The predictive value of exhaled nitric oxide measurements in assessing changes in asthma control

Nasal nitric oxide: longitudinal reproducibility and the effects of a nasal allergen challenge in patients with allergic rhinitis

BACKGROUND

Exhaled nitric oxide (eNO) is a validated noninvasive marker of airway inflammation in asthma. In patients with allergic rhinitis (AR), increased levels of nasal nitric oxide (nNO) have also been measured. However, the applicability of nNO as a marker of upper airway inflammation awaits validation.

AIM

To test the longitudinal reproducibility of standardized nNO measurements in patients with AR and the effects of nasal allergen challenge.

METHODS

Twenty patients with clinically stable, untreated AR participated in a combined study design. First, reproducibility of nNO was tested over 1, 7, and 14-21 days. Subsequently, the effect of nasal allergen challenge on nNO was studied in a placebo-controlled, parallel design. Nasal NO was measured with a chemoluminescence analyzer. Ten subjects randomly underwent a standardized nasal allergen challenge; 10 subjects received placebo. Response to nasal challenge was monitored by composite symptom scores.

RESULTS

There was a good reproducibility of nNO up to 7 days [coefficient of variation (CV) over 1 (16.45%) and 7 days (21.5%)], decreasing over time [CV (14-21 days): 38.3%]. As compared with placebo, allergen challenge caused a significant increase in symptom scores (P < 0.001), accompanied by a decrease in nNO at 20 min postchallenge (P = 0.001). Furthermore, there was a gradual increase in nNO at 7 h, reaching significance at 24-h postallergen (P = 0.04).

CONCLUSIONS

Similar to eNO in asthma, nNO is a noninvasive marker, potentially suitable to monitor upper airway inflammation following allergen-induced late response. Present data show a good reproducibility of nNO measurements, decreasing over time, probably because of subclinical seasonal influences.

Validation study of fractional exhaled nitric oxide measurements using a handheld monitoring device

We tested reproducibility of exhaled nitric oxide (FE(NO)) and inter-operator handling when measured with a handheld device, NIOX MINO. We enrolled 20 volunteers using a priori goals of acceptable reproducibility to be mean within-subject standard deviation less than 3 parts per billion (ppb) for FE(NO) measurements less than 30 ppb, and mean coefficient of variation less than 10% for FE(NO) measurements more than 30 ppb. Seventeen subjects with measurements less than 30 ppb displayed a mean standard deviation of 1.15, and 3 subjects with FE(NO) more than 30 ppb had a mean coefficient of variation of 2.4%. We conclude that NIOX MINO demonstrates excellent reproducibility for all ranges of FE(NO).

Association of inducible nitric oxide synthase with asthma severity, total serum immunoglobulin E and blood eosinophil levels

BACKGROUND

Nitric oxide is released by immune, epithelial and endothelial cells, and plays an important part in the pathophysiology of asthma.

OBJECTIVE

To investigate the association of inducible nitric oxide synthases (iNOS) gene repeat polymorphisms with asthma.

METHODS

230 families with asthma (842 individuals) were recruited to identify and establish the genetic association of iNOS repeats with asthma and associated phenotypes. Serum nitric oxide levels in selected individuals were measured and correlated with specific genotypes. Multiple logistic regression analysis was performed to determine the effect of age and sex.

RESULTS

A total of four repeats-a (CCTTT)n promoter repeat, a novel intron 2 (GT)n repeat (BV680047), an intron 4 (GT)n repeat (AFM311ZB1) and an intron 5 (CA)n repeat (D17S1878)-were identified and genotyped. A significant transmission distortion to the probands with asthma was seen for allele 3 of the AFM311ZB1 gene (p = 0.006). This allele was also found to be significantly associated with percentage blood eosinophils (p < 0.001) and asthma severity (p = 0.04). Moreover, it was functionally correlated with high serum nitric oxide levels (p = 0.006). Similarly, the promoter repeat was found to be associated with serum total immunoglobulin (Ig)E (p = 0.028). Individuals carrying allele 4 of this repeat have high serum IgE (p < 0.001) and nitric oxide levels (p = 0.03).

CONCLUSION

This is the first study to identify the repeat polymorphisms in the iNOS gene that are associated with severity of asthma and eosinophils. The functional relevance of the associated alleles with serum nitric oxide levels was also shown. Therefore, these results could be valuable in elucidating the role of nitric oxide in asthma pathogenesis.

Exhaled biomarkers

Assessing airway and lung inflammation is important for investigating the underlying mechanisms of asthma and COPD. Yet these cannot be measured directly in clinical research and practice because of the difficulties in monitoring inflammation. Noninvasive monitoring may assist in early recognition of asthma and COPD, assessment of its severity, and response to treatment, especially during disease exacerbations. There is increasing evidence that breath analysis may have an important place in clinical management of asthma and COPD. The article reviews the role of current noninvasive measurements of exhaled gases, such as nitric oxide (NO), inflammatory markers in exhaled breath condensate (EBC), and exhaled breath temperature, as well as novel methods in monitoring and management of asthma and COPD.

History of serious asthma exacerbations should be included in guidelines of asthma severity

BACKGROUND

It is unclear whether asthma severity measured with consensus guidelines is better than a history of a serious asthma exacerbation in predicting current disease activity and future clinical course.

OBJECTIVES

We sought to (1) compare asthma severity determined by using the Global Initiative for Asthma guidelines with a history of a serious asthma exacerbation as predictors of pulmonary function, bronchial hyperreactivity, and disease activity and (2) determine whether exacerbation history significantly adds to asthma severity in its ability to predict the same variables.

METHODS

Forty-eight adolescents with a history of a serious asthma exacerbation were compared with 69 adolescents with asthma but without such a history. Groups were matched for age, sex, and ethnicity (age, 14.59 +/- 1.74 years; 56% male; 58% white).

RESULTS

Forty-two percent of subjects had severe, 28% had moderate, 15% had mild persistent, and 15% had mild intermittent asthma. Asthma severity and exacerbation history were associated with pulmonary function and markers of disease activity, whereas only exacerbation history predicted bronchial hyperreactivity (P <or= .001). Including exacerbation history significantly augmented the ability of the severity categories to predict the asthma measures.

CONCLUSION

Although asthma severity and a history of a serious asthma exacerbation both predict pulmonary function abnormalities and current disease activity, bronchial hyperreactivity was only associated with exacerbation history. Exacerbation history improves the ability of severity to predict these key asthma measures.

CLINICAL IMPLICATIONS

Adding a history of a serious asthma exacerbation to the consensus guidelines for asthma severity is likely to improve the ability of these clinical tools to predict current disease activity and future clinical course.

Features of severe asthma in school-age children: Atopy and increased exhaled nitric oxide

BACKGROUND

Children with severe asthma have persistent symptoms despite treatment with inhaled corticosteroids (ICSs). The differentiating features of severe asthma in children are poorly defined.

OBJECTIVE

To identify features of severe versus mild-to-moderate asthma in school-age children using noninvasive assessments of lung function, atopy, and airway inflammation.

METHODS

A total of 75 children (median age, 10 years) with asthma underwent baseline characterization including spirometry and lung volume testing, methacholine bronchoprovocation, allergy evaluation, and offline measurement of exhaled nitric oxide (F(ENO)). Twenty-eight were followed longitudinally over 6 months. Participants were assigned to the severe asthma subgroup if they required high-dose ICS plus 2 or more minor criteria.

RESULTS

Children with severe versus mild-to-moderate asthma had more symptoms, greater airway obstruction, more gas trapping, and increased bronchial responsiveness to methacholine. Subjects with severe asthma also had higher concentrations of F(ENO) and significantly greater sensitization to aeroallergens. With long-term study, both the reduction in FEV(1) and increase in F(ENO) persisted in the severe versus mild-to-moderate group. Furthermore, despite adjustments in ICS doses, the frequency of exacerbations was significantly higher in subjects with severe (83%) versus mild-to-moderate asthma (43%).

CONCLUSION

Severe asthma in childhood is characterized by poor symptom control despite high-dose ICS treatment and can be differentiated from mild-to-moderate asthma by measurement of lung function and F(ENO).

CLINICAL IMPLICATIONS

Clinicians should suspect severe asthma in children with poor response to ICS, airway obstruction, and high F(ENO).

Is there a best outcome measurement for patients with asthma?

OBJECTIVES

To summarize the outcomes used to evaluate inhaled corticosteroid intervention in terms of the Economic, Clinical, and Humanistic Outcomes (ECHO) model and to discuss the value of this more comprehensive approach in assessing therapeutic efficacy in asthma.

DATA SOURCES

Relevant articles were identified by a search of the PubMed database for English-language articles published from 1991 to 2006 and references identified from bibliographies of relevant articles.

STUDY SELECTION

The author's expert opinion was used to select studies for inclusion in this review.

RESULTS

Studies that assessed therapeutic effectiveness of inhaled corticosteroids in patients with asthma have traditionally focused on clinical indicators of treatment effect, including pulmonary function and symptoms. However, reliance on clinical indicators alone may not represent the full effect of the treatment on patients with asthma. The ECHO model is proposed as a more comprehensive and useful alternative to evaluate therapeutic effectiveness in patients with asthma. The model takes into account more recent concerns of patients and health care practitioners, including quality of life and treatment cost. Clinical studies using various ECHO outcomes are presented and the limitations of using individual outcomes are discussed. The Pediatric Asthma Episodes of Care Program, which exemplifies successful application of the ECHO model in the real-world setting, is also discussed.

CONCLUSIONS

The more comprehensive approach to determining therapeutic effectiveness in asthma provided by the ECHO model should enable optimization of asthma treatment, with limited health care resources.

Personal and ambient air pollution is associated with increased exhaled nitric oxide in children with asthma

BACKGROUND

Research has shown associations between pediatric asthma outcomes and airborne particulate matter (PM). The importance of particle components remains to be determined.

METHODS

We followed a panel of 45 schoolchildren with persistent asthma living in Southern California. Subjects were monitored over 10 days with offline fractional exhaled nitric oxide (FeNO), a biomarker of airway inflammation. Personal active sampler exposures included continuous particulate matter < 2.5 microm in aerodynamic diameter (PM2.5), 24-hr PM2.5 elemental and organic carbon (EC, OC), and 24-hr nitrogen dioxide. Ambient exposures included PM2.5, PM2.5 EC and OC, and NO2. Data were analyzed with mixed models controlling for personal temperature, humidity and 10-day period.

RESULTS

The strongest positive associations were between FeNO and 2-day average pollutant concentrations. Per interquartile range pollutant increase, these were: for 24 microg/m3 personal PM2.5, 1.1 ppb FeNO [95% confidence interval (CI), 0.1-1.9]; for 0.6 microg/m3 personal EC, 0.7 ppb FeNO (95% CI, 0.3-1.1); for 17 ppb personal NO2, 1.6 ppb FeNO (95% CI, 0.4-2.8). Larger associations were found for ambient EC and smaller associations for ambient NO2. Ambient PM2.5 and personal and ambient OC were significant only in subjects taking inhaled corticosteroids (ICS) alone. Subjects taking both ICS and antileukotrienes showed no significant associations. Distributed lag models showed personal PM2.5 in the preceding 5 hr was associated with FeNO. In two-pollutant models, the most robust associations were for personal and ambient EC and NO2, and for personal but not ambient PM2.5.

CONCLUSION

PM associations with airway inflammation in asthmatics may be missed using ambient particle mass, which may not sufficiently represent causal pollutant components from fossil fuel combustion.

Fractional exhaled nitric oxide concentration is increased in asbestosis and pleural plaques

OBJECTIVE AND BACKGROUND

Asbestos exposure induces generation of reactive oxygen and nitrogen species. Nitric oxide is involved in asbestos-related lung toxicity in vitro and can be measured non-invasively in humans in exhaled breath. The authors hypothesized that fractional exhaled nitric oxide concentration (FENO) would be increased in subjects with asbestos-related lung disorders.

METHODS

FENO was measured in 56 subjects with asbestos-related disorders (asbestosis: 12; pleural plaques: 32; asbestos-related diffuse pleural thickening: 12) and in 35 normal subjects. The authors also measured exhaled carbon monoxide, another marker of lung inflammation.

RESULTS

Median (25-75 percentile) FENO was increased in subjects with asbestosis (7.9 (6.6-15.7) p.p.b.; P=0.001) and pleural plaques (6.3 (5.3-9) p.p.b.; P=0.03) compared with normal controls (4.6 (3.5-6) p.p.b.). Subjects with DPT had a median FENO of 5.6 p.p.b., similar to controls. No significant differences in exhaled carbon monoxide were observed between controls (1.0+/-0.3 p.p.m.) and subjects with asbestosis (1.3+/-0.3 p.p.m.), pleural plaques (1.2+/-0.3 p.p.m.) or diffuse pleural thickening (1.1+/-0.3 p.p.m.).

CONCLUSIONS

FENO is raised in asbestosis consistent with lung inflammation, and also in pleural plaques.

Exhaled nitric oxide measurements: clinical application and interpretation

The use of exhaled nitric oxide measurements (F(E)NO) in clinical practice is now coming of age. There are a number of theoretical and practical factors which have brought this about. Firstly, F(E)NO is a good surrogate marker for eosinophilic airway inflammation. High F(E)NO levels may be used to distinguish eosinophilic from non-eosinophilic pathologies. This information complements conventional pulmonary function testing in the assessment of patients with non-specific respiratory symptoms. Secondly, eosinophilic airway inflammation is steroid responsive. There are now sufficient data to justify the claim that F(E)NO measurements may be used successfully to identify and monitor steroid response as well as steroid requirements in the diagnosis and management of airways disease. F(E)NO measurements are also helpful in identifying patients who do/do not require ongoing treatment with inhaled steroids. Thirdly, portable nitric oxide analysers are now available, making routine testing a practical possibility. However, a number of issues still need to be resolved, including the diagnostic role of F(E)NO in preschool children and the use of reference values versus individual F(E)NO profiles in managing patients with difficult or severe asthma.

Non-invasive measurement of airway inflammation in asthma

Assessing the severity and control of a patient's asthma is of great importance to ensure that pharmacotherapy is optimized. Measures such as lung function, symptoms, and reliever use have traditionally been used as objective means of undertaking this assessment, but until now the level of airway inflammation has not been quantified. As asthma is primarily an inflammatory disorder, it would be desirable to include a measure of this process when evaluating disease control. The following article outlines methods of non-invasively measuring asthmatic airway inflammation and highlights their potential role in clinical practice.

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.

Exhaled nitric oxide in the management of childhood asthma: a prospective 6-months study

Fractional exhaled nitric oxide (FeNO) is elevated in asthma and reflects eosinophilic airway inflammation. The aim of this prospective, randomized, single-blind study was to examine whether the inclusion of repeated FeNO measurements into asthma monitoring leads to an improvement in asthma outcome. Forty-seven children with mild to moderate asthma were allocated to a FeNO group (n = 22) and to a control group (n = 25). In the FeNO group therapy was based on symptoms, beta-agonist use, lung function, and FeNO whereas in the control group therapy was based on symptoms, beta-agonist use and lung function only. Patients performed five visits in 6 weeks intervals. Frequency of respiratory symptoms, beta-agonist use, FEV(1)% predicted and the frequency of exacerbations were similar between groups. Patients in the FeNO group received higher doses of inhaled corticosteroids (ICS) (control group: median (interquartile range): 241 microg (26-607 microg); FeNo group: 316 microg (200-500 microg) and had significantly higher MEF(50)% predicted (control group: median (interquartile range): 68.5% (55.8-83.1%); FeNO group: 83.2% (62.9%-98.3%). At a cut-off point of 22.9 ppb FeNO the best predictive value for exacerbations with a sensitivity of 80% and specificity of 60% was found. Significant relationships were observed between FeNO and dose of ICS (beta = -8.77; P < 0.002), beta-agonist use 2 weeks prior to a visit (beta = 0.11; P < 0.05), asthma symptoms (beta = 0.02; P < 0.0001), and bronchial hyperresponsiveness (beta = 0.04; P = 0.02). In conclusion, FeNO was related to important markers of asthma control. A therapy regimen aimed at lowering FeNO in children with asthma improved parameters of small airway function, but was not able to improve clinical markers of asthma control.

Pharmacological management of mild or moderate persistent asthma

Patients with mild persistent asthma rarely see their doctor with symptoms of the disease. Partly as a result of this situation, mild asthma is generally undertreated. Findings of several large randomised clinical trials have shown benefits for this population of regular treatment with low doses of inhaled corticosteroids. Additional drugs are rarely needed, and although leukotriene modifiers are effective, they are less so than inhaled corticosteroids. People with moderate persistent asthma are not well controlled on low doses of inhaled corticosteroids. A combination of this drug and long-acting inhaled beta2 agonists provides improved control compared with doubling of the maintenance dose of inhaled corticosteroids. The combination of budesonide and formoterol has been assessed as both maintenance and reliever treatment. This approach further reduces the risk for severe exacerbations. With these strategies, most individuals can achieve good control of their asthma. For patients who do not achieve asthma control despite taking drugs, measurement of the inflammatory response in the airway in induced sputum could provide further information to guide treatment.

Respiratory symptoms, bronchial hyper-responsiveness, and eosinophilic airway inflammation in patients with moderate-to-severe atopic dermatitis

BACKGROUND

Patients with atopic dermatitis (AD) often have symptoms suggestive of asthma or rhinitis. The prevalence and signs of respiratory disease in AD patients have been studied to a limited extent.

OBJECTIVES

To assess the prevalence and clustering of respiratory symptoms, bronchial hyper-responsiveness (BHR), and eosinophilic airway inflammation in patients with moderate-to-severe AD.

METHODS

Eighty-six consecutive patients with moderate-to-severe AD and 49 randomly selected control subjects without AD were studied by questionnaire, flow volume spirometry, histamine challenge to detect BHR, induced sputum test to detect eosinophilic airway inflammation, and skin prick tests (SPTs) and total serum immunoglobulin (Ig)E measurements to detect atopy.

RESULTS

The patients with AD showed increased risk of physician-diagnosed asthma (36% vs. 2%, odds ratio (OR) 10.1, confidence interval (CI) 1.3-79.7, P=0.03), physician-diagnosed allergic rhinitis (AR) (45% vs. 6%, OR 4.5, CI 1.2-16.7, P=0.02), BHR (51% vs. 10%, OR 5.5, CI 1.5-20.1, P=0.01), and sputum eosinophilia (81% vs. 11%, OR 76.1, CI 9.3-623.5, P<0.0001) compared with the control subjects. In AD patients, elevated s-IgE and positive SPTs were associated with the occurrence of physician-diagnosed asthma and AR, BHR, and the presence of sputum eosinophilia.

CONCLUSIONS

BHR and eosinophilic airway inflammation are more common in patients with AD than in control subjects. The highest prevalences were seen in patients with AD who were SPT positive and had high IgE levels. Longitudinal studies are needed to assess the outcome of patients with signs of airway disease, in order to identify those who need early initiation of asthma treatment.

Monitoring of asthma control in children

PURPOSE OF REVIEW

The focus in managing asthma has undergone a paradigm shift from the concept of assessing severity to assessing control. The recent Practice Parameter on attaining optimal asthma control highlights the need to titrate the step-care management of asthma to the level of control assessed at each clinic encounter.

RECENT FINDINGS

Recent advances in the monitoring of asthma control in children include the use of questionnaires such as the Childhood Asthma Control Test, use of biomarkers such as fractional concentration of exhaled nitric oxide, sophisticated hand-held electronic monitoring of lung function such as peak flow and forced expiratory volume, indicators of lung growth and bronchial hyper-responsiveness such as post-bronchodilator forced expiratory volume, outcomes-utilization data, markers of atopy, and electronic measures of adherence.

SUMMARY

Three recent proof-of-concept studies in adults have demonstrated the relevance of criteria other than guidelines-recommended asthma symptoms and pulmonary function tests. These studies used airway hyper-responsiveness, sputum eosinophilia, and fraction of exhaled nitric oxide as indices to facilitate fine-tuning of asthma control and use of controller-inhaled steroids. The next logical step would be to determine the applicability of these and other measures to children in both research and clinical settings.

Attaining asthma control

PURPOSE OF REVIEW

Despite our knowledge of asthma pathophysiology and several guidelines, studies have indicated growing morbidity. This review highlights the rationale for the trend in asthma care of separating asthma control from asthma severity.

RECENT FINDINGS

Recent research has highlighted why asthma morbidity continues to be such a conundrum. This includes the variability of asthma control over time, inability to achieve total asthma control in some patients, disagreement between various measures of asthma control and the lack of an agreed tool for determining asthma control.

SUMMARY

By dissociating asthma control and severity, the clinician may focus on the level of control during each encounter, independent of asthma medication. One can still build upon the step-up and step-down algorithm, while reinforcing control of asthma as the ultimate goal. Asthma control connotes the status of the disease, highlighting the dynamic nature of this illness both as the response to a trigger as well as therapy. Although more aggressive intervention may be required to achieve adequate control in severe persistent asthma versus mild persistent disease, the goal of appropriate asthma control remains constant in the spectrum of asthma severity.

Role of spirometry and exhaled nitric oxide to predict exacerbations in treated asthmatics

OBJECTIVE

To evaluate the complementary roles of exhaled nitric oxide (NO) and spirometry to predict asthma exacerbations requiring one or more tapering courses of systemic corticosteroids.

METHODS

We prospectively studied 44 nonsmoking asthmatics (24 women) aged 51 +/- 21 years (mean +/- SD) who were clinically stable for 6 weeks and receiving 250 mug of fluticasone/50 mug of salmeterol or equivalent for 3 years. Total exhaled NO (FENO), small airway/alveolar NO (CANO), large airway NO flux (J'awNO), and spirometry were measured.

RESULTS

Baseline FEV(1) was 2.1 +/- 0.7 L, 70 +/- 20% of predicted after 180 mug of albuterol. Twenty-two of 44 asthmatics had one or more exacerbations over 18 months, 16 of 22 asthmatics had two exacerbations, and 6 of 22 asthmatics were hospitalized, including 1 asthmatic with near-fatal asthma. When baseline FEV(1) was </= 76% predicted, exacerbations occurred in 20 of 31 asthmatics (65%). If baseline FEV(1) was > 76% of predicted, exacerbations occurred only in 2 of 13 asthmatics (15%) [p = 0.003, chi(2)]. Using a receiver operating characteristic (ROC) curve for first exacerbation, the area under the curve was 0.67 with cutoff FEV(1) of 76% of predicted (sensitivity, 0.91; specificity, 0.50; positive predictive value, 0.65; negative predictive value, 0.85; positive likelihood ratio [LR(+)], 1.8; negative likelihood ratio [LR(-)], 0.18). When baseline FENO was >/= 28 parts per billion (ppb), exacerbations occurred in 13 of 17 asthmatics (76%); if baseline FENO was < 28 ppb, exacerbations occurred in only 9 of 27 asthmatics (33%) [p = 0.005, chi(2)]. Using the ROC curve for first exacerbation, the area under the curve was 0.71 with FENO cutoff point of 28 ppb (sensitivity, 0.59; specificity, 0.82; positive predictive value, 0.77; negative predictive value, 0.87; LR(+), 3.3; LR(-), 0.5). Independent of baseline FEV(1), FENO >/= 28 ppb increased the relative risk (RR) for exacerbation by 3.4 (95% confidence interval [CI], 1.3 to 9.1; Mantel-Haenszel, p = 0.007). An abnormal increase in CANO increased RR by 3.0 (95% CI, 0.9 to 9.9; p = 0.04), and abnormal J'awNO increased RR by 2.4 (95% CI, 1.0 to 5.6; p = 0.04). Independent of baseline FENO, FEV(1) </= 76% predicted increased RR by 1.7 (95% CI, 1.0 to 2.7; p = 0.02). Combined baseline FENO >/= 28 ppb and FEV(1) </= 76% of predicted identified 13 stable asthmatics with 85% probability for future exacerbation, whereas 9 asthmatics with FENO < 28 ppb and FEV(1) > 76% of predicted had a 0% probability of exacerbation.

CONCLUSION

Combining FENO and FEV(1) percentage of predicted can stratify risk for asthma exacerbation.

Effect of particulate air pollution on lung function in adult and pediatric subjects in a Seattle panel study

STUDY OBJECTIVE

To determine whether increased exposure to particulate matter air pollution (PM), measured with personal, residential, or central site monitoring, was associated with pulmonary function decrements in either adults with COPD or children with asthma.

PARTICIPANTS

We studied 57 adults with or without COPD and 17 children aged 6 to 13 years with physician-diagnosed asthma in Seattle during a 3-year panel study.

STUDY DESIGN AND MEASUREMENTS

Indoor and outdoor PM measurements were made at subjects' homes. The subjects wore personal exposure monitors for 10 consecutive 24-h periods, and PM was also measured at a central outdoor location. We assessed the within-subject effect of particulate exposure on FEV(1) and peak expiratory flow (PEF) in adults, and maximal midexpiratory flow (MMEF), PEF, FEV(1), and symptoms in children.

RESULTS

FEV(1) decrements were associated with 1-day lagged central site PM </= 2.5 microm in diameter (PM(2.5)) in adult subjects with COPD. In children not receiving antiinflammatory medication, same day indoor, outdoor, and central site exposures to PM(2.5) were associated with decrements in MMEF, PEF, and FEV(1). Associations with PM(2.5) and lung function decrements were also observed for 1-day lagged indoor (MMEF, PEF, FEV(1)) and personal (PEF only) exposures. Antiinflammatory medication use in children significantly attenuated the PM effect on airflow rates and volumes.

CONCLUSIONS

This study found consistent decrements in MMEF in children with asthma who were not receiving medications. It is notable that effects were observed even though PM exposures were low for an urban area. These findings suggest the need for future larger studies of PM effects in this susceptible population that repeatedly measure spirometry to include MMEF and potentially more sensitive markers of airway inflammation such as exhaled breath condensate and exhaled nitric oxide.

Clinical applications of exhaled nitric oxide for the diagnosis and management of asthma: a consensus report

BACKGROUND

Patients with asthma routinely exhibit elevated levels of fractionated exhaled nitric oxide (FE(NO)), and this observation has led to studies investigating FE(NO) as a potential marker of airway inflammation. FE(NO) has been shown to enhance the diagnosis of asthma, detect deterioration in control of patients with asthma, and monitor response to anti-inflammatory therapy.

OBJECTIVES

The aim of this work was to determine if FE(NO) measurement provides a noninvasive, well-tolerated, and standardized technique to monitor airway inflammation, and if it has the potential to complement standard asthma monitoring tools (eg, symptom diaries, control questionnaires, and pulmonary function testing) and to improve asthma control and patient outcomes.

METHODS

Thirteen experts in the diagnosis and treatment of asthma met to discuss the use of FE(NO) in the diagnosis and management of patients with asthma. Participants were selected by Aerocrine, a medical, technical company with headquarters in Stockholm, Sweden, in consultation with their medical education partner Cadent Medical Communications located in Irving, Texas, to represent a diversity of specialists, including both clinicians and investigators, in the fields of allergy, immunology, and pulmonology. All participants were nominally compensated for their time to attend this closed scientific roundtable discussion. The meeting was supported by an educational grant from Aerocrine. This report represents the overall consensus reached by the participants on the clinical applicability of this technique.

RESULTS

Our understanding of asthma has expanded so that investigators are now focusing on inflammation in addition to airway obstruction and hyper-reactivity. Whereas patient history, symptoms, and pulmonary function testing can assist in diagnosing asthma, they are not direct measures of the extent of airway inflammation. Elevated FE(NO) levels have been shown to reflect airway inflammation and to occur together with other conventional markers used to detect inflammation. Studies have confirmed increased levels of FE(NO) in both adults and children with asthma. In most studies, FE(NO) was found to be elevated 2- to 3-fold compared with normal controls. There are many determinants of FE(NO) levels, however, and factors other than inflammation must be considered when FE(NO) measurement is used to diagnose and monitor asthma. FE(NO) measurement alone is not sufficient for diagnosing or monitoring asthma, but it can be a valuable addition to current clinical tools.

CONCLUSIONS

FE(NO) measurement is a noninvasive and reproducible test that is a surrogate measure of airway inflammation in patients with asthma. The test has demonstrated utility in diagnosing and managing asthma and in predicting response to therapy and, therefore, may be an important tool to incorporate into clinical care.

Noninvasive monitoring of airway inflammation and steroid reduction in children with asthma

PURPOSE OF REVIEW

Management of pediatric asthma is currently based on symptoms (often a second-hand report from parents) and lung function. Inhaled steroids are the mainstay of asthma management targeted at controlling airway inflammation. They should be used in the lowest possible doses. A number of noninvasive methods to assess inflammation have been developed in an effort to optimize anti-inflammatory treatment.

RECENT FINDINGS

The first longitudinal studies have been published demonstrating an improvement in asthma control in children by adding noninvasive monitoring of inflammation into the clinical management. New methods include exhaled nitric oxide measurements, induced sputum and markers in exhaled breath condensate.

SUMMARY

Further studies will show the practicability of including these measurement methods into everyday clinical practice. Their addition to the conventional assessment of asthma control appears promising. Using these methods to evaluate the current inflammatory state seems obligatory in research into new asthma therapeutics and management strategies. Managing asthma in children in specialist practice relying only on symptoms and lung function is no longer state of the art.

Severe asthma: an overview

Severe asthma represents less than 10% of all asthma, but these patients are responsible for a disproportionate share of the health care costs and morbidity associated with the disease. A significant challenge in the diagnosis and management of severe asthma is the ability to identify accurately the patients most at risk for adverse outcomes, such as medication side effects, emergency department visits, hospitalization, near-fatal events, or disability from persistent symptoms or chronic lung function abnormalities. To improve the treatment of these patients, we must improve our understanding of the mechanisms responsible for severe disease. To achieve this goal, it is imperative to develop a common definition of severe asthma to allow adequate characterization of the disease clinically and provide the opportunity to compare results from many studies. Several severe asthma phenotypes have been described in the literature on the basis of the age of patients, age of disease onset, corticosteroid resistance, chronic airflow obstruction, and evidence for eosinophilic airway inflammation on biopsy. These phenotypes have led to an emerging interest in the use of noninvasive methods to monitor airway inflammation in severe asthma. Treatment algorithms based on markers of airway inflammation may decrease measures of health care utilization in severe asthma.

Severity, control, and responsiveness in asthma

Guidelines for asthma management have proposed that initial treatment should be based on assessment of asthma severity. The treatments proposed for different degrees of asthma severity are essentially estimates of the intensity of treatment needed to achieve asthma control. Responsiveness to treatment is heterogeneous, however, even among asthmatic patients with asthma of similar severity. This heterogeneity calls attention to the importance of assessing asthma control and adjusting treatment accordingly. Application of a guidelines-based approach to asthma management thus requires general agreement on what is meant by severity, control, and responsiveness and requires further an awareness of asthma as causing symptoms and functional impairment in the present and also as causing risk of adverse events in the future.

Single breath N2-test and exhaled nitric oxide in men

The N(2) slope is an index of inhomogeneous distribution of ventilation and has been suggested to be suited for early testing of chronic obstructive pulmonary disease (COPD) in smokers. The aim of the present study was to examine the association between the fraction of exhaled nitric oxide (FENO) and the N(2) slope in a random population of smoking and non-smoking men. Altogether 57 subjects were included in the study, 24 never-smokers, seven ex-smokers and 26 current smokers. Subjects were examined twice, in 1995 when they regarded themselves as healthy, and in a follow-up in 2001. Spirometry, N(2) slope and high-resolution computed tomography (HRCT) were performed in 1995 while the follow-up examination included also measurement of FENO. The FENO value was significantly lower and the N(2) slope higher in current smokers. In smokers but not in never- or ex-smokers FENO was correlated to the difference in N(2) slope between 1995 and 2001 (r(s)=0.49, P=0.01). We analysed the data by multiple linear regression adjusted for smoking, mild respiratory symptoms and inhaled steroids. There were significant associations between FENO and the N(2) slope both in 1995 and in 2001. The strongest association was found to exist with the change in N(2) slope during these years. Sixteen of the subjects could be classified as having COPD, six with mild and ten with moderate COPD. There was a trend for an increase in N(2) slope with increased severity of COPD; among subjects with no COPD the N(2) slope in 2001 was 2.3% N(2)/L, and those with mild and moderate COPD had 2.5% N(2)/L and 3.9% N(2)/L, respectively (P=0.0004). No such trend was seen for FENO (17.8, 15.5 and 20.3 parts per billion (ppb), respectively, P=0.8). The results show that FENO is associated with the N(2) slope, indicating that FENO reflects inflammatory changes in the peripheral airways of both non-smoking and smoking subjects.

Revisiting asthma control: how should it best be defined?

Management guidelines for asthma emphasize a stepwise approach in treating this disease based on daytime symptoms, nighttime symptoms, and lung function assessed by peak expiratory flow or forced expiratory volume at 1s (FEV(1)). Although improvement of lung function is a key goal in managing asthma, clinicians often see patients who may have achieved a normal FEV(1) with guideline-recommended treatment but continue to experience limitations in their daily activities. In such situations, focusing the assessment solely on pulmonary function (e.g. FEV(1)) is often inadequate and may lead to undertreatment. Alternate assessment measures are therefore often needed to assess asthma control and achieve a successful treatment outcome. This review will provide practical guidance relevant to the clinical assessment of asthma control.

Markers of lung disease in exhaled breath: nitric oxide

Management of airway inflammation requires proper monitoring and treatment to improve long-term outcomes. However, achieving this goal is difficult, as current methods have limitations. Although nitric oxide (NO) was first identified 200 years ago, its physiological importance was not recognized until the early 1980s. Many studies have established the role of NO as an essential messenger molecule in body systems. In addition, studies have demonstrated a significant relationship between changes in exhaled NO levels and other markers of airway inflammation. The technique used to measure NO in exhaled breath is noninvasive, reproducible, sensitive, and easy to perform. Consequently, there is growing interest in the use of exhaled NO in the management of asthma and other pulmonary conditions. The purpose of this review is to promote a basic understanding of the physiologic actions of NO, measurement techniques, and ways that research findings might translate to future application in clinical practice. Specifically, the article will review the role of exhaled NO in regard to its historical background, mechanisms of action, measurement techniques, and implications for clinical practice and research.

Daily ambulatory exhaled nitric oxide measurements in asthma

Exhaled NO (FENO) is a non-invasive, validated marker for asthmatic airway inflammation. Recently, a new hand-held NO-analyzer has been developed which makes it possible to monitor FENO at home. We assessed feasibility and analyzed variability of daily FENO home measurements. Twenty-one asthmatics (mean age 14.5 yr; range 8-25 yr) participated. Nineteen used a stable dose of inhaled corticosteroids and all of them were in a stable clinical condition. FENO was measured twice daily for 14 consecutive days. Measurements and symptom scores were recorded on a smart card in the analyzer. Symptom score items included well-being, wheeze, activity, and nocturnal symptoms. Measurements showed a success rate of 93%. We found a significant diurnal variation in FENO with geometric mean morning levels 14% higher than evening levels (95% CI: 4%-25%; p = 0.013). Individual subjects showed marked fluctuation of FENO. The mean intrasubject coefficient of variation of FENO was 40% for morning and 36% for evening values. FENO and cumulative symptom scores did not correlate. Home FENO measurements are feasible, and offer the possibility to asses airway inflammation on a daily basis. Further study is needed to interpret and evaluate possible benefits of FENO home monitoring.

The Effects of Age on Exhaled Breath Nitric Oxide Levels

A variety of factors influence exhaled breath nitric oxide (ENO) but few studies have examined ENO at the extremes of adult age. This investigation explores whether there is a difference in ENO between groups of older and younger individuals. A total of 48 normal subjects consisting of 23 younger (median age - 24 years) and 25 older (median age - 72 years) participants were studied. Carefully defined clinical and spirometric parameters, smoking history, and drug/medication documentation were determined to insure normalcy. Measurements of ENO were made using ATS/ERS recommended methodologies. The older group consistently showed higher ENO concentrations than-the younger subjects; median ENO values were 36.9 and 18.7 ppb, respectively (p < 0.001). The statistical significance held true when adjusting for multiple testing with the Holm method and accounting for outliers and medication usage. ENO levels are significantly higher in a normal older population. Comparing ENO between individuals at the extremes of age may depict differences more decidedly. Whether elevated ENO reflects underlying airway inflammation in older persons remains unanswered. It is possible that the difference in NO concentrations between older and younger groups represents only a marker of past oxidant exposures and holds no clinical significance. Additional investigations are necessary to elucidate the mechanisms and significances of elevated NO levels in the aged.

Peripheral inflammation in patients with asthmatic symptoms but normal lung function

Some patients with asthmatic symptoms and eosinophilic airway inflammation have normal lung function and thus do not meet the current diagnostic criteria of asthma. Exhaled nitric oxide (NO) measurement at multiple exhalation flow rates can be used to assess alveolar and bronchial NO output and inflammation. We tested whether alveolar or bronchial NO output is increased in subjects having asthmatic symptoms but normal lung function. Exhaled NO concentration was measured at three exhalation flow rates (100, 175, and 370 mL/s) to assess alveolar NO concentration and bronchial NO flux in 23 patients with asthmatic symptoms but normal lung function ("asthmatic symptoms group"), 40 patients with asthma, and 40 healthy control subjects. The asthmatic symptoms group had increased bronchial NO flux (1.7 +/- 0.3 nL/s, p = 0.016) and alveolar NO concentration (1.8 +/- 0.2 parts per billion (ppb), p = 0.010) compared with healthy controls (0.7 +/- 0.1 nL/s and 1.0 +/- 0.1 ppb, respectively). Patients with asthma had even higher bronchial NO flux (2.5 +/- 0.3 nL/s, p = 0.024) but normal alveolar NO concentration (1.1 +/- 0.2 ppb, p = 0.664). In asthmatic symptoms group, alveolar NO concentration correlated positively with blood eosinophil count and negatively with small airway function (FEF50% and FEF75%). In conclusion, patients with asthmatic symptoms but normal lung function have increased alveolar NO concentration and mildly elevated bronchial NO flux suggesting a more peripheral inflammation than in patients with asthma.

Nitric oxide as a clinical guide for asthma management

Asthma is a pathologically heterogeneous disease, and the phenotype is characterized by different types of airway inflammation. Exhaled nitric oxide (F(E)NO) measurements are a surrogate marker specific for eosinophilic airway inflammation. The latter is usually associated with steroid responsiveness, and hence, F(E)NO may be used to guide steroid requirements in certain clinical situations. High F(E)NO levels may be used to predict likely benefits with inhaled corticosteroid (ICS) therapy. Both high and low F(E)NO levels are prognostically significant when withdrawal of ICS treatment is being considered. Studies have shown that, just as for induced sputum, repeated F(E)NO measurements improve the cost-effectiveness of ICS therapy when used to guide dose requirements. In practice, F(E)NO measurements are useful in the management of severe or difficult asthma. High and low F(E)NO levels in symptomatic patients provide the clinician with information that enables active eosinophilic airway inflammation to be included or excluded. Either outcome is helpful in decision making. F(E)NO measurements complement the use of other tests in asthma, but more work is required to determine reference values and cut-points for appropriate interpretation.

Overcoming gaps in the management of asthma in older patients: new insights

Asthma is under-recognised and undertreated in older populations. This is not surprising, given that one-third of older people experience significant breathlessness. The differential diagnosis commonly includes asthma, chronic obstructive pulmonary disease (COPD), heart failure, malignancy, aspiration and infections. Because symptoms and signs of several cardiorespiratory diseases are nonspecific in older people and diseases commonly co-exist, investigations are important. A simple strategy for the investigation of breathlessness in older people should include a full blood count, chest radiograph, ECG, peak flow diary and/or spirometry with reversibility as a minimum. If there are major abnormalities on the ECG, an echocardiogram should also be performed. Diurnal variability in peak flow readings >or=20% or >or=15% reversibility in forced expiratory volume in 1 second, spontaneously or with treatment, support a diagnosis of asthma. Distinguishing asthma from COPD is important to allow appropriate management of disease based on aetiology, accurate prediction of treatment response, correct prognosis and appropriate management of the chest condition and co-morbidities. The two conditions are usually readily differentiated by clinical features, particularly age at onset, variability of symptoms and nocturnal symptoms in asthma, supported by the results of reversibility testing. Full lung function tests may not necessarily help in differentiating the two entities, although gas transfer factor is characteristically reduced in COPD and usually normal or high in asthma. Methacholine challenge tests previously mainly used in research are now also used widely and safely to confirm asthma in clinical settings. Interest in exhaled nitric oxide as a biomarker of airways inflammation is increasing as a noninvasive tool in the diagnosis and monitoring of asthma. Regular inhaled corticosteroids (ICS) are the mainstay of treatment of asthma. Even in mild disease in older adults, regular preventive treatment should be considered, given the poor perception of bronchoconstriction by older asthmatic patients. If symptoms persist despite ICS, addition of long-acting beta(2)-adrenoceptor agonists (LABA) should be considered. Addition of LABA to ICS improves asthma control and allows reduction in ICS dose. However, older people have been grossly under-represented in trials of LABA, many trials having excluded those >or=65 years of age. On meta-analysis, beta(2)-adrenoceptor agonists (both short acting and long acting) are associated with increased cardiovascular mortality and morbidity in asthma and COPD. While the evidence for excess cardiovascular mortality is stronger for short-acting beta(2)-adrenoceptor agonists, it would be prudent to exercise particular care in using beta(2)-adrenoceptor agonists (long acting and short acting) in those at risk of adverse cardiovascular outcomes, including older people. Regular review of cardiovascular status (and monitoring of serum potassium concentration) in patients taking beta(2)-adrenoceptor agonists is crucial. The response to LABA should be carefully monitored and alternative 'add-on' therapy such as leukotriene receptor antagonists (LRA) should be considered. LRA have fewer adverse effects and in individual cases may be more effective and appropriate than LABA. Long-term trials evaluating beta(2)-adrenoceptor agonists and other bronchodilator strategies are needed particularly in the elderly and in patients with cardiovascular co-morbidities. There is no evidence that addition of anticholinergics improves control of asthma further, although the role of long-acting anticholinergics in the prevention of disease progression is currently being researched. Older patients need to be taught good inhaler technique to improve delivery of medications to lungs, minimise adverse effects and reduce the need for oral corticosteroids. Nurse-led education programmes that include a written asthma self-management plan have the potential to improve outcomes.

Correlation of exhaled nitric oxide, spirometry and asthma symptoms

Asthma is the most common chronic disease of childhood. Asthma severity is monitored by spirometry. However, this does not directly measure airway inflammation. Exhaled nitric oxide (FeNO) is a proposed method to measure airway inflammation non-invasively. Previous studies have shown that FeNO correlates with endobronchial biopsies and symptoms in patients with asthma. We monitored daily asthma symptoms compared to monthly spirometry and FeNO. Total monthly symptom scores correlated with both forced expiratory volume at 1 sec (FEV1) and FeNO. FeNO had a strong correlation than FEV1. FeNO and FEV1 were not correlated. We propose that FeNO should be used as an additional monitoring tool for asthma.

A critical appraisal of methods used in early clinical development of novel drugs for the treatment of asthma

Asthma is a heterogeneous disorder characterized by chronic airway inflammation, hyperresponsiveness and remodeling. Being the hallmark of asthma, airway inflammation has become the most important target for therapeutic agents. Consequently, during the past decade various semi-and non-invasive methods have been explored to sample the airway inflammation in asthma. In this review, we provide a practical overview of the current status of various sampling techniques including sputum induction, exhaled breath analysis, and bronchoprovocation tests (BPTs). We focus on their applicability for monitoring in clinical practice and in intervention trials in asthma.

Effectiveness of budesonide nebulising suspension compared to disodium cromoglycate in early childhood asthma

OBJECTIVE

The optimal treatment for early childhood asthma remains controversial. Budesonide (BUD) has shown superiority over placebo in infants, and over disodium cromoglycate (DSCG) in children aged > 2 years. The aim of this double-blind, randomised, parallel-group study was to compare the effectiveness of nebulised BUD and DSCG in asthmatic children aged < 36 months.

RESEARCH DESIGN AND METHODS

82 infants (mean age 18.0 months [range, 11.6-31.2 months]) with suspected asthma (three exacerbations of dyspnoea and wheezing during the past 12 months, with one or more exacerbations in the past 3 months) were treated for 3 months with nebulised BUD (Pulmicort Respules) 0.5 mg/2 mL bid or DSCG 20 mg/2 mL tid. Follow-up was at 6 months.

MAIN OUTCOME MEASURES AND RESULTS

Patients treated with BUD had a lower exacerbation rate than DSCG-treated patients after 3 months of treatment (5.4% vs. 31.7%; p = 0.003) and towards the end of follow-up (30% vs. 49%; p = 0.062). During treatment, days without cough were 80% and 65% for BUD and DSCG, respectively (p = 0.014), and nights without cough were 89% and 78%, respectively (p = 0.016). Side-effects were mild and of similar frequency in both groups.

CONCLUSIONS

Inhaled nebulised BUD was well tolerated and more effective than nebulised DSCG in reducing the incidence of asthma exacerbations and days with symptoms. These beneficial effects of BUD were maintained throughout the 6-month follow-up.

High fractional concentration of nitric oxide in exhaled air despite steroid treatment in asthmatic children

BACKGROUND

The fractional concentration of nitric oxide in exhaled air (FENO) is elevated in atopic asthma and typically responds to treatment with inhaled corticosteroids (ICS). However, some patients have persistently high FENO levels despite treatment.

OBJECTIVE

We studied how optimizing the inhalation technique and increasing ICS doses would affect FENO in stable atopic asthmatic children who had elevated FENO while using ICS.

METHODS

In 41 stable asthmatic children who were treated with ICS (median daily dose 800 microg budesonide equivalent, range 100-1600 microg) and maintained FENO> or =20 p.p.b., we optimized the inhalation technique by thorough instruction and measured FENO 2 weeks later. Then, if FENO remained > or =20 p.p.b., we increased the ICS dose and reassessed FENO 2 weeks later.

RESULTS

Improving the inhalation technique did not reduce FENO. Increasing ICS from a daily median dose of 800 to 1200 microg budesonide had no significant effect on FENO. FENO correlated positively with symptom scores in the following 2 and 4 weeks (P=0.001, 0.002) and beta2-agonist use the 2 and 4 weeks following FENO measurement (P=0.02, 0.004).

CONCLUSION

We conclude that common steps in asthma treatment, i.e. inhalation instruction and increasing ICS dose, were both ineffective in reducing FENO in atopic asthmatic children with elevated FENO values despite treatment with ICS. This implies that FENO cannot simply be incorporated in current treatment guidelines.

Outcomes in pediatric asthma

Pediatric asthma is one of the most common chronic conditions seen in children throughout the world. Even with our better understanding of the pathology of pediatric asthma and improved pharmaceutical management for this disorder, we are still far from reaching the goals of optimal asthma outcomes as outlined by the National Heart, Lung, and Blood Institute of the National Institutes of Health. What we mean by outcomes is the change in the patient's current and future health due to the care given. The outcomes in pediatric asthma can be divided into three categories: clinical, humanistic, and economic. This article provides information regarding the different components of outcomes in pediatric asthma and how one can use outcomes to improve asthma control for the child.

The use of exhaled nitric oxide concentration to identify eosinophilic airway inflammation: an observational study in adults with asthma

BACKGROUND

Assessment of eosinophilic airway inflammation may be helpful in the management of asthma. Nitric oxide (NO) has potential advantages as a tool to monitor airway inflammation although little is known about the relationship between NO and eosinophilic airway inflammation and the factors which influence it.

METHODS

We set out to define the relationship between exhaled NO and the sputum eosinophil count, identify the exhaled NO concentration that best identified a sputum eosinophil count >3% and investigate the impact of several potential confounding factors in 566 consecutive patients with varying severity of asthma. Finally we examined the ability of exhaled NO concentrations measured at differing exhalation flows to identify the presence of a sputum eosinophilia.

RESULTS

We found a significant positive relationship between exhaled NO and sputum eosinophil count (R(2)=0.26, P<0.001) which was best described using a non-linear model. There were no clinically important confounding factors to this model. In non-smokers an exhaled NO concentration of >8.3 p.p.b. at 250 mL/s gave 71% sensitivity and 72% specificity for identifying a sputum eosinophil count of >3%.

CONCLUSIONS

This value of exhaled NO would seem to be the best for identifying significant eosinophilic airway inflammation. It is applicable to a wide range of non-smoking patients with asthma; exhalation flow does not alter the ability of exhaled NO concentration to detect a sputum eosinophilia.

Asthma: diagnosis and management

The diagnosis and management of asthma continue to be of critical importance, as recent trends have demonstrated its increasing prevalence, morbidity, and perhaps mortality. Because current treatments for asthma are effective and safe, it is important to diagnose asthma early and to use treatments effectively, particularly those directed toward airway inflammation. The diagnostic measures and array of medications, both those currently available and on the horizon, provide an armamentarium for effective diagnosis, management, and monitoring of asthma. In the coming years, it is expected that additional testing modalities will be available for more precise monitoring of asthma control, and an increased understanding of pharmacogenetics will enable the tailoring of asthma medications to specific patients, providing customized therapy to maximize asthma control.

Characteristics of asthma resistant to moderate dose inhaled corticosteroid treatment on bronchial hyperresponsiveness

OBJECT

This study was performed to determine the clinical characteristics of asthmatics with bronchial hyperresponsiveness (BHR) that could not be normalized by 6 months of treatment with a moderate dose of an inhaled corticosteroid (ICS).

METHODS

Thirty-four symptomatic patients with mild to moderate asthma, who had never received any ICS, were treated with 200 mug of inhaled fluticasone propionate twice a day for 6 months. Spirometry, BHR to methacholine, exhaled nitric oxide (NO) and eosinophils in induced sputum were examined before and 2 and 6 months after beginning treatment.

RESULTS

FEV1 was increased and bronchial responsiveness, exhaled NO and sputum eosinophilia were significantly decreased 2 and 6 months after starting ICS treatment. Bronchial responsiveness was further decreased at 6 months together with a further increase in FEV1. In 13 patients, BHR was not normalized despite the 6 months of treatment. This group showed a higher prevalence of males, those with a smoking history and airflow limitation, a higher eosinophil count in the sputum following 6 months of treatment and a longer history of asthma. Multiple, stepwise, linear regression analysis showed that sputum eosinophilia and lower FEV1/FVC following 6 months of treatment and a longer history of asthma were significant independent determinants for BHR after 6 months of ICS treatment.

CONCLUSIONS

These findings suggest that the resistance to a moderate dose of ICS for BHR in asthmatics may be significantly associated with remained airflow limitation, eosinophilic airway inflammation resistive to moderate dose of ICS, and delayed introduction of ICS therapy.

Exhaled nitric oxide in paediatric asthma

Assessment of airway function is difficult in young children with asthma, and in addition, only reflects the status of the disease at the time of the measurement. Thus, there is increasing interest in monitoring airway inflammation in asthma, which may provide a longer term assessment of disease activity. Most methods of assessing asthmatic inflammation are invasive, and are not feasible in the paediatric population. This review discusses exhaled nitric oxide as a marker of asthmatic inflammation, and compares it with other recognized markers. Exhaled nitric oxide has the potential to become a noninvasive method of assessing asthma control in the paediatric population.

Exhaled nitric oxide in children with asthma and short-term PM2.5 exposure in Seattle

The objective of this study was to evaluate associations between short-term (hourly) exposures to particulate matter with aerodynamic diameters < 2.5 microm (PM2.5) and the fractional concentration of nitric oxide in exhaled breath (FE(NO) in children with asthma participating in an intensive panel study in Seattle, Washington. The exposure data were collected with tapered element oscillation microbalance (TEOM) PM2.5 monitors operated by the local air agency at three sites in the Seattle area. FE(NO) is a marker of airway inflammation and is elevated in individuals with asthma. Previously, we reported that offline measurements of FE(NO) are associated with 24-hr average PM2.5 in a panel of 19 children with asthma in Seattle. In the present study using the same children, we used a polynomial distributed lag model to assess the association between hourly lags in PM2.5 exposure and FE(NO) levels. Our model controlled for age, ambient NO levels, temperature, relative humidity, and modification by use of inhaled corticosteroids. We found that FE(NO) was associated with hourly averages of PM2.5 up to 10-12 hr after exposure. The sum of the coefficients for the lag times associated with PM2.5 in the distributed lag model was 7.0 ppm FE(NO). The single-lag-model FE(NO) effect was 6.9 [95% confidence interval (CI), 3.4 to 10.6 ppb] for a 1-hr lag, 6.3 (95% CI, 2.6 to 9.9 ppb ) for a 4-hr lag, and 0.5 (95% CI, -1.1 to 2.1 ppb) for an 8-hr lag. These data provide new information concerning the lag structure between PM2.5 exposure and a respiratory health outcome in children with asthma.

Exhaled nitric oxide predicts airway hyper-responsiveness to hypertonic saline in children that wheeze

BACKGROUND

Exhaled nitric oxide (eNO) has shown good validity for the assessment of airway inflammation in asthmatic children. In large-scale epidemiological studies, this method would be preferred above airway challenge tests, because it is a quick and easy applicable tool.

OBJECTIVE

In this study, we aimed to assess the discriminatory capacity of eNO, and prechallenge FEV1 for airway hyper-responsiveness (AHR) in 8-13-year old schoolchildren.

MATERIALS AND METHODS

Parents completed the ISAAC questionnaire, and children were tested for atopy, AHR to hypertonic (4.5%) saline (HS), and eNO. Diagnostic value was assessed by the area under the receiver operating curves (ROC), and calculation of positive and negative predicted values at different cut-off points for eNO and prechallenge FEV1.

RESULTS

Areas under the ROC-curves of AHR were 0.65 for eNO and 0.62 for FEV1. Values increased to 0.71 and respectively 0.75 for a combined occurrence of AHR and current wheeze. Highest sensitivity and specificity were obtained at a cut-off value of 43 ppb for eNO and 103% predicted for FEV1. At these cut-off values, the positive predictive values for the presence of AHR in symptomatic children were respectively 83% (eNO) and 33% (FEV1), and negative predictive values in asymptomatic children were, respectively, 90 (eNO) and 80% (FEV1).

CONCLUSION

Exhaled nitric oxide is a valid screening tool for AHR to HS in children that present with current wheeze, and it outperforms FEV1 as a predictor of AHR.

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

BACKGROUND

Exercise-induced bronchoconstriction (EIB) is of particular importance in children with asthma. It is an important measure of asthma control and should be monitored by exercise testing. However, exercise testing puts a large demand on health-care resources and is therefore not widely used in routine monitoring of pediatric asthma control. The fractional concentration of exhaled nitric oxide (FeNO) also reflects uncontrolled asthma. We hypothesized that FeNO may be used for prescreening of asthmatic children to exclude those with good asthma control unlikely to have EIB, thereby reducing the need for exercise testing.

OBJECTIVE

The aim of this study was to estimate the value of FeNO as a predictor of EIB in asthmatic children.

METHODS

Stable outpatient asthmatic school children performed standard exercise challenge tests and measurement of FeNO.

RESULTS

FeNO and response to a standardized submaximal exercise test on the treadmill were measured in 111 school children with asthma. EIB could be excluded with a probability of 90% in asthmatic children with FeNO levels < 20 parts per billion (ppb) without current inhaled corticosteroid treatment, and < 12 ppb in children with current inhaled corticosteroid treatment.

CONCLUSION

Measurement of FeNO is a simple, and time- and resource-efficient tool that may be used to screen for EIB testing and therefore optimizes the resources for exercise testing in pediatric asthma monitoring.

Exaled nitric oxide and air trapping correlation in asthmatic children

Exhaled nitric oxide (eNO) levels have been shown to correlate with atopy and with airway hyperresponsiveness but not with standard spirometry. The aim of our study was to evaluate the correlation between eNo levels and functional residual capacity (FRC), residual volume (RV), RV to total lung capacity (TLC) ratio, and pulmonary resistances in asthmatic children ages 6-13 years. Forty-nine patients (35 males) were enrolled in the study. Nineteen of them were not receiving inhaled corticosteroids. The eNO levels were measured by chemiluminescence's analyzer and lung function study were performed by body box plethysmography. As expected, there was no correlation between eNO levels and forced vital capacity (FVC); forced expiratory volume in the first second (FEV1); mid respiratory flow between 25 and 75% of the vital capacity (MEF(25 -75)), FEV1/FVC, and pulmonary resistances. Instead a correlation was found between eNO level and RV both considering all the study population together (r = 0.51, P = 0.001) and separately the asthmatic children not receiving ICS (r = 0.6, P = 0.003). In the patients receiving ICS the correlation was still present (r = 0.43, P = 0.01). The correlation between eNo levels and RV may reflect the effect of airway inflammation on NO production and diffusion as well as peripheral airway trapping and consequent RV.

Local nitric oxide levels reflect the degree of allergic airway inflammation after segmental allergen challenge in asthmatics

Nitric oxide (NO) levels are increased in the exhaled air of asthmatics. As NO levels correlate with allergic airway inflammation, NO measurement has been suggested for disease monitoring. In patients with asthma, we previously demonstrated that intrabronchial treatment with a natural porcine surfactant enhanced airway inflammation after segmental allergen provocation. We studied whether local levels of NO reflect the degree of allergic airway inflammation following segmental allergen challenge with or without surfactant pretreatment. Segmental NO, as well as nitrite and nitrate in bronchoalveolar lavage (BAL) fluid, was measured before and after segmental challenge with either saline, saline plus allergen, or surfactant plus allergen in 16 patients with asthma and five healthy subjects. The data were compared with inflammatory BAL cells. Segmental NO levels were increased after instillation of saline (p < 0.05), or surfactant plus allergen in asthmatics (p < 0.05), and values were higher after surfactant plus allergen compared to saline challenge. Nitrate BAL levels were not altered after saline challenge but increased after allergen challenge (p < 0.05) and further raised by surfactant (p < 0.05), whereas nitrite levels were not altered by any treatment. Segmental NO and nitrate levels correlated with the degree of eosinophilic airway inflammation, and nitrate levels also correlated with neutrophil and lymphocyte numbers in BAL. In healthy subjects, NO, nitrite, and nitrate were unaffected. Thus, segmental NO and nitrate levels reflect the degree of allergic airway inflammation in patients with asthma. Measurement of both markers can be useful in studies using segmental allergen provocation, to assess local effects of potential immunomodulators.