Exhaled nitric oxide predicts exercise-induced bronchoconstriction in asthmatic school children

Exercise-induced bronchoconstriction, allergy and sports in children

Exercise-induced bronchoconstriction (EIB) is characterized by the narrowing of airways during or after physical activity, leading to symptoms such as wheezing, coughing, and shortness of breath. Distinguishing between EIB and exercise-induced asthma (EIA) is essential, given their divergent therapeutic and prognostic considerations. EIB has been increasingly recognized as a significant concern in pediatric athletes. Moreover, studies indicate a noteworthy prevalence of EIB in children with atopic predispositions, unveiling a potential link between allergic sensitivities and exercise-induced respiratory symptoms, underpinned by an inflammatory reaction caused by mechanical, environmental, and genetic factors. Holistic management of EIB in children necessitates a correct diagnosis and a combination of pharmacological and non-pharmacological interventions. This review delves into the latest evidence concerning EIB in the pediatric population, exploring its associations with atopy and sports, and emphasizing the appropriate diagnostic and therapeutic approaches by highlighting various clinical scenarios.

Analysis of the correlation between serum Klotho and FeNO: a cross-sectional study from NHANES (2007-2012)

BACKGROUND

Klotho is an anti-aging protein that has multiple functions and may play a key role in the pathogenesis and progression of chronic respiratory diseases such as chronic obstructive pulmonary disease (COPD). Fractional Exhaled Nitric Oxide (FeNO) is a non-invasive and novel biomarker that has the advantages of being simple, fast and reproducible. It can effectively assess the degree of airway inflammation in diseases such as asthma and COPD. Despite these insights, the relationship between serum Klotho levels and FeNO has not been explored yet.

METHODS

Leveraging data from the National Health and Nutrition Examination Survey (NHANES) spanning 2007 to 2012, we investigated the correlation between FeNO and serum Klotho levels. This association was scrutinized both as continuous variables and within quartile distributions, utilizing the Kruskal-Wallis H test. The correlation between the two variables was assessed through Spearman rank analysis. Employing survey weight-adjusted linear regression models, we gauged the strength of these associations.

RESULTS

This study included 6,527 participants with a median FeNO level of 14.5 parts per billion (ppb). We found that FeNO levels varied significantly across different quartiles of Klotho protein (H = 7.985, P = 0.046). We also found a significant positive correlation between serum Klotho levels and FeNO levels in the whole population (Spearman's rho = 0.029, P = 0.019). This correlation remained significant after adjusting for covariates such as age, gender, lung function, smoking status, alcohol use, BMI, cardiovascular disease (including hypertension, heart failure, coronary heart disease, and myocardial infarction), diabetes, inflammatory markers, serum vitamin D level and BUN (P < 0.05 for all). Furthermore, this correlation was stronger at the high (K3) and super high (K4) levels of Klotho than at the low (K1) and medium (K2) levels (β = 1.979 ppb and β = 1.993 ppb for K3 and K4 vs. K1, respectively; 95% CI: 0.497 ~ 2.953 and 95% CI: 0.129 ~ 2.827, respectively; P = 0.007 and P = 0.032, respectively). The β coefficient for serum Klotho was 0.002 ppb/pg/ml.

CONCLUSIONS

Our study illuminates a positive correlation between serum Klotho levels and FeNO. Further study is needed to verify the causality of this association and elucidate the underlying mechanisms.

Use of exhaled nitric oxide in the diagnosis and monitoring of childhood asthma: myth or maxim?

Asthma is a common condition in children. This review describes the evidence from the literature and international asthma guidelines for using fractional exhaled nitric oxide (FENO) in the diagnosis and monitoring of childhood asthma. The accuracy of FENO measuring devices could be further improved, the difference in FENO results between devices are equivalent to what is considered a clinically important difference. For diagnosing asthma no guideline currently recommends FENO is used as the first test, but many recommend FENO as part of a series of tests. A cut-off of 35 ppb is widely recommended as being supportive of an asthma diagnosis, but evidence from children at risk of asthma suggests that a lower threshold of 25 ppb may be more appropriate. Nine randomised clinical trials including 1885 children have added FENO to usual asthma care and find that exacerbations are reduced when care is guided by FENO (OR for exacerbation compared to usual care 0.77, 95% CI 0.62-0.94). What is not clear is what cut-off(s) of FENO should be used to trigger a change in treatment. After 30 years of intensive research there is not sufficient evidence to recommend FENO for routine diagnosing and monitoring asthma in children.

Educational aims

To give the reader an overview of literature that supports and does not support the role of FENO in diagnosing asthma in children.To give the reader an overview of literature that supports and does not support the role of FENO in monitoring asthma in children.To give the reader an understanding of the role of FENO in international guidelines for diagnosing and monitoring asthma in children.

Fractional exhaled nitric oxide in the assessment of exercise-induced bronchoconstriction: A multicenter retrospective analysis of UK-based athletes

INTRODUCTION

Exercise-induced bronchoconstriction (EIB) is not only highly prevalent in people with asthma, but can also occur independently, particularly in athletes. Fractional exhaled nitric oxide (FeNO) is an indirect biomarker of type 2 airway inflammation that has an established role in the assessment and management of asthma. The aim was to evaluate the value of FeNO in the assessment of EIB in athletes.

METHOD

Multicenter retrospective analysis. In total, 488 athletes (male: 76%) performed baseline FeNO, and spirometry pre- and post-indirect bronchial provocation via eucapnic voluntary hyperpnea (EVH). Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for established FeNO thresholds-that is, intermediate (≥25 ppb) and high FeNO (≥40 ppb and ≥ 50 ppb)-and were evaluated against objective evidence of EIB (≥10% fall in FEV₁ ). The diagnostic accuracy of FeNO was calculated using receiver operating characteristics area under the curve (ROC-AUC).

RESULTS

Thirty-nine percent of the athletes had a post-EVH fall in FEV₁ consistent with EIB. FeNO values ≥25 ppb, ≥40 ppb, and ≥ 50 ppb were observed in 42%, 23%, and 17% of the cohort, respectively. The sensitivity of FeNO ≥25 ppb was 55%, which decreased to 37% and 27% at ≥40 ppb and ≥ 50 ppb, respectively. The specificity of FeNO ≥25 ppb, ≥40 ppb, and ≥ 50 ppb was 66%, 86%, and 89%, respectively. The ROC-AUC for FeNO was 0.656.

CONCLUSIONS

FeNO ≥40 ppb provides good specificity, that is, the ability to rule-in a diagnosis of EIB. However, due to the poor sensitivity and predictive values, FeNO should not be employed as a replacement for indirect bronchial provocation in athletes.

Cut-off value for exercise-induced bronchoconstriction based on the features of the airway obstruction

The current cut-off value for diagnosing exercise-induced bronchoconstriction (EIB) in adults—percent fall in FEV₁ (ΔFEV₁) ≥ 10% after exercise challenge test (ECT)—has low specificity and weak evidences. Therefore, this study aimed to identify the cut-off value for EIB that provides the highest diagnostic sensitivity and specificity. Participants who underwent the ECT between 2007 and 2018 were categorized according to ΔFEV₁: definite EIB (ΔFEV₁ ≥ 15%), borderline (10% ≤ ΔFEV₁ < 15%), and normal (ΔFEV₁ < 10%). Distinct characteristics of the definite EIB group were identified and explored in the borderline EIB group. A receiver operating characteristic curve was plotted to determine the optimal cut-off value. Of 128 patients, 60 were grouped as the definite EIB group, 23 as the borderline group, and 45 as the normal group. All participants were men, with a median age of 20 years (interquartile range [IQR:] 19–23 years). The definite EIB group exhibited wheezing on auscultation (P < 0.001), ΔFEV₁/FVC ≥ 10% (P < 0.001), and ΔFEF_25–75% ≥ 25% (P < 0.001) compared to other groups. Eight (8/23, 34.8%) patients in the borderline group had at least one of these features, but the trend was more similar to that of the normal group than the definite EIB group. A cut-off value of ΔFEV₁ ≥ 13.5% had a sensitivity of 98.5% and specificity of 93.5% for EIB. Wheezing on auscultation, ΔFEV₁/FVC ≥ 10%, and ΔFEF_25–75% ≥ 25% after ECT may be useful for the diagnosis of EIB, particularly in individuals with a ΔFEV₁ of 10–15%. For EIB, a higher cut-off value, possibly ΔFEV₁ ≥ 13.5%, should be considered as the diagnostic criterion.

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.

Exercise-Induced Bronchoconstriction in Children

Exercise-induced bronchoconstriction (EIB) is a transient airflow obstruction, typically 5-15 min after physical activity. The pathophysiology of EIB is related to the thermal and osmotic changes of the bronchial mucosa, which cause the release of mediators and the development of bronchoconstriction in the airways. EIB in children often causes an important limitation to physical activities and sports. However, by taking appropriate precautions and through adequate pharmacological control of the condition, routine exercise is extremely safe in children. This review aims to raise awareness of EIB by proposing an update, based on the latest studies, on pathological mechanisms, diagnosis, and therapeutic approaches in children.

Use of Fractional Exhaled Nitric Oxide to Guide the Treatment of Asthma: An Official American Thoracic Society Clinical Practice Guideline

Background: The fractional exhaled nitric oxide (FE_NO) test is a point-of-care test that is used in the assessment of asthma.

Objective: To provide evidence-based clinical guidance on whether FE_NO testing is indicated to optimize asthma treatment in patients with asthma in whom treatment is being considered.

Methods: An international, multidisciplinary panel of experts was convened to form a consensus document regarding a single question relevant to the use of FE_NO. The question was selected from three potential questions based on the greatest perceived impact on clinical practice and the unmet need for evidence-based answers related to this question. The panel performed systematic reviews of published randomized controlled trials between 2004 and 2019 and followed the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) evidence-to-decision framework to develop recommendations. All panel members evaluated and approved the recommendations.

Main Results: After considering the overall low quality of the evidence, the panel made a conditional recommendation for FE_NO-based care. In patients with asthma in whom treatment is being considered, we suggest that FE_NO is beneficial and should be used in addition to usual care. This judgment is based on a balance of effects that probably favors the intervention; the moderate costs and availability of resources, which probably favors the intervention; and the perceived acceptability and feasibility of the intervention in daily practice.

Conclusions: Clinicians should consider this recommendation to measure FE_NO in patients with asthma in whom treatment is being considered based on current best available evidence.

Asthma Phenotypes as a Guide for Current and Future Biologic Therapies

Asthma has been increasingly recognized as being a heterogeneous disease with multiple distinct mechanisms and pathophysiologies. Evidence continues to build regarding the existence of different cell types, environmental exposures, pathogens, and other factors that produce a similar set of symptoms known collectively as asthma. This has led to a movement from a "one size fits all" symptom-based methodology to a more patient-centered, individualized approach to asthma treatment targeting the underlying disease process. A significant contributor to this shift to more personalized asthma therapy has been the increasing availability of numerous biologic therapies in recent years, providing the opportunity for more targeted treatments. When targeted biologics began to be developed for treatment of asthma, the hope was that distinct biomarkers would become available, allowing the clinician to determine which biologic therapy was best suited for which patients. Presence of certain biomarkers, like eosinophilia or antigen-specific IgE, is important features of specific asthma phenotypes. Currently available biomarkers can help with decision making about biologics, but are generally too broad and non-specific to clearly identify an asthma phenotype or the single biologic best suited to an asthmatic. Identification of further biomarkers is the subject of intense research. Yet, identifying a patient's asthma phenotype can help in predicting disease course, response to treatment, and biologic therapies to consider. In this review, major asthma phenotypes are reviewed, and the evidence for the utility of various biologics, both those currently on the market and those in the development process, in each of these phenotypes is explored.

Fractional Exhaled Nitric Oxide and Nanomaterial Exposure in Workplaces

Background:

The widespread application of engineered nanomaterials (ENMs) and the increasing likelihood of general and occupational exposure raised concerns on their possible human health impact. ENMs, in fact, may induce alterations in different organ systems, and particularly in the respiratory tract. This makes it important to identify possible biomarkers of early lung effect in exposed workers. In this regard, the possibility to use the fractional exhaled levels of nitric oxide (FENO) in biological monitoring has attracted considerable interest.

Objective:

To comprehensively assess the role of FENO as a possible biomarker of lung effect in ENM exposed workers.

Methods:

A systematic search was performed on Pubmed, Scopus, and ISI Web of Knowledge databases according to the PRISMA guidelines.

Results:

Seven studies investigated FENO in workers exposed to different kinds of metal-(i.e. silver and gold), metal oxide- (titanium and silica dioxide), and carbon-based ENMs (carbon nanotubes). In general, no significant alterations were detected between exposed workers and controls.

Conclusions:

Definite conclusion on the function of FENO in occupational biological monitoring cannot be extrapolated due to the limited number of available studies and the small size of investigated populations. Additionally, the lack of environmental monitoring data and the fragmented knowledge on ENM modes of action prevent to establish dose-response relationships. Future research appears necessary to deeply define the possibility to employ FENO as an early biomarker of lung effects taking in consideration possible occupational exposure issues, i.e. differently characterized ENMs and work tasks, as well as individual influencing factors, i.e. smoking and atopy.

Effect of age on exercise-induced bronchoconstriction in children and adolescents with asthma

OBJECTIVE

The relationship between exercise-induced bronchoconstriction (EIB) and exertional dyspnea in children and adolescents is yet to be fully established. This study examined whether indicators of fractional exhaled nitric oxide (FeNO), forced expiratory volume in 1 s (FEV₁) percent predicted at baseline, and dyspnea are useful for predicting children and adolescents with EIB.

METHODS

We enrolled 184 children and adolescents diagnosed with asthma (mean age 11.2 years); participants were divided into two groups according to age (12 years) and were subjected to a 6-min exercise challenge test. Lung function tests and modified Borg scale scores were used to examine perceptions of dyspnea at 0, 5 and 15 min after exercise.

RESULTS

Among children, the maximum percentage drop in FEV₁ after exercise correlated significantly with FeNO (adjusted β = 2.3, P < 0.001) and with the perception of dyspnea at 5 min after exercise (adjusted β = 1.9, P < 0.001). Among adolescents, the maximum percentage drop in FEV₁ correlated with FeNO (adjusted β = 2.7, P = 0.007) and with lung function (FEV₁, percent predicted; adjusted β = -0.28, P = 0.006). Children with EIB had significantly stronger dyspnea after exercise than did children without EIB. Adolescents even without EIB may experience more exertional dyspnea than children without EIB.

CONCLUSIONS

Overall, our findings indicated that EIB was associated with FeNO and exertional dyspnea in asthmatic children. By contrast, EIB was associated with FEV₁ percent predicted at baseline and FeNO but not with exertional dyspnea in asthmatic adolescents.

Oil supplementation with a special combination of n-3 and n-6 long-chain polyunsaturated fatty acids does not protect for exercise induced asthma: a double-blind placebo-controlled trial

BACKGROUND

Many patients suffering from exercise-induced asthma (EIA) have normal lung function at rest and show symptoms and a decline in FEV₁ when they do sports or during exercise-challenge. It has been described that long-chain polyunsaturated fatty acids (LCPUFA) could exert a protective effect on EIA.

METHODS

In this study the protective effect of supplementation with a special combination of n-3 and n-6 LCPUFA (sc-LCPUFA) (total 1.19 g/ day) were investigated in an EIA cold air provocation model.

PRIMARY OUTCOME MEASURE

Decrease in FEV₁ after exercise challenge and secondary outcome measure: anti-inflammatory effects monitored by exhaled NO (eNO) before and after sc-LCPUFA supplementation versus placebo.

RESULTS

Ninety-nine patients with exercise-induced symptoms aged 10 to 45 were screened by a standardized exercise challenge in a cold air chamber at 4 °C. Seventy-three patients fulfilled the inclusion criteria of a FEV₁ decrease > 15% and were treated double-blind placebo-controlled for 4 weeks either with sc-LCPUFA or placebo. Thirty-two patients in each group completed the study. Mean FEV₁ decrease after cold air exercise challenge and eNO were unchanged after 4 weeks sc-LCPUFA supplementation.

CONCLUSION

Supplementation with sc-LCPUFA at a dose of 1.19 g/d did not have any broncho-protective and anti-inflammatory effects on EIA.

TRIAL REGISTRATION

Clinical trial registration number: NCT02410096. Registered 7 February 2015 at Clinicaltrial.gov.

Predictors and reproducibility of exercise-induced bronchoconstriction in cold air

Background

Physical activity is an important part of life, and hence exercise-induced bronchoconstriction (EIB) can reduce the quality of life. A standardized test is needed to diagnose EIB. The American Thoracic Society (ATS) guidelines recommend an exercise challenge in combination with dry air. We investigated the feasibility of a new, ATS guidelines conform exercise challenge in a cold chamber (ECC) to detect EIB. The aim of this study was to investigate the surrogate marker reaction to methacholine, ECC and exercise challenge in ambient temperature for the prediction of a positive reaction and to re-evaluate the reproducibility of the response to an ECC.

Methods

Seventy-eight subjects aged 6 to 40 years with suspected EIB were recruited for the study. The subjects performed one methacholine challenge, two ECCs, and one exercise challenge at an ambient temperature. To define the sensitivity and specificity of the predictor, a receiver-operating characteristic curve was plotted. The repeatability was evaluated using the method described by Bland and Altman (95% Limits of agreement).

Results

The following cut-off values showed the best combination of sensitivity and specificity: the provocation dose causing a 20% decrease in the forced expiratory volume in 1 s (PD₂₀FEV₁) of methacholine: 1.36 mg (AUC 0.69, p < 0.05), the maximal decrease in FEV₁ during the ECC: 8.5% (AUC 0.78, p < 0.001) and exercise challenges at ambient temperatures: FEV₁ 5.2% (AUC 0.64, p = 0.13). The median decline in FEV₁ was 14.5% (0.0–64.2) during the first ECC and 10.7% (0.0–52.5) during the second ECC. In the comparison of both ECCs, the Spearman rank correlation of the FEV₁ decrease was r = 0.58 (p < 0.001). The 95% limits of agreement (95% LOAs) for the FEV₁ decrease were − 17.7 to 26.4%.

Conclusions

The surrogate markers PD₂₀FEV₁ of methacholine and maximal decrease in FEV₁ during ECC can predict a positive reaction in another ECC, whereas the maximal FEV₁ decrease in an exercise challenge at an ambient temperature was not predictive. Compared with previous studies, we can achieve a similar reproducibility with an ECC.

Clinical trial registration

NCT02026492 (retrospectively registered 03/Jan/2014).

Serum levels of periostin and exercise-induced bronchoconstriction in asthmatic children

Background

Periostin is induced by IL-13 and has been studied as a biomarker of asthma. The present study explored the relationship between serum levels of periostin and exercise-induced bronchoconstriction (EIB) in asthmatic children.

Methods

The study population consisted of 86 children 6-15 years old divided into an asthmatic group (n = 56) and healthy controls (n = 30). We measured the levels of periostin in serum and performed pulmonary function tests including baseline measurements, post-bronchodilator inhalation tests, exercise bronchial provocation tests (BPTs), and mannitol BPTs.

Results

The 56 asthmatic children were divided into four groups: asthmatics with positive exercise BPT and positive mannitol BPT (n = 30), asthmatics with positive exercise BPT but negative mannitol BPT (n = 7), asthmatics with negative exercise BPT but positive mannitol BPT (n = 10), and asthmatics with negative exercise BPT and negative mannitol BPT (n = 9). Serum levels of periostin in asthmatic children with both positive exercise and mannitol BPT were significantly greater than those in asthmatic children with both negative exercise and mannitol BPT (95.0 [75.0-104.0] vs. 79.0 [68.0-82.5] ng/mL, P = 0.008) and controls (74.0 [69.75-80.0] ng/mL, P < 0.001). Periostin levels were significantly correlated with both the maximum decrease in %FEV₁ and mannitol PD₁₅ value.

Conclusion

Serum levels of periostin in asthmatic children with both positive exercise and mannitol BPT were significantly greater than those in asthmatic children with both negative exercise and mannitol BPT and also greater than in healthy controls.

ERS technical standard on bronchial challenge testing: pathophysiology and methodology of indirect airway challenge testing

Recently, this international task force reported the general considerations for bronchial challenge testing and the performance of the methacholine challenge test, a "direct" airway challenge test. Here, the task force provides an updated description of the pathophysiology and the methods to conduct indirect challenge tests. Because indirect challenge tests trigger airway narrowing through the activation of endogenous pathways that are involved in asthma, indirect challenge tests tend to be specific for asthma and reveal much about the biology of asthma, but may be less sensitive than direct tests for the detection of airway hyperresponsiveness. We provide recommendations for the conduct and interpretation of hyperpnoea challenge tests such as dry air exercise challenge and eucapnic voluntary hyperpnoea that provide a single strong stimulus for airway narrowing. This technical standard expands the recommendations to additional indirect tests such as hypertonic saline, mannitol and adenosine challenge that are incremental tests, but still retain characteristics of other indirect challenges. Assessment of airway hyperresponsiveness, with direct and indirect tests, are valuable tools to understand and to monitor airway function and to characterise the underlying asthma phenotype to guide therapy. The tests should be interpreted within the context of the clinical features of asthma.

Exhaled nitric oxide and mannitol test to predict exercise-induced bronchoconstriction

BACKGROUND

Exercise-induced bronchoconstriction (EIB) is diagnosed via exercise challenge on a treadmill, but such testing requires complex equipment and sufficient health-care resources. The fraction of exhaled nitric oxide (FeNO) test and mannitol bronchial provocation test (BPT) may serve as a surrogate for exercise testing.

METHODS

We compared the diagnostic utilities of the FeNO test and mannitol BPT in predicting EIB in asthmatic children. We retrospectively analyzed data from 60 asthmatic children aged 6-16 years. We compared the exercise BPT results, FeNO levels, and mannitol BPT data.

RESULTS

All subjects were divided into exercise-positive (n = 41) or -negative (n = 19) BPT groups. Of the 41 exercise-positive patients, 32 were mannitol BPT positive and nine were mannitol BPT negative. Of the 19 exercise-negative patients, nine and 10, respectively, were mannitol BPT positive and BPT negative. The maximum % forced expiratory volume in 1 s (FEV₁ ) decrease after exercise was positively correlated with FeNO (r = 0.556, P < 0.001), and with mannitol response-dose ratio (RDR; r = 0.416, P = 0.001). The receiver operating characteristic (ROC) curve for FeNO to discriminate between asthmatic subjects with and without EIB had an area under the curve (AUC) of 0.771 (95%CI: 0.643-0.870). The discriminatory ROC curve for mannitol RDR had an AUC of 0.763 (95%CI: 0.633-0.864). The AUC of FeNO and mannitol RDR did not differ significantly.

CONCLUSIONS

EIB significantly correlated with both FeNO and mannitol BPT data. Given that both methods similarly predicted EIB in asthmatic children, the simpler and safer FeNO test alone may be a clinically useful diagnostic tool.

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.

FeNO and Exercise Testing in Children at Risk of Asthma

BACKGROUND

Exercise testing is the gold standard for diagnosing exercise-induced bronchoconstriction in children, but requires considerable cooperation and medical resources. Therefore, fraction of exhaled nitric oxide (FeNO) has been proposed as a tool to predict the need for exercise testing.

OBJECTIVE

The objective of this study was to investigate the relationship between FeNO, exercise test results, and a history of respiratory symptoms during exercise in children at risk of asthma.

METHODS

FeNO measurement, exercise testing, and interview about respiratory symptoms during exercise were completed in 224 seven-year-old children from the at-risk Copenhagen Prospective Studies on Asthma in Childhood₂₀₀₀ birth cohort. The associations between FeNO, exercise test results, and reported respiratory symptoms during exercise were analyzed adjusting for gender, respiratory infections, and inhaled corticosteroid treatment. The associations were also analyzed stratified by asthma and atopic status.

RESULTS

Of the 224 children, 28 (13%) had an established asthma diagnosis and 58 (26%) had a positive exercise test (≥15% drop in forced expiratory volume in 1 second [FEV₁] from baseline). FeNO and bronchial obstruction after exercise were linearly associated with a doubling of FeNO corresponding to a 2.4% drop in FEV₁ (95% confidence interval, 0.8-4.1; P < .01). However, a receiver operating characteristic curve analysis showed that the best cutoff of FeNO for predicting exercise test outcome among children who reported respiratory symptoms during exercise was 17 ppb, which only had 74% negative predictive value. There was no association between FeNO and reported respiratory symptoms during exercise (odds ratio = 1.3 [0.8-1.9]; P = .29) or reported symptoms during exercise and exercise test results (odds ratio = 1.0 [1.0-1.1]; P = .12).

CONCLUSIONS

A history of respiratory symptoms during exercise was not associated with either elevated FeNO or a positive exercise test in children at risk of asthma. FeNO and exercise test results were linearly associated traits, but FeNO could not reliably be used dichotomized to predict the need of exercise testing.

Exhaled nitric oxide decreases during exercise in non-asthmatic children

INTRODUCTION

Exhaled nitric oxide (FENO) measurements are recommended to be performed before spirometry and exercise challenge tests because forced breathing might influence FENO values. Information on the effect of exercise on FENO is lacking in non-asthmatic children.

AIM

  To investigate the effect on FENO of a standardized exercise challenge test on a treadmill in non-asthmatic children with and without allergic rhinoconjunctivitis (AR) symptoms.

METHODS

From the case-control study 'Asthma and allergy among school children in Nordland', 330 non-asthmatic pupils age 8-16 years were enrolled. FENO was measured at baseline and at 1 min and 30 min after exercise challenge test by the single breath technique with EcoMedics Exhalazer® (Eco Physics, Duernten, Switzerland).

RESULTS

Pair-wise comparison of FENO from baseline demonstrated a highly significant reduction in FENO post-exercise for all children at 1 min (27.4%) and at 30 min (16.1%) (P < 0.001). The AR group had a significantly higher decline in FENO value at 1 min post-exercise compared to the non-AR group, 4.2 parts per billion (ppb) vs 2.6 ppb (P < 0.001). Decline in FENO immediately post-exercise was more significant if baseline FENO was ≥ 20 ppb; mean reduction 9.9 (95% CI: 8.7-11.4) ppb.

CONCLUSION

FENO is reduced by 27.4% immediately after a standardized treadmill exercise test in non-asthmatic children. Pupils reporting AR symptoms demonstrate a larger decline in FENO value at 1 min post-exercise compared to pupils without AR symptoms. These findings confirm that children should refrain from physical activity before FENO measurement.

Can exhaled nitric oxide be a surrogate marker of bronchial hyperresponsiveness to adenosine 5'-monophosphate in steroid-naive asthmatic children?

BACKGROUND

The interrelation between airway inflammation, bronchial hyperresponsiveness (BHR) and atopy remains controversial.

OBJECTIVE

The aim of this study was to document whether exhaled nitric oxide (eNO) may be used as a surrogate marker that predicts BHR to adenosine 5'-monophosphate (AMP) in steroid-naive school children with asthma.

METHODS

This study was a retrospective analysis of steroid-naive school age children with atopic and non-atopic asthma. All patients whose eNO levels had been measured and who had been challenged with both methacholine (MCH) and AMP were included. Receiver operation characteristic analysis was performed, in both the atopic and the non-atopic groups, to evaluate the ability of eNO to detect the BHR to AMP.

RESULTS

One hundred and sixteen patients, sixty-nine (59.5%) of whom had been atopic, were included in the analysis. In the atopic group, eNO values were significantly higher in patients with BHR to AMP compared to those without BHR to AMP (51.9 ± 16.9 p.p.b. vs. 33.7 ± 16.4 p.p.b.; P < 0.001), whereas in the non-atopic group, the differences were not statistically significant (29.7 ± 16.9 p.p.b. vs. 22.6 ± 8.1 p.p.b.; P = 0.152). In the atopic group, eNO levels (R(2) : 0.401; β: 0.092; 95% CI: 1.19-14.42; OR: 7.12; P = 0.008) were found to be the only independent factor for BHR to AMP, whereas none of the parameters predicted BHR to AMP in the non-atopic group. The best cut-off value of eNO that significantly predicts BHR to AMP was 33.3 p.p.b. in the atopic group (P < 0.001), whereas a significant cut-off value for eNO that predicts BHR to AMP was not determined in the non-atopic group (P = 0.142). An eNO ≤ 17.4 p.p.b. has 100% negative predictive values and 100% sensitivity and 60.47% PPV for prediction of BHR to AMP in the atopic group.

CONCLUSIONS

Exhaled NO may be used to predict BHR to AMP in atopic but not in non-atopic steroid-naïve asthmatic children.

Exercise test using dry air in random adolescents: Temporal profile and predictors of bronchoconstriction

BACKGROUND AND OBJECTIVE

Guidelines recommend exercise tests using dry air to diagnose exercise-induced bronchoconstriction (EIB). Lung function changes subsequent to these tests have not been investigated in a general adolescent population, and it remains unknown whether signs of airway inflammation, measured using exhaled nitric oxide (FeNO), can predict a positive response. The aim of this study was to investigate the temporal aspect of decline in forced expiratory volume in 1 s (FEV1 ) after an exercise test using dry air, and to investigate predictors of EIB.

METHODS

From a cross-sectional study on adolescents aged 13-15 years (n = 3838), a random subsample of 146 adolescents (99 with and 47 without self-reported exercise-induced dyspnoea) underwent standardized treadmill exercise tests for EIB while breathing dry air.

RESULTS

Of the adolescents, 34% had a positive EIB test (decline of ≥10% in FEV1 from baseline) within 30 min. Of the subjects with EIB, 53% showed the greatest decline in FEV1 at 5 to 10 min (mean decline 18.5%), and the remaining 47% of the subjects showed the greatest decline at 15 to 30 min (mean decline 18.9%) after exercise. Increased FeNO (>20 ppb), female gender and self-reported exercise-induced dyspnoea were independently associated with a positive EIB test.

CONCLUSION

When assessing general adolescents for EIB with exercise test using dry air, there is a temporal variation in the greatest FEV1 decline after exercise. Therefore, lung function should be measured for at least 30 min after the exercise. Increased FeNO, female gender and self-reported exercise-induced dyspnoea can be predictors of a positive EIB test.

The effect of exercise on exhaled nitric oxide depends on allergic rhinoconjunctivitis in children

OBJECTIVE

Fractional exhaled nitric oxide (FENO) and exercise testing are widely used for the evaluation of pediatric asthma. The evidence relating to the effects of strenuous exercise on FENO in children is conflicting. Little information is available on the association between exercise and FENO in relation to allergic rhinoconjunctivitis (AR). We aimed to investigate the effects of AR on children's FENO in response to a standardized treadmill exercise test.

METHODS

A total of 124 children with current asthma and 124 non-asthmatic children aged 8-16 years were studied. FENO was measured at baseline, at 1 and 30 min after an exercise challenge test using the single breath technique with EcoMedics Exhalyzer. A structured parental interview, spirometry, serum allergen-specific IgE and skin prick tests were performed.

RESULTS

Baseline FENO was higher in both asthmatics and non-asthmatics with AR than without AR (both p < 0.001). The FENO time trend was dependent on AR (p = 0.039), irrespective of asthma (p = 0.876). In children with AR, FENO had declined at 1 min by a mean of 6.1 ppb with a 95% confidence level of 5.1-7.5 ppb; at 30 min, the reduction was 2.8 (2.5-3.3) ppb. In children without AR, at 1 min the decline in FENO was 2.7 (2.1-3.5) ppb and by 30 min post-exercise it was 1.6 (1.3-2.0) ppb.

CONCLUSIONS

The impact of exercise on FENO was dependent on the allergic phenotype, regardless of asthma status. FENO decreased immediately after exercise, and did not return to baseline level within 30 min.

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.

Asthma diagnosis and severity monitoring in primary school children: essential role of sequential testing of exhaled nitric oxide

BACKGROUND

Chronic eosinophilic airway inflammation, airflow limitation, and airway hyper-responsiveness are the mainstays of asthma diagnosis. The increased levels of exhaled nitric oxide (FeNO) in asthma are closely related to the extent of airway inflammation. Sequential measurement of FeNO concentrations may accurately predict asthma severity and guide therapeutic decisions.

METHODS

A total of 22,083 grade 1 students in Taipei city primary schools were screened for wheezing episodes using the International Study of Asthma and Allergies in Childhood questionnaire (ISAAC) questionnaires while their sero-atopic conditions were confirmed by Fluorescent Enzyme Immune Assay (FEIA). All students with allergies were tested by FeNO electrochemical test. 100 age-matched healthy students were used as control group (FeNO levels<25ppb).

RESULTS

From the 2650 students (12%) initially included via the wheezing criteria, 2065 (78.0%) were confirmed to have allergy by FEIA (sensitisation to at least two common aero-allergens in Taiwan) and diagnosed by a paediatric allergologist. Among them, 1852 (89.6%) had elevated FeNO values (>25ppb) and 266 (10%) had FeNO values<25ppb. Using the GINA guidelines, 140 mild-to-moderate asthma students who had received inhaled corticosteroids (ICS) with or without Singulair treatment completed serial FeNO testing every three months for one year. The FeNO levels decreased in 121 students (86.4%) and increased in 19 students (13.6%), which was compatible to changing childhood asthma control score and response to step-down treatment, respectively.

CONCLUSION

FeNO is an easy, used non-invasive tool for the diagnosis of allergic asthma. Sequential FeNO testing can accurately reflect asthma severity and provide for successful stepwise therapy for asthmatic children.

The role of fractional exhaled nitric oxide in asthma management

Measuring fractional exhaled nitric oxide (FeNO) is a relatively new option for assessing allergic inflammation in the lungs. Clinical management of asthma is challenging, and measuring exhaled nitric oxide can provide another type of data to assist in meeting this challenge. FeNO is easy to perform, and the equipment is not forbiddingly expensive. FeNO provides a complement to traditional measures of asthma control and can help guide diagnostic and treatment choices. This article explains what it is, how the measurements are performed, what the norms are, and its use and limitations in the management of asthma.

FeNO as a predictor of asthma control improvement after starting inhaled steroid treatment

INTRODUCTION

The fraction of NO in exhaled air (FeNO) is a marker of inflammation in asthma. The aim of the present study was to assess, in a real-world setting, whether only high (⩾50 ppb) FeNO levels predict improvement in asthma control when being treated with inhaled corticosteroids (ICS), as suggested by current guidelines on the clinical use of FeNO.

METHODS

FeNO and asthma control were assessed in a retrospective observational study in 153 non-smoking, steroid-naïve, adult subjects with asthma with a mean age of 40 years both before and after 6 weeks (median follow-up time) of treatment with 500 μg beclomethasone (median).

RESULTS

Having at the initial visit intermediate FeNO (⩾25 and <50 ppb) and high FeNO (⩾50 ppb), compared to normal FeNO (<25 ppb), were associated with a larger proportion of subjects achieving an improvement of Asthma Control Questionnaire (ACQ) score with ⩾1 (78% and 67% vs 43%, p<0.05) or both ⩾1 improvement and asthma control at follow-up (31% and 37% vs 4%, p<0.05). These associations were consistent in multiple logistic regression models after adjustments for confounders.

CONCLUSIONS

It is not only high but also intermediate FeNO levels that are associated with a significant improvement in asthma control after starting ICS treatment. This challenges current clinical guidelines stating that only high FeNO levels predict response to ICS treatment.

Pulmonary function testing in children and infants

Pulmonary function testing is performed in children and infants with the aim of documenting lung development with age and making diagnoses of lung diseases. In children and infants with an established lung disease, pulmonary function is tested to assess the disease progression and the efficacy of therapy. It is difficult to carry out the measurements in this age group without disturbances, so obtaining results of good quality and reproducibility is challenging. Young children are often uncooperative during the examinations. This is partly related to their young age but also due to the long testing duration and the unpopular equipment. We address a variety of examination techniques for lung function assessment in children and infants in this review. We describe the measuring principles, examination procedures, clinical findings and their interpretation, as well as advantages and limitations of these methods. The comparability between devices and centres as well as the availability of reference values are still considered a challenge in many of these techniques. In recent years, new technologies have emerged allowing the assessment of lung function not only on the global level but also on the regional level. This opens new possibilities for detecting regional lung function heterogeneity that might lead to a better understanding of respiratory pathophysiology in children.

Vitamin C may alleviate exercise-induced bronchoconstriction: a meta-analysis

OBJECTIVE

To determine whether vitamin C administration influences exercise-induced bronchoconstriction (EIB).

DESIGN

Systematic review and meta-analysis.

METHODS

MEDLINE and Scopus were searched for placebo-controlled trials on vitamin C and EIB. The primary measures of vitamin C effect used in this study were: (1) the arithmetic difference and (2) the relative effect in the postexercise forced expiratory volume in 1 s (FEV1) decline between the vitamin C and placebo periods. The relative effect of vitamin C administration on FEV1 was analysed by using linear modelling for two studies that reported full or partial individual-level data. The arithmetic differences and the relative effects were pooled by the inverse variance method. A secondary measure of the vitamin C effect was the difference in the proportion of participants suffering from EIB on the vitamin C and placebo days.

RESULTS

3 placebo-controlled trials that studied the effect of vitamin C on EIB were identified. In all, they had 40 participants. The pooled effect estimate indicated a reduction of 8.4 percentage points (95% CI 4.6 to 12) in the postexercise FEV1 decline when vitamin C was administered before exercise. The pooled relative effect estimate indicated a 48% reduction (95% CI 33% to 64%) in the postexercise FEV1 decline when vitamin C was administered before exercise. One study needed imputations to include it in the meta-analyses, but it also reported that vitamin C decreased the proportion of participants who suffered from EIB by 50 percentage points (95% CI 23 to 68); this comparison did not need data imputations.

CONCLUSIONS

Given the safety and low cost of vitamin C, and the positive findings for vitamin C administration in the three EIB studies, it seems reasonable for physically active people to test vitamin C when they have respiratory symptoms such as cough associated with exercise. Further research on the effects of vitamin C on EIB is warranted.

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.

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.

Exhaled nitric oxide in asthma: progress since the introduction of standardized methodology

The measurement of nitric oxide (NO) in exhaled breath has given us the ability to learn about and monitor the inflammatory status of the airway through a non-invasive method that is easy to perform and repeat. This has been most useful in the diagnosis and management of asthma and has promised a seemingly unlimited potential for evaluating the airways and how clinical decisions are made (Grob N M and Dweik R A 2008 Chest133 837-9). The exhaled NO field was initially limited, however, due to the absence of standardized methodology. The ATS and ERS jointly released recommendations for standardized methods of measuring and reporting exhaled NO in 1999 that were revised in 2005 (1999 Am. J. Respir. Crit. Care. Med. 160 2104-17; 2005 Am. J. Respir. Crit. Care. Med. 171 912-30). In this paper, we summarize the literature that followed this standardization. We searched the literature for all papers that included the term 'exhaled nitric oxide' and selected those that followed ATS guidelines for online measurement for further review. We also reviewed cut-off values suggested by groups studying exhaled nitric oxide. We found a wide range of NO values reported for normal and asthma populations. The geometric mean for FE(NO) ranged from 10 ppb to 33 ppb in healthy adult control populations. For asthma, the FE(NO) geometric mean ranged from 6 ppb to 98 ppb. This considerable variation likely reflects the different clinical settings and purposes of measurement. Exhaled NO has been used for a multitude of reasons that range from screening, to diagnosis, to monitoring the effect of therapy. The field of exhaled NO has made undeniable progress since the standardization of the measurement methods. Our challenge now is to have guidelines to interpret exhaled NO levels in the appropriate context. As the utility of exhaled NO continues to evolve, it can serve as a good example of the crucial role of the standardization of collection and measurement methods to propel any new test in the right direction as it makes its way from a research tool to a clinically useful test.

Fractional exhaled nitric oxide (FeNO) may predict exercise-induced bronchoconstriction (EIB) in schoolchildren with atopic asthma

BACKGROUND

There is a need for the performance of exercise-induced bronchoconstriction (EIB) tests in the monitoring of childhood asthma control. We aimed to evaluate whether in children with atopic asthma, EIB can be predicted by one or more of the following parameters or by their combination: fractional exhaled nitric-oxide (FeNO), allergy profile, asthma treatment, total IgE serum concentration and eosinophil blood count (EBC).

METHODS

It was a retrospective, cross-sectional study. We evaluated data from medical documentation of children with atopic asthma who had performed standardized spirometric exercise challenge test.

RESULTS

One hundred and twenty six patients with atopic asthma, aged 5-18, were included in the analysis. There were two groups of patients: the EIB group (n=54) and the no-EIB group (n=72). The median FeNO level prior to exercise in the EIB group was 27.6 vs. 16.3 ppb in the no-EIB group (p=0.002). FeNO level higher than 16 ppb had the highest diagnostic value to confirm EIB. When using the FeNO level of >16 ppb, the sensitivity, specificity, negative predictive and positive predictive values for EIB were 83%, 46.9%, 74.2%, and 60%, respectively. In the EIB group, the degree of FeNO elevation did correlate positively with the absolute fall in FEV(1) (p=0.002; r=0.45). The FeNO value of >16 ppb, EBC value of >350 cell/mm(3) and allergy to house dust mites presented the highest odds ratios of EIB. However, the FeNO value of >16 ppb was the only independent odds ratio of EIB.

CONCLUSIONS

Elevated FeNO level increased the odds of EIB in asthmatic schoolchildren, independently of other asthma severity markers and the intensity of anti-asthma therapy. It seems likely that FeNO measurement may act as a screening tool and help to prevent under-diagnosis and under-treatment of exercise-induced bronchoconstriction in schoolchildren with atopic asthma.

Diagnostic accuracy of exhaled nitric oxide in exercise-induced bronchospasm: Systematic review

INTRODUCTION

The gold-standard method for the diagnosis of exercise-induced bronchospasm (EIB) is an exercise test combined with spirometry. However, this test is expensive, time consuming and requires specialized equipment and trained personnel. Exhaled nitric oxide (eNO) is a fast, easy, noninvasive method for the diagnosis of EIB. The aim of the present study was to assess the accuracy of the measurement of eNO for the diagnosis of EIB through a systematic review of the literature.

METHODS

A search was carried out in the PubMed, Lilacs, SciELO and SCOPUS databases by two independent researchers.

RESULTS

Fifty-six papers were found. Following the application of the eligibility criteria to the title, abstract and text, six papers remained for analysis. There was a significant heterogeneity in sex (X(2)=56.44, p=0.000) and clinical spectrum (X(2)=504.00, p=0.000) between studies. In children between 3.8 and 7.8 years old a cutoff point >28ppb EIB can be ruled in and in children between 5 and 16 years old at a cutoff point <20EIB can be ruled out. For adults a cutoff point <7EIB can be ruled out and it can be ruled in with a cutoff point >12. Four papers reported negative predictive values above 88%.

CONCLUSION

The measurement of eNO seems to be effective for ruling in and ruling out EIB in some specific groups. Therefore, the measurement of eNO levels could be an important tool to safely avoid the need for an exercise test when the result is negative, reducing the individual and economic impact of this disease.

Asthma outcomes: biomarkers

BACKGROUND

Measurement of biomarkers has been incorporated within clinical research studies of asthma to characterize the population and associate the disease with environmental and therapeutic effects.

OBJECTIVE

National Institutes of Health institutes and federal agencies convened an expert group to propose which biomarkers should be assessed as standardized asthma outcomes in future clinical research studies.

METHODS

We conducted a comprehensive search of the literature to identify studies that developed and/or tested asthma biomarkers. We identified biomarkers relevant to the underlying disease process progression and response to treatment. We classified the biomarkers as either core (required in future studies), supplemental (used according to study aims and standardized), or emerging (requiring validation and standardization). This work was discussed at an National Institutes of Health-organized workshop convened in March 2010 and finalized in September 2011.

RESULTS

Ten measures were identified; only 1, multiallergen screening to define atopy, is recommended as a core asthma outcome. Complete blood counts to measure total eosinophils, fractional exhaled nitric oxide (Feno), sputum eosinophils, urinary leukotrienes, and total and allergen-specific IgE are recommended as supplemental measures. Measurement of sputum polymorphonuclear leukocytes and other analytes, cortisol measures, airway imaging, breath markers, and system-wide studies (eg, genomics, proteomics) are considered as emerging outcome measures.

CONCLUSION

The working group participants propose the use of multiallergen screening in all asthma clinical trials to characterize study populations with respect to atopic status. Blood, sputum, and urine specimens should be stored in biobanks, and standard procedures should be developed to harmonize sample collection for clinical trial biorepositories.

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-Induced Lung Disease: Too Much of a Good Thing?

Exercise in children has important health benefits. However, in elite endurance athletes, there is an increased prevalence of exercise-induced bronchoconstriction and airway inflammation. Particularly at risk are those who practice in cold weather, ice rinks, swimming pools, and air pollution. The inflammation is caused by repetitive episodes of hyperventilation of cold, dry air, allergens, or toxins such as chlorine or air pollution. Children may be particularly at risk for lung injury under these conditions because of the immaturity and ongoing development of their lung. However, studies in pediatric athletes and exercising young children are sparse. Epithelial injury associated with hyperventilation of cold, dry air has not been described in children. However, exercise in the presence of air pollution and chlorine is associated with airway injury and the development of asthma in children; the effect appears to be modulated by both atopy and genetic polymorphisms. While management of exercise-induced bronchoconstriction and asthma is well established, there is little data to guide treatment or prevention of remodeling in athletes or inhalational lung injury in children. Studies underscore the need to maintain high levels of air quality. More investigations should be undertaken to better define the natural history, pathophysiology, and treatment of exercise-induced pulmonary inflammation in both elite athletes and exercising children.

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.

Exercise-induced wheeze: Fraction of exhaled nitric oxide-directed management

BACKGROUND AND OBJECTIVE

Exercise-induced wheeze (EIW) is common. Several treatment options exist. Patients with low fraction of exhaled nitric oxide (F(E)NO) are unlikely to be steroid-responsive and might benefit from non-steroidal therapies. We assessed: the efficacy of cromoglycate, formoterol and montelukast in patients with EIW and low F(E)NO (<35 ppb) in a randomized cross-over trial, and the efficacy of inhaled corticosteroid in a high F(E)NO (>35 ppb) group.

METHODS

Patients had EIW and airway hyperresponsiveness (AHR) to mannitol and/or exercise. Those with low F(E)NO (n = 19) received cromoglycate (20 mg inh. bd + before challenge tests), formoterol (12 microg inh. bd + before challenge tests) and montelukast (10 mg p.o. od), each for 2 weeks. Those with high F(E)NO (n = 20) took inhaled fluticasone (500 microg) daily for 4 weeks. Primary end-points were: 50% reduction in maximum FEV(1) %fall (clinical protection) and decrease in AHR to mannitol.

RESULTS

In patients with low F(E)NO, cromoglycate, formoterol and montelukast significantly decreased AHR to mannitol in 63%, 61% and 47% of patients, respectively. In this group, the magnitude of exercise-induced bronchoconstriction (EIB) was significantly reduced with montelukast and formoterol; between-treatment differences were not significant. Of 6/19 with low F(E)NO and EIB, protection occurred in 67% (cromoglycate), 83% (formoterol) and 50% (montelukast), respectively. In the high F(E)NO group, AHR to mannitol and EIB decreased significantly with fluticasone (P < 0.001, P = 0.005, respectively), and protection occurred in 7/8 (88%) with EIB.

CONCLUSIONS

In patients with EIW and low F(E)NO, the number of 'responders' to cromoglycate, formoterol and montelukast was similar. In a high F(E)NO population the response to inhaled corticosteroid was highly significant and comparable to previous studies.

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.

Comparability of a hand-held nitric oxide analyser with online and offline chemiluminescence-based nitric oxide measurement

Practicability is crucial for successful implementation of fractional exhaled nitric oxide (FeNO) measurement into asthma management. The study aimed at comparing a conventional chemiluminescence NO analyser (EcoMedics) with a hand-held device (NIOX MINO) and offline FeNO measurement using a commercially available system in an unselected cohort of children aged 6-16 yr. A secondary objective was to confirm FeNO stability over time in 15 samples from adult volunteers obtained using the offline system. Sixty-six children (mean +/- s.d. age 11.8 +/- 3.0 yr) underwent single breath FeNO measurement in triplets with each device. Offline collected FeNO was measured after offline breath collection into a Mylar balloon and subsequent analysis using the chemiluminescence NO analyser. Variability and between-method agreement were assessed, and stability over time within the Mylar balloons was tested by repeated hourly measurements. FeNO levels ranged from 2 to 113 p.p.b. Intra-class correlation was excellent (r = 0.98, p < 0.001 for each pair). Bland-Altman plots and back-transformation of logarithmic mean differences revealed fair agreement between methods. Stability over time was confirmed over 10 h both at room temperature and when stored under cooling conditions. FeNO values obtained using the chemiluminescence NO analyser, the portable NIOX MINO system and the offline collection technique show between-method agreement within clinically acceptable range.

Asthma in infants and children

Asthma is the most common chronic illness in childhood and represents a significant burden to health care and educational systems. Between one quarter and two thirds of childhood asthma cases persist into adulthood. Childhood asthma may be particularly difficult to diagnose because of the high prevalence of episodic wheezing and cough in childhood illnesses such as upper respiratory tract infections. National and worldwide guidelines for the management of asthma in children are continually being updated. These guidelines recommend first establishing a diagnosis and assessing the severity of disease, initiating pharmacologic therapy based on symptoms and lung function, and adjusting doses and agents as required based on the level of asthma control. Inhaled corticosteroids are the cornerstone of long-term asthma management in children of all ages. Recent research efforts have focused on ways to improve inhalant drug delivery to the lungs and minimize oral and systemic bioavailability so as to improve the therapeutic benefit:risk ratio.

8-Isoprostane in exhaled breath condensate and exercise-induced bronchoconstriction in asthmatic children and adolescents

BACKGROUND

Exercise-induced bronchoconstriction (EIB) in the asthmatic child is associated with persistent airway inflammation and poor disease control. EIB could arise partly from airway oxidative stress. Exhaled breath condensate (EBC) levels of 8-isoprostane (IsoP), which is a known marker of oxidative stress, might therefore be helpful for monitoring asthma noninvasively.

METHODS

We recruited 46 asthmatic children and adolescents 6 to 17 years of age (29 boys), all of whom underwent lung function testing, measurement of the fractional concentration of exhaled nitric oxide (FENO), and collection of EBCs for 8-IsoP measurement before and after exercise challenge. FENO was measured before exercise and 5 min and 20 min after exercise. Spirometry was repeated 1, 5, 10, 15, and 20 min after exercise.

RESULTS

Baseline 8-IsoP levels (but not baseline FENO levels) correlated with the fall in FEV(1) 5 min after exercise (r = - 0.47; p = 0.002). 8-IsoP levels measured after exercise remained unchanged from baseline levels; conversely, FENO levels decreased in parallel with the decline in FEV(1) at 5 min (r = 0.44; p = 0.002). The mean baseline 8-IsoP concentrations were higher in patients with EIB (n = 12) than in those without EIB (n = 34; 44.9 pg/mL [95% confidence interval (CI), 38.3 to 51.5] vs 32.3 pg/mL [95% CI, 27.6 to 37.0], respectively; p < 0.01). No difference was found in the mean baseline FENO between groups (with EIB group: 38.7 ppb; 95% CI, 24.5 to 61.1; without EIB group: 29.1 ppb; 95% CI, 22.0 to 38.4).

CONCLUSIONS

Increased 8-IsoP concentrations in EBC samples of asthmatic children and adolescents with EIB suggest a role for oxidative stress in bronchial hyperreactivity.

Exercise-induced bronchospasm in children

This review will encompass definition, history, epidemiology, pathogenesis, diagnosis, and management of exercise -induced bronchospasm in the pediatric individual with and without known asthma. Exercise induced asthma is the conventional term for transient airway narrowing in a known asthma in association with strenuous exercise usually lasting 5-10 minutes with a decline in pulmonary function by at least 10%. Exercise induced asthma will be referred to as exercise induced bronchospasm in an asthmatic. Exercise-induced bronchospasm (EIB ) is the same phenomenon in an individual without known asthma. EIB can be seen in healthy individuals including children as well as defense recruits and competitive or elite athletes. The diagnosis with objective exercise challenge methods in conjunction with history is delineated. Management is characterized with pharmacotherapy and non pharmacotherapeutic measures for underlying asthma as well as exercise induced bronchospasm and inhalant allergy. Children can successfully participate in all sports if asthma is properly managed.

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 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.

Sputum eosinophils and the response of exercise-induced bronchoconstriction to corticosteroid in asthma

BACKGROUND

The relationship between eosinophilic airway inflammation and exercise-induced bronchoconstriction (EIB), and the response to inhaled corticosteroid (ICS) therapy was examined.

METHODS

Twenty-six steroid-naïve asthmatic patients with EIB were randomized to two parallel, double-blind, crossover study arms (13 subjects in each arm). Each arm compared two dose levels of inhaled ciclesonide that were administered for 3 weeks with a washout period of 3 to 8 weeks, as follows: (1) 40 vs 160 microg daily; and (2) 80 vs 320 microg daily. Baseline and weekly assessments with exercise challenge and sputum analysis were performed.

RESULTS

Data were pooled and demonstrated that 10 subjects had baseline sputum eosinophilia >or= 5%. Only high-dose ICS therapy (ie, 160 and 320 microg) significantly attenuated the sputum eosinophil percentage. Sputum eosinophil percentage significantly correlated with EIB severity, and predicted the magnitude and temporal response of EIB to high-dose therapy, but not to low-dose therapy (ie, 40 and 80 microg). Low-dose ICS therapy provided a significant reduction in EIB at 1 week, with little additional improvement thereafter, irrespective of baseline sputum eosinophil counts. In contrast, high-dose ICS therapy provided a significantly greater improvement in EIB in subjects with sputum eosinophilia compared to those with an eosinophil count of < 5%. The difference between the eosinophilic groups in the magnitude of improvement in EIB was evident after the first week of high-dose ICS therapy and increased with time.

CONCLUSIONS

These results suggest that eosinophilic airway inflammation may be important in modifying the severity of EIB and the response to ICS therapy. Measurements of sputum eosinophil percentage may, therefore, be useful in predicting the magnitude and temporal response of EIB to different dose levels of ICSs.

TRIAL REGISTRATION

clinicaltrial.gov; Identifier: NCT00525772.