Correlation between exhaled nitric oxide, sputum eosinophils, and methacholine responsiveness in patients with mild asthma

Is exhaled nitric oxide measurement a useful clinical test in asthma?

PURPOSE OF REVIEW

Exhaled nitric oxide measurements (FENO) are easy to perform and are repeatable. Given the strong correlations between FENO and bronchial biopsy and induced sputum eosinophilia, as well as airway hyper-responsiveness, FENO may now be advocated as a surrogate for these tests in certain circumstances. They provide the opportunity to assess pathological rather than physiological changes in asthma. This review highlights recent advances in applying this technology to the diagnosis and ongoing assessment of asthma in the clinical and epidemiological settings.

RECENT FINDINGS

Epidemiological data confirm that whereas FENO measurements reflect the presence and severity of airway inflammation, levels do not correlate strongly with symptoms or lung function abnormalities. Although reference values and thresholds for an abnormal test still need to be agreed internationally, there are now sufficient data for clinicians to use the test meaningfully in clinical practice. Studies confirm the relatively high diagnostic accuracy of FENO measurements compared with conventional tests to distinguish asthma from nonasthma. Further, dose-response relationships for changes in FENO with inhaled steroids have been confirmed, and provide the basis for using FENO to assess asthma control and, potentially, to determine antiinflammatory treatment requirements.

SUMMARY

The measurement of FENO is evolving to provide a complementary role alongside existing pulmonary function tests. Further work is required to establish reference values and possibly prediction equations in relation to age and height. Its role in determining optimum steroid requirements in chronic asthma and to identify steroid responsiveness in chronic obstructive pulmonary disease are two important areas for future research.

Gut mucosal granulocyte activation precedes nitric oxide production: studies in coeliac patients challenged with gluten and corn

BACKGROUND AND AIMS

To elucidate the dynamics of nitric oxide (NO) production induced by rectal gluten challenge and the relation between NO production and mucosal granulocyte activation.

SUBJECTS AND METHODS

Release of rectal NO was measured in 13 patients with coeliac disease and in 18 controls before and after rectal wheat gluten challenge. Rectal gas was collected with a rectal balloon using a newly developed instrument/technique, the "mucosal patch technique". The instrument allows simultaneous measurements of concentrations of granulocyte mediators in the rectal mucosa. We measured myeloperoxidase (MPO), eosinophil cationic protein (ECP), and histamine. For comparison, we made similar measurements after corn (maize) gluten challenge.

RESULTS

In all coeliac patients rectal NO concentration increased after gluten challenge and reached a peak after 15 hours (mean 9464 (SEM 2393) parts per billion (ppb); range 250-24982). The maximum MPO and ECP increase occurred five hours after challenge. A correlation was found between mucosal MPO and NO production at 15 hours. Six of the patients showed an increase in NO production 15 hours after rectal corn gluten challenge but this was much smaller than after gluten challenge. No increases were seen in the control group after either challenge.

CONCLUSION

Mucosal activation of neutrophils and eosinophils precedes pronounced enhancement of mucosal NO production after rectal wheat gluten challenge in patients with coeliac disease. Some of our coeliac patients displayed signs of an inflammatory reaction, as measured by NO and granulocyte markers, after rectal corn gluten challenge.

Use of exhaled nitric oxide measurements to guide treatment in chronic asthma

BACKGROUND

International guidelines for the treatment of asthma recommend adjusting the dose of inhaled corticosteroids on the basis of symptoms, bronchodilator requirements, and the results of pulmonary-function tests. Measurements of the fraction of exhaled nitric oxide (FE(NO)) constitute a noninvasive marker that may be a useful alternative for the adjustment of inhaled-corticosteroid treatment.

METHODS

In a single-blind, placebo-controlled trial, we randomly assigned 97 patients with asthma who had been regularly receiving treatment with inhaled corticosteroids to have their corticosteroid dose adjusted, in a stepwise fashion, on the basis of either FE(NO) measurements or an algorithm based on conventional guidelines. After the optimal dose was determined (phase 1), patients were followed up for 12 months (phase 2). The primary outcome was the frequency of exacerbations of asthma; the secondary outcome was the mean daily dose of inhaled corticosteroid.

RESULTS

Forty-six patients in the FE(NO) group and 48 in the group whose asthma was treated according to conventional guidelines (the control group) completed the study. The final mean daily doses of fluticasone, the inhaled corticosteroid that was used, were 370 microg per day for the FE(NO) group (95 percent confidence interval, 263 to 477) and 641 microg per day for the control group (95 percent confidence interval, 526 to 756; P=0.003), a difference of 270 microg per day (95 percent confidence interval, 112 to 430). The rates of exacerbation were 0.49 episode per patient per year in the FE(NO) group (95 percent confidence interval, 0.20 to 0.78) and 0.90 in the control group (95 percent confidence interval, 0.31 to 1.49), representing a nonsignificant reduction of 45.6 percent (95 percent confidence interval for mean difference, -78.6 percent to 54.5 percent) in the FE(NO) group. There were no significant differences in other markers of asthma control, use of oral prednisone, pulmonary function, or levels of airway inflammation (sputum eosinophils).

CONCLUSIONS

With the use of FE(NO) measurements, maintenance doses of inhaled corticosteroids may be significantly reduced without compromising asthma control.

Exhaled nitric oxide: a predictor of steroid response

RATIONALE

The initial management of patients who present with persistent respiratory symptoms includes recognizing those with the potential to benefit from inhaled steroid therapy. To date, this has required undertaking a "trial of steroid" to identify responders. There is increasing evidence that steroid response is more likely in patients with eosinophilic airway inflammation, and this can be assessed indirectly using exhaled nitric oxide (FENO) measurements.

OBJECTIVES

We aimed to assess the predictive accuracy of FENO to identify steroid response in 52 patients presenting with undiagnosed respiratory symptoms in a single-blind, fixed-sequence, placebo-controlled trial of inhaled fluticasone for 4 weeks.

METHODS

Comparisons of predictive accuracy were made between FENO and other conventional predictors: peak flows, spirometry, bronchodilator response, and airway hyperresponsiveness measured at baseline. "Steroid response" was defined as change in symptoms, peak flows, spirometry, or airway hyperresponsiveness to adenosine based on established guidelines and recommendations.

RESULTS

Steroid response was significantly greater in the highest FENO tertile (> 47 ppb) for each endpoint. This outcome was independent of the diagnostic label. The predictive values for FENO were significantly greater than for almost all other baseline predictors, with an optimum cut point of 47 ppb.

CONCLUSIONS

FENO measurements greater than 47 ppb provide a means of predicting steroid response in patients with undiagnosed respiratory symptoms. Assessing airway inflammation is of more practical value than diagnostic labeling when considering the potential usefulness of inhaled antiinflammatory therapy.

Sputum induction in children with difficult asthma: safety, feasibility, and inflammatory cell pattern

Difficult childhood asthma is defined by persistent symptoms despite maximal conventional therapy. We aimed to establish a safe method of sputum induction for these children and to study cytology and the relationship to exhaled nitric oxide (eNO). Sputum induction was performed in 38/40 children (aged 6-16 years) with difficult asthma, using 3.5% saline for four 5-min periods after bronchodilator pretreatment. Two children were excluded from sputum induction because postbronchodilator forced expired volume in 1 sec (FEV(1)) was <65% predicted. Seven of 38 children had symptoms (dyspnea and wheezing) during induction; of these, 3 experienced a fall in FEV(1) of >20% from postbronchodilator FEV(1), readily reversed with salbutamol. Sputum induction was successful in 28/38 children, with a higher success rate in children >/= 12 years than in younger children (87% vs. 50%, P = 0.02). Only 9/28 had abnormal sputum cytology; of these, 6 had predominant sputum eosinophilia (>2.5% eosinophils, </=54% neutrophils), while 3 had sputum neutrophilia (</=2.5% eosinophils, >54% neutrophils). Of 23 children with elevated eNO values, only 6 had sputum eosinophilia. In conclusion, sputum induction can be used to assess airway inflammation in children with difficult asthma, but abnormal sputum cytology is only present in a minority. Raised nitric oxide is only poorly predictive of sputum eosinophilia in these children.

Sputum eosinophil counts predict asthma control after discontinuation of inhaled corticosteroids

BACKGROUND

Although inhaled corticosteroids (ICSs) are effective in preventing deterioration in asthma control, at least half of subjects with mild-to-moderate asthma will remain stable when these agents are discontinued.

OBJECTIVE

We sought to determine whether noninvasive markers of inflammation predict which individuals maintain asthma control after discontinuation of ICSs.

METHODS

We analyzed data obtained from 164 subjects with mild-to-moderate asthma who participated in a 16-week trial comparing the effects of continued ICS use with the effects of a switch to salmeterol or placebo.

RESULTS

In comparison with continued ICS use, a switch to salmeterol or placebo was associated with increased rates of asthma deterioration over 16 weeks (9.3% vs 24.1% and 37.5%, respectively; P = .04 and P < .001, respectively). We found that neither exhaled nitric oxide nor methacholine PC 20 , when measured at randomization or 2 weeks after randomization, were significant predictors of subsequent asthma control in subjects who discontinued ICSs. However, both induced sputum eosinophil counts measured 2 weeks after a switch from ICS to placebo and changes in sputum eosinophil counts from before cessation of ICSs to after a switch to placebo predicted subsequent asthma deterioration (area under the receiver-operating characteristic curve, 0.771 [ P < .001] and 0.825 [ P < .001], respectively).

CONCLUSION

On the basis of a model treatment strategy, we estimate that allocating subjects to ICS therapy on the basis of changes in sputum eosinophil counts after a trial discontinuation could allow 48% of subjects with mild-to-moderate asthma to discontinue ICS therapy without an increased risk of asthma deterioration over a period of at least 14 weeks.

Characterization of within-subject responses to fluticasone and montelukast in childhood asthma

BACKGROUND

Responses to inhaled corticosteroids (ICSs) and leukotriene receptor antagonists (LTRAs) vary among asthmatic patients.

OBJECTIVE

We sought to determine whether responses to ICSs and LTRAs are concordant for individuals or whether asthmatic patients who do not respond to one medication respond to the other.

METHODS

Children 6 to 17 years of age with mild-to-moderate persistent asthma were randomized to one of 2 crossover sequences, including 8 weeks of an ICS, fluticasone propionate (100 microg twice daily), and 8 weeks of an LTRA, montelukast (5-10 mg nightly depending on age), in a multicenter, double-masked, 18-week trial. Response was assessed on the basis of improvement in FEV 1 and assessed for relationships to baseline asthma phenotype-associated biomarkers.

RESULTS

Defining response as improvement in FEV 1 of 7.5% or greater, 17% of 126 participants responded to both medications, 23% responded to fluticasone alone, 5% responded to montelukast alone, and 55% responded to neither medication. Compared with those who responded to neither medication, favorable response to fluticasone alone was associated with higher levels of exhaled nitric oxide, total eosinophil counts, levels of serum IgE, and levels of serum eosinophil cationic protein and lower levels of methacholine PC(20) and pulmonary function; favorable response to montelukast alone was associated with younger age and shorter disease duration. Greater differential response to fluticasone over montelukast was associated with higher bronchodilator use, bronchodilator response, exhaled nitric oxide levels, and eosinophil cationic protein levels and lower methacholine PC(20) and pulmonary function values.

CONCLUSIONS

Response to fluticasone and montelukast vary considerably. Children with low pulmonary function or high levels of markers associated with allergic inflammation should receive ICS therapy. Other children could receive either ICSs or LTRAs.

Additive effect of eosinophilia and atopy on exhaled nitric oxide levels in children with or without a history of respiratory symptoms

Although atopy and blood eosinophilia both influence exhaled nitric oxide (eNO) measurements, no study has quantified their single or combined effect. We assessed the combined effect of atopy and blood eosinophilia on eNO in unselected schoolchildren. In 356 schoolchildren (boys/girls: 168/188) aged 9.0-11.5 yr, we determined eNO, total serum IgE, blood eosinophil counts and did skin prick tests (SPT) and spirometry. Parents completed a questionnaire on their children's current or past respiratory symptoms. Atopy was defined by a SPT >3 mm and eosinophilia by a blood cell count above the 80th percentile (>310 cells/ml). eNO levels were about twofold higher in atopic-eosinophilic subjects than in atopic subjects with low blood eosinophils [24.3 p.p.b. (parts per billion) vs. 14.1 p.p.b.] and than non-atopic subjects with high or low blood eosinophils (24.3 p.p.b. vs. 12.2 p.p.b. and 10.9 p.p.b.) (p <0.001 for both comparisons). The additive effect of atopy and high eosinophil count on eNO levels remained unchanged when subjects were analyzed separately by sex or by a positive history of wheeze (n=60), respiratory symptoms other than wheeze (n=107) or without respiratory symptoms (n=189). The frequency of sensitization to Dermatophagoides (Dpt or Dpf) was similar in atopic children with and without eosinophilia (66.2% and 67.4%, respectively); eosinophilia significantly increased eNO levels in Dp-sensitized children as well in children sensitized to other allergens. In a multiple linear regression analysis, eNO levels were mainly explained by the sum of positive SPT wheals and a high blood eosinophil count (t=4.8 and 4.3, p=0.000), but also by the presence of respiratory symptoms (especially wheeze) and male sex (t=2.6 and 2.0, p=0.009 and 0.045, respectively). Measuring eNO could be a simple, non-invasive method for identifying subjects at risk of asthma in unselected school populations.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Enhanced nitric oxide production associated with airway hyporesponsiveness in the absence of IL-10

Interleukin (IL)-10 is an anti-inflammatory cytokine implicated in the regulation of airway inflammation in asthma. Among other activities, IL-10 suppresses production of nitric oxide (NO); consequently, its absence may permit increased NO production, which can affect airway smooth muscle contractility. Therefore, we investigated airway reactivity (AR) in response to methacholine (MCh) in IL-10 knockout (-/-) mice compared with wild-type C57BL/6 (C57) mice, in which airway NO production was measured as exhaled NO (E(NO)), and NO production was altered with administration of either NO synthase (NOS)-specific inhibitors or recombinant murine (rm)IL-10. AR, measured as enhanced pause in vivo, and tracheal ring tension in vitro were lower in IL-10(-/-) mice by 25-50%, which was associated with elevated E(NO) levels (13 vs. 7 ppb). Administration of NOS inhibitors N(G)-nitro-L-arginine methyl ester (8 mg/kg ip) or L-N(6)-(1-iminoethyl)-lysine (3 mg/kg ip) to IL-10(-/-) mice decreased E(NO) by an average of 50%, which was associated with increased AR, to levels similar to C57 mice. E(NO) in IL-10(-/-) mice decreased in a dose-dependent fashion in response to administered rmIL-10, to levels similar to C57 mice (7 ppb), which was associated with a 30% increment in AR. Thus increased NO production in the absence of IL-10, decreased AR, which was reversed with inhibition of NO, either by inhibition of NOS, or with reconstitution of IL-10. These findings suggest that airway NO production can modulate airway smooth muscle contractility, resulting in airway hyporesponsiveness when IL-10 is absent.

Monitoring response to treatment in asthma management: food for thought

Asthma is a chronic inflammatory disorder of the airways that is characterized by episodic symptoms. In this regard, asthma management has classically involved periodic re-assessment by the health-care provider, during which therapy is altered mainly based on clinical and physiological parameters, such as assessment of symptoms, spirometry and peak expiratory flow monitoring. In this context, various markers of airway inflammation (e.g. eosinophils in the induced sputum, nitric oxide in the exhaled air) have been proposed to assess the severity of asthma and to adjust the therapy accordingly. The evaluation of airway hyper-responsiveness with different stimuli has also been suggested as a new tool to monitor asthma. However, the lack of definite relationships between airway inflammation and asthmatic symptoms strongly limit the use of markers of asthma severity in the clinical setting. Therefore, the need of new tools to assess the severity of asthma is raised. The ideal measurement employed to establish the proper asthmatic therapy should be safe, non-invasive, easy to perform, reproducible and accurate, and have the capability to monitor the changes induced by the therapeutic interventions. A careful review of the available techniques, and the evaluation of their sensitivity and specificity in the clinical setting is warranted.

Inhaled fluticasone dipropionate decreases levels of nitric oxide in recurrenty wheezy infants

We examined the effect of inhaled fluticasone diproprionate (FDP) on symptoms, lung function (FEV(0.5)), and exhaled nitric oxide (Fe(NO)) in infants with recurrent wheeze and raised Fe(NO). Thirty-one infants aged 6-19 months (mean, 12.7 months; 12 girls) completed the study. All infants had a history of recurrent wheeze and a parental history of atopy. All children had raised Fe(NO), as determined by an offline tidal breathing technique prior to randomization. Lung function and Fe(NO) were assessed before and after 4 weeks of treatment with FDP or placebo. The parents recorded daily symptoms during the treatment period. Sixteen infants received FDP and 15 the placebo for 4 weeks. At completion of the study, infants treated with FDP had a significant reduction in Fe(NO) (35.0 ppb to 16.5 ppb) compared to those that received placebo (35.2 ppb to 30.2 ppb) (P = 0.05). Small increases in FEV(0.5) were observed in both groups, but these changes were not different between groups (P = 0.8). Symptom scores were not significantly different in either group following the intervention. We showed that a moderate dose of inhaled FDP reduces levels of Fe(NO), a potential marker of airway inflammation, even in the absence of significant changes in lung function and symptoms.

Nitric oxide in health and disease of the respiratory system

During the past decade a plethora of studies have unravelled the multiple roles of nitric oxide (NO) in airway physiology and pathophysiology. In the respiratory tract, NO is produced by a wide variety of cell types and is generated via oxidation of l-arginine that is catalyzed by the enzyme NO synthase (NOS). NOS exists in three distinct isoforms: neuronal NOS (nNOS), inducible NOS (iNOS), and endothelial NOS (eNOS). NO derived from the constitutive isoforms of NOS (nNOS and eNOS) and other NO-adduct molecules (nitrosothiols) have been shown to be modulators of bronchomotor tone. On the other hand, NO derived from iNOS seems to be a proinflammatory mediator with immunomodulatory effects. The concentration of this molecule in exhaled air is abnormal in activated states of different inflammatory airway diseases, and its monitoring is potentially a major advance in the management of, e.g., asthma. Finally, the production of NO under oxidative stress conditions secondarily generates strong oxidizing agents (reactive nitrogen species) that may modulate the development of chronic inflammatory airway diseases and/or amplify the inflammatory response. The fundamental mechanisms driving the altered NO bioactivity under pathological conditions still need to be fully clarified, because their regulation provides a novel target in the prevention and treatment of chronic inflammatory diseases of the airways.

Clinical implications of airway inflammation in mild intermittent asthma

OBJECTIVE

To determine whether inhaled corticosteroids should be prescribed to patients with milder forms of asthma and whether markers of airway inflammation should be considered when making therapy decisions.

DATA SOURCES

A PubMed search was performed of the English-language literature published in the preceding 10 years (January 1, 1993, through December 31, 2003) concerning epidemiology, pathophysiology, therapy, and prognosis of mild intermittent asthma, with asthma, mild, and intermittent as indexing terms.

STUDY SELECTION

All relevant studies including author's expert opinions were selected.

RESULTS

Several studies have addressed the question of a possible benefit of maintenance therapy (ie, inhaled steroids) in patients with mild intermittent asthma. Although a diminishing effect on airway inflammation has been widely demonstrated, even in patients with mild disease, the impact of inhaled steroids on the long-term prognosis is much less clear. For patients with mild disease who are long-term inhaled steroid users, alternative therapy strategies, including low-dose inhaled steroids and leukotriene receptor antagonists, have been advocated.

CONCLUSIONS

Mild intermittent asthma is a disease characterized not only by infrequent symptoms and normal lung function but also by chronic airway inflammation, possibly resulting in irreversible airflow limitation if left unattended. Therefore, maintenance therapy, such as (low-dose) inhaled steroids or leukotriene receptor antagonists, should be considered in patients with mild disease. Future studies should give more insight into the impact of prolonged anti-inflammatory therapy on the long-term prognosis of mild intermittent asthma patients. Whether results from these studies will justify a more aggressive treatment for these patients remains to be answered.

Effect of inhalation aspirin challenge on exhaled nitric oxide in patients with aspirin-inducible asthma

BACKGROUND

A complex relationship between arachidonic acid metabolites and nitric oxide (NO) synthesis has been reported in asthma. The effects of inhaled aspirin on fractional exhaled NO (FENO) in patients with aspirin-tolerant (ATA) and aspirin-inducible (AIA) asthma compared with normal controls have been investigated.

METHODS

The FENO was measured baseline, after saline and lysine-aspirin (L-ASA) bronchial challenge in 10 patients with ATA and in 10 patients with AIA [mean (PD(20)FEV(1) L-ASA): 14.7 +/- 12.7 mg], who had comparable age and baseline FEV(1). Ten healthy subjects served as controls. Sputum eosinophils were counted after saline and after L-ASA challenge in the two groups of asthmatics.

RESULTS

Asthmatic patients had baseline FENO significantly higher than controls (29.7 +/- 6.8 vs 9.8 +/- 2.05 p.p.b. respectively, P < 0.0001). No difference was observed in methacholine PD(20)FEV(1) and baseline FENO between ATA and AIA patients. After L-ASA inhalation, FENO increased significantly only in patients with AIA, reaching the peak value 4 h after bronchoconstriction (from 31.1 +/- 6 to 43 +/- 4.8 p.p.b., P < 0.001), while no change was observed in patients with ATA and in controls. Sputum eosinophils increased significantly after L-ASA inhalation only in patients with AIA (from 8.1 +/- 2.7 to 11.1 +/- 2.8%, P < 0.005) and there was a significant relationship between the increase in sputum eosinophils and the increase in FENO after ASA challenge.

CONCLUSION

Exhaled NO may indicate eosinophilic airway inflammation during ASA exposure in patients with ASA inducible asthma.

Nitric oxide synthase inhibition: therapeutic potential in asthma

Nitric oxide (NO) is synthesized from L-arginine in the human respiratory tract by enzymes of the NO synthase (NOS) family. Levels of NO in exhaled air are increased in asthma, and measurement of exhaled NO has been advocated as a noninvasive tool to monitor the underlying inflammatory process. However, the relation of NO to disease pathophysiology is uncertain, and in particular the fundamental question of whether it should be viewed primarily as beneficial or harmful remains unanswered. Exogenously administered NO has both bronchodilator and bronchoprotective properties. Although it is unlikely that NO is an important regulator of basal airway tone, there is good evidence that endogenous NO release exerts a protective effect against various bronchoconstrictor stimuli. This response is thought to involve one or both of the constitutive NOS isoforms, endothelial NOS (eNOS) and neuronal NOS (nNOS). Therefore, inhibition of these enzymes is unlikely to be therapeutically useful in asthma and indeed may worsen disease control. On the other hand, the high concentrations of NO in asthma, which are believed to reflect upregulation of inducible NOS (iNOS) by proinflammatory cytokines, may produce various deleterious effects. These include increased vascular permeability, damage to the airway epithelium, and promotion of inflammatory cell infiltration. However, the possible effects of iNOS inhibition on allergic inflammation in asthma have not yet been described and studies in animal models have yielded inconsistent findings. Thus, the evidence to suggest that inhibition of iNOS would be a useful therapeutic strategy in asthma is limited at present. More definitive information will require studies combining agents that potently and specifically target individual NOS isoforms with direct measurement of inflammatory markers.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Decrease of interleukin-10-producing T cells in the peripheral blood of severe unstable atopic asthmatics

BACKGROUND

Although IL-10 is known as an immunoregulatory cytokine produced by various cells including T cells, its basic profile in atopic asthma remains uncertain.

OBJECTIVE

The profiles of IL-10 production in circulating CD4+ T cells of atopic asthmatics were investigated with respect to clinical severity.

METHODS

Forty atopic asthmatics were divided into three groups: mild, and severe but stable and severe unstable asthmatics. Eosinophils were counted in the peripheral blood and sputum, and exhaled nitric oxide was assessed. PBMCs were stimulated with or without anti-CD3 and anti-CD28 antibodies and then processed for detecting IL-10-producing CD4+ cells using flow cytometry.

RESULTS

There was no difference in the eosinophil count in blood or sputum and in nitric oxide level among the three groups. IL-10-producing CD4+ cells were mainly detected in a CD45RO+ memory population. The frequency of IL-10-producing cells after stimulation was significantly lower in the severe unstable group compared to the mild group. In addition, the frequency of IL-10-producing cells in the severe unstable group was significantly lower than that in the severe stable group despite the fact that both groups received similar treatments with high-dose inhaled corticosteroids. The IL-10 production of CD4+CD45RO+ cells in response to dexamethasone did not differ among the three groups.

CONCLUSIONS

IL-10-producing CD4+CD45RO+ cells in the peripheral blood are decreased in severe unstable asthmatics, which is not explained by the effect of high-dose inhaled corticosteroid medication.

Single-breath exhaled nitric oxide in preschool children facilitated by a servo-controlled device maintaining constant flow

Fractional concentration of exhaled nitric oxide (FENO), an index of airway inflammation, is optimally measured in adults and school-age children using a single-breath online (SBOL) exhalation at constant flow. However, preschool-aged (<6 years old) children have difficulty exhaling at constant flow, and alternative methods are needed. We employed a servo-controlled variable resistance device (servo device) that controls expiratory flow while allowing the child to vary expiratory pressure. To validate this device, 8 children (aged 6-12 years) performed SBOL exhalations with and without the servo device at expired flow rates between 20-50 ml/sec. We then studied 32 young children aged 24-71 months with the servo device alone at exhalation flows of 30, 40, and 50 ml/sec. Test difficulty (TD) with each method was rated by questioning the older children, or as observed by the physician obtaining the data in the younger children (0 = no difficulty, 1 = mild difficulty, 2 = moderate difficulty, and 3 = unable to perform test). In the older children, SBOL exhalations with and without the servo device demonstrated equivalent flow-dependence of FENO values. Test difficulty was low (0.125-0.625) at all flow rates, with excellent agreement between the two methods (P < 0.001). Twenty-eight young children (<6 years old) were able to complete measurements at all three flow rates evaluated. The 4 subjects who were not able to successfully complete all the measurements were between 2-3 years old (mean 2.75 +/- SD). Exhaled NO (mean +/- SD; ppb) was 8.8 (+/-6.2), 10.6 (+/-6.7), and 13.2 (+/-8.8) ppb at flows of 50 ml/sec, 40 ml/sec, and 30 ml/sec, respectively. Mean values of SD scores were 1.00, 1.14, and 1.43 at flows of 50, 40, and 30 ml/sec, respectively (P = NS). In conclusion, exhaled NO measurement by the SBOL method was facilitated in preschool children by the use of a servo-controlled variable resistance device. This device may allow these measurements to be applied to aid in the diagnosis and treatment of asthma in the preschool child, where spirometry is generally impossible.

Exhaled nitric oxide: relation to sensitization and respiratory symptoms

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Relationship between exhaled carbon monoxide and airway hyperresponsiveness in asthmatic patients

The study objectives were to analyze the changes in exhaled carbon monoxide (COex) induced by histamine provocation challenge in asthmatic patients and to evaluate the relationship between COex and airway sensitivity and reactivity. Levels of COex were measured in 105 nonsmoking mildly asthmatic subjects before and after histamine provocation challenge. Dose-response curves were characterized by their sensitivity (PD20) and reactivity. Dose-response slope (DRS), continuous index of responsiveness (CIR), and bronchial reactivity index (BRI) were determined as reactivity indices. Bronchial challenge was positive for 47 subjects and negative for 58. The COex levels rose significantly after bronchial challenge in the positive response group (4.49 +/- 0.4 vs. 5.74 +/- 0.57 ppm, p = 0.025) and in the negative response group (2.84 +/- 0.25 vs. 4.00 +/- 0.41 ppm, p = 0.000). An inverse relation between basal COex and PD20 was found (r = -0.318, p = 0.030). In all subjects, a proportional direct relationship between COex and DRS (r = 0.214, p = 0.015), CIR (r = 0.401, p = 0.000), and BRI (r = 0.208, p = 0.012) was observed. On stepwise multiple linear regression analysis, COex only significantly correlated with CIR (multiple r2 = 0.174, p = 0.000). In conclusion, exhaled CO determination is a noninvasive inflammatory marker of the respiratory tract, which shows an acceptable association with airway hyperresponsiveness.

Exhaled nitric oxide in children with asthma receiving Xolair (omalizumab), a monoclonal anti-immunoglobulin E antibody

OBJECTIVE

To evaluate the effect of a humanized monoclonal antibody to immunoglobulin E, omalizumab (Xolair, Novartis Pharmaceuticals, East Hanover, NJ; Genentech Inc, South San Francisco, CA), on airway inflammation in asthma, as indicated by the fractional concentration of exhaled nitric oxide (FE(NO)), a noninvasive marker of airway inflammation. Xolair was approved recently by the US Food and Drug Administration for moderate-to-severe allergic asthma in adolescents and adults.

STUDY DESIGN

As an addendum at 2 sites to a randomized, multicenter double-blind, placebo-controlled trial, FE(NO) was assessed in children with allergic asthma over 1 year. There were 3 consecutive study periods: 1) stable dosing of inhaled beclomethasone dipropionate (BDP) when the dose was optimized (period of 16 weeks); 2) inhaled steroid-reduction phase (period of 12 weeks), during which BDP was tapered if subjects remained stable; and 3) open-label extension phase, during which subjects receiving placebo were switched to active omalizumab (period of 24 weeks). The primary outcome was area under the FE(NO) versus time curve (AUC) for adjusted FE(NO), defined as the ratio of FE(NO) at each time point compared with the value at baseline.

RESULTS

Twenty-nine subjects participated and were randomized to omalizumab (n = 18) and placebo (n = 11) treatment groups in a 2:1 ratio dictated by the main study. There was a significant difference for age, resulting in a difference in absolute forced expiratory volume in 1 second but no difference in asthma severity based on the forced expiratory volume in 1 second percentage predicted. Baseline BDP dose was comparable between groups, as were baseline values of mean FE(NO) (active: 38.6 +/- 25.6 ppb; placebo: 52.7 +/- 52.9 ppb). The degree of BDP dose reduction during the steroid-reduction and open-label phases was equivalent between the omalizumab and placebo-treated groups; subjects in the omalizumab- and placebo-treated groups had reduced their BDP dose by an average of 51% and 60%, respectively, at the end of the steroid-reduction phase and by 68% and 94%, respectively, by the end of the open-label period. In the active and placebo groups, 44% and 27% and 75% and 73% of subjects had stopped use of inhaled corticosteroids at the end of the steroid-reduction and open-label phases, respectively. There was no significant difference between the active and placebo groups during the steroid-stable phase for AUC of adjusted nitric oxide (1.31 +/- 1.511 vs 1.45 +/- 0.736). However, during the steroid-reduction phase, the variability of adjusted FE(NO) in the placebo-treated group was greater than that of the omalizumab-treated group at most visits, with a significant difference between groups for AUC of adjusted nitric oxide (0.88 +/- 0.69 vs 1.65 +/- 1.06). FE(NO) fell from 82.1 +/- 55.6 ppm at the end of the steroid-reduction phase to 33.3 +/- 21.6 ppb at the end of the open-label period in the placebo group who were placed on active omalizumab. This decrease occurred while the mean dose of BDP remained very low. Analysis of FE(NO) over 52 weeks of omalizumab treatment in the active group demonstrated that there was a significant reduction from baseline to the end of the open-label period (41.9 +/- 29.0 to 18.0 +/- 21.8 ppb) despite a high degree of steroid reduction.

CONCLUSION

In this preliminary study based on FE(NO), a noninvasive marker of airway inflammation, treatment with omalizumab may inhibit airway inflammation during steroid reduction in children with allergic asthma. The degree of inhibition of FE(NO) was similar to that seen for inhaled corticosteroids alone, suggesting an antiinflammatory action for this novel therapeutic agent in asthma. This is in keeping with recent evidence that omalizumab inhibits eosinophilic inflammation in induced sputum and endobronchial tissue.

Asthma severity and asthma control: symptoms, pulmonary function, and inflammatory markers

PURPOSE OF REVIEW

Asthma severity and asthma control are distinct yet related concepts. Asthma severity describes the underlying disease in the absence of therapy and is ideally defined without concurrent treatment confounding its assessment. Asthma control describes the clinical status of disease in the face of intervention. However, the individual parameters by which we define asthma severity and asthma control overlap significantly. A MEDLINE search between July 1, 2002, and June 30, 2003, was performed using keywords related to concepts of asthma severity of illness and asthma control. From these articles the author selected the articles most relevant for discussion.

RECENT FINDINGS

Asthma is a complex syndrome. Although correlations exist between the various parameters used in clinical assessment, no single parameter can accurately classify all individuals. Assessment of multiple parameters including physiologic measures, symptoms, and activity limitation are necessary to categorize asthma clinical status accurately. In addition, the role biomarkers play in the assessment of disease status is an area of increasing interest. Several validated multidimensional measures for assessing asthma control are now available. Each of these measures includes the parameters of symptoms, activity limitation, and rescue medication use, yet they vary on inclusion of other important components such as physiologic measures and biomarkers.

SUMMARY

Asthma is a complex syndrome. Currently available instruments demonstrate an improved understanding of the multidimensional approach required to assess asthma control accurately. However, debate continues on the optimal parameters to be included and the role biomarkers play in the clinical assessment of asthma.

Heterogeneity of FeNO response to inhaled steroid in asthmatic children

BACKGROUND

Nitric oxide in exhaled air is regarded as an inflammation marker, and may be used to monitor the anti-inflammatory control from inhaled corticosteroids (ICSs). However, this response to ICSs exhibits a heterogeneous pattern.

OBJECTIVE

The study aimed to describe the independent variables associated with the heterogeneity in the response of exhaled nitric oxide to ICSs.

METHODS

Exhaled nitric oxide (FeNO), lung function, bronchial hyper-responsiveness (BHR), specific IgE to common inhalant allergens, blood eosinophils, other atopic manifestations and variants in nitric oxide synthethase 1 (NOS1) gene were studied in a double-blind, placebo-controlled crossover comparison of budesonide (BUD) Turbohaler 1600 mcg daily vs. placebo in asthmatic schoolchildren.

RESULTS

Forty children were included in the study from a screening of 184 asthmatic children with moderately persistent asthma, well controlled on regular BUD 400 mcg daily: 20 children with normal FeNO and 20 with raised FeNO. FeNO, BHR and forced expiratory volume in 1 s improved significantly after BUD 1600 mcg (BUD1600). However, FeNO after ICS treatment exhibited a Gaussian distribution and FeNO was significantly raised in 15 children. Allergy and BHR, but none of the other independent variables under study were significantly related to FeNO after BUD1600.

CONCLUSION

Exhaled nitric oxide exhibited a heterogeneous response to ICS in asthmatic schoolchildren. Allergy and BHR were driving FeNO level independently of high-dose steroid treatment. This should be considered when using FeNO for steroid dose titration and monitoring of ICS anti-inflammatory control in asthmatic children.

Correlation of nitrites in breath condensates and lung function in asthmatic children

We aimed to evaluate the value of exhaled breath condensates in monitoring airway inflammation in childhood asthma before and after high altitude climate therapy. Forty-eight asthmatic children on regular anti-asthma treatment with a normal FEV1 and positive skin prick test for house dust mites were recruited. All children had been referred to an alpine clinic for high altitude climate therapy, because of persistent asthmatic symptoms despite use of daily anti-inflammatory treatment. Subjects were assessed on their arrival and before departure from the alpine clinic. Spirometry, bronchial provocation tests and measurements of nitrites in breath condensates were performed. Median levels of nitrites were significantly higher before than after high altitude climate therapy (1.27 vs. 0.93 microm; p = 0.008). In addition, MEF50 improved significantly (p < 0.0005). There was a significant correlation between nitrites in breath condensates and MEF50 (r = -0.63, p < 0.0001), symptoms (r = 0.47, p = 0.0007) and airway hyper-reactivity (AHR) (r = -0.41, p = 0.004). In summary, we found a reduction in nitrites in breath condensates after a high altitude climate therapy. Significant correlations were found between nitrites and MEF50, AHR and symptoms. We conclude that the measurement of nitrites may be feasible to objectively assess airway inflammation in asthmatic children in order to detect ongoing inflammation in children with normal FEV1 but persistent symptoms.

Measuring exhaled nitric oxide in infants during tidal breathing: methodological issues

Exhaled nitric oxide (FENO) may provide a tool for identifying infants at risk of developing allergic disease in childhood. In infants there is no standardized collection technique; however, the easiest method is to measure FENO during tidal breathing. In this study we investigated various methodological issues for tidal breathing (TB) FENO in infants. These included the effect of ambient NO, oral or nasal breathing, sedation, and tidal expiratory flow. Furthermore, we compared TB FENO in 88 infants with and without wheeze. Ambient NO greater than 5 ppb significantly affected FENO. There was no significant difference between NO levels measured during either oral or nasal breathing; however, there was a significant difference between levels collected from infants before and after sedation (P < 0.001). Tidal breathing FENO decreased with increasing tidal flows (P < 0.001) and increased with age (P = 0.002). There was no significant difference in mixed expired NO between healthy and wheezy children, but children with doctor-diagnosed eczema had significantly raised levels (P = 0.014). There seem to be important methodological limitations for measuring FENO in infants during TB.

Exhaled nitric oxide reflects asthma severity and asthma control

INTRODUCTION

This study was undertaken to a) evaluate whether exhaled nitric oxide (fraction of exhaled nitric oxide [FENO]) levels are reflective of asthma severity in concordance with the National Asthma Education and Prevention Program categorization and b) determine the usefulness of FENO using the single-breath exhalation technique for monitoring asthma control and compliance with steroid treatment.

METHODS

Thirty patients with asthma (7-17 yrs old; 14 males and 16 females) that was mild (n=8), moderate (n=17), or severe (n=5) were included in the study. Fifteen patients were seen on more than one occasion for a total of 53 visits. Information obtained at each visit included asthma symptoms, beta-agonists and corticosteroids use, compliance to steroids, and forced expiratory volume in 1 sec (FEV1) and FENO measurements. Asthma control was judged by a pulmonologist based on overall evaluation of symptoms, FEV1 measurements, and the frequency of beta-agonists use at each visit.

RESULTS

The mean +/- SD FENO was significantly different in the mild, moderate, and severe asthma categories (30 +/- 12, 65 +/- 48, 104 +/- 68, respectively; F(2,52)=6.02 p=.005). FENO was significantly correlated with asthma severity (r=.44, p=.001), compliance (r=-.75, p=.001), and control (r=-.51, p=.001). There were no statistically significant differences between asthma severity and compliance or FEV1.

DISCUSSION

Our data suggest that a) FENO may be a practical tool to evaluate asthma severity and asthma control over time and b) FENO may be used as a marker of compliance with steroids even when FEV1 has not decreased significantly.

Host defense function of the airway epithelium in health and disease: clinical background

Respiratory infection is extremely common and a major cause of morbidity and mortality worldwide. The airway epithelium has an important role in host defense against infection and this is illustrated in this review by considering infection by respiratory viruses. In patients with asthma or chronic obstructive pulmonary disease, respiratory viruses are a common trigger of exacerbations. Rhinoviruses (RV) are the most common virus type detected. Knowledge of the immunopathogenesis of such RV-induced exacerbations remains limited, but information is available from in vitro and from in vivo studies, especially of experimental infection in human volunteers. RV infects and replicates within epithelial cells (EC) of the lower respiratory tract. EC are an important component of the innate-immune response to RV infection. The interaction between virus and the intracellular signaling pathways of the host cell results in activation of potentially antiviral mechanisms, including type 1 interferons and nitric oxide, and in the production of cytokines and chemokines [interleukin (IL)-1 beta, IL-6, IL-8, IL-11, IL-16, tumor necrosis factor alpha, granulocyte macrophage-colony stimulating factor, growth-regulated oncogene-alpha, epithelial neutrophil-activating protein-78, regulated on activation, normal T expressed and secreted, eotaxin 1/2, macrophage-inflammatory protein-1 alpha], which influence the subsequent induced innate- and specific-immune response. Although this is beneficial in facilitating clearance of virus from the respiratory tract, the generation of proinflammatory mediators and the recruitment of inflammatory cells result in a degree of immunopathology and may amplify pre-existing airway inflammation. Further research will be necessary to determine whether modification of EC responses to respiratory virus infection will be of therapeutic benefit.

Exhaled nitric oxide continues to reflect airway hyperresponsiveness and disease activity in inhaled corticosteroid-treated adult asthmatic patients

OBJECTIVE

Exhaled nitric oxide (eNO) has been used as a surrogate of airway inflammation in mild asthma. However, whether eNO levels reflect disease activity in symptomatic asthmatics receiving moderate doses of inhaled corticosteroid (ICS) is more uncertain.

METHODOLOGY

To examine the relationship between eNO levels, sputum and blood eosinophils (SpE and PbE), PD(20) methacholine as a marker of airway hyperresponsiveness (AHR) and clinical status in 28 ICS-treated asthmatic subjects with persistent asthma compared to that in 25 symptomatic asthmatics managed with beta2-agonists alone.

RESULTS

As expected, eNO levels were normalized in ICS-treated subjects and significantly elevated in the beta2-agonist only group (P < 0.001). SpE, PbE and PD20M did not differ between asthmatic groups but FEV1 was significantly worse in ICS-treated subjects (P < 0.01). Exhaled NO levels correlated with PbE within both asthmatic groups (P < 0.005), but with SpE only in ICS-untreated subjects (r(s) = 0.6, P < 0.05). In contrast, PD20M was negatively correlated with eNO and PbE in ICS-treated subjects only (r(s) = - 0.4, r(s) = - 0.4, respectively, P < 0.05). SpE and PbE were strongly correlated in both asthmatic groups (r(s) = 0.8, r(s) = 0.7, respectively, P < 0.005). Exhaled NO levels, SpE and PbE were all positively associated with increased nocturnal awakenings ( P < 0.05) in ICS-treated subjects, but not in ICS-untreated subjects.

CONCLUSIONS

In ICS-treated asthma, eNO reflects clinical activity, PbE and AHR but not eosinophilic airway inflammation. Exhaled NO levels are quantitatively and relationally different in asthmatic subjects treated with ICS and continue to have potential for use as a surrogate of asthma pathophysiology in this group.

Airway responsiveness to adenosine 5'-monophosphate and exhaled nitric oxide measurements: predictive value as markers for reducing the dose of inhaled corticosteroids in asthmatic subjects

OBJECTIVES

To investigate the utility of the determination of airway responsiveness to inhaled adenosine 5'-monophosphate (AMP) and exhaled nitric oxide (ENO) levels as markers for safely reducing the dose of inhaled corticosteroids (ICS) in patients with asthma well controlled with a moderately high ICS dose.

METHODS

A total of 37 patients with asthma well controlled for at least 3 months by treatment with a moderately high ICS dose (beclomethasone dipropionate, 500 to 1,000 microg or equivalent daily) were included in the study. Patients were treated for a 2-week run-in (baseline) period with their usual dose of ICS. For the next 12 weeks, patients were treated with ICS at half the previous dose, maintaining the same inhalation device. At the end of the baseline period and after 2 weeks, 8 weeks, and 12 weeks of treatment with a reduced dose of ICS, measurements were made in the following order: ENO, spirometry, and AMP challenge. Furthermore, patients completed a diary twice daily recording peak expiratory flow, daytime and nighttime symptoms, and use of rescue albuterol.

RESULTS

Ten patients had an asthma exacerbation. Using a Kaplan-Meier survival analysis, the significant predictors of a failure of ICS reduction were having both bronchoconstriction in response to AMP and ENO levels > or = 15 parts per billion (ppb) at baseline (p = 0.006), as well as having both bronchoconstriction in response to AMP and ENO levels > or = 20 ppb at baseline (p = 0.033). Having a decrease in the provocative concentration of AMP causing a 20% fall in FEV(1) of at least one doubling concentration 2 weeks after the dose of ICS was halved was a borderline significant predictor for failure of ICS reduction (p = 0.062).

CONCLUSION

These observations suggest that in asthmatic patients well controlled with ICS, the determination of AMP responsiveness and ENO levels may be useful to identifying those subjects whose condition will or will not deteriorate when the dose of ICS is reduced.

Diagnosing asthma: comparisons between exhaled nitric oxide measurements and conventional tests

International guidelines recommend a range of clinical tests to confirm the diagnosis of asthma. These focus largely on identifying variable airflow obstruction and responses to bronchodilator or corticosteroid. More recently, exhaled nitric oxide (FE(NO)) measurements and induced sputum analysis to assess airway inflammation have been highlighted. However, to date, no systematic comparisons to confirm the diagnostic utility of each of these methods have been performed. To do so, we investigated 47 consecutive patients with symptoms suggestive of asthma, using a comprehensive fixed-sequence series of diagnostic tests. Sensitivities and specificities were obtained for peak flow measurements, spirometry, and changes in these parameters after a trial of steroid. Comparisons were made against FE(NO) and sputum cell counts. Sensitivities for each of the conventional tests (0-47%) were lower than for FE(NO) (88%) and sputum eosinophils (86%). Overall, the diagnostic accuracy when using FE(NO) and sputum eosinophils was significantly greater. Results for conventional tests were not improved, using a trial of steroid. We conclude that FE(NO) measurements and induced sputum analysis are superior to conventional approaches, with exhaled nitric oxide being most advantageous because the test is quick and easy to perform.

Exhaled nitric oxide as a simple assessment of airway hyperresponsiveness in bronchial asthma and chronic cough patients

Exhaled nitric oxide (NO) has been suggested to be a marker of airway inflammation. The aim of this study was to evaluate the role of exhaled NO in bronchial asthma and chronic cough patients to predict bronchial hyperresponsiveness (BHR). We measured the exhaled NO concentration using the chemiluminescence method in 52 asthma patients (group I consisting of 24 without prior inhaled corticosteroid (ICS) use, and group II consisting of 28 previously on ICS and 16 chronic cough patients in group III). In addition to regular examinations, spirometry and methacholine inhalation tests using the Astograph were done. In group I, a significantly negative correlation was observed regarding the exhaled NO concentration with FEV1/FVC%, V50, and BHR that was assessed as Dmin and PD35-Grs, and a positive correlation with peripheral blood eosinophils. In group III, a significantly negative correlation was seen regarding the exhaled NO concentration with BHR. We thus concluded that measuring exhaled NO concentration appears to be a useful noninvasive method to predict the BHR, airway obstruction, and inflammation in asthma and chronic cough patients.

Effect of bradykinin on allergen induced increase in exhaled nitric oxide in asthma

BACKGROUND

Exposure of patients with atopic asthma to allergens produces a long term increase in exhaled nitric oxide (FENO), probably reflecting inducible NO synthase (NOS) expression. In contrast, bradykinin (BK) rapidly reduces FENO. It is unknown whether BK suppresses increased FENO production after allergen exposure in asthma, and whether it modulates FENO via NOS inhibition.

METHODS

Levels of FENO in response to aerosolised BK were studied before (day 3) and 48 hours after (day 10) randomised diluent (diluent/placebo/BK (Dil/P/BK)), allergen (allergen/placebo/BK (All/P/BK), and allergen/L-NMMA/BK (All/L/BK)) challenges (day 8) in 10 atopic, steroid naïve, mild asthmatic patients with dual responses to inhaled house dust mite extract. To determine whether BK modulates FENO via NOS inhibition, subjects performed pre- and post-allergen BK challenges after pretreatment with the NOS inhibitor L-NMMA in the All/L/BK period.

RESULTS

Allergen induced a fall in FENO during the early asthmatic reaction (EAR) expressed as AUC(0-1) (ANOVA, p=0.04), which was followed by a rise in FENO during the late asthmatic reaction (LAR) expressed as AUC(1-48) (ANOVA, p=0.008). In the Dil/P/BK period, FENO levels after BK on pre- and post-diluent days were lower than FENO levels after placebo (difference 23.5 ppb (95% CI 6.2 to 40.9) and 22.5 ppb (95% CI 7.3 to 37.7), respectively; p<0.05). Despite the long lasting increase in FENO following allergen challenge in the LAR, BK suppressed FENO levels at 48 hours after allergen challenge in the All/P/BK period, lowering the increased FENO (difference from placebo 54.3 ppb (95% CI 23.8 to 84.8); p=0.003) to the baseline level on the pre-allergen day (p=0.51). FENO levels were lower after L-NMMA than after placebo on pre-allergen (difference 10.85 ppb (95% CI 1.3 to 20.4); p=0.03) and post-allergen (difference 36.2 ppb (95% CI 5.5 to 66.9); p=0.03) days in the All/L/BK and All/P/BK periods, respectively. L-NMMA did not significantly potentiate the pre- and post-allergen reduction in BK induced FENO.

CONCLUSIONS

Bradykinin suppresses the allergen induced increase in exhaled NO in asthma; this is not potentiated by L-NMMA. Bradykinin and L-NMMA may follow a common pathway in reducing increased NO production before and after experimental allergen exposure. Reinforcement of this endogenous protective mechanism should be considered as a therapeutic target in asthma.

Nitric oxide airway diffusing capacity and mucosal concentration in asthmatic schoolchildren

Asthmatic patients show increased concentrations of nitric oxide (NO) in exhaled air (Feno). The diffusing capacity of NO in the airways (Dawno), the NO concentrations in the alveoli and the airway wall, and the maximal airway NO diffusion rate have previously been estimated noninvasively by measuring Feno at different exhalation flow rates in adults. We investigated these variables in 15 asthmatic schoolchildren (8-18 y) and 15 age-matched control subjects, with focus on their relation to exhaled NO at the recommended exhalation flow rate of 0.05 L/s (Feno0.05), age, and volume of the respiratory anatomic dead space. NO was measured on-line by chemiluminescence according to the European Respiratory Society's guidelines, and the NO plateau values at three different exhalation flow rates (11, 99, and 382 mL/s) were incorporated in a two-compartment model for NO diffusion. The NO concentration in the airway wall (p < 0.001), Dawno (p < 0.01), and the maximal airway NO diffusion rate (p < 0.001) were all higher in the asthmatic children than in control children. In contrast, there was no difference in the NO concentration in the alveoli (p = 0.13) between the groups. A positive correlation was seen between the volume of the respiratory anatomic dead space and Feno0.05 (r = 0.68, p < 0.01), the maximal airway NO diffusion rate (r = 0.71, p < 0.01), and Dawno (r = 0.56, p < 0.01) in control children, but not in asthmatic children. Feno0.05 correlated better with Dawno in asthmatic children (r = 0.65, p < 0.01) and with the NO concentration in the airway wall in control subjects (r < 0.77, p < 0.001) than vice versa. We conclude that Feno0.05 increases with increasing volume of the respiratory anatomic dead space in healthy children, suggesting that normal values for Feno0.05 should be related to age or body weight in this age group. Furthermore, the elevated Feno0.05 seen in asthmatic children is related to an increase in both Dawno and NO concentration in the airway wall. Because Dawno correlates with the volume of the respiratory anatomic dead space in control subjects and Feno0.05 correlates with Dawno in asthmatic children, we suggest that Dawno partly reflects the total NO-producing surface area and that a larger part of the bronchial tree produces NO in asthmatic children than in control children.

Exhaled nitric oxide as a predictor of exercise-induced bronchoconstriction

INTRODUCTION

Exercise-induced bronchoconstriction (EIB) is present in 40 to 90% of patients with asthma. Exhaled NO (eNO) levels have been correlated with bronchial hyperresponsiveness to methacholine, and have correlated with the degree of decrease in FEV(1) with exercise. The purpose of our study was to examine whether eNO measurements prior to or after exercise could be used as a surrogate marker of exertional bronchoconstriction in a population referred specifically for the evaluation of EIB.

METHODS

We studied 50 consecutive subjects without a history of asthma who were referred for the clinical evaluation of EIB. eNO levels were measured prior to exercise challenge and every 5 min for a total of 30 min after exercise. Forced expiratory flows were measured prior to and serially after exercise challenge.

RESULTS

Seven subjects had a decrease in FEV(1) of > or = 15% with exercise. The mean eNO level prior to exercise was 41 parts per billion (ppb) [median +/- SD, 23 +/- 42.2 ppb] in the EIB group and 25.6 ppb (median, 19.95 +/- 18.47 ppb) in the group without EIB. A receiver operator characteristic curve yielded a value of 0.636. When using an eNO level of < 12 ppb, the sensitivity, specificity, negative predictive value, and positive predictive value for EIB were 1.0, 0.31, 0.19, and 1.0, respectively; therefore, no one with a baseline eNO of < 12 ppb demonstrated EIB.

CONCLUSIONS

No subjects with very low pre-exercise eNO levels (< 12 ppb) demonstrated bronchial hyperresponsiveness to exercise. eNO measurement may obviate the need for bronchoprovocation testing in patients who complain of exertional dyspnea.

Assessment of exhaled nitric oxide kinetics in healthy infants

Exhaled nitric oxide (Fe(NO)) measurements provide a noninvasive approach to the evaluation of airway inflammation. Flow-independent NO exchange parameters [airway NO transfer factor (D(NO)) and airway wall NO concentration (Cw(NO))] can be estimated from Fe(NO) measurements at low flows and may elucidate mechanisms of disturbances in NO exchange. We measured Fe(NO) in sedated infants by using an adaptation of a raised lung volume rapid thoracic compression technique that creates forced expiration through a mass-flow controller that lasts 5-10 s, at a constant preset flow. We measured Fe(NO) at expired flows of 50, 25, and 15 ml/s in five healthy infants (7-31 mo). Median Fe(NO) increased [24, 40, and 60 parts per billion (ppb)] with decreasing expiratory flows (50, 25, and 15 ml/s). Group median (range) for D(NO) and Cw(NO) were 12.7 (3.2-37) x 10(-3) nl. s(-1). ppb(-1) and 108.9 (49-385) ppb, respectively, similar to values reported in healthy adults. Exhaled NO is flow dependent; flow-independent parameters of exhaled NO kinetics can be assessed in infants and are similar to values described in adults.

Sustained reduction in bronchial hyperresponsiveness with inhaled fluticasone propionate within three days in mild asthma: time course after onset and cessation of treatment

BACKGROUND

Bronchial hyperresponsiveness (BHR) is characteristic of asthmatic airways, is induced by airway inflammation, and is reduced by inhaled corticosteroids (ICS). The time course for the onset and cessation of the effect of ICS on BHR is unclear. The effect of inhaled fluticasone propionate (FP) on BHR in patients with mild persistent asthma was assessed using time intervals of hours, days and weeks.

METHODS

Twenty six asthmatic patients aged 21-59 years were selected for this randomised, double blind, parallel group study. The effect of 250 micro g inhaled FP (MDI) administered twice daily was compared with that of placebo on BHR assessed using a dosimetric histamine challenge method. The dose of histamine inducing a decrease in forced expiratory volume in 1 second (FEV(1)) by 15% (PD(15)FEV(1)) was measured before and 6, 12, 24 and 72 hours, and 2, 4 and 6 weeks after starting treatment, and 48 hours, 1 week and 2 weeks after cessation of treatment. Doubling doses of changes in PD(15)FEV(1) were calculated and area under the curve (AUC) statistics were used to summarise the information from individual response curves.

RESULTS

The increase in PD(15)FEV(1) from baseline was greater in the FP group than in the placebo group; the difference achieved significance within 72 hours and remained significant until the end of treatment. In the FP group PD(15)FEV(1) was 1.85-2.07 doubling doses above baseline between 72 hours and 6 weeks after starting treatment. BHR increased significantly within 2 weeks after cessation of FP treatment.

CONCLUSIONS

A sustained reduction in BHR to histamine in patients with mild asthma was achieved within 3 days of starting treatment with FP at a daily dose of 500 micro g. The effect tapered within 2 weeks of cessation of treatment.

Relations between exhaled nitric oxide and measures of disease activity among children with mild-to-moderate asthma

OBJECTIVE

Exhaled nitric oxide (FE(NO)) was evaluated in children with asthma after 4 to 6 years of treatment with budesonide, nedocromil, or albuterol as needed.

STUDY DESIGN

FE(NO), spirometry, total eosinophil count, and serum eosinophil cationic protein levels were obtained from 118 children at the Denver site of the Childhood Asthma Management Program upon completion of treatment and after a 2- to 4-month washout.

RESULTS

Budesonide-treated patients had significantly lower median (1st, 3rd quartile) FE(NO) (21.5 [13.2, 84.4] vs 62.5 [26.2, 115.0] ppb, P <.01) and eosinophil cationic protein levels (17.4 [10.1, 24.3] vs 24.0 [15.4, 33.9] mg/dL, P =.05) compared with placebo, whereas no differences were noted between nedocromil and placebo groups. After washout, FE(NO) levels were similar between the three treatments. FE(NO) levels significantly correlated with degree of bronchial hyperresponsiveness, bronchodilator reversibility, allergen skin prick tests, serum IgE, and total eosinophil count. FE(NO) levels were also higher in patients with nocturnal symptoms and in patients requiring beta-agonist use at least once weekly.

CONCLUSIONS

Budesonide therapy was more effective than nedocromil in reducing FE(NO). Unfortunately, the effects of long-term budesonide were not sustained after its discontinuation. FE(NO) may be a complementary tool to current practice guidelines in assessing asthma control and medication response.

Effectiveness of pharmacotherapy in asthmatic preschool children

The term "effectiveness" relates to the question of whether or not a certain treatment works in practice. Usually, such a treatment was first evaluated under tightly controlled conditions in selected patient populations, and the potential benefits were shown. There is, however, a great difference between the efficacy of a given treatment, indicating its optimal therapeutic action in controlled trials, and its effectiveness when applied to a less well-defined population of patients in daily practice. This is especially relevant for asthma in young children, where many factors are responsible for the difference. Among these are, first of all, the heterogeneity of the wheezing phenotype. Other factors include the compliance with prescribed treatments, as determined by the attitude of doctors and parents towards such treatment, the ease of administration and the perceived effects and side effects. Also, the performance of different inhaler devices may be insufficient for a good, reliable dose deposition in young children in daily life. As a result, the current treatment guidelines for preschool children with recurrent wheeze are probably too optimistic in assuming that inhaled treatment is most effective and feasible at all ages. We propose careful re-evaluation of such recommendations in a first-line setting resembling daily life as closely as possible, and consideration of oral treatments as well. Also, we need methods to separate the different phenotypes within the group of recurrently wheezing preschool children to optimize targeting of asthma treatment to those who have ongoing airway inflammation.

Prospective evaluation of the validity of exhaled nitric oxide for the diagnosis of asthma

STUDY OBJECTIVE

Exhaled nitric oxide (NO) levels are significantly elevated in patients with inflammatory airways disorders such as asthma, and the measurement of exhaled NO has been proposed as a noninvasive marker of airways inflammation. The aim of this study was to assess the accuracy of exhaled NO levels for the diagnosis of asthma.

METHODS

Two hundred forty consecutive, nonsmoking, steroid-naive patients, who were referred to our outpatient clinic with symptoms suggestive of obstructive airways disease, were investigated. Asthma was diagnosed in 160 patients on the basis of the presence of significant airways reversibility (DeltaFEV(1) > 12% predicted) and/or airways hyperresponsiveness (provocative concentration of histamine causing a 20% fall in FEV(1) < or = 8 mg/mL). Prior to lung function measurements, exhaled NO was measured during a single-breath exhalation, according to European Respiratory Society and American Thoracic Society guidelines.

RESULTS

The measurement of exhaled NO in our study population showed, at a cutoff level of 16 parts per billion, a specificity for the diagnosis of asthma of 90% and a positive predictive value of > 90%.

CONCLUSIONS

These findings suggest that the simple and absolutely noninvasive measurement of exhaled NO can be used as an additional diagnostic tool for the screening of patients with a suspected diagnosis of asthma.

Relationship between exhaled NO, respiratory symptoms, lung function, bronchial hyperresponsiveness, and blood eosinophilia in school children

BACKGROUND

Exhaled nitric oxide (eNO) may serve as a non-invasive marker of airway inflammation but its relationship with other commonly used measures has not been evaluated.

METHODS

Levels of eNO in a sample of 450 children aged 7-12 years out of a total sample of 2504 school children living in different urban areas near motorways were determined. The aim of this cross-sectional study was to explore the relationship between eNO, impairment of lung function (PEF, FVC, FEV(1) and MMEF), bronchial hyperresponsiveness (BHR), and blood eosinophilia in children with and without atopy as assessed by skin prick testing.

RESULTS

Regression analysis showed that wheezing and nasal discharge and conjunctivitis that had occurred during the previous 12 months were positively associated with eNO levels in atopic children (relative increase of 1.48 and 1.41, respectively; p<0.05) but not in non-atopic children. Similarly, BHR and the number of blood eosinophils per ml were positively associated with eNO levels in atopic children (relative increase of 1.55 and 2.29, respectively; p<0.05) but not in non-atopic children. The lung function indices PEF, FVC, FEV(1) and MMEF were not associated with eNO levels.

CONCLUSIONS

In addition to conventional lung function tests and symptom questionnaires, eNO is a suitable measure of airway inflammation and its application may reinforce the power of epidemiological surveys on respiratory health.

Nitric oxide in respiratory diseases

The formation and modulation of nitric oxide (NO) in the lungs is reviewed. Its beneficial and deleterious roles in airways diseases, including asthma, chronic obstructive pulmonary disease, and cystic fibrosis, and in animal models is discussed. The pharmacological effects of agents that modulate NO production or act as NO donors are described. The clinical pharmacology of these agents is described and the therapeutic potential for their use in airways disease is considered.

The relationship between exhaled nitric oxide and allergic sensitization in a random sample of school children

BACKGROUND

Exhaled nitric oxide (NO) has been proposed as novel a non-invasive marker of airway inflammation.

OBJECTIVE

The level of exhaled NO was determined in a random sample of school children (7-12 years old) with the aim of investigating the relationship between exhaled NO and sensitization to common allergens.

RESULTS

In the 450 children tested by skin prick tests (SPT), the prevalence of sensitization was 29.5% (overall), 21.9% (sensitization to indoor allergens), and 15.0% (sensitization to outdoor allergens). Regression analysis showed that levels of exhaled nitric oxide were closely associated with various measures of sensitization to aeroallergens. Sensitization to indoor allergens was associated with higher levels of exhaled NO (eNO) than sensitization to outdoor allergens when assessed by IgE but not when assessed by SPT. Children with reported wheeze in the past 12 months had much stronger associations between sensitization and eNO than children without wheeze.

CONCLUSION

We conclude that allergic sensitization is strongly associated with increased levels of exhaled NO, especially in children with wheeze.

Exhaled nitric oxide in asthma: from bench to bedside

With more than 600 publications, exhaled nitric oxide (NO) has been extensively investigated as a noninvasive marker of airway inflammation in a research setting. This clinical rostrum presents a synopsis of the latest research about this novel marker in asthma and suggests how it might move from bench to bedside. Specifically, we review the evidence citing the applicability of exhaled NO in diagnosing asthma, monitoring the response to therapy, evaluating current symptom control, and predicting exacerbations of asthma. These studies support a role for exhaled NO in the evaluation and treatment of asthma in the clinical arena.

Multiple roles of nitric oxide in the airways

Nitric oxide is endogenously released in the airways by nitric oxide synthase. Functionally, two isoforms of this enzyme exist: constitutive and inducible. The former seems to protect airways from excessive bronchoconstriction while the latter has a modulatory role in inflammatory disorders of the airways such as asthma. This review explores the physiological and pathophysiological role of endogenous nitric oxide in the airways, and the clinical aspects of monitoring nitric oxide in exhaled air of patients with respiratory disease.

Relationship of skin-prick reactivity to aeroallergens and hyperresponsiveness to challenges with methacholine and adenosine monophosphate

BACKGROUND

Clarification of the relationship between atopy and bronchial hyperresponsiveness (BHR), both key features of asthma, is critical to our understanding of the disease. We therefore investigated the putative relationship between skin-prick reactivity to aeroallergens and BHR to direct and indirect stimuli.

METHODS

We performed a retrospective analysis of data from 332 patients presenting with a diagnosis of asthma. Patients were characterized by skin prick tests (SPT), spirometry and bronchial challenge with methacholine and adenosine monophosphate (AMP).

RESULTS

For patients who had BHR to methacholine but not AMP, the presence of atopy was associated with a lower PD20 (the provocative dose of methacholine producing a fall in FEV1 of 20%), amounting to a geometric mean (95% confidence interval (CI)) of 2.3-fold (1.4-4.0) difference. Furthermore, the number of skin-prick positive (SPP) responses was related to methacholine reactivity: 0-1 SPP, PD20 = 69.9 micro g; 2-4 SPP, PD20 = 47.8 micro g; 5-8 SPP, PD20 = 35.6 micro g. There was a 2.0- fold (1.1-3.6) difference between the groups with a low (0-1 SPP) and high (5-8 SPP) degree of skin-prick reactivity. A similar pattern was seen when data were analyzed including only perennial allergens. Spirometry was unrelated to the degree of skin-prick reactivity.

DISCUSSION

These results suggest that skin-prick reactivity to aeroallergens is associated with BHR to methacholine.

Effects of cysteinyl leukotrienes and leukotriene receptor antagonists on markers of inflammation

The understanding that asthma pathophysiology includes an inflammatory component has spurred the more aggressive use of anti-inflammatory therapies and created a need for effective tools to measure inflammation. Biomarkers of airway inflammation proposed are obtained by methods that are direct but highly invasive (bronchial biopsy, bronchoalveolar lavage), moderately direct, and less invasive (indirect sputum, exhaled air, breath condensate) or indirect and least invasive (blood, urine). Several studies described in this review have implicated the cysteinyl leukotrienes (CysLTs) as inflammatory mediators in a wide range of diseases, implying that their biological activities reach far beyond acute bronchoconstriction, the activity traditionally ascribed to them. The validity of examining sputum for "biomarkers" has improved the understanding of asthma pathophysiology, optimization of asthma treatment and management, and investigation of the relation between CysLTs and airway inflammation in asthma. Nitric oxide is also a surrogate marker of asthma and reflects airway inflammation. The anti-inflammatory effects of the leukotriene receptor antagonists and the markers of their activity continue to grow.