Exhaled monoxides in asymptomatic atopic subjects

Utility of exhaled nitric oxide to guide mild asthma treatment in atopic patients and its correlation with asthma control test score: a randomized controlled trial

BACKGROUND

Fractional exhaled nitric oxide (FeNO) is used for the diagnosis and monitoring of asthma, although its utility to guide treatment and its correlation with other tools is still under discussion. We study the possibility to withdraw inhaled corticosteroid treatment in atopic patients with mild asthma based on the FeNO level, as well as to study its correlation with other clinical control tools.

METHODS

Prospective and randomized study including atopic patients aged 18 to 65 with mild asthma, stable, on low-dose inhaled corticosteroid (ICS) treatment, who had their treatment withdrawn based on a FeNO level of 40 ppb. Patients were randomized into two groups: control group (treatment with ICS was withdrawn regardless of FeNO level) and experimental group (according to the FeNO levels, patients were assigned to one of two groups: FeNO > 40 ppb on treatment with budesonide 200 mcg every 12 h and SABA on demand; FeNO ≤ 40 ppb only with SABA on demand). Follow-up was conducted for one year, during which medical assessment was performed with FeNO measurements, asthma control test (ACT), lung function tests (FEV1, FEV1/FVC, PEF, and RV/TLC), and recording of the number of exacerbations.

RESULTS

Ninety-two patients were included, with a mean age of 39.92 years (SD 13.99); 46 patients were assigned to the control group, and 46 patients to the experimental group. The number of exacerbations was similar between the groups (p = 0.301), while the time to the first exacerbation was significantly shorter in the control group (30.86 vs. 99.00 days), p < 0.001, 95% CI (43.332-92.954). Lung function tests (FEV1, FEV1/FVC, PEF, and RV/TLC) showed no differences between the groups (p > 0.05). Both FeNO and ACT showed significant changes in the groups in which ICS was withdrawn (p < 0.05 for both parameters). A significant negative correlation was observed between FeNO and ACT (r = -0.139, p = 0.008).

CONCLUSIONS

In atopic patients with mild asthma, withdrawal of ICS based on an FeNO of 40 ppb led to worsened symptoms but without changes in lung function tests or an increase in exacerbations. There was a negative correlation between FeNO values and symptomatic control measured by the ACT.

TRIAL REGISTRATION

Clinical Trial Number: 2012-000372-42. Start Date: 2012-07-23. Trial registered prospectively ( https://www.clinicaltrialsregister.eu/ctr-search/search?query=2012-000372-42 ). This study adheres to CONSORT guidelines of randomised control trials.

The Pattern of Sensitization Influences Exhaled and Nasal Nitric Oxide Levels in Young Adults

Nitric oxide (NO) from upper (nasal NO, nNO) or lower airways (fractional exhaled NO, FeNO) is considered a surrogate marker for Th2-type inflammation, which is influenced by atopy. The aim of this study was to analyze nNO and FeNO in regard to qualitative and quantitative aspects of sensitization. We evaluated 244 non-smoking young adults. All of them were first-year students recruited for a longitudinal study. An inhalation allergy screening tool was used for atopy definition (specific immunoglobulin E (sIgE) to sx1 ≥ 0.35 kU/L), and also sIgE response to three inhalant perennial allergens, house dust mite (HDM, d1), cat (e1), and dog (e5), was determined in the non-pollen season. With respect to sx1, 100 subjects could be classified as atopic. Sensitization to one, two, or three perennial allergens could be demonstrated in 46, 10, and 16 students, respectively. The subjects with positive IgE response to sx1, but not sensitized to HDM, cat, and/or dog, had FeNO levels comparable to those of non-atopic subjects (13.5 vs. 13.0 ppb, respectively; p = 0.485). These levels were significantly lower compared to atopic subjects being sensitized to any perennial allergen (19.0 ppb; p = 0.0003). After grouping the atopic subjects for perennial sensitization patterns, significantly higher FeNO could be detected in subjects with poly-sensitization (n = 26; 26.0 ppb) compared to the mono-sensitized ones (n = 46; 18.0 ppb; p = 0.023). Regarding nNO, no differences could be observed. Applying a two-way ANOVA, we could reveal a significant correlation of specific HDM-IgE CAP-class with FeNO (p < 0.0001) and nNO levels (p = 0.007). Finally, a significant relationship was found between nNO and FeNO for the whole cohort (p < 0.0001). In summary, our findings support the argument that atopy and perennial sensitization should be considered for the interpretation of NO.

Correlation of exhaled carbon monoxide level with disease severity in chronic obstruction pulmonary disease

Introduction:

Amplification of airway inflammation and its destruction due to oxidative stress is a major step in the pathogenesis of chronic obstruction pulmonary disease (COPD). Exhaled carbon monoxide (eCO) may be quantified to evaluate the airway inflammation and oxidative stress in such patients.

Objectives:

To assess the disease severity of COPD and treatment response by measuring eCO as a biomarker.

Materials and Methods:

COPD patients diagnosed according to the global initiative for chronic obstructive lung disease guidelines and healthy individuals as controls were selected. One hundred and fifty patients with COPD and 125 controls were included in the study. Participants were further subdivided on the basis of their smoking habits. Clinical examinations and spirometry were done to diagnose COPD by following the standard protocol. eCO was measured using a piCO + Smokerlyzer (Breath CO Monitor, Bedfont Scientific Ltd., Kent, UK). It was a single-center cross-sectional study.

Results:

Mean (± standard error of mean) CO levels in ex-smokers with COPD were higher (5.21 ± 1.546 ppm; P < 0.05) than in nonsmoking controls (1.52 ± 0.571 ppm) but were lower than in current smokers with COPD (12.55 ± 4.514 ppm; P < 0.05). eCO levels were higher in current smokers with COPD (12.55 ± 4.514 ppm; P < 0.05) compared to healthy smokers (9.71 ± 5.649). There was a negative correlation between eCO and forced expiratory volume in 1 s (FEV1) in COPD (r = −0.28; P < 0.05). The mean eCO level was decreased (6.291–4.332; P < 0.001) with improvement in lung function (FEV1 38.75%–50.65%: P < 0.05) after treatment with inhaled steroid.

Conclusion:

Our study concludes that quantification of eCO level in COPD varies with different grades of airway obstruction and to measure the treatment response. Measuring the level of eCO can be used to assess the indirect assessment of airway inflammation, oxidative stress, and severity of airway obstruction in COPD patients.

Association of longitudinal fractional exhaled nitric oxide measurements with asthma control in atopic children

OBJECTIVES

We sought to determine whether longitudinal measurements of FeNO are informative for future loss of asthma control in children with atopic asthma.

METHODS

One hundred seventy-eight patients aged 8-16 years with atopic asthma were enrolled. FeNO and lung functions were serially monitored 10 times or more over 2 years when subjects were not receiving controller medications. After completion of monitoring, 1-year observation on the occurrence of loss of asthma control was performed and associations of loss of asthma control with spirometric and FeNO measurements were analyzed.

RESULTS

Loss of asthma control occurred during observation periods in 110 (76%) of 145 patients who completed the study. Of all monitored parameters including airway reactivity, the highest FeNO of serial measurements (H-FeNO) (adjusted odds ratio (aOR), 1.21; 95% CI, 1.08-1.36) and the rate of FeNO levels higher than 21 ppb (R21FeNO) (aOR, 1.06; 95% CI, 1.01-1.11) were the only independent predictors of upcoming control loss in the multiple logistic regression analysis. In receiver-operator characteristic curve analysis, H-FeNO > 37 ppb and R21FeNO > 20% demonstrated 91% and 88% sensitivity for a future loss of asthma control at the cost of low specificity (60% and 65%, respectively). In contrast, H-FeNO > 47 ppb and R21FeNO > 41% gave 96% and 88% specificity, but these sacrificed sensitivity to 70% and 72%, respectively.

CONCLUSIONS

Our data show that both amount and frequency of a FeNO increase during longitudinal monitoring are helpful in predicting asthma control status.

Emerging molecular phenotypes of asthma

Although asthma has long been considered a heterogeneous disease, attempts to define subgroups of asthma have been limited. In recent years, both clinical and statistical approaches have been utilized to better merge clinical characteristics, biology, and genetics. These combined characteristics have been used to define phenotypes of asthma, the observable characteristics of a patient determined by the interaction of genes and environment. Identification of consistent clinical phenotypes has now been reported across studies. Now the addition of various 'omics and identification of specific molecular pathways have moved the concept of clinical phenotypes toward the concept of molecular phenotypes. The importance of these molecular phenotypes is being confirmed through the integration of molecularly targeted biological therapies. Thus the global term asthma is poised to become obsolete, being replaced by terms that more specifically identify the pathology associated with the disease.

Social support as a predictor exhaled nitric oxide in healthy individuals across time

Psychosocial factors such as social support and depression have long been associated with health outcomes. Elevated depressive symptoms are usually associated with worse health outcomes, whereas social support has been related to improvements in health. Nitric oxide levels are an important marker of both cardiovascular health and immune function. Research suggests that exhaled nitric oxide is affected by stress, negative affect, and depression; however, the effect of social support has not been previously explored. Thus, we sought to examine the association of social support, negative affect, and depression with exhaled nitric oxide in a group of 35 healthy individuals (10 males and 25 females) with a mean age of 20.5years across five weekly assessments. Results showed that changes in social support within individuals were positively associated with levels of exhaled nitric oxide independent of other psychosocial factors. Further exploration of the health implications of this positive relationship between airway nitric oxide and social support is necessary.

Does carbon monoxide inhibit proinflammatory cytokine production by fetal membranes?

AIM

Infection-induced inflammation is a common cause of preterm birth. Pharmacologic inhibition of proinflammatory cytokines improves pregnancy outcome in animal models but there are no universally effective therapies for preterm birth in women. Carbon monoxide (CO) has anti-inflammatory properties at low concentrations but its effects on reproductive tissues is unclear. Therefore, we studied the effect of supplemental CO on the production of cytokines associated with preterm birth by fetal membranes.

METHODS

Cross-sections of whole fetal membranes, isolated choriodecidua, and isolated amnion were prepared using tissues collected from women who had normal vaginal deliveries at term. Tissues were placed in an organ explant culture system and stimulated with up to 10(8) CFU/mL Escherichia coli. Cultures were incubated under room air or room air+250 ppm CO for 18 h and cytokine concentrations in conditioned medium were quantified by ELISA.

RESULTS

CO inhibited IL-1β and TNF-α (P≤0.001) production by cultures stimulated with 10(7) CFU/mL bacteria but had no detectable effect on IL-10 by full-thickness membranes. Although CO also tended to reduce TNF-α production (P=0.053), no effect of CO was detected for IL-10 or IL-1β for membranes stimulated with 10(8) CFU/mL E. coli. TNF-α, but not IL-1β or IL-10 production, was inhibited by CO for choriodecidual cultures stimulated with 10(7) or 10(8) CFU/mL E. coli (P<0.001). IL-1β production was significantly inhibited by CO for amnion cultures stimulated with 10(7) (P=0.002) and 10(8) (P=0.017) CFU/mL E. coli. Exposure to bacteria had no effect on TNF-α or IL-10 production but CO tended to increase IL-10 production by amnion cultures stimulated with 10(8) CFU/mL E. coli (P=0.037).

CONCLUSIONS

These results suggest that CO may help promote an anti-inflammatory environment during intrauterine infections by inhibiting TNF-α and IL-1β production.

Dose-dependent relationship between prenatal exposure to fine particulates and exhaled carbon monoxide in non-asthmatic children. A population-based birth cohort study

OBJECTIVES

The main goal of the study was to assess possible association between fetal exposure to fine particulate matter (PM2.5) and exhaled carbon monoxide (eCO) measured in non-asthmatic children.

MATERIAL AND METHODS

The subjects include 118 children taking part in an ongoing population-based birth cohort study in Kraków. Personal samplers of PM2.5 were used to measure fine particle mass in the fetal period and carbon monoxide (CO) in exhaled breath from a single exhalation effort at the age of 7. In the statistical analysis of the effect of prenatal PM2.5 exposure on eCO, a set of potential confounders, such as environmental tobacco smoke (ETS), city residence area, sensitization to house dust allergens and the occurrence of respiratory symptoms monitored over the seven-year follow-up was considered.

RESULTS

The level of eCO did not correlate with the self-reported ETS exposure recorded over the follow-up, however, there was a positive significant relationship with the prenatal PM2.5 exposure (non-parametric trend p = 0.042). The eCO mean level was higher in atopic children (geometric mean = 2.06 ppm, 95% CI: 1.58-2.66 ppm) than in non-atopic ones (geometric mean = 1.57 ppm, 95% CI: 1.47-1.73 ppm) and the difference was statistically significant (p = 0.036). As for the respiratory symptoms, eCO values were associated positively only with the cough severity score recorded in the follow-up (nonparametric trend p = 0.057). In the nested multivariable linear regression model, only the effects of prenatal PM2.5 and cough severity recorded in the follow-up were related to eCO level. The prenatal PM2.5 exposure represented 5.1%, while children's cough represented only 2.6% of the eCO variability.

CONCLUSION

Our study suggests that elevated eCO in non-asthmatic children may result from oxidative stress experienced in the fetal period and that heme oxygenase (HO) activity in body tissues may be programmed in the fetal period by the exposure to fine particulate matter.

Academic exam stress and depressive mood are associated with reductions in exhaled nitric oxide in healthy individuals

Nitric oxide (NO) has beneficial effects on cardiovascular and immune health. Stress and depression have been linked to a reduction in serum NO. In this study, we examined the effect of academic exam stress on the fraction of NO in exhaled air (FeNO) and spirometric lung function in 41 healthy college students. Participants completed assessments at mid-semester as well as in the early and late phase of an academic exam period. Negative affect, depressive mood, and salivary cortisol were elevated during exams, whereas FeNO and lung function decreased. Higher depressive mood was associated with lower FeNO, whereas higher negative affect was associated higher FeNO across time. These findings provide initial evidence that depression and prolonged stress can alter FeNO and lung function in healthy individuals, which could have adverse consequences for cardiovascular, airway, and immune health.

Fractional exhaled nitric oxide and forced expiratory flow between 25% and 75% of vital capacity in children with controlled asthma

Purpose

Fractional exhaled nitric oxide (FeNO) and forced expiratory flow between 25% and 75% of vital capacity (FEF_25-75) are not included in routine monitoring of asthma control. We observed changes in FeNO level and FEF_25-75 after FeNO-based treatment with inhaled corticosteroid (ICS) in children with controlled asthma (CA).

Methods

We recruited 148 children with asthma (age, 8 to 16 years) who had maintained asthma control and normal forced expiratory volume in the first second (FEV₁) without control medication for ≥3 months. Patients with FeNO levels >25 ppb were allocated to the ICS-treated (FeNO-based management) or untreated group (guideline-based management). Changes in spirometric values and FeNO levels from baseline were evaluated after 6 weeks.

Results

Ninety-three patients had FeNO levels >25 ppb. These patients had lower FEF_25-75% predicted values than those with FeNO levels ≤25 ppb (P<0.01). After 6 weeks, the geometric mean (GM) FeNO level in the ICS-treated group was 45% lower than the baseline value, and the mean percent increase in FEF_25-75 was 18.% which was greater than that in other spirometric values. There was a negative correlation between percent changes in FEF_25-75 and FeNO (r=-0.368, P=0.001). In contrast, the GM FeNO and spirometric values were not significantly different from the baseline values in the untreated group.

Conclusion

The anti-inflammatory treatment simultaneously improved the FeNO levels and FEF_25-75 in CA patients when their FeNO levels were >25 ppb.

Childhood asthma management guided by repeated FeNO measurements: a meta-analysis

The fraction of exhaled nitric oxide (FeNO) has gained interest as a non-invasive tool to measure airway inflammation in asthma since it reflects allergic inflammation. Recent controlled clinical studies have, however, questioned its role in the management of asthma in children. To assess the clinical value of FeNO in paediatric asthma management, a meta-analysis was performed on the controlled studies of childhood asthma management guided by repeated FeNO measurements, and relevant publications on the confounders of FeNO were reviewed. The data suggests that utilising FeNO to tailor the dose of inhaled corticosteroids in children cannot be recommended for routine clinical practice since there is a danger of excessive inhaled corticosteroid doses in children without meaningful changes in clinical outcomes. Many disease and non-disease related factors (most importantly atopy, height/age and infection) affect FeNO levels which can easily confound the interpretation.

Orally exhaled nitric oxide in patients with seasonal allergic rhinitis during natural pollen season

BACKGROUND

Nitric oxide (NO) is the endogenous molecule involved in regulatory, protective, and defensive mechanisms. Although exhaled NO (ENO) has been used to monitor patients with asthma, possible usage of ENO in allergic rhinitis (AR) still needs to be evaluated. The authors wanted to determine the levels of NO exhaled orally both out of the pollen season and during the natural pollen exposure in patients with AR without asthma.

METHODS

Forty-six patients without asthma, with seasonal AR (SAR) and 15 healthy, nonreactive, nonatopic subjects as a control group were investigated. ENO, congestion score, and peak nasal inspiratory flows (PNIFs) were measured in all subjects 6 weeks before the pollen season, at the height of the pollen season, and 6 weeks after the end of the pollen season.

RESULTS

Patients with SAR had significantly higher basal ENO values compared with healthy control. The number of parts of NO increased in both groups during the pollen season but only in AR patients was the increase significant compared with the levels before the pollen season. Those with SAR and high levels of NO in exhaled air at the height of the pollen season had significantly lower PNIF rates and higher obstruction scores than out of the pollen season and in the healthy group.

CONCLUSION

Natural exposure may lead to an elevation of ENO in the patients with SAR without asthma. We estimate that the increased ENO may result from subclinical allergic inflammation present within the lower airways of nonasthmatic patients with SAR.

Bronchial responsiveness is related to increased exhaled NO (FE(NO)) in non-smokers and decreased FE(NO) in smokers

RATIONALE

Both atopy and smoking are known to be associated with increased bronchial responsiveness. Fraction of nitric oxide (NO) in the exhaled air (FE(NO)), a marker of airways inflammation, is decreased by smoking and increased by atopy. NO has also a physiological bronchodilating and bronchoprotective role.

OBJECTIVES

To investigate how the relation between FE(NO) and bronchial responsiveness is modulated by atopy and smoking habits.

METHODS

Exhaled NO measurements and methacholine challenge were performed in 468 subjects from the random sample of three European Community Respiratory Health Survey II centers: Turin (Italy), Gothenburg and Uppsala (both Sweden). Atopy status was defined by using specific IgE measurements while smoking status was questionnaire-assessed.

MAIN RESULTS

Increased bronchial responsiveness was associated with increased FE(NO) levels in non-smokers (p = 0.02) and decreased FE(NO) levels in current smokers (p = 0.03). The negative association between bronchial responsiveness and FE(NO) was seen only in the group smoking less <10 cigarettes/day (p = 0.008). Increased bronchial responsiveness was associated with increased FE(NO) in atopic subjects (p = 0.04) while no significant association was found in non-atopic participants. The reported interaction between FE(NO) and smoking and atopy, respectively were maintained after adjusting for possible confounders (p-values<0.05).

CONCLUSIONS

The present study highlights the interactions of the relationship between FE(NO) and bronchial responsiveness with smoking and atopy, suggesting different mechanisms behind atopy- and smoking-related increases of bronchial responsiveness.

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.

Exhaled carbon monoxide in airway diseases: from research findings to clinical relevance

Breath tests have gained increasing interest in recent years mainly driven by the unmet clinical need to monitor airway diseases and to obtain information of unravelled aspects of respiratory disorders. Carbon monoxide is present in the exhaled breath and has been suggested to reflect ongoing oxidative stress, even if there are some confounding factors limiting its clinical usefulness. Increased concentration of exhaled carbon monoxide has been demonstrated in different acute and chronic airway diseases including allergic rhinitis, asthma, bronchiectasis, and post transplant bronchiolitis obliterans syndrome. Although exhaled carbon monoxide might not prove as a clinically useful biomarker of airway diseases, its measurement has helped to understand the place of heme oxygenase activity in allergic and non-allergic airway diseases. The scope of this review is the exciting field of exhaled carbon monoxide in airway diseases.

Exhaled carbon monoxide in asthmatics: a meta-analysis

Background

The non-invasive assessment of airway inflammation is potentially advantageous in asthma management. Exhaled carbon monoxide (eCO) measurement is cheap and has been proposed to reflect airway inflammation and oxidative stress but current data are conflicting. The purpose of this meta-analysis is to determine whether eCO is elevated in asthmatics, is regulated by steroid treatment and reflects disease severity and control.

Methods

A systematic search for English language articles published between 1997 and 2009 was performed using Medline, Embase and Cochrane databases. Observational studies comparing eCO in non-smoking asthmatics and healthy subjects or asthmatics before and after steroid treatment were included. Data were independently extracted by two investigators and analyzed to generate weighted mean differences using either a fixed or random effects meta-analysis depending upon the degree of heterogeneity.

Results

18 studies were included in the meta-analysis. The eCO level was significantly higher in asthmatics as compared to healthy subjects and in intermittent asthma as compared to persistent asthma. However, eCO could not distinguish between steroid-treated asthmatics and steroid-free patients nor separate controlled and partly-controlled asthma from uncontrolled asthma in cross-sectional studies. In contrast, eCO was significantly reduced following a course of corticosteroid treatment.

Conclusions

eCO is elevated in asthmatics but levels only partially reflect disease severity and control. eCO might be a potentially useful non-invasive biomarker of airway inflammation and oxidative stress in nonsmoking asthmatics.

Diagnostic value of exhaled nitric oxide in childhood asthma and allergy

Fractional exhaled nitric oxide (FE(NO) ) has been proposed as a diagnostic test of asthma. We aimed to investigate in a population based birth cohort of children the usefulness of FE(NO) as a diagnostic tool. The 10-yr follow up of the Environment and Childhood Asthma Study in Oslo included 616 children representative of the prospective birth cohort. Both FE(NO) (single breath technique) and skin prick test (SPT) were measured in 331, limited at the time by equipment availability. Structural parental interview, spirometry, methacholine challenge and exercise test were performed. FE(NO) was significantly elevated in children with current asthma (geometric mean 9.6 (95% confidence interval (CI) (6.9, 13.4) p.p.b.) compared with healthy children (5.8 (5.4, 6.3) p.p.b.; p < 0.001). FE(NO) was highest among children with current allergic asthma (asthma and positive SPT) (14.0 (8.9, 22.1) p.p.b.), whereas children with non-allergic asthma (6.1 (4.0, 9.2) p.p.b.) had comparable FE(NO) levels to healthy children (p = 0.99). Allergic sensitization was most closely associated with FE(NO) . A FE(NO) cut-off value of 20.4 p.p.b. had a high specificity (0.97), but a low sensitivity (0.41) and a Positive Likelihood Ratio of 16.1 for current allergic asthma. In the present childhood population-based study, high FE(NO) levels were closely associated with current allergic asthma and not with current asthma without allergic sensitization. Estimating the individual predictive probability of having asthma by use of FE(NO,) improves the diagnostic utility of the test.

Effect of natural seasonal pollen exposure and repeated nasal allergen provocations on elevation of exhaled nitric oxide

BACKGROUND

Exhaled nitric oxide (FENO) is a marker for allergic airway inflammation. We wondered whether in patients with intermittent allergic rhinitis only (i) natural pollen exposure and (ii) artificial pollen exposure by repeated nasal allergen provocations may lead to an elevation of FENO.

METHODS

In two prospective studies, we compared the FENO of nonatopic controls with the FENO of nonasthmatic individuals with mild intermittent rhinitis to tree and/or grass pollen. Study I: 13 atopic individuals and seven controls had measurements of FENO, blood eosinophils and eosinophilic cationic protein (ECP) before, during and after pollen season. Study II: 16 atopic individuals and 12 controls had nasal allergen provocations on four following days out of pollen season, with daily measurements of FENO before, 2 and 6 h after provocation, and determination of blood eosinophils, ECP and FEV1 at baseline, on days 5 and 10-12.

RESULTS

Natural pollen exposure (study I) caused a significant elevation of FENO in allergic individuals. Nasal allergen provocations (study II) did not elicit a statistically significant rise neither of FENO nor of blood eosinophils between baseline and day 5. However, a subgroup of four individuals with a rise of blood eosinophils during nasal allergen provocations showed also a rise of FENO.

CONCLUSIONS

We suppose that in allergic rhinitis a concomitant reaction of the bronchial system is dependent on a strong local inflammation leading to a generalized immune stimulation.

Exhaled nitric oxide in diagnosis and management of respiratory diseases

The analysis of biomarkers in exhaled breath constituents has recently become of great interest in the diagnosis, treatment and monitoring of many respiratory conditions. Of particular interest is the measurement of fractional exhaled nitric oxide (FENO) in breath. Its measurement is noninvasive, easy and reproducible. The technique has recently been standardized by both American Thoracic Society and European Respiratory Society. The availability of cheap, portable and reliable equipment has made the assay possible in clinics by general physicians and, in the near future, at home by patients. The concentration of exhaled nitric oxide is markedly elevated in bronchial asthma and is positively related to the degree of esinophilic inflammation. Its measurement can be used in the diagnosis of bronchial asthma and titration of dose of steroids as well as to identify steroid responsive patients in chronic obstructive pulmonary disease. In primary ciliary dyskinesia, nasal NO is diagnostically low and of considerable value in diagnosis. Among lung transplant recipients, FENO can be of great value in the early detection of infection, bronchioloitis obliterans syndrome and rejection. This review discusses the biology, factors affecting measurement, and clinical application of FENO in the diagnosis and management of respiratory diseases.

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.

Both allergic and nonallergic asthma are associated with increased FE(NO) levels, but only in never-smokers

BACKGROUND

Allergic asthma is consistently associated with increased FE(NO) levels whereas divergence exists regarding the use of exhaled nitric oxide (NO) as marker of inflammation in nonallergic asthma and in asthmatic smokers. The aim of this study is to analyze the effect of having allergic or nonallergic asthma on exhaled nitric oxide levels, with special regard to smoking history.

METHODS

Exhaled NO measurements were performed in 695 subjects from Turin (Italy), Gothenburg and Uppsala (both Sweden). Current asthma was defined as self-reported physician-diagnosed asthma with at least one asthma symptom or attack recorded during the last year. Allergic status was defined by using measurements of specific immunoglobulin E (IgE). Smoking history was questionnaire-assessed.

RESULTS

Allergic asthma was associated with 91 (60, 128) % [mean (95% CI)] increase of FE(NO) while no significant association was found for nonallergic asthma [6 (-17, 35) %] in univariate analysis, when compared to nonatopic healthy subjects. In a multivariate analysis for never-smokers, subjects with allergic asthma had 77 (27, 145) % higher FE(NO) levels than atopic healthy subjects while subjects with nonallergic asthma had 97 (46, 166) % higher FE(NO) levels than nonatopic healthy subjects. No significant asthma-related FE(NO) increases were noted for ex- and current smokers in multivariate analysis.

CONCLUSIONS

Both allergic and nonallergic asthma are related to increased FE(NO) levels, but only in never-smoking subjects. The limited value of FE(NO) to detect subjects with asthma among ex- and current smokers suggests the predominance of a noneosinophilic inflammatory phenotype of asthma among ever-smokers.

Factors that influence exhaled nitric oxide in Italian schoolchildren

BACKGROUND

Conflicting results exist about the meaning of exhaled nitric oxide (eNO) in epidemiologic studies, mainly because of the numerous factors that may affect the measurement.

OBJECTIVES

To evaluate the role of the factors that influence eNO levels in a sample of schoolchildren with or without respiratory diseases. We studied 335 schoolchildren, ages 10 to 16 years, from 8 schools in Palermo, Italy. After a respiratory questionnaire was completed, spirometry, skin tests, and eNO measurements were performed.

RESULTS

Among 335 children, 13.7% reported symptoms of bronchial asthma, 46.9% reported symptoms of rhinitis, and 39.4% were asymptomatic. The ratio of forced expiratory volume in 1 second to forced vital capacity was 87.6% (SD, 6.4%) in the bronchial asthma group, 90.6% (SD, 5.0%) in the rhinitis group, and 90.4% (SD, 5.1%) in the asymptomatic group (P < .002). Atopic children constituted 52.2% of the bronchial asthma group, 40.1% of the rhinitis group, and 28.8% of the asymptomatic group. Among atopic children, 102 (82%) had a positive skin test result for Dermatophagoides. Median eNO was 12.6 ppb in nonatopic children and 21.2 ppb in atopic children (P < .001, by Mann-Whitney U test). Among asymptomatic children, atopic children had significantly higher eNO levels than did nonatopic children (P < .001). In nonatopic children, no difference was found in log transformation eNO among healthy, rhinitic, or asthmatic children. Log transformation eNO increased with the number of positive skin test results (P < .001). Atopy, asthma, male sex, and indoor allergens were predictors of increased eNO in a logistic model.

CONCLUSIONS

Atopy (in particular, sensitization to indoor and perennial allergens) is strongly associated with higher eNO levels. Such association is enhanced by asthma.

Atopic sensitization to common allergens without symptoms or signs of airway disorders does not increase exhaled nitric oxide

BACKGROUND

Elevated fractional exhaled nitric oxide (FENO) associates positively with symptomatic atopy among asthmatics and in the general population. It is, however, unclear whether sensitization to common allergens per se- as verified with positive skin prick tests--affects FENO in healthy individuals.

OBJECTIVE

The aim of this study was to examine the association between FENO and sensitization to common allergens in healthy nonsmoking adults with no signs or symptoms of airway disorders.

METHODS

FENO measurements (flow rate: 50 mL/s), skin prick tests to common inhalant allergens, structured interviews, spirometry, bronchodilatation tests and bronchial histamine challenges were performed on a randomly selected population of 248 subjects. Seventy-three of them (29%) were nonsmoking asymptomatic adults with no history of asthma, persistent or recurrent upper or lower airway symptoms and no signs of airway disorders in the tests listed above.

RESULTS

FENO concentrations were similar in skin prick test positive (n = 32) and negative (n = 41) healthy subjects, with median values of 13.2 and 15.5 ppb, respectively (P = 0.304). No correlation appeared between FENO and the number of positive reactions (r = -0.138; P = 0.244), or the total sum of wheal diameters (r = -0.135; P = 0.254). The nonparametric one-tailed 95% upper limits of FENO among skin prick positive and negative healthy nonsmoking subjects were 29 and 31 ppb, respectively.

CONCLUSIONS

Atopic constitution defined as positive skin prick test results does not increase FENO in healthy nonsmoking adults with no signs or symptoms of airway disorders. This suggests that same reference ranges for FENO can be applied to both skin prick test positive and negative subjects.

The use of fraction of exhaled nitric oxide in pulmonary practice

The measurement of the fractional concentration of exhaled nitric oxide (FeNO) is a convenient, noninvasive, point-of-service office test for airway inflammation. The first half of this practice management review presents the methodological, interpretative, and clinical applications of FeNO. The second half discusses practical management issues, including current and future technology, equipment specifications, US Food and Drug Administration regulations, cost, current procedural terminology coding, and reimbursement. The measurement of FeNO is helpful in the diagnosis of asthma. It is predictive of a response to inhaled corticosteroids (ICSs). Monitoring FeNO is useful in maintaining asthma control by allowing the assessment of adherence to medication and dose titration of ICSs. An elevated level of FeNO is predictive of asthma relapse following corticosteroid withdrawal especially in children. The advances in technology, ease of use, and clinical utility will lead to greater availability, acceptance, and routine application in the care of asthma.

The value of FeNO measurement in asthma management: the motion against FeNO to help manage childhood asthma--reality bites

Since exhaled nitric oxide (FeNO) was first demonstrated to be raised in asthmatic patients in the early 1990s, there has been a strong interest in its potential role in the diagnosis and management of asthma. This culminated in 2003 when the US Food and Drug Administration cleared the NIOX nitric oxide analyser for clinical application in patients with asthma. The interest in FeNO is based on the assumptions that FeNO is a marker of asthma and asthma control, and that it reflects eosinophilic airway inflammation. However, the literature remains unconvincing and inconclusive. Furthermore, studies which have management algorithms that include FeNO as a guide to asthma treatment have failed to observe any improvement in asthma control compared with the use of standard asthma guidelines. At present, the cost of including FeNO in management guidelines far outweighs any potential benefits.

Exhaled nitric oxide: independent effects of atopy, smoking, respiratory tract infection, gender and height

Measurement of exhaled nitric oxide is widely used in respiratory research and clinical practice, especially in patients with asthma. However, interpretation is often difficult, due to common interfering factors, and little is known about interactions between factors. We assessed the influences and interactions of factors such as smoking, respiratory tract infections and respiratory allergy concerning exhaled nitric oxide values, with the aim to derive a scheme for adjustment. We studied 897 subjects (514 females, 383 males; mean age+/-standard deviation 34.5+/-13.0 years) with and without respiratory allergy (allergic rhinitis and/or asthma), smoking and respiratory tract infection. Logarithmic nitric oxide levels were described by an additive model comprising respiratory allergy, smoking, respiratory tract infection, gender and height (p0.001 each), without significant interaction terms. Geometric mean was 17.5ppb in a healthy female non smoker of height 170cm, whereby respiratory allergy corresponded to a change by factor 1.50, smoking 0.63, infection 1.24, male gender 1.17, and each 10cm increase (decrease) in height to 1.11 (0.90). Factors were virtually identical when excluding asthma and using the category allergic rhinitis instead of respiratory allergy (n=863). Within each category formed by combinations of these different predictors, the range of residual variation was approximately constant. We conclude that the factors influencing exhaled nitric oxide, which we analyzed, act independently of each other. Thus, circumstances such as smoking and respiratory tract infection do not appear to affect the usefulness of exhaled nitric oxide, provided that appropriate factors for adjustment are applied.

Exhaled nitric oxide and carbon monoxide in respiratory diseases

Breath tests have gained increasing interest in recent years mainly driven by the unmet clinical need to monitor airway diseases and to obtain information on unravelled aspects of respiratory disorders. A prototype of such measurement reaching clinical significance besides its use as a research tool is the measurement of exhaled nitric oxide (NO). It took hardly more than a decade after the discovery that exhaled breath contains NO for this measurement to be approved for clinical practice to monitor anti-inflammatory treatment in asthma. Recent studies demonstrate that using exhaled NO measurement to guide anti-inflammatory treatment in asthma may help clinical decision making. A similarly small molecule present in exhaled breath is carbon monoxide, which is not only a biomarker of cigarette smoking but has also been suggested to reflect ongoing oxidative stress/antioxidant defense. The scope of this review is the exciting field of exhaled monoxides. Since several other biomarkers have also been studied in the exhaled breath this review will provide a brief introduction to them.

Lipopolysaccharide administration to the allergic nose contributes to lower airway inflammation

BACKGROUND

Allergic rhinitis (AR) is an inflammatory reaction not confined to a single local compartment, but rather involving the whole airway system. Allergens known to induce AR are not always the sole trigger of the inflammatory reaction as infections and organic dust might also cause exacerbations of rhinitis and associated conditions.

OBJECTIVE

To examine the effects of intranasal lipopolysaccharide (LPS) exposure, as a surrogate for upper airway bacterial infections, in patients with symptomatic AR.

METHODS

Fourteen patients with a history of moderate to severe pollen-induced AR were challenged intranasally with LPS. After 3-6 weeks, the same patients were challenged again, first with allergen and 24 h later with LPS. Nasal symptom scores, nasal lavage leucocyte counts and nasal airway resistance were assessed at 6-24 h after each provocation along with measurements of nitric oxide (NO) levels in the nose and lung.

RESULTS

Six hours after the LPS challenge, an increased level of leucocytes could be obtained in the lavage fluid, but no symptoms were experienced and no increase in nasal resistance could be recorded. The NO production in the upper and lower airways was similar before and 6 h after the provocation. In contrast, in patients exposed to pollen before the LPS challenge, both the nasal and the pulmonary NO levels were enhanced. This was accompanied by an increase in leucocytes.

CONCLUSION

The present study demonstrates a priming effect of allergen on the nasal response to LPS as well as the presence of a systemic link between airway mucosal sites in the upper and lower airways. This suggests that exogenously derived signals, like upper airway infections, can interfere with the initiation, maintenance and progression of asthma.

[Exhaled nitric oxide in the diagnosis and monitoring of lung diseases]

In recent 10 years there has been an explosion of interest in the analysis of breath constituents as a way of monitoring airway inflammation in lung diseases. Monitoring of inflammation may assist in differential diagnosis of lung diseases, assessment of their severity and response to appropriate treatment. Among these novel non-invasive methods, exhaled nitric oxide has been the most extensively studied. Its measurement has recently been standardized, and there are now commercially available nitric oxide analyzers. Concentration of exhaled nitric oxide is markedly elevated in asthma, and its elevation is positively related to the degree of eosinophilic airway inflammation, airway hyperresponsiveness and symptoms. Furthermore, evidence suggests that exhaled nitric oxide-driven asthma treatment provides more precise asthma control compared to conventional treatment protocols. With regard to other lung diseases, in chronic obstructive pulmonary disease exhaled nitric oxide may be useful in predicting steroid responsiveness, while in lung transplant recipients its measurement could contribute to the detection of asymptomatic infections and rejection processes.

Exhaled nitric oxide in a population sample of adults

BACKGROUND

The relationship between exhaled nitric oxide (FENO) and the diagnosis of asthma in the general adult population is not completely clear.

OBJECTIVES

To investigate the association between FENO and asthma, after controlling for atopy and rhinitis, in a general population sample of adults (mean age 43 years).

METHODS

The cohort of subjects was a sample of subjects who gave their consent to participate in the European Community Respiratory Health Survey II study.

RESULTS

Atopy, rhinitis and current asthma were positively and current smoking was negatively associated with FENO. Multivariate analysis showed that asthma had a significant predictive effect on FENO (beta = 0.53; 95% CI 0.21-0.84, p = 0.001), and the increase in FENO was significantly associated with the risk of current asthma (OR = 1.07, 95% CI 1.00-1.14) by the logistic regression model. Receiver-operator characteristic curve showed that FENO >or=18.5 ppb had the best combination of sensitivity (69.2%) and specificity (71%), with a positive predictive value of 24% and a negative predictive value of 95%, for the diagnosis of asthma.

CONCLUSIONS

Measuring FENO seems to be suitable as an adjunct to questionnaire in the evaluation of asthma in the general population.

The effect of allergic rhinitis on adenosine concentration in exhaled breath condensate

BACKGROUND

Patients with allergic rhinitis (AR) frequently develop asthma. This initiating inflammation in the lower airways may result in increased levels of inflammatory mediators such as adenosine in the exhaled breath.

OBJECTIVE

We compared adenosine levels in exhaled breath condensate (EBC) and both exhaled and nasal nitric oxide (NO) levels of AR patients and healthy control subjects. We also tested whether inhalation through inflamed nasal cavity during EBC sampling influences adenosine concentrations in exhaled air.

METHODS

Exhaled and nasal NO levels were measured and EBC samples (at oral inhalation) were collected from 27 patients and 15 healthy controls. EBC collection was repeated after 15 min with subjects inhaling through their nose. Adenosine was measured by HPLC and NO was determined by chemiluminescence.

RESULTS

The concentration of EBC adenosine was higher in patients with AR than in healthy controls (12.4+/-1.3 nM vs. 6.5+/-0.7 nM, P=0.0019) and this was accompanied by an increase in the concentration of exhaled NO (10.2+/-1.3 ppb vs. 5.3+/-0.5 ppb; P=0.0099, respectively). No difference in nasal NO was detected. EBC adenosine concentration showed a significant positive correlation with the level of exhaled NO. In contrast to healthy control subjects, patients with rhinitis had higher levels of exhaled adenosine when inhaling via the nose instead of the mouth (17.7+/-2.8 nM, P=0.007).

CONCLUSION

When compared with healthy subjects, patients with AR exhibit an increased concentration of exhaled adenosine and a related increase in exhaled NO concentration. EBC adenosine is further increased when rhinitis patients inhale through their nose than via their mouth. Our data suggest that non-asthmatic patients with rhinitis may have subclinical inflammation in their lower airways.

IgE sensitisation in relation to flow-independent nitric oxide exchange parameters

BACKGROUND

A positive association between IgE sensitisation and exhaled NO levels has been found in several studies, but there are no reports on the compartment of the lung that is responsible for the increase in exhaled NO levels seen in IgE-sensitised subjects.

METHODS

The present study comprised 288 adult subjects from the European Community Respiratory Health Survey II who were investigated in terms of lung function, IgE sensitisation (sum of specific IgE), smoking history and presence of rhinitis and asthma. Mean airway tissue concentration of NO (CawNO), airway transfer factor for NO (DawNO), mean alveolar concentration of NO (CalvNO) and fractional exhaled concentration of NO at a flow rate of 50 mL s(-1) (FENO 0.05) were determined using the extended NO analysis.

RESULTS

IgE-sensitised subjects had higher levels (geometric mean) of FENO 0.05 (24.9 vs. 17.3 ppb) (p < 0.001), DawNO (10.5 vs. 8 mL s(-1)) (p = 0.02) and CawNO (124 vs. 107 ppb) (p < 0.001) and positive correlations were found between the sum of specific IgE and FENO 0.05, CawNO and DawNO levels (p < 0.001 for all correlations). Sensitisation to cat allergen was the major determinant of exhaled NO when adjusting for type of sensitisation. Rhinitis and asthma were not associated with the increase in exhaled NO variables after adjusting for the degree of IgE sensitisation.

CONCLUSION

The presence of IgE sensitisation and the degree of allergic sensitisation were related to the increase in airway NO transfer factor and the increase in NO concentration in the airway wall. Sensitisation to cat allergen was related to the highest increases in exhaled NO parameters. Our data suggest that exhaled NO is more a specific marker of allergic inflammation than a marker of asthma or rhinitis.

Exhaled carbon monoxide levels in atopic asthma: a longitudinal study

Exhaled carbon monoxide (eCO) is a potential non-invasive marker of airway inflammation. We have investigated the cross-sectional and longitudinal relationship between eCO and lung function and bronchial reactivity in 69 adults with atopic asthma, in the course of participation in a 6-week randomised placebo-controlled trial of vitamin E supplementation. At baseline, there was no cross-sectional association between absolute eCO levels and either forced expiratory volume (FEV(1)), forced vital capacity (FVC) or bronchial reactivity. However, in the longitudinal analysis within the placebo group, a rise in mean eCO was significantly associated with improvement in bronchial reactivity (change in eCO (parts per million) per natural log unit change in bronchial hyperreactivity 0.498, 95% confidence interval 0.071 to 0.924, P=0.024). These findings suggest that, contrary to previous data, there is no cross-sectional relationship between eCO and lung function or bronchial reactivity, but that there may be a longitudinal trend with bronchial reactivity that is worth further investigation.

Relationship between exhaled nitric oxide and atopy in Asian young adults

OBJECTIVES

The relationship between exhaled nitric oxide and atopy is controversial. The aim of this study was to determine the relationship between exhaled nitric oxide (FE(NO)) and atopy in Asian young adults.

METHODOLOGY

Subjects were assessed by: (i) the International Study of Asthma and Allergies in Childhood questionnaire to differentiate asthmatic from nonasthmatic and rhinitis from non-rhinitis subjects; (ii) skin prick testing to 10 allergens; and (iii) FE(NO) measurements performed online at a flow rate of 50 mL/s.

RESULTS

Complete results were available for 84 subjects. FE(NO) values were highest in atopic asthmatics (n = 34; median FE(NO), 59.8 p.p.b.; interquartile range, 30.4-85.5 p.p.b), followed by atopic nonasthmatics (n = 34; median, 38.4 p.p.b.; range, 16.7-49.3 p.p.b), nonatopic asthmatics (n = 5; median, 19.1 p.p.b.; range, 17.9-33.4 p.p.b), and lowest in nonatopic nonasthmatics (n = 11; median, 15.7 p.p.b.; range, 11.5-21.7 p.p.b). FE(NO) values were significantly higher in atopic (n = 68; median, 44.7 p.p.b.; range, 27.3-75.2 p.p.b) compared to nonatopic subjects (n = 16; median, 17.0 p.p.b.; range, 11.7-23.8 p.p.b.; P < 0.0001), regardless of asthma and rhinitis status. FE(NO) levels correlated with the severity of atopy (wheal size) for both asthmatic (r = 0.44, P = 0.005) and nonasthmatic subjects (r = 0.48, P = 0.001). There was no significant difference in FE(NO) levels between nonatopic asthmatics and nonatopic nonasthmatic subjects (P = 0.25).

CONCLUSIONS

Increased FE(NO) levels are more reflective of atopy rather than asthma, and increased nitric oxide production may be predominantly a feature of atopy in asthmatics.

[The measurement of exhaled nitric oxide, a new tool in the management of asthma?]

A GOOD DIAGNOSTIC TEST FOR ASTHMA: Chronic airway inflammation, main feature of asthma, can be assessed by measuring the exhaled nitric oxide (NO) level. Measurement of NO is standardized, non-invasive and easy to use in both children and adults. Studies have shown that it is a good diagnostic test for asthma when NO is high. However, other conditions or pathologies must be searched for because they may influence the results. ITS PLACE IN TREATMENT: Although exhaled NO helps to characterise the patients with asthma, other studies are required to show that it can help to improve the follow-up of such patients. Nevertheless, this tool has not yet been validated in the daily treatment of asthma and further research is still ongoing.

Fractional exhaled nitric oxide (FENO), lung function and airway hyperresponsiveness in naïve atopic asthmatic children

BACKGROUND

Measurement of fractional exhaled nitric oxide (FENO) is a noninvasive, simple, well-tolerated, and reproducible marker of airway inflammation. Asthmatic children with normal respiratory function could be affected by airway inflammation. The aim of this study was to assess the correlation between FENO and bronchial hyperesponsiveness (BHR) to methacholine, and between FENO and lung function in atopic children with intermittent asthma.

METHODS

Thirty-seven children (21 male), aged 7.2-14.4 years (median: 10.9 years), suffering from mild intermittent atopic asthma with a physician-diagnosed history of wheezing and/or chest tightness were studied. None had taken anti-asthmatic therapy for at least three months before the study. No child had symptoms of respiratory tract infection in the month before the study. All subjects underwent FENO measurement, pulmonary function testing and the methacholine provocation tests.

RESULTS

The mean percentages of FEV1 and FEF25-27 were 91.9+/-10.5 and 88.3+/-11.8, respectively. The mean FENO was 62.2+/-39.2 ppb and PC20 methacholine was 0.93 mg/ml+/-0.54. Significant correlations were identified between FENO and FEV1 (p<0.0059, r=0.468) and between FENO and FEF25-75 (p<0.0098, r=0.439). There was no correlation between FENO and logPC20 (p=0.14).

CONCLUSIONS

A single FENO measurement is probably of scarce prognostic and predictive value and it is not surprising to find discordance with BHR. We suggest that FENO measurement could represent a good marker of airway inflammation also in naïve atopic children with intermittent asthma. Repeated measurements over time are probably necessary to understand better the clinical implications of the data obtained in this study.

Exhaled nitric oxide levels and airway responsiveness to adenosine 5'-monophosphate in subjects with nasal polyposis

BACKGROUND

It is widely appreciated that asthma is an inflammatory disease of the airways associated with airway hyperresponsiveness, and that nasal polyposis and asthma are related diseases. The objective of this study was to determine differences in exhaled nitric oxide (ENO) levels and airway responsiveness to adenosine 5'-monophosphate (AMP) between nonasthmatic patients with nasal polyposis and healthy controls.

METHODS

Twenty patients without asthma with nasal polyposis and 16 healthy control subjects were enrolled in the study. Participants were challenged with increasing concentrations of AMP and methacholine. ENO was measured with the single-exhalation method.

RESULTS

Bronchoconstriction in response to AMP was detected in 7 (35%) subjects with nasal polyposis. The geometric mean (95% CI) of ENO for subjects with nasal polyposis was 33.1 parts per billion (ppb) (24.0-45.7 ppb) compared with 12.3 ppb (8.5-18.2 ppb) for the healthy controls (p = 0.0002). ENO values were significantly higher in atopic than in nonatopic subjects with nasal polyposis [51.3 ppb (32.3-83.2 ppb) vs. 24.5 ppb (16.2-37.1 ppb), p = 0.02]. Nonatopic subjects with nasal polyposis also had higher concentrations of ENO than healthy control subjects (p = 0.016).

CONCLUSIONS

Inhaled AMP causes airway narrowing in a significantly higher proportion of nonasthmatic subjects with nasal polyposis than in healthy controls. Furthermore, increased concentrations of ENO are detected in atopic and nonatopic subjects with nasal polyposis. These results suggest that bronchial inflammation is present in nonasthmatic subjects with nasal polyposis.

The measurement of exhaled carbon monoxide in healthy smokers and non-smokers

The measurement of exhaled carbon monoxide (CO) level may provide an immediate, non-invasive method of assessing smoking status. The aims of this study were to use a portable CO monitor to compare the exhaled CO levels in established smokers and non-smokers. The exhaled CO levels were measured in 322 subjects (243 healthy smokers, 55 healthy non-smokers, 24 passive smokers) who applied to healthy stand during the spring student activity of Firat University in Elaziğ. Exhaled CO concentration was measured using the EC50 Smokerlyser. The mean exhaled CO level was 17.13+/-8.50 parts per million (ppm) for healthy smokers and 3.61+/-2.15 ppm for healthy non-smokers, and 5.20+/-3.38 ppm for passive smokers. There were significant positive correlation between CO levels and daily cigarette consumption, and CO levels and duration of smoking in healthy smokers (r=+0.550, P<0.001, r=+0.265, P<0.001, respectively. Spearman's test). When smokers and non-smokers were looked at as a whole, a cutoff of 6.5 ppm had a sensitivity of 90% and specificity of 83%. In conclusion, exhaled CO level provides an easy, an immediate way of assessing a subject's smoking status.

Exhaled nitric oxide: relation to sensitization and respiratory symptoms

BACKGROUND

Conflicting data have been presented as to whether nitric oxide (NO) in exhaled air is merely reflecting atopy rather than airway inflammation.

OBJECTIVE

To investigate the relationship between exhaled NO (eNO) and nasal NO (nNO), respiratory symptoms, and atopy, in the context of a cross-sectional study of the respiratory health of bleachery workers.

METHODS

Two hundred and forty-six non-smoking bleachery and paper-mill workers answered a questionnaire and were examined by measurements of eNO and nNO and spirometry, outside the pollen season. Blood samples were collected and analysed for specific IgE against common aeroallergens (birch, timothy, cat and house dust mite). Atopy was defined as a positive Phadiatop trade mark test.

RESULTS

The atopic and the non-atopic subjects without asthma or rhinitis had similar levels of eNO. Subjects reporting asthma or rhinitis who were also sensitized to perennial allergens had higher levels of eNO, whereas those sensitized to only seasonal allergens had similar eNO levels as non-atopic subjects with asthma or rhinitis. In multiple linear regression models adjusted for nNO, eNO was associated with asthma and sensitization to perennial allergens.

CONCLUSION

The results indicate that only atopic subjects who have recently been exposed to the relevant allergen have elevated levels of eNO. Atopic subjects who are not being exposed to a relevant allergen or have never experienced symptoms of asthma or rhinitis show normal eNO. These data indicate that eNO relates to airway inflammation in atopic subjects.

Interrelationships among asthma, atopy, rhinitis and exhaled nitric oxide in a population-based sample of children

BACKGROUND

Exhaled nitric oxide (eNO) has attracted increasing interest as a non-invasive marker of airway inflammation in asthma. However, little evidence exists on the influences exerted on eNO by the interrelations among atopic status, asthma and rhinitis.

METHODS

Among the 1156 children who participated in a large-scale epidemiological survey on asthma and allergies (ISAAC II: International Study of Asthma and Allergies in Childhood Phase II) in the city of Clermont-Ferrand, 53 asthmatics without corticosteroid treatment and 96 non-asthmatics were invited to perform eNO and skin prick tests (SPTs) to 12 common allergens.

RESULTS

Atopic asthmatic children had higher eNO than non-atopic asthmatic children (28.9+/-9.1 vs. 17.1+/-13.1 p.p.b.; P=0.0004) with a significant increase when one SPT or more are positive (26.5+/-7.8 vs. 17.1+/-13.1 p.p.b.; P=0.03). Similarly, non-asthmatic, atopic subjects had higher eNO than non-atopic subjects with a significant increase when two SPTs or more are positive (19.4+/-9.8 vs. 11.7 +/-6.7 p.p.b.; P=0.003). In the case of equal levels of positive SPTs (0, 1, >/=2), asthmatic children always had higher eNO than non-asthmatic ones. Furthermore, among non-asthmatic children, the eNO level increased only in atopics who had rhinitis (20.7+/-13 vs. 12.5+/-6.4 p.p.b. in atopic controls (subjects without rhinitis and asthma) and 12.3+/-6.6 p.p.b. in non-atopic controls; P=0.001), whereas among asthmatic children, eNO level increased in atopics independently of rhinitis (28.2+/-9.5 p.p.b. in those with rhinitis and 30.9+/-8.1 p.p.b. in those without) as well as in non-atopics with rhinitis (22.5+/-17.2 p.p.b.).

CONCLUSIONS

Our data suggest that besides atopy and asthma, allergic rhinitis should also be taken into account in the assessment of eNO.

Concentrations of exhaled nitric oxide in asthmatics and subjects with allergic rhinitis sensitized to the same pollen allergen

BACKGROUND

Some studies have reported that the levels of exhaled nitric oxide (ENO) in asthmatics are similar to those in subjects with allergic rhinitis, and it has been postulated that atopic status might be the determinant of enhanced nitric oxide production in asthma.

OBJECTIVES

The aim of this study was to determine differences in ENO levels between asthmatics and subjects with allergic rhinitis sensitized to the same allergen, and to correlate these levels with airway responsiveness.

METHODS

Nineteen patients with asthma and 18 subjects with allergic rhinitis monosensitized to Parietaria pollen were enrolled in the study. ENO values and airway responsiveness to methacholine and adenosine 5'-monophosphate (AMP) were measured during the pollen season. The response to each bronchoconstrictor agent was measured by the provocative concentration required to produce a 20% fall in FEV1 (PC20). ENO was measured with the single-exhalation method.

RESULTS

The geometric mean (95% confidence interval) ENO values were significantly higher in asthmatics than in subjects with allergic rhinitis: 72.4p.p.b. (54.9-93.3p.p.b) vs. 44.7p.p.b. (30.9-64.6p.p.b., P = 0.03). In asthmatics, a significant correlation was found between ENO and PC20 AMP values (p = -0.57, P=0.02), whereas no correlation was detected between ENO and PC20 methacholine (p = -0.35, P = 0.14).

CONCLUSIONS

Our results suggest that atopy is not the only determinant of increased ENO levels detected in subjects with asthma, and that responsiveness to AMP may be a more sensitive marker for assessing airway inflammation in asthma compared to methacholine.

Modifications of airway responsiveness to adenosine 5'-monophosphate and exhaled nitric oxide concentrations after the pollen season in subjects with pollen-induced rhinitis

STUDY OBJECTIVE

s: To determine the effect of cessation of exposure to pollen on airway responsiveness to adenosine 5'-monophosphate (AMP) in subjects with pollen-induced rhinitis, and to explore the relationship between changes in airway responsiveness and changes in exhaled nitric oxide (ENO) levels.

STUDY DESIGN

Subjects were studied during the pollen season and out of season.

SETTING

Specialist allergy unit in a university hospital.

PATIENTS

Fourteen subjects without asthma with pollen-induced rhinitis who showed bronchoconstriction in response to methacholine and AMP during the pollen season and 10 healthy nonatopic control subjects.

MEASUREMENTS AND RESULTS

In subjects with pollen-induced rhinitis, ENO concentrations, provocative concentration of agonist causing a 20% fall in FEV(1) (PC(20)) methacholine, and PC(20) AMP were determined during the pollen season and out of season. Healthy control subjects were studied during the pollen season. In subjects with allergic rhinitis, PC(20) AMP increased from a geometric mean of 79.4 mg/mL (95% confidence interval [CI], 31.6 to 199.5 mg/mL) during the pollen season to 316.2 mg/mL (95% CI, 158.5 to 400.0 mg/mL) out of season (p = 0.004). The ENO concentrations decreased from 63.1 parts per billion (ppb) [95% CI, 50.1 to 79.4 ppb] during the pollen season to 30.2 ppb (95% CI, 23.4 to 38.0 ppb) out of season (p < 0.001). The ENO concentrations out of pollen season were still significantly increased in subjects with pollen-induced rhinitis when compared with healthy control subjects. There was no relationship between individual changes in ENO levels and changes in either PC(20) methacholine or PC(20) AMP.

CONCLUSIONS

In pollen-sensitive subjects with allergic rhinitis, the cessation of exposure to pollen is associated with a significant reduction of airway responsiveness to inhaled AMP. However, no association was found between allergen-induced changes in ENO values and in airway responsiveness to either direct or indirect bronchoconstrictors. These findings suggest that modifications in ENO and in airway responsiveness are the consequence of different alterations induced by allergen exposure on the lower airways.

Oxidative stress in allergic respiratory diseases

There is ample evidence that allergic disorders, such as asthma, rhinitis, and atopic dermatitis, are mediated by oxidative stress. Excessive exposure to reactive oxygen and nitrogen species is the hallmark of oxidative stress and leads to damage of proteins, lipids, and DNA. Oxidative stress occurs not only as a result of inflammation but also from environmental exposure to air pollution and cigarette smoke. The specific localization of antioxidant enzymes in the lung and the rapid reaction of nitric oxide with reactive oxygen species, such as superoxide, suggest that antioxidant enzymes might also function as cell-signaling agents or regulators of cell signaling. Therapeutic interventions that decrease exposure to environmental reactive oxygen species or augment endogenous antioxidant defenses might be beneficial as adjunctive therapies for allergic respiratory disorders.

Effect of salmeterol on seasonal changes in airway responsiveness and exhaled nitric oxide in pollen-sensitive asthmatic subjects

OBJECTIVE

Using a model of natural allergen exposure, we examined the effect of regular treatment with salmeterol on allergen-induced changes in airway responsiveness and exhaled nitric oxide (ENO).

DESIGN

Double-blind, randomized, parallel-group study.

SETTING

Specialist allergy unit in a university hospital.

PATIENTS

Asthmatic patients sensitized to pollen allergens were randomly allocated to monotherapy with salmeterol (n = 14) or placebo (n = 13).

INTERVENTIONS

Salmeterol, 25 micro g, and placebo inhalers, two puffs bid, for 6 weeks.

MEASUREMENTS

Spirometry, the level of a provocative concentration of a substance (methacholine) causing a 20% fall in FEV(1) (PC(20)), the PC(20) level for adenosine 5'-monophosphate (AMP), and ENO were measured before the pollen season and were repeated at the height of the pollen season after 6 weeks of treatment with salmeterol or placebo.

RESULTS

The decrease in FEV(1) during the pollen season was significantly larger in the placebo group than in the salmeterol group, the mean difference in the change between the groups being 0.20 L (95% confidence interval, 0.03 to 0.35; p = 0.047). Changes in PC(20) for methacholine, PC(20) for AMP, and ENO levels were not significantly different between treatment groups. However, a mean (+/- SEM) decrease in the PC(20) for methacholine of -1.0 +/- 0.4 doubling concentrations was observed within the placebo group (p = 0.03), whereas no significant changes were observed within the salmeterol group. A significant decrease in PC(20) for AMP (doubling concentrations) was observed within the placebo group (-2.1 +/- 0.6; p = 0.003) and the salmeterol group (-1.5 +/- 0.4; p = 0.003). ENO concentrations increased significantly among the placebo and the salmeterol groups during natural pollen exposure.

CONCLUSION

These observations indicate that natural allergen exposure and the regular use of salmeterol are not associated with a greater increase in ENO and airway responsiveness than allergen exposure alone.

Exhaled nitric oxide levels in atopic children: relation to specific allergic sensitisation, AHR, and respiratory symptoms

BACKGROUND

Exhaled nitric oxide (eNO), which has been proposed as a measure of airway inflammation, is increased in atopic subjects. This raises the question of whether eNO provides any additional information about airway inflammation in asthmatic subjects, other than as a marker for atopy. A study was undertaken to determine whether eNO levels in a population of atopic children are associated with sensitisation or natural exposure to specific allergens, and to examine the relationship between eNO, airway responsiveness, and current respiratory symptoms.

METHODS

Exhaled NO and airway responsiveness to histamine were measured in winter and in summer in 235 children aged 8-14 years who had been classified as atopic by skin prick testing. Current respiratory symptoms, defined as wheeze or cough during the month preceding the test, were measured by a parent completed questionnaire. Airway hyperresponsiveness (AHR) was defined as a dose response ratio (DRR) of >8.1 (% fall in forced expiratory volume in 1 second (FEV(1))/micromol + 3).

RESULTS

Sensitisation to house dust mite was associated with raised eNO levels in winter while sensitisation to Cladosporium was associated with raised eNO levels in both winter and summer. Grass pollen sensitisation was not associated with raised eNO levels in either season. Exhaled NO correlated significantly with DRR histamine (r=0.43, p<0.001) independently of whether the children had current symptoms or not. In children with current wheeze, those with AHR had eNO levels 1.53 (95% CI 1.41 to 1.66) times higher than those without AHR (p=0.006). Neither DRR (p=1.0) nor eNO levels (p=0.92) differed significantly between children with or without persistent dry cough in the absence of wheeze.

CONCLUSIONS

In atopic children, raised eNO levels are associated with sensitisation to perennial allergens, but not to seasonal allergens such as grass pollen. In this population, an increase in eNO is associated with AHR and current wheezing, suggesting that eNO is more than just a marker for atopy.

Up-regulation of heme oxygenase-I in alveolar macrophages of newly diagnosed asthmatics

Exhaled carbon monoxide (CO), which has been found to be elevated in asthma, is generated primarily by heme oxygenase I (HO-I), an enzyme induced by oxidant stress and cytokines. The aim of this study was to assess the distribution and expression of HO-I in various human lung cells in acute and stable asthma. Normal lung tissue biopsies (from 6 non-smoking subjects operated on for a lung tumour) and macrophages from induced sputum (from 5 healthy controls, 5 untreated asthmatics, 7 stable treated asthmatics and 5 asthmatics recovering from exacerbation and being on systemic steroids) were investigated for HO-I by immunohistochemistry. The time response of HO-I induction was examined in cultured monocytes, which are known to maturate into monocyte-derived macrophages in culture. Lung biopsies showed prominent HO-I immunoreactivity only in alveolar macrophages. Macrophages in the induced sputum of healthy controls showed no HO-I immunoreactivity, with the exception of one case. Moderate or intense HO-I immunoreactivity could be observed in alveolar macrophages in 4/5 cases with recent asthma, and 2/7 with stable asthma, but in none ofthe patients treated with systemic corticosteroids for acute exacerbation. Experiments with cultured cells revealed that HO-I was induced by oxidants within the first 24 h, but the induction was reversed during the next 48 h. HO-I is mainly expressed in alveolar macrophages of human lung. Macrophages of induced sputum show prominent but transient HO-I immunoreactivity, in untreated asthmatics, but not in asthmatics treated with corticosteroids.