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

Reference ranges for exhaled nitric oxide derived from a random community survey of adults

RATIONALE

Measurement of the fraction of nitric oxide in exhaled breath (Fe(NO)) has been proposed as a noninvasive marker of airway inflammation. Before the widespread use of this test, there is a need to develop reference ranges to allow clinicians to interpret Fe(NO) measurements.

OBJECTIVES

To derive reference ranges for Fe(NO) and to determine which factors in health and disease influence Fe(NO) levels.

METHODS

Subjects aged between 25 and 75 years were drawn from a random sample of the predominantly white population of Wellington, New Zealand.

MEASUREMENTS AND MAIN RESULTS

Fe(NO) was measured using an online nitric oxide monitor in accordance with international guidelines. A detailed respiratory questionnaire and pulmonary function tests were performed. The geometric mean Fe(NO) was 17.9 parts per billion (ppb) with a 90% confidence interval for an individual prediction (reference range) for normal subjects of 7.8 to 41.1 ppb. Sex, atopy, and smoking status significantly affected Fe(NO) levels, and several reference ranges are presented adjusting for these factors. Asthma and allergic rhinitis were associated with higher Fe(NO). Measurement of Fe(NO) had poor discriminant ability to identify steroid-naive subjects with asthma.

CONCLUSIONS

The reference ranges presented may be used to assist in the interpretation of Fe(NO) measurements in white adults.

Performance of an exhaled nitric oxide and carbon dioxide sensor using quantum cascade laser-based integrated cavity output spectroscopy

Exhaled nitric oxide (NO) is an important biomarker in asthma and other respiratory disorders. The optical performance of a NOCO(2) sensor employing integrated cavity output spectroscopy (ICOS) with a quantum cascade laser operating at 5.22 microm capable of real-time NO and CO(2) measurements in a single breath cycle is reported. A NO noise-equivalent concentration of 0.4 ppb within a 1-sec integration time is achieved. The off-axis ICOS sensor performance is compared to a chemiluminescent NO analyzer and a nondispersive infrared (NDIR) CO(2) absorption capnograph. Differences between the gas analyzers are assessed by the Bland-Altman method to estimate the expected variability between the gas sensors. The off-axis ICOS sensor measurements are in good agreement with the data acquired with the two commercial gas analyzers. This work demonstrates the performance characteristics and merits of mid-infrared spectroscopy for exhaled breath analysis.

Tailored interventions based on sputum eosinophils versus clinical symptoms for asthma in children and adults

BACKGROUND

Asthma severity and control can be measured both subjectively and objectively. Sputum analysis for evaluation of percentage of sputum eosinophilia directly measures airway inflammation, and is one method of objectively monitoring asthma. Interventions for asthma therapies have been traditionally based on symptoms and spirometry.

OBJECTIVES

To evaluate the efficacy of tailoring asthma interventions based on sputum analysis in comparison to clinical symptoms (with or without spirometry/peak flow) for asthma related outcomes in children and adults.

SEARCH STRATEGY

We searched the Cochrane Airways Group Specialised Register of Trials, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and reference lists of articles. The last search was on 31 October 2006.

SELECTION CRITERIA

All randomised controlled comparisons of adjustment of asthma therapy based on sputum eosinophils compared to traditional methods (primarily clinical symptoms and spirometry/peak flow).

DATA COLLECTION AND ANALYSIS

Results of searches were reviewed against pre-determined criteria for inclusion. Three sets of reviewers selected relevant studies. Two review authors independently assessed trial quality extracted data. Authors were contacted for further information but none were received. Data was analysed as "treatment received" and sensitivity analyses performed.

MAIN RESULTS

Three adult studies were included; these studies were clinically and methodologically heterogenous (use of medications, cut off for percentage of sputum eosinophils and definition of asthma exacerbation). There were no eligible paediatric studies. Of 246 participants randomised, 221 completed the trials. In the meta-analysis, a significant reduction in number of participants who had one or more asthma exacerbations occurred when treatment was based on sputum eosinophils in comparison to clinical symptoms; pooled odds ratio (OR) was 0.49 (95% CI 0.28 to 0.87); number needed to treat to benefit (NNTB) was 6 (95% CI 4 to 32). There were also differences between groups in the rate of exacerbation (any exacerbation per year) and severity of exacerbations defined by requirement for use of oral corticosteroids but the reduction in hospitalisations was not statistically significant. Data for clinical symptoms, quality of life and spirometry were not significantly different between groups. The mean dose of inhaled corticosteroids per day was similar in both groups and no adverse events were reported. However sputum induction was not always possible.

AUTHORS' CONCLUSIONS

Tailored asthma interventions based on sputum eosinophils is beneficial in reducing the frequency of asthma exacerbations in adults with asthma. This review supports the use of sputum eosinophils to tailor asthma therapy for adults with frequent exacerbations and severe asthma. Further studies need to be undertaken to strengthen these results and no conclusion can be drawn for children with asthma.

Severe asthma in adults: what are the important questions?

The term severe refractory asthma (SRA) in adults applies to patients who remain difficult to control despite extensive re-evaluation of diagnosis and management following an observational period of at least 6 months by a specialist. Factors that influence asthma control should be recognized and adequately addressed prior to confirming the diagnosis of SRA. This report presents statements according to the literature defining SRA in order address the important questions. Phenotyping SRA will improve our understanding of mechanisms, natural history, and prognosis. Female gender, obesity, and smoking are associated with SRA. Atopy is less frequent in SRA, but occupational sensitizers are common inducers of new-onset SRA. Viruses contribute to severe exacerbations and can persist in the airways for long periods. Inflammatory cells are in the airways of the majority of patients with SRA and persist despite steroid therapy. The T(H)2 immune process alone is inadequate to explain SRA. Reduced responsiveness to corticosteroids is common, and epithelial cell and smooth muscle abnormalities are found, contributing to airway narrowing. Large and small airway wall thickening is observed, but parenchymal abnormalities may influence airway limitation. Inhaled corticosteroids and bronchodilators are the mainstay of treatment, but patients with SRA remain uncontrolled, indicating a need for new therapies.

Formoterol, montelukast, and budesonide in asthmatic children: effect on lung function and exhaled nitric oxide

BACKGROUND

It has been proposed that asthma control may be achieved in part by minimizing airway inflammation. The simultaneous effects of inhaled steroids associated with long-acting beta-agonists and leukotriene antagonists on pulmonary function and airway inflammation are still largely unexplored in children with moderate persistent asthma.

OBJECTIVES

The aim of this study was to investigate the effects of add-on therapy with long-acting beta-agonists and leukotriene antagonists on FEV1 and exhaled nitric oxide levels (FENO) in children.

METHODS

Forty-eight steroid-naïve atopic asthmatic children, 7-11 years of age, were randomly treated in four groups for two consecutive one-month periods, as follows: (1) first month: budesonide 200 microg twice daily; second month: budesonide 400 microg twice daily; (2) first month: budesonide 200 microg twice daily+formoterol 9 microg twice daily; second month: budesonide 200 microg twice daily+montelukast 5mg once daily; (3) first month: budesonide 200 microg twice daily+montelukast 5mg once daily; second month budesonide 200 microg+formoterol 9 microg twice daily; (4) first and second month: budesonide 400 microg twice daily.

RESULTS

All treatments resulted in a significant increase in lung function and a decrease in FENO compared with values at baseline. Budesonide+montelukast in combination was the most effective treatment for reducing FENO levels.

CONCLUSION

This study demonstrates that add-on therapy with montelukast plus low-dose budesonide is more effective than the addition of long-acting beta-agonists or doubling the dose of budesonide for controlling FENO in asthmatic children.

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.

Reports of clinical trials should begin and end with up-to-date systematic reviews of other relevant evidence: a status report

OBJECTIVE

Scientific and ethical justification for new clinical trials requires them to have been designed in the light of scientifically defensible assessments of relevant previous research. Reliable interpretation of the results of new clinical trials entails setting them in the context of updates of the reviews upon which they were deemed scientifically and ethically justifiable. We have shown previously that most reports of randomized trials published in five general medical journals in May 1997 and in May 2001 failed to set their results in the context of the findings from similar research. In the current study, we assess whether there had been progress in this respect in 2005 and also investigate the extent to which reports begin by referring to systematic reviews providing the justification for the new research reported.

DESIGN

Assessment of the Introduction and Discussion sections in all reports of randomized trials published during May 2005 in five general medical journals.

SETTING

Reports of randomized trials in five general medical journals.

PARTICIPANTS

Annals of Internal Medicine, BMJ, JAMA, Lancet and New England Journal of Medicine.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

The inclusion or mention of one or more systematic reviews in the Introduction or Discussion section of each report assessed.

RESULTS

We found 18 reports of randomized trials. The Introduction sections referred to systematic reviews in five (27%) of these reports. None of the discussion sections of the 15 reports of trials that were not the first published trials to address the question studied placed the results of the new trial in the context of an updated systematic review of other research. Although reference was made to relevant systematic reviews in five of these 15 reports, there was no integration - quantitative or qualitative - of the results of the new trials in an update of these reviews. In the remaining ten reports there was no evidence that any systematic attempt had been made to set the new results in the context of previous trials.

CONCLUSIONS

There is no evidence of progress between 1997 and 2005 in the proportion of reports of trials published in general medical journals which discussed new results within the context of up-to-date systematic reviews of relevant evidence from other controlled trials. Although the proportion of trials referring to systematic reviews in Discussion sections has increased, the majority of reports continued to fail even to do this. Similarly, most researchers appear not to have considered a systematic review when designing their trial. Researchers and journal editors do a disservice to the interests of the public and others involved in healthcare decision-making by acquiescing in this situation.

Quantitative sputum cell counts as a marker of airway inflammation in clinical practice

PURPOSE OF REVIEW

Bronchitis, meaning airway inflammation, is an important component of airway disease. Yet respirologists and allergists, who have stressed the importance of measurements of airway function, have been slow to introduce airway inflammation measurements into clinical practice. Of the measurements available, quantitative sputum cell counts have the most clinical value. This article provides additional information on this topic from studies published in 2005 and 2006.

RECENT FINDINGS

Airway diseases are heterogeneous within patients in terms of the disease present and the type of airway inflammation. Quantitative sputum cell counts (total cell count as well as the differential) identify noneosinophilic, mainly neutrophilic, probably infective exacerbations as common in patients with asthma and chronic obstructive pulmonary disease that may be unresponsive to corticosteroid treatment. In contrast, measurements of sputum eosinophils can be used to guide the minimum dose of corticosteroid required to control eosinophilic bronchitis and reduce eosinophilic exacerbations.

SUMMARY

Measurements of quantitative sputum cell counts need to be made available, initially by tertiary care centres, to diagnose bronchitis in airway disease and to optimize treatment. Examination of how these are complemented by indirect measures of airway inflammation, specifically exhaled nitric oxide and airway hyperresponsiveness to stimuli acting indirectly through mediator release, requires further investigation.

New insights into occupational asthma

PURPOSE OF REVIEW

To examine recent publications on the types of agents involved in occupational asthma, the mechanisms by which they induce asthma, and how best to evaluate and treat workers suspected of this respiratory condition.

RECENT FINDINGS

High rates of occupational asthma and inhalation accidents were found in workers in crafts and related occupations in the manufacturing industries, and in plant and machine operatives; cleaners and construction workers may also be at risk. Further data support a role for CD4 T cells in low-molecular-weight agent-induced asthma, such as with isocyanates, and neurogenic mechanisms may also be involved. The use of noninvasive measures of airway inflammation in the diagnosis and management of occupational asthma such as sputum eosinophils monitoring is promising, although this is less obvious for exhaled nitric oxide. Finally, the persistence of troublesome asthma even after withdrawal from relevant exposure has been re-emphasized and surveillance programs have been proposed.

SUMMARY

Further data have been gathered on the prevalence of occupational asthma in various working populations, its mechanisms of development, the contribution of noninvasive measures of airway inflammation in the diagnosis and management of this condition, and its management and prevention.

The reclassification of asthma based on subphenotypes

PURPOSE OF REVIEW

Despite asthma being widely regarded as a heterogeneous disease, a consensus for an accurate system of classification has not been agreed. Recent studies have suggested that the recognition of subphenotypes of asthma based on the pattern of airway inflammation may be particularly useful in increasing our understanding of the disease. The present review discusses the important literature in this field, placing current work in its historical context.

RECENT FINDINGS

The use of noninvasive markers of airway inflammation has suggested the presence of four distinct phenotypes: eosinophilic, neutrophilic, mixed inflammatory and paucigranulocytic asthma. Recent studies suggest that these subgroups may differ in their aetiology, immunopathology and response to treatment. Several studies have focused on refractory asthma as a distinct phenotype with evidence of a more distal pattern of airway inflammation and of upregulation of the tumour necrosis factor-alpha axis. Finally, novel treatment approaches targeted at specific patterns of airway inflammation are emerging, making an appreciation of subphenotypes particularly relevant.

SUMMARY

The present review will discuss limitations to current classification systems, identify key current studies based on identifying inflammatory subphenotypes and provide suggestions for a novel approach that may further improve our understanding in this area.

Portable exhaled nitric oxide measurement: Comparison with the "gold standard" technique

BACKGROUND

The measurement of fractional exhaled nitric oxide (FENO) can assist in the diagnosis of asthma and may also act as a useful surrogate inflammatory marker on which to base treatment decisions in asthma management algorithms. Until recently, this technique was confined to research facilities and secondary care institutions. A portable nitric oxide analyzer (MINO; Aerocrine AB; Smidesvägen, Sweden) has been developed, but few data exist comparing this device with established, larger laboratory-based analyzers (NIOX; Aerocrine AB).

METHODS

A total of 101 asthmatic patients (64 treated with regular inhaled corticosteroids) and 50 healthy volunteers had simultaneous FENO measurements undertaken using NIOX and MINO devices.

RESULTS

In both asthmatic patients and healthy volunteers, there was a good correlation between the measurements obtained using each device (r = 0.94 and 0.96, respectively). Altman-Bland plots confirmed this agreement. Receiver operating characteristic curves discriminating asthmatic patients from healthy volunteers obtained using the NIOX and MINO showed a sensitivity of 83.2% and a specificity of 72% using cutoff values of 13 and 12.5 parts per billion, respectively.

CONCLUSION

FENO values obtained using a portable analyzer correlate well with those obtained using an established laboratory analyzer and can be used to discriminate asthmatic from nonasthmatic patients. This may facilitate the measurement of asthmatic airway inflammation in primary care.

Addressing issues of asthma in inner-city children

For children living in the inner city, asthma tends to be more frequent and severe. Although the causes for this heightened severity of asthma are not clearly established, environmental allergens likely play a major role. To characterize, understand, and treat children with asthma living in the inner city better, the National Institutes of Allergy and Infectious Diseases of the National Institutes of Health established an Inner City Asthma Program in 1991. Over the past 15 years, 3 separate inner-city asthma research networks have been formed and funded by this institute. The work from these programs has led to important observations including evidence that environmental allergens, particularly cockroach, are important for sensitization and severity of asthma of the affected children. Furthermore, reductions in the allergen load can lead to improved asthma control. The most recent program, the Inner City Asthma Consortium, was formed in 2002 with a goal to develop immune-based therapy for children with asthma in the inner city and to determine mechanisms of these therapies as well as immunopathogenesis of asthma in these high-risk children. This article reviews these programs and how they have begun the effort to understand and treat children with asthma who live in inner cities better and what their findings mean in relationship to unique features of asthma in inner city children.

The Predicting Response to Inhaled Corticosteroid Efficacy (PRICE) trial

BACKGROUND

Although guidelines recommend anti-inflammatory therapy for persistent asthma, recent studies suggest that 25% to 35% of patients with asthma may not improve lung function with inhaled corticosteroids.

OBJECTIVE

To evaluate potential biomarkers of predicting short-term (6-week) response to inhaled corticosteroid with subsequent evaluation of responders and nonresponders to asthma control over a longer interval (16 additional weeks).

METHODS

Eighty-three subjects with asthma off steroid were enrolled in this multicenter study. Biomarkers and asthma characteristics were evaluated as predictors of inhaled corticosteroid response over a 6-week trial for changes in FEV(1) and methacholine PC(20). After this, an additional 4-month trial evaluated asthma control.

RESULTS

Although multiple baseline predictors had significant correlations with improvements for short-term inhaled steroid success, the only strong correlations (r >or= +/- 0.6) were albuterol reversibility (r = 0.83; P < .001), FEV(1)/forced vital capacity (r = -0.75; P < .001), and FEV(1) % predicted (r = -0.71; P < .001). Dividing the subjects in the short-term inhaled steroid trial into responders (>5% FEV(1) improvement) and nonresponders (<or=5%) determined the longer-term need for steroids. For the nonresponders, asthma control remained unchanged whether inhaled corticosteroids were continued or were substituted with a placebo (P = .99). The good short-term responders maintained asthma control longer-term only if maintained on inhaled steroids (P = .007).

CONCLUSION

The short-term response to inhaled corticosteroids with regard to FEV(1) improvement predicts long-term asthma control.

CLINICAL IMPLICATIONS

The decision to use long-term inhaled steroids could be based on a short-term trial. Different therapeutic strategies would need to be established for nonresponders.

Fractional exhaled nitric oxide and induced sputum

Conventional asthma management aimed at controlling the underlying airway inflammation is classically based on symptoms and lung function. More recently, various non invasive markers of airway inflammation have become available. The ideal measurement method should be safe, non-invasive, easy to perform, reproducible and accurate. Fractional exhaled nitric oxide (FeNO) measurements fulfil these criteria, however some issues concerning cut off values and clinical variability as well as the interpretation of high values in the absence of symptoms still need to be solved. Induced sputum measurements are more labour intensive, however have the advantage of providing direct, additional information on the current inflammatory status of the airways. The most frequently analysed marker is sputum eosinophil percentage, although other markers of inflammation have also been under investigation. Both methods, FeNO and induced sputum should be seen as complementary to the conventional tools such as spirometry and bronchial hyperresponsiveness (BHR) testing.

The relationship between exhaled nitric oxide measured with an off-line method and airway reversible obstruction in Japanese adults with asthma

BACKGROUND

Exhaled nitric oxide (eNO) is a useful marker of eosinophilic airway inflammation in asthma patients. There is no study to show the relationship between the eNO measured by using an off-line method and the degree of reversibility of airflow limitation in Japanese asthma patients. We sought to investigate the relationship between the eNO level measured by using an off-line method and the degree of reversibility of bronchial constriction in Japanese asthma patients.

METHODS

The study population comprised 97 asthma patients in our outpatient clinic with some patients in both groups who received inhaled corticosteroid treatment. We measured eNO levels, forced expiratory volume in one second (FEV1) before and after treatment, reversible airway obstruction (DeltaFEV1) after inhalation of bronchodilator, and other parameters.

RESULTS

eNO was significantly correlated with peripheral blood eosinophil counts in asthma patients (in steroid-naïve asthma patients, r=0.544, p<0.0001; in asthma patients treated with inhaled corticosteroid, r=0.463, p=0.026), and subjects with severe eosinophilia in sputum showed high levels of eNO (mild eosinophilia versus severe, p=0.0152). Among patients with obstructive impairment, eNO levels were correlated with DeltaFEV1 regardless of whether patients received (r=0.527, p=0.0435) or did not receive (r=0.64, p = 0.0056) inhaled corticosteroid. In subjects with normal pulmonary function, there was no significant relationship between eNO and DeltaFEV1 with or without inhaled corticosteroid.

CONCLUSIONS

In patients with obstructive impairment, eNO reflects the degree of reversible airflow limitation. In subjects with normal pulmonary function, eNO may facilitate the diagnosis and management of asthma, rather than indicate reversible bronchial obstruction. eNO measurement by off-line methods is applicable as a potential tool for the diagnosis of asthma and management of asthma patients.

Effect of inhaled steroid therapy on exhaled nitric oxide and bronchial responsiveness in children with asthma

Inhaled steroid therapy is reported to reduce the level of exhaled nitric oxide (eNO), but the effects of inhaled corticosteroids (ICS) on bronchial hyperresponsiveness (BHR) have been controversial. The aim of this study was to determine the effects of ICS on the relationship between eNO and BHR. Twenty-six children with asthma were recruited, including 14 children who were receiving ICS (ICS group) and 12 who were not (ICS-naive group). The fractional exhaled nitric oxide concentration (FE(NO)) was examined by the recommended online method. To evaluate BHR, an acetylcholine challenge test was performed. In the ICS-naive group, FE(NO) was significantly correlated with PC20 (p < 0.05, r = -0.70), but not in the ICS group. In conclusion, FE(NO) was significantly correlated with BHR in the ICS-naive group, but this relationship was not present in the ICS group. Our results suggest that the use of ICS should be taken into consideration when evaluating the relation between BHR and airway inflammation.

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).

Asthma: new developments concerning immune mechanisms, diagnosis and treatment

PURPOSE OF REVIEW

This brief review discusses how recent research may modify our understanding of the immunology of asthma. Consideration is given to the possible impact that these observations may have upon diagnostic and therapeutic strategies.

RECENT FINDINGS

New studies indicate that current conceptions regarding the balance between Th1 and Th2 systems may need modification. The relationship between infection and the development of asthma in children has proven to be much more complex than originally suggested by the 'hygiene hypothesis'. In addition, important genetic differences have been found in the response of asthmatic patients to therapeutic agents.

SUMMARY

Greater insight into the mechanisms responsible for asthma and the introduction of new drugs will depend in part upon the development of reliable and simple methods for detecting airway inflammation. As the immunologic aspects of asthma are dissected, we can expect that many more potential targets for treatment will be discovered, but treatment may have to be individualized for genetic differences between different individuals.

Targeted interventions for difficult-to-treat asthma

Chronic persistent asthma has a significant burden in terms of healthcare-related expenses, decreased productivity and reduced quality of life for patients. Currently available guideline-directed therapy can control the majority of patients, but roughly one-third of patients will require additional care. This article reviews the barriers that hinder the ability of practitioners and patients to gain and maintain control of asthma, including inaccurate assessment measures, variability in patient response, and poor adherence. Strategies aimed at controlling difficult-to-treat disease, such as the use of biomarkers to assess control, are discussed. Newer and developing therapies that cater to specific types of asthmatic patients and may lead to improved outcomes in those patients for whom standard care is insufficient are also looked at.

Asthma control or severity: that is the question

In the first National Heart Lung and Blood Institute and Global Initiative for Asthma (GINA) guidelines, the level of symptoms and airflow limitation and its variability allowed asthma to be subdivided by severity into four subcategories (intermittent, mild persistent, moderate persistent, and severe persistent). It is important to recognize, however, that asthma severity involves both the severity of the underlying disease and its responsiveness to treatment. Thus, the first update of the GINA guidelines defined asthma severity depending on the clinical features already proposed as well as the current treatment of the patient. In addition, severity is not a fixed feature of asthma, but may change over months or years, whereas the classification by severity suggests a static feature. Moreover, using severity as an outcome measure has limited value in predicting what treatment will be required and what the response to that treatment might be. Because of these considerations, the classification of asthma severity is no longer recommended as the basis for treatment decisions, a periodic assessment of asthma control being more relevant and useful.

Advances in adult asthma 2006: its risk factors, course, and management

This Advances article updates our understanding of risk factors for asthma and its course and management. Studies relevant to clinical practice are discussed, with special attention to their clinical research methods.

A simple technique to characterize proximal and peripheral nitric oxide exchange using constant flow exhalations and an axial diffusion model

The most common technique employed to describe pulmonary gas exchange of nitric oxide (NO) combines multiple constant flow exhalations with a two-compartment model (2CM) that neglects 1) the trumpet shape (increasing surface area per unit volume) of the airway tree and 2) gas phase axial diffusion of NO. However, recent evidence suggests that these features of the lungs are important determinants of NO exchange. The goal of this study is to present an algorithm that characterizes NO exchange using multiple constant flow exhalations and a model that considers the trumpet shape of the airway tree and axial diffusion (model TMAD). Solution of the diffusion equation for the TMAD for exhalation flows >100 ml/s can be reduced to the same linear relationship between the NO elimination rate and the flow; however, the interpretation of the slope and the intercept depend on the model. We tested the TMAD in healthy subjects ( n = 8) using commonly used and easily performed exhalation flows (100, 150, 200, and 250 ml/s). Compared with the 2CM, estimates (mean ± SD) from the TMAD for the maximum airway flux are statistically higher ( J′awNO = 770 ± 470 compared with 440 ± 270 pl/s), whereas estimates for the steady-state alveolar concentration are statistically lower (CANO = 0.66 ± 0.98 compared with 1.2 ± 0.80 parts/billion). Furthermore, CANO from the TMAD is not different from zero. We conclude that proximal (airways) NO production is larger than previously predicted with the 2CM and that peripheral (respiratory bronchioles and alveoli) NO is near zero in healthy subjects.

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.

Adiposity, asthma, and airway inflammation

BACKGROUND

Several studies have found obesity to be associated with an increased prevalence of asthma. For reasons that remain unclear, this association has often been reported to be stronger in women than in men. One possible explanation might be that these studies have used body mass index to identify adiposity, which might be a less reliable measure of body fat in men than in women.

OBJECTIVE

We sought to explore the association between body fat percentage measured by means of bioelectrical impedance analysis and asthma, airflow obstruction, and airway inflammation in men and women.

METHODS

Respiratory questionnaires, spirometry, bronchodilator response, exhaled nitric oxide level, and percentage of body fat were measured in a population-based cohort of approximately 1000 individuals at age 32 years.

RESULTS

There was a significant association between the percentage of body fat and asthma in women (P = .043) but not in men (P = .75). Airflow obstruction was associated with percentage of body fat in women (P = .046), but there was an inverse association in men (P = .010). Bronchodilator responsiveness was also associated with lower body fat in men (P = .004). Airway inflammation, measured by means of exhaled nitric oxide, was not associated with body fat in either women (P = .17) or men (P = .25).

CONCLUSION

Adiposity is associated with asthma and airflow obstruction in women. This does not appear to be mediated by airway inflammation. In men airflow obstruction and bronchodilator responsiveness are associated with a lower percentage of body fat.

CLINICAL IMPLICATIONS

In women, but not in men, obesity is associated with asthma and airflow obstruction, but there was no association with airway inflammation.

What are the determinates of asthma control?

The evolution of our understanding of treatment of asthma begins with assessment of severity which is primarily related to the natural history of the disease. Control is defined as normalizing of the physiologic abnormalities and lessening economic and social burden of the disease. This paper reviews the factors that influence the variability and determinants of asthma control. The tools to validate and access asthma control should be employed in daily clinical practice. Therefore, it is important to determine asthma control based on a multidimensional approach including physiologic assessment, global assessment of functionality, daytime symptoms, nighttime symptoms, healthcare utilization, and adherence to therapy.

Asthma treatment and asthma prevention: a tale of 2 parallel pathways

Three recent clinical trials used different study designs to test the hypothesis that early introduction of inhaled corticosteroids in infants and young children at high risk for the development of asthma could change the natural course of the disease. All 3 trials reached the same conclusion: treatment requirement, symptom frequency while off treatment, and lung function did not differ between children receiving active drug or placebo, with outcomes measured 2 to 4 years after randomization. These findings challenge the concept that the inflammatory processes that cause asthma symptoms and are responsive to inhaled corticosteroids are also responsible for the chronic changes in airway structure and function that are believed to predispose to the development of persistent asthma. This conclusion is supported by studies showing that bronchial hyperresponsiveness, independent of current asthma symptoms, is associated with subsequent deficits in airway function growth during childhood. Successful strategies for the prevention of asthma will require a better understanding of the genetic, environmental, and developmental factors that predispose toward inappropriate responses to airway injury. Abnormal airway remodeling and persistent dysregulation of airway tone might be the final common pathway for different disease mechanisms, and this might explain the heterogeneity of clinical phenotypic syndromes that go under the common label of "asthma."

Asthma exacerbations . 4: Prevention

Asthma exacerbations are common. They account for a significant morbidity and contribute a disproportionate amount to the cost of asthma management. The optimal strategies for the prevention of asthma exacerbations include the early introduction of anti-inflammatory treatment-most commonly, low dose inhaled corticosteroids. This should be coupled with a structured education programme which has a written action plan as an integral component. Where patients continue to be poorly controlled, the addition of a long acting beta agonist should be considered. The latter should not be used as monotherapy and should always be used with inhaled corticosteroids. Atopic patients with a history of repeated exacerbations, especially if they are steroid dependent and with a raised IgE, may be considered as potential candidates for omalizumab. In the early stages of an asthma exacerbation, doubling the dose of inhaled corticosteroids has been shown to be ineffective. The ideal strategy for the management of worsening asthma in patients on combination treatment, especially salmeterol and fluticasone, is uncertain. There is an emerging body of evidence for strategies on how to prevent progression to an exacerbation in patients taking a combination of budesonide and formoterol.

Validation of a hand-held exhaled nitric oxide analyzer for use in children

Measurements of exhaled nitric oxide (FE(NO)) may be useful in the diagnosis and management of asthma in children. A new hand-held device (MINO, Aerocrine) for measuring FE(NO) has been marketed but has not been validated in a pediatric population. The objective is to validate the MINO against the NIOX analyzer. This was a randomized cross-over study where FE(NO) was measured in a single assessment using the MINO and NIOX. Children were recruited from a respiratory clinic and had six attempts to provide a FE(NO) measurement with each analyzer. Fifty-five children were enrolled, 33 boys, median age 9 years. A mean FE(NO) value was obtained in 39 children with MINO and 44 with NIOX. Paired mean FE(NO) values were obtained in 34 children and the values were higher for the NIOX (mean difference 3.9 ppb limits of agreement -1.1, 8.9). The differences between analyzers became greater at higher FE(NO) values. The first FE(NO) value using the MINO was 24 ppb and the mean of all FE(NO) values using the MINO was 27 ppb (difference not significant). Exhaled NO values were comparable between the two analyzers although there was greater consistency at lower values. The findings of the study do not contradict the manufacturer's recommendation that only one FE(NO) value is required with the MINO, however, we suggest that the mean of at least two values should be reported in children.

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.

Respiratory health and lung research in New Zealand

This article summarizes the recent history of respiratory research in New Zealand which was triggered by an epidemic of asthma mortality in the 1980s and which led to the rapid emergence of quality research groups. This unique event led to major initiatives to improve the standards of care for people with asthma in New Zealand. Perspectives on other lung health issues including tobacco control, the COPD epidemic and the emergence of bronchiectasis as a serious respiratory disease are also provided.

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.

Asthma: defining of the persistent adult phenotypes

The common disease asthma is probably not a single disease, but rather a complex of multiple, separate syndromes that overlap. Although clinicians have recognised these different phenotypes for many years, they have remained poorly characterised, with little known about the underlying pathobiology contributing to them. Development of targeted therapies for asthma, and phenotype-specific clinical trials have raised interest in these phenotypes. Improved understanding of these phenotypes in complex diseases such as asthma will also improve our ability to link specific genotypes to their associated disease, which should help development of biomarkers. However, there is no standardised method to define asthma phenotypes. This Review analyses some of the methods that have been used to define asthma phenotypes and proposes an integrated method of classification to improve our understanding of these phenotypes.

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.

What are the best estimates of pediatric asthma control?

PURPOSE OF REVIEW

To evaluate asthma outcome measures in the face of the variable nature of asthma. The outcome measures are divided into objective and subjective clinical measures, humanistic measures such as quality of life, and costs of asthma control.

RECENT FINDINGS

Objective measures of asthma include those traditionally used such as spirometry, peak expiratory flow rate, and airway hyperresponsiveness. Recently, more attention has been geared towards markers of inflammation including exhaled nitric oxide and sputum eosinophils. Subjective measures of asthma control include patient-derived parameters such as number of wheezing episodes, nocturnal symptoms, exercise-induced symptoms, short-acting beta-agonist use, steroid bursts, emergency-department visits, and hospitalizations. Asthma-related quality of life is related to asthma morbidity, and patients with better baseline quality of life have improved outcomes. Asthma-related costs include direct costs mostly comprised of hospitalizations and emergency-room visits, and indirect costs including school absenteeism.

SUMMARY

There is no ideal outcome measure for evaluating pediatric asthma control, but each of these outcome measures must be used together to evaluate a patient at each outpatient visit. Patient-centered measures of asthma control must also be further incorporated into office visits for improved asthma management.