Exhaled nitric oxide and exercise-induced bronchoconstriction in young male conscripts: association only in atopics

Evaluating Children and Adolescents with Suspected Exercise Induced Asthma: Real Life Data

OBJECTIVE

Exercise-induced bronchoconstriction (EIB) occurs frequently in children and adolescents and may be a sign of insufficient asthma control. EIB is often evaluated by respiratory symptoms, spirometry, eNO measurement and methacholine testing (MCT) instead of time consuming exercise test. Aim of this study was to analyse the amount of patients for which an exercise challenge in a cold chamber (ECC) was needed for a clear EIB diagnosis, to characterize EIB phenotypes and the incidence of exercise induced laryngeal obstruction (EILO) in a large cohort of patients with EIB.

METHODS

A retrospective analysis was performed in 595 children and adolescents (mean age 12.1 years) with suspected EIB from January 2014 to December 2018. Complete data sets of skin prick test, spirometry, eNO and MCT were available from 336 patients.

RESULTS

An ECC to confirm the EIB diagnosis was performed in 125 (37.2%) of patients. Three EIB phenotypes were detected: group 1: EIB without allergic sensitization (n=159); group 2: EIB with other than house dust mite (HDM) sensitization (n=87) and group 3: EIB with HDM sensitization (n=90). MCT and eNO showed significant differences between the subgroups: An eNO>46 ppb and/or a MCT<0.1 mg was found in 23.9% vs. 50.6% vs. 57.8% in group 1-3, respectively. Significantly more patients suffered from EILO in group 1 compared to group 2 and 3 (n=13 vs. n=1).

CONCLUSION

EIB without sensitization is as often as EIB with sensitization. In patients without sensitization, EILO has to be considered as a possible cause of symptoms during exercise.

Exhaled NO as a predictor of exercise-induced asthma in cold air

PURPOSE

Physical activity is an important part of life, and exercise-induced asthma (EIA) can reduce the quality of life. A standardized exercise challenge is needed to diagnose EIA, but this is a time consuming, effortful and expensive method. Exhaled nitric oxide (eNO) as a marker of eosinophil inflammation is determined rapidly and easily. The aim of this study was to investigate eNO as surrogate marker for predicting a positive reaction in an exercise challenge in a cold chamber (ECC).

METHODS

A total of 143 subjects aged 6-45 years with suspected EIA were recruited for the study. The subjects underwent an eNO measurement, an ECC and a skin prick test (SPT). To define the sensitivity and specificity of eNO as predictor, a receiver-operating characteristic (ROC) curve was plotted. The individual probability of the occurrence of a positive reaction after ECC based on an eNO value was calculated using a logistic regression model.

RESULTS

An eNO cut-off value of 18.5 ppb (area under the curve (AUC) 0.71, p < 0.001) showed the best combination of sensitivity and specificity for a positive reaction (forced expiratory volume in 1 s (FEV₁) decrease ≥ 10% after ECC) for the whole group. An eNO cut-off value of 46.0 ppb had a specificity of 100.0% to predict a significant FEV₁ decrease and may save exercise testing in 22.4% of patients. A negative predictive level with a high sensitivity and negative predictive value (NPV) could not be defined. In the subgroup that was house dust might (HDM) allergy positive (HDM pos; n = 68, 45.5% of all subjects), an eNO cut-off value of 35.5 ppb (AUC 0.79, p < 0.01) showed the best combination of sensitivity and specificity for a positive reaction after the ECC with a specificity 100.0% and may save exercise testing in 45.6% of HDM pos patients. Using logistic regression, a 95% probability for a positive FEV₁ decrease after ECC was estimated at 53 ppb for the whole group and at 47 ppb for the HDM pos subgroup.

CONCLUSIONS

Exhaled NO measurement is a screening tool for EIA, especially in HDM pos subjects. In a real-life setting, a cut-off value of 46.0 ppb detects EIA at 100% in all suspected patients, and a cut-off level of 35.5 ppb is valuable marker of EIA in patients with an HDM allergy. These levels can save time and costs in a large proportion of patients and will be helpful for clinicians.

Airway hyperresponsiveness to mannitol and methacholine and exhaled nitric oxide in children with asthma

OBJECTIVE

Asthma is characterized by airway hyperresponsiveness (AHR), inflammation, and obstruction. AHR to stimuli that indirectly cause bronchial smooth muscle (BSM) contractions via release of endogenous mediators is thought to better reflect airway inflammation than AHR to stimuli that act directly on BSM. Fractional exhaled nitric oxide (FeNO) is a useful parameter for noninvasive clinical airway inflammation assessments. Accordingly, this study aimed to examine the relationships of mannitol and methacholine challenge test outcomes with FeNO and the influence of inhaled corticosteroid treatment in children with asthma.

METHODS

One hundred thirty-four asthmatic children (89 males; ages: 5-17 years, median: 9 years) underwent spirometry, FeNO measurement, serum total/specific IgE testing, and blood eosinophil count. All subjects were challenged with mannitol dry powder (MDP; AridolH, Pharmaxis, Australia) and methacholine at 7-day intervals. Data of steroid-treated and steroid-naïve children were compared.

RESULTS

Positive responses to MDP and methacholine challenge tests were observed in 74.6% and 67.2% of total subject group, respectively, and 72 children had positive response to both challenge tests. The median FeNO level, response-dose ratio (RDR) of PC₂₀ methacholine, and RDR of PD₁₅ MDP were significantly higher in the steroid-treated group than in the steroid-naïve group (p < 0.001, 0.226, and 0.004, respectively). FeNO levels associated significantly with PD₁₅ MDP and RDR PD₁₅ MDP in total subject populations (p = 0.016 and 0.003, respectively); however, a significant correlation between FeNO and RDR PD₁₅ MDP was observed only in the steroid-naïve group.

CONCLUSIONS

Compared with AHR to methacholine, AHR to MDP more closely reflected the level of FeNO in steroid-naïve asthmatic children.

Exhaled Nitric Oxide and Airway Hyperresponsiveness to Adenosine 5'-monophosphate and Methacholine in Children with Asthma

BACKGROUND

There is increasing interest in the role of indirect bronchial challenges because clinical studies have shown that indirect airway hyperresponsiveness (AHR) reflects underlying airway inflammation better than direct AHR. Fractional exhaled nitric oxide (FeNO) appears to be a useful clinical tool for assessing airway inflammation noninvasively. We examined whether FeNO is more closely related to AHR to indirect stimuli than AHR to direct stimuli in children with mild to moderate asthma.

METHODS

Fifty-nine asthmatic children aged 6-16 years without rhinitis, underwent spirometry, FeNO measurement and blood tests for serum total IgE, blood eosinophil count and serum eosinophil cationic protein (ECP). All subjects underwent methacholine and adenosine 5-monophosphate (AMP) challenge tests at intervals of 3 days.

RESULTS

In a univariate linear regression analysis, FeNO was significantly associated with both PC20 AMP (R(2) = 0.341, p < 0.001) and PC20 methacholine (R(2) = 0.188, p = 0.001). After adjustment for age, sex, serum total IgE and blood eosinophil count, the association between FeNO and PC20 AMP (β = -1.98, p = 0.001) was more robust than that between FeNO and PC20 methacholine (β = -0.87, p = 0.081). The significant correlation between FeNO and PC20 AMP was observed in the steroid-naïve group (β = -2.48, p = 0.001), but not in the steroid-treated group (β = 0.88, p = 0.463).

CONCLUSIONS

FeNO levels were more closely associated with PC20 AMP than with PC20 methacholine. This relationship could only be seen in the steroid-naïve subjects. These results suggest that FeNO levels in children with asthma may be more closely related to indirect AHR than to direct AHR.

Do children with stable asthma benefit from addition of montelukast to inhaled corticosteroids: randomized, placebo controlled trial

BACKGROUND

To determine the effects of montelukast added to maintenance inhaled steroids (ICS) therapy during the school year in children with stable asthma on the ICS use, frequency of exacerbations, lung function, asthma symptoms, fractional exhaled nitric oxide (FeNO) level and exercise-induced bronchoconstriction (EIB).

METHODS

Seventy six asthmatic children aged 6-14 years, allergic to house dust mites were randomized to a double-blinded trial comparing montelukast therapy to a matching placebo. We studied following end-points: the reduction in the ICS dose, the frequency of exacerbations, lung function, asthma control test score, and the change from baseline in FEV1 during a standardized exercise treadmill challenge. ICS dose was adjusted in a stepwise fashion to determine the lowest dose necessary to control asthma symptoms.

RESULTS

We showed that children with baseline value of FeNO above 31 ppb and well controlled asthma symptoms on low doses of ICS, benefit the most from additive therapy with montelukast; their cumulative ICS dose is lower than in children treated with ICS only. Also, the addition of montelukast to regular treatment in asthmatic children resulted in a significant reduction in the frequency of exacerbations and EIB protection.

CONCLUSION

It is reasonable to add montelukast to ICS therapy in asthmatic children during the school year, to lower cumulative ICS dose in children with well controlled asthma symptoms, as well as to reduce number of exacerbations, and to achieve better control of EIB.

TRIAL REGISTRATION

NCT01266772.

Exhaled nitric oxide and other exhaled biomarkers in bronchial challenge with exercise in asthmatic children: current knowledge

The fractional concentration of exhaled nitric oxide (FENO), a known marker of atopic-eosinophilic inflammation, may be used as a surrogate to assess exercise-induced bronchoconstriction (EIB) in asthmatic children. The predictive value of baseline FENO for EIB appears to be influenced by several factors, including age, atopy, current therapy with corticosteroids and measurement technique. Nonetheless, FENO cut-off values appear to be able to rule out EIB. FENO levels decrease during EIB, apparently through neural mechanisms rather than by decreased airway-epithelial surface. Partition of FENO into proximal and peripheral contributions of the respiratory tract may improve our understanding on NO exchange during exercise and help to screen subjects prone to EIB. Other biomarkers of inflammation and oxidative stress contained in exhaled gases and exhaled breath condensate (EBC) may shed light on the pathophysiology of EIB. Exhaled breath temperature is a promising real-time measurement whose routine use for assessing EIB warrants further investigation.

Exhaled nitric oxide indicates poorly athlete's asthma

INTRODUCTION

In athletes, exercise-induced respiratory symptoms are common and their assessment is time and resource consuming.

OBJECTIVE

The objective was to evaluate fractional concentration of exhaled nitric oxide (FENO) as a predictor of bronchial hyperresponsiveness (BHR) and of asthma.

MATERIALS AND METHODS

Eighty-seven elite athletes and a control group of 87 sedentary patients with symptoms suggesting asthma underwent measurements of FENO and of BHR by using methacholine provocation test (MCH) and eucapnic voluntary hyperpnoea (EVH) (athletes) or histamine provocation test (HIST) (controls).

RESULTS

In athletes, elevated FENO (>30 ppb) was not associated with lung function-confirmed asthma or with MCH positivity, but receiver operating characteristics (ROC) analysis showed some predictive value for EVH positivity [Area Under Curve (AUC) 0.652, 95% confidence interval (CI): 0.53 to 0.78, P = 0.020]. However, the sensitivity (55%) and the specificity (71%) were poor. In sedentary patients, FENO was significantly associated with both confirmed asthma and HIST positivity, ROC analysis showing FENO to be significantly predictive for HIST positivity (AUC 0.83, 95% CI: 0.70 to 0.96, P = 0.001) and for asthma (AUC 0.74, 95% CI: 0.63 to 0.85, P < 0.001).

CONCLUSION

The results suggest that in contrast to sedentary patients, FENO seems to be a poor predictor of BHR and of clinical asthma in elite athletes. We find it unlikely that FENO could be a useful screening tool in athletes with exercise-induced respiratory symptoms.

Where to from here for exercise-induced bronchoconstriction: the unanswered questions

The role of epithelial injury is an unanswered question in those with established asthma and in elite athletes who develop features of asthma and exercise-induced bronchorestriction (EIB) after years of training. The movement of water in response to changes in osmolarity is likely to be an important signal to the epithelium that may be central to the onset of EIB. It is generally accepted that the mast cell and its mediators play a major role in EIB and the presence of eosinophils is likely to enhance EIB severity.

Bronchial and alveolar nitric oxide in exercise-induced bronchoconstriction in asthmatic children

BACKGROUND

Epidemiological studies have shown an association between the severity of exercise-induced bronchoconstriction (EIB) and fractional exhaled nitric oxide at the flow of 50 mL/s (FeNO(50)). However, no study has assessed the correlation between alveolar production (C(alv)) and bronchial flux (J(NO)) of nitric oxide (NO) and EIB in asthmatic children.

OBJECTIVE

To identify the relationship between severity of EIB and bronchial or alveolar nitric oxide.

METHODS

Our group included 36 allergic children with intermittent asthma. The EIB was determined by a standard exercise challenge and the severity was expressed as the maximum change in percentage from the baseline value of lung function (ΔFEV(1)%, ΔFEF(25-75)%) after exercising. A chemiluminescence analyser at multiple flows was used to calculate FeNO(50), J(NO) and C(alv,) which reflect large airways, J(NO) and alveolar concentration of NO respectively.

RESULTS

Sixteen (44.4%) children presented a ∆FEV(1) ≥ 10%, eight (22.2%) had ∆FEV(1) ≥ 15% and nine (25%) children had a ∆FEF(25-75) ≥ 26%. A significant correlation was observed between severity of EIB and FeNO(50) , J(NO) and C(alv.) EIB was significantly more severe in children sensitive to indoor allergens compared with outdoor allergens only (P = 0.014); those children showed also higher levels of C(alv) (P = 0.003) and of J(NO) (P = 0.044).

CONCLUSIONS AND CLINICAL RELEVANCE

Our results suggest that inflammation is present in the central and peripheral airways and that it is associated with the severity of EIB. Clinicaltrials.gov NCT00952835.

Positive exercise test and obstructive spirometry in young male conscripts associated with persistent asthma 20 years later

BACKGROUND

Asthma often begins in childhood or early adulthood and is a common disease among conscripts. The identification of long-term predictive factors for persistent asthma may lead to improved treatment opportunities and better disease control.

OBJECTIVE

Our aim was to study the prognostic factors of the severity of asthma among 40-year-old male conscripts whose asthma began in youth.

METHODS

We studied 119 conscripts who were referred to the Central Military Hospital during 1987-1990 due to asthma and who attended a follow-up visit approximately 20 years later. Asthma severity was evaluated during military service according to the medical records, and 20 years later during a follow-up visit using Global Initiative for Asthma guidelines. We used the results of lung function and allergy tests at baseline as predictors of current persistent asthma.

RESULTS

Compared with baseline, asthma was less severe at follow-up: 11.8% of subjects were in remission, 42.0% had intermittent asthma, 10.9% had mild persistent asthma, and 35.3% had moderate/severe persistent asthma (p < .001). In multivariate models, a positive exercise test at baseline yielded an odds ratio (OR) of 3.2 (95% CI 1.0-9.8, p = .046), a decreased FEV1/FVC % predicted an OR of 4.0 (95% CI 1.7-9.3, p = .002), and a decreased FEF50% % predicted an OR of 2.8 (95% CI 1.3-6.4, p = .012) for current persistent asthma.

CONCLUSIONS

About half of the men had persistent asthma at the 20-year follow-up. Positive exercise tests and obstructive spirometry results were related to the persistence of asthma and may be useful long-term prognostic factors for asthma severity.

Relation of bronchial and alveolar nitric oxide to exercise-induced bronchoconstriction in atopic children and adolescents

BACKGROUND AND OBJECTIVE

Exercise challenge test is widely used in diagnostics and follow-up of childhood asthma, but the method is complex, time consuming, and expensive. In this study, we aimed to find out whether flow-independent nitric oxide (NO) parameters (bronchial NO flux [J'aw(NO)] and alveolar NO concentration [CA(NO)]) predict exercise-induced bronchoconstriction (EIB) in atopic children and adolescents with asthma-like symptoms. Also, the respective NO parameters corrected for axial backward diffusion (J'aw(NO) [TMAD] and CA(NO) [TMAD]) were calculated and included in the analysis.

METHODS

Thirty patients (6-19 yr old) with confirmed atopy (positive skin prick tests or allergen-specific IgE) and asthma-like respiratory symptoms were included in the study. Before the current investigations, none of the patients had been diagnosed to have asthma and none were on inhaled corticosteroids. Exhaled NO was measured at multiple exhalation flow rates, and exercise challenge test was carried out. Bronchial NO flux and alveolar NO concentration were calculated according to the linear method with and without correction for axial backward diffusion. Sixty-six healthy school children served as controls.

RESULTS

The patients were divided into two groups according to EIB. Patients with EIB (EIB+ group, n = 18) had enhanced bronchial NO output as compared to patients without EIB (EIB- group, n = 12); but the EIB- group did not differ from healthy controls. EIB+ group had also higher alveolar NO concentration than EIB- group and healthy controls, but EIB- group did not differ from healthy controls. When bronchial NO flux and alveolar NO concentration were corrected for axial diffusion, J'aw(NO) (TMAD) had equal difference as J'aw(NO) between the groups as expected. However, only EIB+ had higher CA(NO) (TMAD) than healthy controls, and the patient groups did not differ from each other. In patients, bronchial NO output correlated with the magnitude of exercise-induced change in PEF (r(s) = -0.388, p = 0.034), FEV(1) (r(s) = -0.395, p = 0.031), and FEF(50%) (r(s) = -0.431, p = 0.020), i.e., the higher the bronchial NO output, the larger the decrease in PEF/FEV(1) /FEF(50%) . Alveolar NO concentrations correlated with the change in FEV(1) (r(s) = -0.439, p = 0.015), FEF(50%) (r(s) = -0.454, p = 0.013), FEF(75%) (r(s) = -0.447, p = 0.017), and FVC (r(s) = -0.375, p = 0.045). For J'aw(NO) (TMAD), the correlations and p-values were equal to those of J'aw(NO) , but, interestingly, CA(NO) (TMAD) had no significant correlations with any of the exercise-induced changes in lung function.

CONCLUSION

The results showed that in atopic children and adolescents, increased bronchial NO output as well as J'aw(NO) (TMAD) were associated with EIB, while alveolar NO concentration (but not CA(NO) [TMAD]) correlated with the degree of obstruction in smaller airways induced by exercise challenge.

Exhaled breath temperature and exercise-induced bronchoconstriction in asthmatic children

It has been hypothesized that exhaled breath temperature (EBT) is related to the degree of airway inflammation/remodeling in asthma. The purpose of this study was to evaluate the relationship between the level of airway response to exercise and EBT in a group of controlled or partly controlled asthmatic children. Fifty asthmatic children underwent measurements of EBT before and after a standardized exercise test. EBT was 32.92 ± 1.13 and 33.35 ± 0.95°C before and after exercise, respectively (P < 0.001). The % decrease in FEV(1) was significantly correlated with the increase in EBT (r = 0.44, P = 0.0013), being r = 0.49 (P < 0.005) in the children who were not receiving regular inhaled corticosteroids (ICS) and 0.37 (n.s.) in those who were. This study further supports the hypothesis that EBT can be considered a potential composite tool for monitoring asthma.

Exercise increases exhaled breath condensate cysteinyl leukotriene concentration in asthmatic patients

BACKGROUND

Although the importance of cysteinyl leukotrienes (Cys-LTs) in exercise-induced bronchoconstriction (EIB) is supported by various sources of evidence, how the concentration of these mediators change during the development of EIB has not been investigated.

OBJECTIVES

Our goal was to determine the effect of exercise on the concentration of airway Cys-LT in asthmatic patients by measuring Cys-LT in exhaled breath condensate (EBC).

METHODS

Seventeen atopic asthmatic patients with a previous history of EIB and six healthy volunteers were studied. Before and two times within 10 minutes after exercise challenge, FEV₁ was measured and EBC was collected for Cys-LT measurement. Exhaled nitric oxide level, a marker of airway inflammation, was also determined at baseline.

RESULTS

Baseline Cys-LT level was higher in the asthmatic group versus healthy subjects (168 pg/mL /112-223/ vs. 77 pg/mL /36-119/, p = .03). EBC Cys-LT concentration increased in all asthmatic patients post-exercise (n = 17, p = .03), with the increase significantly greater in patients developing exercise-induced bronchospasm (n = 7, p = .03), whereas no change was observed in healthy controls (p = .59). The exercise-induced fall in FEV(1) in asthmatics was related to the increase in EBC Cys-LT concentration (r = -0.40, p = .03).

CONCLUSIONS

Our study shows that Cys-LT concentration of EBC is elevated minutes after physical exercise in asthmatic patients and strongly supports the concept that the release of this mediator is involved in the development of EIB.

The inflammatory basis of exercise-induced bronchoconstriction

Exercise-induced bronchoconstriction (EIB) is common in individuals with asthma, and may be observed even in the absence of a clinical diagnosis of asthma. Exercise-induced bronchoconstriction can be diagnosed via standardized exercise protocols, and anti-inflammatory therapy with inhaled corticosteroids (ICS) is often warranted. Exercise-related symptoms are commonly reported in primary care; however, access to standardized exercise protocols to assess EIB are often restricted because of the need for specialized equipment, as well as time constraints. Symptoms and lung function remain the most accessible indicators of EIB, yet these are poor predictors of its presence and severity. Evidence suggests that exercise causes the airways to narrow as a result of the osmotic and thermal consequences of respiratory water loss. The increase in airway osmolarity leads to the release of bronchoconstricting mediators (eg, histamine, prostaglandins, leukotrienes) from inflammatory cells (eg, mast cells and eosinophils). The objective assessment of EIB suggests the presence of airway inflammation, which is sensitive to ICS in association with a responsive airway smooth muscle. Surrogate tests for EIB, such as eucapnic voluntary hyperpnea or the osmotic challenge tests, cause airway narrowing via a similar mechanism, and a response indicates likely benefit from ICS therapy. The complete inhibition of EIB with ICS therapy in individuals with asthma may be a useful marker of control of airway pathology. Furthermore, inhibition of EIB provides additional, useful information regarding the identification of clinical control based on symptoms and lung function. This article explores the inflammatory basis of EIB in asthma as well as the effect of ICS on the pathophysiology of EIB.

Associations of airway inflammation and responsiveness markers in non asthmatic subjects at start of apprenticeship

Background

Bronchial Hyperresponsiveness (BHR) is considered a hallmark of asthma. Other methods are helpful in epidemiological respiratory health studies including Fractional Exhaled Nitric Oxide (FENO) and Eosinophils Percentage (EP) in nasal lavage fluid measuring markers for airway inflammation along with the Forced Oscillatory Technique measuring Airway resistance (AR). Can their outcomes discriminate profiles of respiratory health in healthy subjects starting apprenticeship in occupations with a risk of asthma?

Methods

Rhinoconjunctivitis, asthma-like symptoms, FEV1 and AR post-Methacholine Bronchial Challenge (MBC) test results, FENO measurements and EP were all investigated in apprentice bakers, pastry-makers and hairdressers not suffering from asthma. Multiple Correspondence Analysis (MCA) was simultaneously conducted in relation to these groups and this generated a synthetic partition (EI). Associations between groups of subjects based on BHR and EI respectively, as well as risk factors, symptoms and investigations were also assessed.

Results

Among the 441 apprentice subjects, 45 (10%) declared rhinoconjunctivitis-like symptoms, 18 (4%) declared asthma-like symptoms and 26 (6%) suffered from BHR. The mean increase in AR post-MBC test was 21% (sd = 20.8%). The median of FENO values was 12.6 ppb (2.6-132 range). Twenty-six subjects (6.7%) had EP exceeding 14%. BHR was associated with atopy (p < 0.01) and highest FENO values (p = 0.09). EI identified 39 subjects with eosinophilic inflammation (highest values of FENO and eosinophils), which was associated with BHR and atopy.

Conclusions

Are any of the identified markers predictive of increased inflammatory responsiveness or of development of symptoms caused by occupational exposures? Analysis of population follow-up will attempt to answer this question.

Asthma tests in the assessment of military conscripts

BACKGROUND

Respiratory diseases such as asthma may affect individuals' fitness for military service. In order to assess fitness for military service in subjects with asthma symptoms at conscription, objective and reliable tests are needed.

OBJECTIVE

To prospectively determine the diagnostic value of the mannitol and methacholine bronchial provocation test (BPT) as well as exhaled nitric oxide in assessing physician-diagnosed asthma in a group of Swiss Armed Forces conscripts.

METHODS

Questionnaire, spirometry, BPT with methacholine and mannitol, exhaled nitric oxide (FeNO) and skin prick testing were conducted in 18-20-year-old male conscripts. Asthma was diagnosed by a military physician not involved in this study according to the medical record, results of BPT, current respiratory symptoms and use of asthma medication.

RESULTS

Two hundred and eighty four subjects participated in the study. Complete data for the BPT with methacholine, mannitol and measurement of FeNO were available on 235 subjects. Forty-two conscripts (17.9%) had physician-diagnosed asthma. The sensitivity/specificity of mannitol to identify physician-diagnosed asthma was 41%/93% and for methacholine it was 43%/92%. Using a cut-off point of 36.5 p.p.b., FeNO had a similar negative predictive value to rule out physician-diagnosed asthma as BPT with mannitol or methacholine.

CONCLUSION

BPT with mannitol has a sensitivity and specificity similar to methacholine for the diagnosis of physician-diagnosed asthma in military conscripts but is less costly to perform without the need to use and maintain a nebulizer.

Exhaled nitric oxide and exercise-induced bronchoconstriction in young wheezy children - interactions with atopy

The association between exercise-induced bronchoconstriction (EIB) and exhaled nitric oxide (FE(NO)) has not been investigated in young children with atopic or non-atopic wheeze, two different phenotypes of asthma in the early childhood. Steroid naïve 3- to 7-yr-old children with recent wheeze (n = 84) and age-matched control subjects without respiratory symptoms (n = 71) underwent exercise challenge test, measurement of FE(NO) and skin prick testing (SPT). EIB was assessed by using impulse oscillometry, and FE(NO) by standard online technique. Although FE(NO) levels were highest in atopic patients with EIB, both atopic and non-atopic wheezy children with EIB showed higher FE(NO) than atopic and non-atopic control subjects, respectively. In atopic wheezy children, a significant relationship between FE(NO) and the severity of EIB was found (r = 0.44, p = 0.0004), and FE(NO) was significantly predictive of EIB. No clear association between FE(NO) and EIB or predictive value was found in non-atopic wheezy children. Both atopic and non-atopic young wheezy children with EIB show increased FE(NO) levels. However, the association between the severity of EIB and FE(NO) is present and FE(NO) significantly predictive of EIB only in atopic subjects, suggesting different interaction between bronchial responsiveness and airway inflammation in non-atopic wheeze.

A quantitative genetic analysis of intermediate asthma phenotypes

AIM

To study the relative contribution of genetic and environmental factors to the correlation between exhaled nitric oxide (FeNO), airway responsiveness, airway obstruction, and serum total immunoglobulin E (IgE).

METHODS

Within a sampling frame of 21,162 twin subjects, 20-49 years of age, from the Danish Twin Registry, a total of 575 subjects (256 intact pairs and 63 single twins) who either themselves and/or their co-twins reported a history of asthma at a nationwide questionnaire survey, were clinically examined. Traits were measured using standard techniques. Latent factor models were fitted to the observed data using maximum likelihood methods.

RESULTS

Additive genetic factors explained 67% of the variation in FeNO, 43% in airway responsiveness, 22% in airway obstruction, and 81% in serum total IgE. In general, traits had genetically and environmentally distinct variance structures. The most substantial genetic similarity was observed between FeNO and serum total IgE, genetic correlation (rhoA) = 0.37, whereas the strongest environmental resemblance was observed between airway responsiveness and airway obstruction, specific environmental correlation (rhoE) = -0.46, and between FeNO and airway responsiveness, rhoE = 0.34.

CONCLUSIONS

Asthma is a complex disease characterized by a set of etiologically heterogeneous biomarkers, which likely constitute diverse targets of intervention.

Equally elevated concentrations of exhaled nitric oxide in nonatopic and low-sensitized atopic asthmatics

BACKGROUND

Some studies show concentrations of exhaled nitric oxide (FENO) in nonatopic asthma and in healthy subjects to be similar, but include asthmatics on inhaled steroids, which is likely to interfere with the results.

AIM

Comparison of FENO between nonatopic asthmatics, low-sensitized and high-sensitized atopic asthmatics, and healthy controls.

METHODS

We studied 85 non-smoking, steroid-naive young men with recently diagnosed symptomatic asthma and 10 healthy controls. FENO was measured according to European Respiratory Society Guidelines. In skin prick tests of 13 common aeroallergens, subjects with a total sum of prick wheals 3-10mm were regarded as low-sensitized and those with >10mm, as high-sensitized. Flow-volume spirometry, standardized histamine challenge, and an exercise test were also carried out.

RESULTS

Prick tests revealed 14 subjects to be nonatopic and 71 atopic. In high-sensitized subjects with atopic asthma, the FENO median (25-75 quartiles) was significantly higher, 34.9 (21.3-53.8) parts per billion (ppb), than in subjects with nonatopic asthma, 15.2 (9.7-24.7)ppb (p<0.001), both being significantly higher than in healthy controls, 6.6 (5.2-8.5)ppb (p<0.001). FENO levels were similar in nonatopic and in low-sensitized atopic asthmatics, with no difference between them in bronchial responsiveness to histamine and exercise.

CONCLUSION

Among steroid-naive young male asthmatics, FENO was equally elevated in nonatopic asthma and in low-sensitized atopic asthma but lower than in those with high-sensitized atopic asthma. These differences in FENO between asthma groups parallel the differences in airway function disturbance in terms of responsiveness to histamine or exercise.

The clinical significance of exhaled nitric oxide in asthma

Asthma is an inflammatory disease of the airways, for which many therapeutic options are available. Guidelines for the management of asthma suggest a stepwise approach to pharmacotherapy based on assessment of asthma severity and control. However, the assessment of asthma control presently relies on surrogate measures, such as the frequency of symptoms or the frequency of use of short-acting beta2-adrenergic agonists. There is no simple, noninvasive technique for the assessment of severity of actual airway inflammation in asthma. The collection and analysis of nitric oxide (NO) levels in exhaled breath has recently become feasible in humans. Based on increased exhaled NO (eNO) levels in patients with asthma, eNO analysis has been proposed as a novel, noninvasive approach to the assessment and monitoring of airway inflammation, and as a basis for adjustments in asthma therapy. In the present paper, the relationship of elevated eNO levels in asthma with inflammatory, physiological and clinical markers of asthma in adults was reviewed. Use of eNO is a promising tool for diagnosing asthma, for monitoring asthma control and for guiding optimal anti-inflammatory asthma therapy. However, because of many unresolved questions, eNO cannot be recommended at present for routine clinical management of adults with asthma.

The value of exhaled nitric oxide in predicting bronchial hyperresponsiveness in children

Reduced attention span and motor skills in children limit the practicability of bronchial provocation tests. To assess exhaled nitric oxide (FeNO) as a surrogate for bronchial hyperresponsiveness (BHR) in children with possible reactive airway disease, FeNO was measured using the single-breath method in 169 successive outpatients 11 +/- 5 years of age before lung function testing and subsequent bronchial provocation by exercise (n = 165) and methacholine (n = 134). Baseline forced expiratory volume in 1 second (FEV(1)) less than 80% of predicted and/or BHR were seen in 59%. FeNO correlated weakly with PD(20) to methacholine (r = -0.24, p < 0.05), but not with the change in FEV(1) due to exercise-induced bronchoconstriction (EIB) (r = 0.1, p > 0.05). The negative predictive value of FeNO less than 10 ppb for EIB was 94%, but overall accuracy for predicting BHR was low. Measurement of FeNO is not a substitute for bronchial provocation in children.

Diagnostic tests for asthma in firefighters

BACKGROUND

Subjects with asthma do not meet medical requirements for professions such as firefighting.

OBJECTIVE

To prospectively determine the diagnostic value of respiratory symptoms and various tests used in the assessment of asthma in a cohort of firefighters.

METHODS

A questionnaire, spirometry, direct and indirect airway challenge tests, exhaled nitric oxide, and skin-prick tests were administered prospectively to 101 of 107 firefighters employed in Basel, Switzerland. Asthma was defined as the combination of respiratory symptoms with airway hyperresponsiveness.

RESULTS

Six of 101 firefighters (6%) had physician-diagnosed asthma, which could be confirmed in 4 firefighters. In contrast, asthma was diagnosed in 14% (14 of 101 firefighters). Wheezing was the most sensitive symptom for the diagnosis of asthma (sensitivity, 78%; specificity, 93%). Other respiratory symptoms showed a higher specificity than wheezing but a markedly lower sensitivity. Bronchial airway challenge with mannitol was the most sensitive (92%) and specific (97%) diagnostic test for asthma. Using a cutoff point of 47 parts per billion, nitric oxide had a similar specificity (96%) but lower sensitivity (42%) compared to the direct (methacholine) and indirect (mannitol) airway challenge tests.

CONCLUSION

Asthma was considerably underdiagnosed in firefighters. The combination of a structured symptom questionnaire with a bronchial challenge test allows to identify patients with asthma and should routinely be used in the assessment of active firefighters and may be of help when evaluating candidates for this profession.

Elevated exhaled nitric oxide in newborns of atopic mothers precedes respiratory symptoms

RATIONALE

Exhaled nitric oxide (NO) is a well-known marker of established airway inflammation in asthma. Its role in the disease process before the onset of respiratory symptoms remains unclear.

OBJECTIVES

To examine whether elevated NO in newborns with clinically naive airways is associated with subsequent respiratory symptoms in infancy.

METHODS

We measured exhaled NO concentration and output after birth and prospectively assessed respiratory symptoms during infancy in a birth cohort of 164 unselected healthy neonates. We examined a possible association between NO and respiratory symptoms using Poisson regression analysis.

RESULTS

In infants of atopic mothers, elevated NO levels after birth were associated with increased risk of subsequent respiratory symptoms (risk ratio [RR], 7.5; 95% confidence interval [CI], 1.7-32.4 for each nl/s increase in NO output; p = 0.007). Similarly, a positive association between NO and symptoms was seen in infants of smoking mothers (RR, 6.6; 95% CI, 2.3-19.3; p = 0.001), with the strongest association in infants whose mothers had both risk factors (RR, 21.8; 95% CI, 5.8-81.3; p < 0.001).

CONCLUSIONS

The interaction of NO with maternal atopy and smoking on subsequent respiratory symptoms is present early in life. Clinically, noninvasive NO measurements in newborns may prove useful as a new means to identify high-risk infants. Future confirmation of a role for NO metabolism in the evolution of respiratory disease may provide an avenue for preventative strategies.

Exercise-induced bronchoconstriction alters airway nitric oxide exchange in a pattern distinct from spirometry

Exhaled nitric oxide (NO) is altered in asthmatic subjects with exercise-induced bronchoconstriction (EIB). However, the physiological interpretation of exhaled NO is limited because of its dependence on exhalation flow and the inability to distinguish completely proximal (large airway) from peripheral (small airway and alveolar) contributions. We estimated flow-independent NO exchange parameters that partition exhaled NO into proximal and peripheral contributions at baseline, postexercise challenge, and postbronchodilator administration in steroid-naive mild-intermittent asthmatic subjects with EIB (24-43 yr old, n = 9) and healthy controls (20-31 yr old, n = 9). The mean +/- SD maximum airway wall flux and airway diffusing capacity were elevated and forced expiratory flow, midexpiratory phase (FEF(25-75)), forced expiratory volume in 1 s (FEV(1)), and FEV(1)/forced vital capacity (FVC) were reduced at baseline in subjects with EIB compared with healthy controls, whereas the steady-state alveolar concentration of NO and FVC were not different. Compared with the response of healthy controls, exercise challenge significantly reduced FEV(1) (-23 +/- 15%), FEF(25-75) (-37 +/- 18%), FVC (-12 +/- 12%), FEV(1)/FVC (-13 +/- 8%), and maximum airway wall flux (-35 +/- 11%) relative to baseline in subjects with EIB, whereas bronchodilator administration only increased FEV(1) (+20 +/- 21%), FEF(25-75) (+56 +/- 41%), and FEV(1)/FVC (+13 +/- 9%). We conclude that mild-intermittent steroid-naive asthmatic subjects with EIB have altered airway NO exchange dynamics at baseline and after exercise challenge but that these changes occur by distinct mechanisms and are not correlated with alterations in spirometry.

Increased oxidative stress in asymptomatic current chronic smokers and GOLD stage 0 COPD

Background

Chronic obstructive pulmonary disease (COPD) is associated with increased oxidative and nitrosative stress. The aim of our study was to assess the importance of these factors in the airways of healthy smokers and symptomatic smokers without airway obstruction, i.e. individuals with GOLD stage 0 COPD.

Methods

Exhaled NO (FENO) and induced sputum samples were collected from 22 current smokers (13 healthy smokers without any respiratory symptoms and 9 with symptoms i.e. stage 0 COPD) and 22 healthy age-matched non-smokers (11 never smokers and 11 ex-smokers). Sputum cell differential counts, and expressions of inducible nitric oxide synthase (iNOS), myeloperoxidase (MPO), nitrotyrosine and 4-hydroxy-2-nonenal (4-HNE) were analysed from cytospins by immunocytochemistry. Eosinophil cationic protein (ECP) and lactoferrin were measured from sputum supernatants by ELISA.

Results

FENO was significantly decreased in smokers, mean (SD) 11.0 (6.7) ppb, compared to non-smokers, 22.9 (10.0), p < 0.0001. Induced sputum showed increased levels of neutrophils (p = 0.01) and elevated numbers of iNOS (p = 0.004), MPO (p = 0.003), nitrotyrosine (p = 0.003), and 4-HNE (p = 0.03) positive cells in smokers when compared to non-smokers. Sputum lactoferrin levels were also higher in smokers than in non-smokers (p = 0.02). Furthermore, we noted four negative correlations between FENO and 1) total neutrophils (r = -0.367, p = 0.02), 2) positive cells for iNOS (r = -0.503, p = 0.005), 3) MPO (r = -0.547, p = 0.008), and 4) nitrotyrosine (r = -0.424, p = 0.03). However, no major differences were found between never smokers and ex-smokers or between healthy smokers and stage 0 COPD patients.

Conclusion

Our results clearly indicate that several markers of oxidative/nitrosative stress are increased in current cigarette smokers compared to non-smokers and no major differences can be observed in these biomarkers between non-symptomatic smokers and subjects with GOLD stage 0 COPD.