selected ion flow tube mass spectrometry, SIFT-MS, is described from its inception as the modified very large SIFT instruments used to demonstrate the feasibility of SIFT-MS as an analytical technique, towards the smaller but bulky transportable instruments and finally to the current smallest Profile 3 instruments that have been located in various places, including hospitals and schools to obtain on-line breath analyses. The essential physics and engineering principles are discussed, which must be appreciated to design and construct a SIFT-MS instrument. The versatility and sensitivity of the Profile 3 instrument is illustrated by typical mass spectra obtained using the three precursor ions H(3)O(+), NO(+) and O(2)(+)·, and the need to account for differential ionic diffusion and mass discrimination in the analytical algorithms is emphasized to obtain accurate trace gas analyses. The performance of the Profile 3 instrument is illustrated by the results of several pilot studies, including (i) on-line real time quantification of several breath metabolites for cohorts of healthy adults and children, which have provided representative concentration/population distributions, and the comparative analyses of breath exhaled via the mouth and nose that identify systemic and orally-generated compounds, (ii) the enhancement of breath metabolites by drug ingestion, (iii) the identification of HCN as a marker of Pseudomonas colonization of the airways and (iv) emission of volatile compounds from urine, especially ketone bodies, and from skin. Some very recent developments are discussed, including the quantification of carbon dioxide in breath and the combination of SIFT-MS with GC and ATD, and their significance. Finally, prospects for future SIFT-MS developments are alluded to.

Stability of sealed-bag samples for off-line measurement of fractional exhaled nitric oxide

BACKGROUND

Fractional exhaled nitric oxide (FeNO) measurement is an index of airway eosinophilic inflammation and is primarily employed to diagnose bronchial asthma and assess airway inflammation. It can be measured with on- and off-line methods. In the latter, sample storage is possible; this is useful in Japan, because the number of facilities in which this instrument has been installed is limited.

OBJECTIVE

We investigated the maximum period in which the samples continued to show stable values, as well as the influences of the storage environment.

METHODS

Exhaled air samples were collected from 19 bronchial asthma patients (male/female: 8/11; mean age: 54.9 ± 15.6 years), and divided into 2 groups: a group with an FeNO level of less than 30 ppb and that with a level of 30 ppb or more. They were stored at 4 and 25°C to examine serial changes.

RESULTS

The off-line-measured FeNO value was 33.7 ± 17.1 ppb, significantly lower than the on-line measured value (71.4 ± 47.7 ppb) (P < .01). In a group with an FeNO level of less than 30 ppb, temperature had no influence. However, in the other group, the period was prolonged to 72 hours when the samples were stored at 4°C. The samples were stable at 4°C for 24 hours, regardless of the initial measurements.

CONCLUSION

The duration of sample storage can be prolonged at 4°C. The standard FeNO measurement method is the on-line method, but the alternative use of the off-line method may contribute to the diagnosis and treatment of the patients.

Exhaled nitric oxide and spirometry in respiratory health surveillance

BACKGROUND

Exposure to pollutants in bakeries and hairdressing salons can cause airway syndromes varying from bronchial irritation to asthma. Workplace respiratory health surveillance aims to identify possible cases requiring further investigation.

AIMS

To compare the performance of fractional exhaled nitric oxide (FE(NO)) and spirometry for health surveillance of apprentice bakers (ABs) and apprentice hairdressers (AHDs). Determinants of FE(NO) were also identified.

METHODS

Symptoms and physician-diagnosed asthma were evaluated by questionnaire. FE(NO) was measured and spirometry was carried out. Subjects with elevated FE(NO) (FE(NO) > upper limit normal), airway obstruction [forced expiratory volume in 1 s (FEV(1))/forced vital capacity (FVC) < 95th percentile] and atopy (history of allergies) were identified.

RESULTS

A total of 126 apprentices (59 ABs and 67 AHDs) participated. Twenty-nine (23%) apprentices had abnormal tests: 4 had associated high FE(NO) and airway obstruction, while 25 had either high FE(NO) (n = 15) or airway obstruction (n = 10) alone. Compared with ABs (n = 16), AHDs (n = 13) had more asthma (38 versus 0%; P < 0.05) and atopy (62 versus 6%; P < 0.05). There was no difference in symptoms, smoking FE(NO) or airways obstruction. Among 97 subjects with normal tests, no differences existed between ABs (n = 53) and AHDs (n = 44). Average FE(NO) was increased in atopic non-smokers compared with atopic smokers and non-atopic subjects (P < 0.05). Smoking, a history of allergies, FEV(1)/FVC % observed and respiratory symptoms were the main determinants of FE(NO).

CONCLUSIONS

FE(NO) and spirometry were not overlapping dimensions in ABs and hairdressers, each test contributing unique information on the physiological status of the respiratory system. FE(NO) may provide added information on airway inflammation not provided by spirometry.

8-Isoprostane in the exhaled breath condensate of children hospitalized for status asthmaticus

OBJECTIVE

To evaluate the safety and feasibility of exhaled breath condensate (EBC) collection in children recovering from status asthmaticus (SA) in a pediatric intensive care unit (PICU); and to investigate whether 8-isoprostane (8-Iso) could be detected in the EBC of these children and to compare its concentration with that in the EBC collected from healthy children.

DESIGN

Prospective study.

SETTING

Multidisciplinary PICU in a teaching hospital.

PATIENTS

Sixteen consecutive patients (7-18 yrs of age) with SA and 16 age- and sex-matched controls.

INTERVENTIONS

The Wood clinical asthma score and the pulmonary index were used to assess the clinical severity of patients with SA upon admission to the PICU. EBC samples were collected within 24 hrs of admission to the PICU and were analyzed for the concentration of 8-Iso.

MEASUREMENTS AND MAIN RESULTS

Data are presented as mean ± sd values. There were no differences in age (12 ± 3.3 yrs vs.12 ± 2 yrs, p > .05) or sex (n = 10 males and n = 6 females in each group), between SA patients and controls. All patients with SA and the controls completed the EBC collection without complications. There was no statistically significant difference in the pulmonary index (3.2 ± 2.7 vs. 3.1 ± 2.8, p 0.9) post collection of EBC compared with the baseline values. There was a statistically significant correlation between Wood score and pulmonary index at the time of admission to the PICU in children with SA (r = .7, p < .01). The concentration of 8-Iso was significantly higher in the EBC of children with SA compared with controls (14.3 ± 1.8 pg/mL vs. 5.2 ± 0.7 pg/mL, p < .001). The correlation between the concentration 8-Iso and either the pulmonary index or Wood score at the time admission to the PICU was not statistically significant.

CONCLUSIONS

EBC collection is well tolerated by children aged 7-18 yrs who are recovering from SA in a PICU. 8-Iso is elevated in the EBC from children with SA and may provide insight into the biochemical changes of oxidative stress in children in this clinical setting.

Effect of different monotherapies on serum nitric oxide and pulmonary functions in children with mild persistent asthma

INTRODUCTION

Common medications used to treat mild persistent asthma are glucocorticoids, leukotriene receptor antagonists and theophylline. The aim of the study was to evaluate monotherapy with either inhaled steroids, oral leukotriene receptor antagonist or theophylline in Egyptian children with mild persistent asthma by determining their clinical, laboratory and spirometric responses to treatment.

MATERIAL AND METHODS

Thirty-nine mild asthmatic children between 8 and 13 years of age were included in the study. Patients were classified according to therapy received into four groups: oral leukotriene receptor antagonist (montelukast), inhaled corticosteroid (fluticasone propionate), sustained-release (SR) theophylline, and no treatment. Pulmonary function testing was performed at the start of therapy and 8 weeks later using spirometry. Eosinophil count and serum nitric oxide were estimated in the blood. Minitab statistical package was used for analysis of data.

RESULTS

Follow-up after 8 weeks revealed significant improvement in FEV1% in groups 1 (p < 0.01) and 3 (p < 0.05), significant improvement in PEFR in groups 1 (p < 0.05) and 2 (p < 0.01), significant decline in serum NO levels in groups 1 (p < 0.05) and 2 (p < 0.05), as well as significant improvement in eosinophil count in groups 1, 2 and 3 (p < 0.01, < 0.001, < 0.01 respectively). There was a statistically significant positive correlation between the decline in serum NO and the decline in blood eosinophil % in group 2 (p < 0.05).

CONCLUSIONS

Inhaled corticosteroids and montelukast have a significant role in controlling the pulmonary functions and the inflammatory process in children with mild persistent asthma, although inhaled corticosteroids seem to yield a better response. Children with mild persistent asthma should receive a controller medication, and SR theophylline may be a good cost-benefit alternative for low socio-economic groups of patients.

Exhaled air temperature in children with bronchopulmonary dysplasia

BACKGROUND

Because they have similar functional and clinical profiles, bronchopulmonary dysplasia (BPD) survivors are often treated as asthmatic patients. In truth, very little is known about the possible biochemical and inflammatory mechanisms playing a part in BPD survivors' lungs. The aim of this study was to measure exhaled breath temperature in BPD survivors by comparison with asthmatic cases and healthy controls.

METHODS

Three groups of age-matched adolescents (n = 17 each), that is, BPD survivors (gestational ages <31 weeks, birth weights <1,500 g), asthmatic subjects and healthy controls, underwent exhaled breath temperature and exhaled nitric oxide measurements, and spirometry.

RESULTS

Exhaled breath temperature was significantly lower in the BPD survivors (26.72°C [25.11-27.57]) than in the asthmatic patients (29.60°C [29.20-30.02], P < 0.001), while no significant difference emerged by comparison with healthy controls (26.97°C [26.58-27.38]). Considering the whole study population, a significant correlation was found between exhaled breath temperatures and exhaled nitric oxide concentrations (R = 0.42, P = 0.004). Spirometry revealed an obstructive lung function pattern in both the asthmatic cases and the BPD survivors, with lower parameters in the latter.

CONCLUSIONS

Exhaled breath temperatures and exhaled nitric oxide concentrations are significantly lower in BPD survivors than in asthmatic cases, suggesting that different pathogenetic mechanisms characterize these two chronic obstructive lung diseases.

Isoprostanes-biomarkers of lipid peroxidation: their utility in evaluating oxidative stress and analysis

Isoprostanes (IsoPs) are key biomarkers for investigating the role of free radical generation in the pathogenesis of human disorders. To solve IsoPs-related problems with regard to isoprostanes, analytical tools are required. This paper reviews the problems and trends in this field focusing on the methodology for assaying biomarkers in exhaled breath condensate (EBC) samples. A large amount of work has been done in the qualitative and quantitative analysis of IsoPs, but a standardized method has yet to emerge. The methodologies described differ, either in the sample preparation steps or in the detection techniques, or both. Requiring a number of chromatographic steps, the relevant extraction and purification procedures are often critical and time-consuming, and they lead to a substantial loss of target compounds. Recent data show that EBC is a promising non-invasive tool for the evaluation of different diseases. Two main analytical approaches have been adopted for IsoPs measurement: immunological methods and mass spectrometry. The methodologies for the extraction, purification and analysis of IsoPs in EBC samples are presented.

Eoxins: a new inflammatory pathway in childhood asthma

BACKGROUND

Increased levels of leukotrienes (LTs) in exhaled breath condensate (EBC) are associated with asthma and bronchial hyperresponsiveness (BHR), whereas eicosanoids generated through the 15-lipoxygenase (LO) pathway (15-hydroxyeicosatetraenoic acid [HETE] and eoxins) have been less studied.

OBJECTIVE

We investigated whether metabolites of the 5- and 15-LO pathways in EBC are associated with childhood asthma, asthma severity, and clinical parameters.

METHODS

The present study included 131 school-aged children (27 children with problematic severe asthma, 80 children with mild-to-moderate asthma, and 24 healthy children) from the Severe Asthma Recognized in Childhood study and 19 children with other nonasthmatic chronic lung diseases. Clinical work-up included spirometry, fractional exhaled nitric oxide measurements, skin prick testing, and methacholine challenge. Eicosanoids were analyzed in EBC by using mass spectrometry and are reported as concentrations (in picograms per milliliter) and eicosanoid/palmitic acid (PA) ratios.

RESULTS

Eoxin C₄/PA, eoxin D₄/PA, eoxin E₄/PA, 15-HETE/PA, and LTC₄/PA ratios were significantly increased in asthmatic versus healthy children. Eoxin D₄/PA and LTE₄/PA ratios were also significantly higher in children with BHR. A nonsignificant trend was observed toward higher eoxin/PA ratios with increasing asthma severity. In contrast to asthma, children with chronic lung disease had the highest 15-HETE/PA, LTC₄/PA, LTE₄/PA, and LTB₄/PA ratios.

CONCLUSION

The results point to increased activity of the 15-LO inflammatory pathway in childhood asthma. Mass spectrometric analyses of EBC demonstrate that increased eoxin levels not only accompany the increased 5-LO product LTC₄ but are also associated with BHR. These markers might represent a new therapeutic target for asthma treatment.

Increased levels of HMGB-1 and endogenous secretory RAGE in induced sputum from asthmatic patients

BACKGROUND

High mobility group box 1 (HMGB-1), a ligand of the receptor for advanced glycation end products (RAGE), is an inflammatory mediator in various disorders. Its endogenous decoy inhibitor, endogenous secretory RAGE (esRAGE), prevents the activation of RAGE signaling, and imbalance between HMGB-1 and esRAGE is known to be a factor determining progression of chronic inflammatory diseases.

METHODS

We measured HMGB-1 and esRAGE levels in induced sputum from 44 asthmatic patients and 15 normal controls, and examined their correlations with asthma indices including pulmonary function test values and induced sputum indices.

RESULTS

HMGB-1 levels in induced sputum were significantly higher in asthmatic patients than in normal controls (p < 0.001). Similarly, esRAGE levels were significantly higher in asthmatic patients than in normal controls (p < 0.001). In asthmatic patients, HMGB-1 levels were inversely correlated with percentage of predicted forced expiratory volume in 1 s (%FEV(1)) and FEV(1)/forced vital capacity (FEV(1)/FVC). There was a significant increase in HMGB-1 level associated with severity of asthma (p < 0.001). However, there was no significant increase in esRAGE level associated with severity of asthma. In asthmatic patients, HMGB-1 levels were significantly correlated with percentage of neutrophils in induced sputum.

CONCLUSIONS

Our findings suggest that the HMGB-1 is a mediator of neutrophilic airway inflammation in asthma and that imbalance between HMGB-1 and esRAGE is related to the severity of asthma. Combined measurement of HMGB-1 and esRAGE may be novel biomarkers in asthma with severe airflow limitation.

Exhaled carbon monoxide and risk of metabolic syndrome and cardiovascular disease in the community

BACKGROUND

Endogenous carbon monoxide (CO) at physiological concentrations is cytoprotective, whereas excess levels reflect underlying oxidative stress, inflammation, and vascular pathology and portend adverse clinical sequelae. However, the relation of exhaled CO to metabolic/vascular risk in the community is unknown.

METHODS AND RESULTS

We related exhaled CO, a surrogate measure of blood CO concentration, to the risk of developing new-onset metabolic syndrome and incident cardiovascular disease following 14 943 routine examinations (4139 unique participants; mean age, 46 years, 53% women) in the Framingham Heart Study. Baseline exhaled CO was associated with the presence of cardiometabolic risk factors (including smoking) and prevalent metabolic syndrome (odds ratio, 1.09 per log CO; 95% confidence interval, 1.02 to 1.17; P=0.01). During up to 4 years of follow-up, 1458 participants developed new-onset metabolic syndrome, and 416 experienced a first cardiovascular disease event. Compared with individuals in the lowest quartile of exhaled CO, those in the highest quartile were more likely to develop metabolic syndrome (odds ratio, 1.48; 95% confidence interval, 1.25 to 1.76; P<0.0001) and cardiovascular disease events (hazard ratio, 1.66; 95% confidence interval, 1.14 to 2.40; P=0.008) in multivariable analyses that included adjustment for smoking status.

CONCLUSION

In our community-based sample, higher exhaled CO levels predicted the development of metabolic syndrome and future cardiovascular disease events, underscoring the importance of this endogenous second messenger in the pathogenesis of metabolic and vascular risk.