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

Concentrations of exhaled nitric oxide in asthmatics and subjects with allergic rhinitis sensitized to the same pollen allergen

BACKGROUND

Some studies have reported that the levels of exhaled nitric oxide (ENO) in asthmatics are similar to those in subjects with allergic rhinitis, and it has been postulated that atopic status might be the determinant of enhanced nitric oxide production in asthma.

OBJECTIVES

The aim of this study was to determine differences in ENO levels between asthmatics and subjects with allergic rhinitis sensitized to the same allergen, and to correlate these levels with airway responsiveness.

METHODS

Nineteen patients with asthma and 18 subjects with allergic rhinitis monosensitized to Parietaria pollen were enrolled in the study. ENO values and airway responsiveness to methacholine and adenosine 5'-monophosphate (AMP) were measured during the pollen season. The response to each bronchoconstrictor agent was measured by the provocative concentration required to produce a 20% fall in FEV1 (PC20). ENO was measured with the single-exhalation method.

RESULTS

The geometric mean (95% confidence interval) ENO values were significantly higher in asthmatics than in subjects with allergic rhinitis: 72.4p.p.b. (54.9-93.3p.p.b) vs. 44.7p.p.b. (30.9-64.6p.p.b., P = 0.03). In asthmatics, a significant correlation was found between ENO and PC20 AMP values (p = -0.57, P=0.02), whereas no correlation was detected between ENO and PC20 methacholine (p = -0.35, P = 0.14).

CONCLUSIONS

Our results suggest that atopy is not the only determinant of increased ENO levels detected in subjects with asthma, and that responsiveness to AMP may be a more sensitive marker for assessing airway inflammation in asthma compared to methacholine.

New developments in work-related asthma

Although work-related asthma is the most commonly recognized occupational lung disease, the condition remains underrecognized and underreported. New-onset occupational asthma and work aggravated asthma can have deleterious medical and socioeconomic consequences for the individual. Although interpretation and comparison between studies are hampered by the use of variable definitions of WRA and criteria for the diagnosis, as many as 20% of cases of new or aggravated adult asthma has important work-related factors. Thus, all asthmatic patients should be asked about their work, if their respiratory symptoms are worse when they work, or if a new job/exposure preceded the onset of symptoms. A series of longitudinal inception and apprentice cohort studies were undertaken to address significant weakness in the previous medical literature. These studies are just beginning to produce results, and provide strong evidence for asthma caused by exposure to specific occupational environments. They have begun to produce new understanding of the risk factors for developing OA, the natural history of OA and immune sensitization, and the existence of the healthy worker effect. New, non-invasive measures of airway inflammation have been developed with the potential for broad applications in the field of WRA. Although the measurement of exhaled NO and induced sputum analysis are primarily used as research tools, their place in clinical practice is likely to become clearer. These methods also have the potential to elucidate the various pathophysiologic mechanisms involved in WRA and may broaden our concept of occupational exposures that can initiate the onset of asthma.

Short-term variability of exhaled nitric oxide in young male patients with mild asthma and in healthy subjects

BACKGROUND

Exhaled nitric oxide (NOexp) is an indicator of eosinophilic airways inflammation. This study evaluated short-term variability of NOexp in 13 healthy subjects (19-41 years, eight males) and in 31 patients with asthmatic respiratory symptoms (19-21 years, all male) to obtain data for assessment of short-term changes of NOexp in clinical situations.

METHODS

Mild asthma was confirmed in 10 patients (Group = asthma). Twenty-one patients with asthmatic respiratory symptoms did not fulfill the functional criteria of asthma (Group = respiratory symptoms). The procedure to determine NOexp followed the European Respiratory Society (ERS) guidelines; the mean expiratory flow used during sampling was 0.09-0.12 l/s. NOexp for each subject was determined as the mean of at least three successive measurements at the baseline, followed by determinations at 10 min, 6 h and 24 h after the baseline.

RESULTS

At the baseline, the mean (SD) value of NOexp was 6.6 (2.3) parts per billion (ppb) in the healthy controls, and significantly higher both in patients with respiratory symptoms (14.6 (11) ppb, P = 0.0076) and in those with asthma (34.2 (43) ppb, P < 0.001). Intraclass correlation coefficient of NOexp measured at baseline and after an interval of 10 min was 0.959 in healthy subjects, 0.986 in patients with respiratory symptoms and 0.936 in asthma patients, respectively. Short-term variability in terms of coefficient of variation (CoV) of repeated measurements of NOexp at 10 min, 6 hand 24 h was 5.1, 10.8 and 11.7% in healthy subjects, 71, 16.4 and 22.2% in patients with respiratory symptoms and 13.5, 19.4 and 26.4% in asthma patients, respectively.

CONCLUSIONS

Reproducibility of NOexp using standardized methods was good both in healthy subjects and in asthmatic patients. However, in asthmatics the short-term variation of NOexp was over two times as high as in healthy subjects. The level of NOexp was elevated, except in asthma, also in patients with asthmatic respiratory symptoms who did not fulfill the functional criteria of asthma.

Exhaled nitric oxide collected with two different mouthpieces: a study in asthmatic patients

Techniques for collecting exhaled nitric oxide (ENO) recommend the use of antibacterial filters of 0.3 m. The aim of the present study was to compare the measurements of ENO obtained with two different filtering devices. Air samples from 17 asthmatic and 17 non-asthmatic subjects were collected by a recommended off-line technique using two different mouthpieces: 1) the Sievers disposable tool (A) under a breathing pressure of 18 cmH2O, and 2) a mouthpiece containing a HEPA filter (B) under a breathing pressure of 12 cmH2O. The nitric oxide samples were collected into an impermeable reservoir bag. Values for ENO were compared using two-way repeated measures ANOVA followed by the Tukey test. Agreement was assessed by Bland-Altman analysis. ENO values obtained with mouthpieces A and B were comparable for asthmatic (mean +/- SEM, 42.9 +/- 6.9 vs 43.3 +/- 6.6 ppb) and non-asthmatic (13.3 +/- 1.3 vs 13.7 +/- 1.1 ppb) subjects. There was a significant difference in ENO between asthmatics and non-asthmatics using either mouthpiece A (P<0.001) or B (P<0.001). There was a positive correlation between mouthpiece A and mouthpiece B for both groups. The Bland-Altman limits of agreement were considered to be acceptable. Mouthpiece B was less expensive than A, and these data show that it can be used without compromising the result. Our data confirm reports of higher ENO values in the presence of airway inflammation.

Effect of salmeterol on seasonal changes in airway responsiveness and exhaled nitric oxide in pollen-sensitive asthmatic subjects

OBJECTIVE

Using a model of natural allergen exposure, we examined the effect of regular treatment with salmeterol on allergen-induced changes in airway responsiveness and exhaled nitric oxide (ENO).

DESIGN

Double-blind, randomized, parallel-group study.

SETTING

Specialist allergy unit in a university hospital.

PATIENTS

Asthmatic patients sensitized to pollen allergens were randomly allocated to monotherapy with salmeterol (n = 14) or placebo (n = 13).

INTERVENTIONS

Salmeterol, 25 micro g, and placebo inhalers, two puffs bid, for 6 weeks.

MEASUREMENTS

Spirometry, the level of a provocative concentration of a substance (methacholine) causing a 20% fall in FEV(1) (PC(20)), the PC(20) level for adenosine 5'-monophosphate (AMP), and ENO were measured before the pollen season and were repeated at the height of the pollen season after 6 weeks of treatment with salmeterol or placebo.

RESULTS

The decrease in FEV(1) during the pollen season was significantly larger in the placebo group than in the salmeterol group, the mean difference in the change between the groups being 0.20 L (95% confidence interval, 0.03 to 0.35; p = 0.047). Changes in PC(20) for methacholine, PC(20) for AMP, and ENO levels were not significantly different between treatment groups. However, a mean (+/- SEM) decrease in the PC(20) for methacholine of -1.0 +/- 0.4 doubling concentrations was observed within the placebo group (p = 0.03), whereas no significant changes were observed within the salmeterol group. A significant decrease in PC(20) for AMP (doubling concentrations) was observed within the placebo group (-2.1 +/- 0.6; p = 0.003) and the salmeterol group (-1.5 +/- 0.4; p = 0.003). ENO concentrations increased significantly among the placebo and the salmeterol groups during natural pollen exposure.

CONCLUSION

These observations indicate that natural allergen exposure and the regular use of salmeterol are not associated with a greater increase in ENO and airway responsiveness than allergen exposure alone.

Exhaled nitric oxide does not reflect the severity of acute lung injury: an experimental study in a rat model of extracorporeal circulation

OBJECTIVE

This study was undertaken to determine whether an increase in exhaled nitric oxide would reflect the severity of the acute lung injury caused by extracorporeal circulation.

DESIGN

Prospective, controlled animal laboratory investigation.

SETTING

University laboratory.

SUBJECTS

Male, anesthetized, paralyzed, and mechanically ventilated Wistar rats (n = 34).

INTERVENTIONS

Twenty-three Wistar rats underwent a partial (100 mL.kg(-1).min(-1)) femoro-femoral extracorporeal circulation in normothermia for 90 mins. Eleven time-matched rats formed the sham group.

MEASUREMENTS AND MAIN RESULTS

Exhaled nitric oxide was monitored with a chemiluminescence analyzer. Acute lung injury was assessed by blood gas analysis and lung water content. Lung Evans blue dye content, lung myeloperoxidase, and heme oxygenase activities were determined. Compared with the sham rats, extracorporeal circulation was responsible for acute lung injury characterized by an increased lung water content (82.4 +/- 1.3% vs. 77.9 +/- 1.1%; p<.05), an increased Evans blue dye content (191.8 +/- 15.8 vs. 112.5 +/- 16.8 mg/g tissue wet weight; <.01), and an increased pulmonary heme oxygenase activity (332.9 +/- 107 vs. 113.7 +/- 46.5 pmol. hr(-1).mg of protein(-1); p<.05). Exhaled nitric oxide remained stable throughout the experiment in all sham rats. Among the 23 rats that underwent extracorporeal circulation, eight rats (35%) experienced an increase in exhaled nitric oxide concentration (16.9 +/- 12.7 ppb). There was no significant difference between rats that did or did not experience an increase in exhaled nitric oxide regarding each index of acute lung injury.

CONCLUSIONS

An increase in exhaled nitric oxide did not reflect the severity of the acute lung injury caused by extracorporeal circulation. Its significance remains to be determined.

Mediators of asthma: nitric oxide

Endogenous nitric oxide is an ubiquitous gaseous molecule that regulates many aspects of human airway biology including the modulation of airway and vascular smooth muscle tone. It is generated from the three different enzymes nitric oxide synthases (NOS) -1, -2 and -3 which are all expressed in pulmonary cells. NOS-1 is localised primarily to neuronal structures, where NO is a mediator of the inhibitory Non-Adrenergic Non-Cholinergic System and NOS-3 is present in endothelial cells. While these enzymes are constitutively expressed, NOS-2 is an inducible enzyme independent of calcium and highly induced in inflammatory diseases such as allergic asthma, where NO may act beneficial or deleterious depending on the site of and amount of generation. The use of NO-donor compounds or classical unselective NOS inhibitors did not lead to significant therapeutical effects in asthmatic patients. Insights on the precise role of NO in asthma can only be achieved by targeting NO generation selectively. More potent and selective NOS-2 inhibitors have to clarify a role of NOS-modification based therapy in clinical routine. NO can also be detected in the exhaled air. Increased levels of exhaled NO in asthmatic patients may be useful for a non-invasive determination of airway inflammation.

Montelukast: a review of its therapeutic potential in asthma in children 2 to 14 years of age

Montelukast is a cysteinyl leukotriene receptor antagonist which is used as a preventive treatment for persistent asthma in patients > or =2 years of age. In children aged 6 to 14 years montelukast (5 mg/day) treatment resulted in a significant increase in FEV(1) (forced expiratory volume in 1 second, primary clinical outcome) during an 8-week randomized, double-blind trial. Moreover, significant improvements were observed for a range of secondary endpoints assessing symptoms, exacerbation rates, beta-agonist usage and quality of life. Concomitant administration of montelukast (5 mg/day) and inhaled budesonide (200 microg twice daily) resulted in a trend towards an increase in FEV(1) (p = 0.06, primary endpoint) and a statistically significant reduction in both as-needed beta(2)-agonist usage and the percentage of days with asthma exacerbations compared with budesonide plus placebo. No significant differences were observed in asthma-related quality of life between the two groups. During clinical trials both improvements in lung function and reductions in as-needed beta(2)-agonist usage were generally observed within 1 day after initiation of therapy in children 2 to 14 years of age with persistent asthma. Data from a randomized, nonblind trial in 6- to 11-year-old children and a 6-month extension to this trial suggest that both compliance to therapy and patient satisfaction are greater for montelukast than for either inhaled sodium cromoglycate or inhaled beclomethasone. In addition, patients and parents preferred oral montelukast over sodium cromoglycate. In 2- to 5-year-old children with persistent asthma, montelukast (4 mg/day) treatment resulted in significant improvements in a range of outcomes, such as as-needed beta(2)-agonist usage, symptom scores and percentage of days with asthma symptoms, as assessed during a randomized, double-blind trial primarily designed to assess tolerability. Data from small randomized, double-blind trials suggest that montelukast reduces exercise-induced bronchoconstriction in 6- to 14-year-old children. Montelukast is generally well tolerated. The frequency of adverse events in montelukast-treated children of all ages was comparable to that in patients receiving placebo.

CONCLUSION

Oral montelukast has shown efficacy as a preventive treatment for asthma during clinical trials in children aged 2 to 14 years. The drug offers benefits over more standard therapies such as inhaled sodium cromoglycate and nedocromil in terms of compliance and convenience. In addition, the drug offers significant benefits when added to inhaled corticosteroids (according to secondary endpoints). Montelukast offers an effective, well tolerated and convenient treatment option for children with asthma.

Activity related increase of exhaled nitric oxide in Crohn's disease and ulcerative colitis: a manifestation of systemic involvement?

Nitric oxide (NO) is an important mediator of inflammation in several pathological conditions. Patients with lung diseases, like asthma, have higher levels of exhaled NO (eNO) in active disease in comparison with healthy volunteers. Aspirated colonic gas in patients with ulcerative colitis (UC) showed more than 100 times higher levels of NO in comparison with normal subjects. Crohn's disease (CD) and UC are associated with a variety of systemic manifestations, although lung diseases as an extra-intestinal expression of inflammatory bowel disease (IBD) are not well investigated. In some studies, clinical and subclinical pulmonary abnormalities are described in active IBD as well as in the stable situation. The aim of the present study is to evaluate whether eNO is increased in patients with active IBD and to investigate whether there exists a correlation between (1) the eNO levels and the disease activity, and (2) the spirometry and the disease activity in a subgroup of patients. In 31 patients with CD (mean age 36.8 +/- 12.9 years) and 24 patients with UC (mean age 38.0 +/- 14.7 years) the Crohn's Disease Activity Index (CDAI) and Colitis Activity Index (CAI) were measured, respectively. Exhaled NO was measured with a chemiluminescence analyzer, according to standardized criteria. In a subgroup of CD patients, spirometry was also performed according to standardized criteria. The mean CDAI in CD patients was 192.4 +/- 94.3 and their mean eNO value was 13.5 +/- 4.6 ppb. For UC the mean CAI was 6.2 +/- 4.8 and the mean eNO value was 15.8 +/- 6.2 ppb. In a matched control group of 27 healthy, non-smoking volunteers (mean age of 33.7 +/- 13.2 years) the eNO was 10.2 +/- 2.5 ppb (P < 0.05 compared to CD and P < 0.01 compared to UC). There was a disease-activity-related increase of the eNO level in patients with IBD. For patients with UC the correlation coefficient (r = 0.63, P < 0.001) was more pronounced than for CD (r = 0.39, P < 0.05). In 17 patients with CD, spirometry was available at the time of the eNO measurement. We found a significant negative correlation between the CDAI and the FEV1 and FVC in these patients (r = -0.559, P = 0.02 and r = -0.634, P = 0.006, respectively). We conclude that eNO is increased in active IBD and correlates with the activity of the disease; furthermore, we found a negative correlation between spirometry and disease activity in patients with CD. These observations strengthen the arguments that IBD is a systemic disease. Further research is needed to try to explain the significance of an increased eNO in IBD.

Step-down therapy with low-dose fluticasone-salmeterol combination or medium-dose hydrofluoroalkane 134a-beclomethasone alone

BACKGROUND

Options for step-down therapy include use of inhaled corticosteroids alone or in combination with a long-acting beta2-agonist.

OBJECTIVE

We sought to evaluate step-down therapy with a fluticasone propionate-salmeterol (FP-SM) combination administered through a dry powder inhaler (DPI; Advair Diskus) versus a medium dose of hydrofluoroalkane 143a-beclomethasone dipropionate (HFA-BDP) administered through a breath-actuated pressurized metered-dose inhaler (QVAR Autohaler).

METHODS

Thirty-nine patients with uncontrolled moderate-to-severe asthma were treated with 1000 microg of DPI-administered BDP twice daily (DPI-BDP) for 4 weeks and then randomized to 200 microg of HFA-BDP twice daily (n = 20) or 100 microg of FP and 50 microg of SM twice daily (FM-SM; n = 19) for 8 weeks in a double-blind, double-dummy, parallel-group design. We measured the provocative dose of methacholine producing a 20% fall in FEV1 (methacholine PD20) as the primary outcome, with secondary outcomes being lung function, surrogate inflammatory markers, diary card responses, quality of life, and safety.

RESULTS

There was a 0.9 (95% confidence interval, 0.5-1.2) doubling dose improvement in methacholine PD20 comparing asthma before versus after DPI-BDP. HFA-BDP maintained this improvement, whereas FP-SM produced a further significant improvement, amounting to a 1.1 (95% confidence interval, 0.2-2.1) doubling dose difference at 8 weeks for FP-SM versus HFA-BDP. Effects on FEV1, peak expiratory flow, and quality of life (symptoms and emotions) were similar to those on methacholine PD20, with a significant difference between FP-SM and HFA-BDP. Suppression of plasma and urinary cortisol and serum osteocalcin levels occurred with DPI-BDP, but values returned to baseline levels within 1 month of HFA-BDP or FP-SM administration.

CONCLUSION

After high-dose inhaled corticosteroid, stepping down with the combination inhaler conferred further improvements in bronchoprotection, bronchodilatation, and clinical control, but not inflammatory markers, compared with that seen with a medium dose of inhaled corticosteroid.

Mite avoidance can reduce air trapping and airway inflammation in allergic asthmatic children

BACKGROUND

We investigated the effects of prolonged allergen avoidance in 18 house dust mite-sensitized asthmatic children during a prolonged residential period at a high altitude, allergen-free environment.

METHODS

Evaluations of residual volume (RV) and exhaled nitric oxide (eNO) were performed (i) at admission to the residential house in September, (ii) in December after 3 months of stay, (iii) in January after 15 days at home, exposed to allergens, and (iv) in June after 9 months of stay.

RESULTS

During the study period RV showed a significant decrease in December (from 117.5 +/- 7.7% to 96.5 +/- 3.2%) (P < 0.02) and a following increase in January (126.2 +/- 17.2%), after allergen re-exposure (P < 0.03). RV decreased again in June at the end of the study period (91.1 +/- 6.0%) (P = 0.001). FEV(1), FEF(25-75) and VC values did not present significant variations. ENO showed a significant decrease in December after 3 months at high altitude (from 21.3 +/- 3.9 p.p.b. to 11.9 +/- 1.7 p.p.b.) (P = 0.03), but no further significant change. No correlation was found between lung volumes and eNO, probably reflecting different aspects of asthma.

CONCLUSIONS

Results suggest that RV may be more sensitive than other respiratory function parameters in identifying children with air trapping, being influenced significantly as the inflammatory indices by effective allergen avoidance/exposure regimen.

Exhaled nitric oxide and bronchial responsiveness to adenosine 5'-monophosphate in subjects with allergic rhinitis

STUDY OBJECTIVES

To determine differences in exhaled nitric oxide (ENO) between subjects with allergic rhinitis with and without increased responsiveness to direct and indirect bronchoconstrictor agents.

STUDY DESIGN

Cross-sectional study with the order of challenge tests randomized.

SETTING

Specialist allergy unit in a university hospital.

PATIENTS

Thirty-eight subjects without asthma with allergic rhinitis and 10 healthy nonatopic control subjects.

MEASUREMENTS AND RESULTS

Participants were challenged with increasing concentrations of adenosine 5'monophosphate (AMP) and methacholine. ENO was measured with the single-exhalation method. A positive response to both bronchoconstrictor agents was detected in nine subjects with allergic rhinitis, whereas four subjects showed increased responsiveness to AMP but not to methacholine. The geometric mean (range) ENO values were significantly higher in subjects with allergic rhinitis with increased responsiveness to either methacholine or AMP than in subjects with normal responsiveness to both agonists: 51.3 parts per billion (ppb) [22.0 to 108.5 ppb] vs 25.1 ppb (5.7 to 102.9 ppb, respectively; p = 0.007) and healthy control subjects (11.2 ppb [5.0 to 31.9 ppb], p < 0.001). Subjects with allergic rhinitis with normal responsiveness to both agonists also had higher concentrations of ENO than healthy control subjects (p = 0.007). No correlation was found between ENO and either of the provocative concentrations of methacholine or AMP causing a 20% fall in FEV(1).

CONCLUSIONS

In subjects without asthma but with allergic rhinitis, the presence of bronchoconstriction in response to methacholine or AMP is associated with increased ENO concentrations. However, elevated concentrations of ENO are detected even in subjects with allergic rhinitis without airway hyperresponsiveness. These results suggest that the presence of airway hyperresponsiveness is not the only factor that determines the increased NO levels detected in subjects with allergic rhinitis.

pH in expired breath condensate of patients with inflammatory airway diseases

Endogenous airway acidification, as assessed by pH in expired breath condensate, has been implicated in asthma pathophysiology. We measured pH in breath condensate of patients with inflammatory airway diseases in stable condition and examined its relationship with the inflammatory process (as assessed by differential cell counts in induced sputum), oxidative stress (as assessed by H(2)O(2) and 8-isoprostane), and nitric oxide metabolism (as assessed by total nitrate/nitrite). We studied 40 patients with bronchial asthma (20 with moderate disease, forced expiratory volume in 1 second 60 [10]% SD predicted), 20 patients with bronchiectasis, 20 patients with chronic obstructive pulmonary disease (COPD), and 10 normal subjects. Mean (95% confidence intervals) pH values were significantly lower in patients with COPD and bronchiectasis compared with patients with asthma and control subjects (7.16, 7.09-7.23 and 7.11, 7.04-7.19 versus 7.43, 7.35-7.52 and 7.57, 7.51-7.64, respectively, p < 0.0001). Patients with moderate asthma had significantly lower values compared with mild and control subjects. In patients with COPD and bronchiectasis, the values of pH were significantly correlated with both sputum neutrophilia and oxidative stress. Respectively, in patients with moderate asthma, a significant correlation was observed between pH and sputum eosinophilia, total nitrate/nitrite, and oxidative stress. The pH of the expired breath condensate might be a simple, noninvasive, inexpensive, and easily repeatable procedure for the evaluation of the inflammatory process in airway diseases.

Exhaled nitric oxide correlates with airway eosinophils in childhood asthma

BACKGROUND

Exhaled nitric oxide has been proposed as a marker for airway inflammation in asthma. The aim of this study was to compare exhaled nitric oxide levels with inflammatory cells and mediators in bronchoalveolar lavage fluid from asthmatic and normal children.

METHODS

Children were recruited from elective surgical lists and a non-bronchoscopic bronchoalveolar lavage (BAL) was performed after induction of anaesthesia. Exhaled nitric oxide (parts per billion) was measured by two techniques: tidal breathing and restricted breath.

RESULTS

Median (interquartile range) exhaled nitric oxide measured by restricted breath was increased in asthmatics compared with normal children (24.3 (10.5-66.5) v 9.7 (6.5-16.5), difference between medians 14.6 (95% CI 5.1 to 29.9), p=0.001). In asthmatic children exhaled nitric oxide correlated significantly with percentage eosinophils (r=0.78, p<0.001 (tidal breathing) and r=0.78, p<0.001 (restricted breath)) and with eosinophilic cationic protein (r=0.53, p<0.01 (restricted breath)), but not with other inflammatory cells in the BAL fluid. The area under the receiver operator characteristic curves for the prediction of the presence of eosinophilic airways inflammation by exhaled nitric oxide (tidal and restricted) was 0.80 and 0.87, respectively.

CONCLUSIONS

Exhaled nitric oxide correlates closely with percentage eosinophils in BAL fluid in asthmatic children and is therefore likely to be a useful non-invasive marker of airway inflammation.

Simultaneous NO and CO(2) measurement in human breath with a single IV-VI mid-infrared laser

A tunable diode laser absorption spectroscopy (TDLAS) system equipped with a IV-VI mid-IR laser operating near 5.2>mu;m was used to measure exhaled nitric oxide (eNO) and carbon dioxide (CO(2)) simultaneously in human breath over a single exhalation. Breath was sampled in real time, and eNO levels were measured from seven volunteers, two steroid-naive asthmatics and five nonasthmatics. Measured CO(2) levels were used as an internal standard to verify correct breath collection and calculate eNO values. Calculated eNO concentrations agreed well with reported values for asthmatic and nonasthmatic individuals.

Measurement of airway inflammation in asthma

Chronic airway inflammation is considered responsible for symptoms and disorders of airway function associated with asthma. This process is the target of anti-inflammatory therapy, so a number of standardized, noninvasive techniques have been developed to assess it. More recent approaches include the measurement of exhaled gases and nonvolatile substances in breath condensate. Results from studies using a wide variety of inflammatory markers have shown group differences between patients with asthma and healthy control subjects, but evidence for the diagnostic use of these markers in individual patients is scarce. Similarly, despite many studies demonstrating some correlation between markers of airway inflammation and a measure of disease control, none has yet convincingly shown a place for the use of these markers in an individual with corticosteroid-treated asthma. However, application of these markers continues to further our understanding of the disease process and provides the potential for more appropriate, customized therapy.

The relationship between airway hyper-responsiveness, markers of inflammation and lung function depends on the duration of the asthmatic disease

BACKGROUND

The combination of airway hyper-responsiveness, eosinophilic airway inflammation, and lung function impairment is considered as a hallmark of bronchial asthma. Since airway function might change with time in chronic asthma, the association between parameters which are characteristic of asthma could be different in subjects with different durations of the disease.

OBJECTIVE

We assessed whether in patients with asthma the relationship between airway hyperresponsiveness, non-invasive markers of airway inflammation, and baseline lung function depended on the duration of the disease.

METHODS

Sixty-six non-smoking patients with mild to moderate allergic asthma without corticosteroids were assigned to two groups, according to a duration of the disease (time interval since doctor's diagnosis) of either < or = 16 years (median 8 years; mean FEV1, 92.6% pred.; n = 34) or > 16 year (median 25 years; mean FEV1, 87.9% pred.; n = 32).

RESULTS

Groups did not differ statistically in PC20FEV1 of methacholine, sputum composition, levels of exhaled nitric oxide (NO), lung function parameters, or history of treatment. There were significant correlations between PC20FEV1, eosinophils and NO in patients with a duration of the disease < or = 16 year, but no relation to lung function. In contrast, patients with a duration > 16 year showed a correlation between PC20FEV1 of methacholine and lung function but not eosinophils or NO. In both groups, eosinophils and NO were associated with each other. These results were corroborated by the statistical procedure of factor analysis that revealed 'inflammation' and 'lung function' as major entities and found 'responsiveness' to be associated with only one of them in each group.

CONCLUSION

Our data demonstrate that with a shorter duration of the asthmatic disease airway hyper-responsiveness is associated with airway inflammation, whereas with a longer duration it is associated with impaired lung function, suggesting that in chronic asthma ongoing alterations become the primary determinant of functional characteristics.

Airway inflammation is present during clinical remission of atopic asthma

Symptoms of atopic asthma often disappear at puberty. However, asthmatic subjects in clinical remission will frequently have a relapse later in life. The aim of this study was to investigate whether subjects in clinical remission of atopic asthma have persistent airway inflammation and/or airway remodeling. Bronchial biopsies were obtained from subjects in clinical remission, asthmatic subjects, and healthy control subjects. The presence and/or activation state of eosinophils, mast cells, macrophages, T lymphocytes, interleukin (IL)-5, eotaxin, and inducible nitric oxide synthase (iNOS) were analyzed. Results were compared with less invasive indicators of airway inflammation. Also aspects of airway remodeling were determined. Eosinophils, T cells, mast cells, and IL-5 were significantly elevated in the airway mucosa of subjects in remission compared with control subjects. Also, blood eosinophil cell counts were significantly higher in subjects in clinical remission. Blood eosinophil cell counts, exhaled nitric oxide (eNO) levels, and bronchial response to adenosine-5'-monophosphate correlated significantly with the quantity of tissue eosinophils. Significant airway remodeling was found in subjects in clinical remission. Our study has shown ongoing airway inflammation and airway remodeling in adolescents in clinical remission of atopic asthma. Subclinical airway inflammation may well determine the risk of an asthma relapse later in life.

Exhaled nitric oxide decreases during exercise-induced bronchoconstriction in children with asthma

Nitric oxide (NO) produced in the airways can be either detrimental or protective to the host. To investigate the role of NO in the pathogenesis of exercise-induced bronchoconstriction (EIB), we measured exhaled NO (ENO) after exercise challenge in 39 asthmatic and six normal children. FEV(1) and ENO were measured before and at 0, 5, 10, and 15 min after exercise performed on a treadmill for 6 min. EIB was defined as a decrease in FEV(1) of more than 15% after the exercise. Normal children (control group) did not have EIB. Twenty-one patients with asthma had EIB (EIB group) whereas the remaining 18 patients did not (non-EIB group). The baseline ENO value was significantly higher in the asthmatic children than in the normal children, and there was a positive correlation between the maximal percent decrease in FEV(1) and the baseline ENO value (r = 0.501, p = 0.012). At the end of the exercise, ENO had decreased in all the subjects. In the non-EIB and control groups, ENO rebounded to above the baseline at 5 min after the exercise and thereafter. In contrast, ENO remained at a decreased level in the EIB group. The change in ENO did not correlate with the change in minute ventilation, and beta-agonist inhalation at the peak of EIB that accelerated the recovery of FEV(1) did not affect the depressed level of ENO, demonstrating that the reduction of ENO is not a simple consequence of increased ventilation nor airway obstruction. Among the EIB group, steroid-treated patients showed sooner recovery in ENO after the exercise than steroid-naive patients. Our study suggests that NO production in response to exercise may be impaired in patients with EIB, and that ENO represents not only airway inflammation but also a protective function of NO in EIB.

Relationship between exhaled nitric oxide and mucosal eosinophilic inflammation in children with difficult asthma, after treatment with oral prednisolone

Exhaled nitric oxide (FE(NO)) has been proposed as a noninvasive marker of airway inflammation in asthma, and may reflect airway eosinophilia. We examined the relationship between FE(NO) and eosinophilic inflammation in endobronchial biopsies from 31 children with difficult asthma (mean age [range] 11.9 [6-17] yr), following 2 wk of prednisolone (40 mg/d). Endobronchial biopsy was also performed in seven children without asthma. Biopsy eosinophils were detected using antibody to major basic protein, and point-counting used to derive an "eosinophil score." FE(NO) readings and suitable biopsies for analysis were both obtained in 21 of 31 children with asthma. Adherence to prednisolone was demonstrated in 17 of these 21. Within this group, there was a correlation between FE(NO) and eosinophil score (r = 0.54, p = 0.03). The relationship was strongest in patients with persistent symptoms after prednisolone, in whom FE(NO) > 7 ppb was associated with a raised eosinophil score. For all patients, FE(NO) < 7 ppb was associated with an eosinophil score within the nonasthmatic range, regardless of symptoms. We propose that FE(NO) is associated with eosinophilic inflammation in children with difficult asthma, following prednisolone, and may help in identifying patients in whom persistent symptoms are associated with airway eosinophilia.

Exhaled nitric oxide in asthmatic and non-asthmatic children: influence of type of allergen sensitization and exposure to tobacco smoke

Asthmatic bronchial inflammation is associated with increased nitric oxide concentrations in exhaled air (eNO). Recent data suggest that this effect arises from atopy. Our aim in this study was to find out whether atopy and sensitization to particular allergens influences eNO levels. A total of 213 subjects (41 asthmatics and 172 controls) (96 boys and 117 girls, 7.3-14 years of age) were studied. Parents completed a questionnaire that sought information on their children's respiratory symptoms and exposure to tobacco smoke. Subjects underwent skin-prick tests for the following common allergens: Dermatophagoides pteronyssinus (Dpt), cat fur, Aspergillus fumigatus, Alternaria tenuis, mixed grass, mixed tree pollen, Parietaria officinalis, egg, and cow's milk. eNO was collected in 1-l mylar bags (exhaled pressure 10 cmH2O, flow 58 ml/s) and analyzed by using chemiluminescence. Atopic and non-atopic children without a history of chronic respiratory symptoms had a similar geometric mean eNO (atopics, n = 28, 11.2 p.p.b.; non-atopics, n = 96, 10.0 p.p.b.; mean ratio 1.1, 95% confidence interval [CI]: 0.7-1.6). Conversely, atopic asthmatic subjects had significantly higher eNO values than non-atopic asthmatic subjects (atopics, n = 25, 24.8 p.p.b.; non-atopics, n = 16, 11.4 p.p.b.; mean ratio 2.2, 95% CI: 1.2-3.9, p= 0.000). In children with rhinitis alone (n = 15) and those with lower respiratory symptoms other than asthma (n = 33), eNO increased slightly, but not significantly, with atopy. eNO levels correlated significantly with Dpt wheal size (r = 0.51) as well with the wheal size for cat, mixed grass, and Parietaria officinalis (r = 0.30-0.29), and with the sum of all wheals (r = 0.47) (p= 0.000). Subjects sensitized only for Dpt (but not those subjects sensitized only for grass pollen or other allergens) showed significantly higher eNO levels than non-atopic subjects (16.4 p.p.b. vs. 10.2 p.p.b., mean ratio 1.6, 95% CI: 1.1-2.3, p= 0.002). In asthmatic subjects, Dpt sensitization markedly increased eNO levels (Dpt-sensitized subjects: 28.0 p.p.b.; Dpt-unsensitized subjects: 12.2 p.p.b.; mean ratio 2.3, 95% CI: 1.5-3.5, p= 0.000). Non-asthmatic Dpt-sensitized subjects also had significantly higher eNO values than non-asthmatic, non-Dpt-sensitized subjects (14.2 p.p.b. vs. 10.1 p.p.b.; mean ratio 1.4, 95% CI: 1.1-1.9, p= 0.008). No difference was found between eNO levels in asthmatic subjects and control subjects exposed or unexposed to tobacco smoke. In conclusion, eNO concentrations are high in atopic asthmatic children and particularly high in atopic asthmatics who are sensitized to house-dust mite allergen.

Inhaled fluticasone decreases bronchial but not alveolar nitric oxide output in asthma

Exhaled nitric oxide (NO) concentration is a noninvasive measure of airway inflammation and is increased in asthma. Inhaled glucocorticoids decrease exhaled NO concentration, but the relative contributions of alveolar and bronchial levels to the decrease in exhaled NO concentration are unknown. Alveolar NO concentration and bronchial NO flux can be separately approximated by measuring exhaled NO at several exhalation flow rates. The effect of steroid treatment on alveolar and bronchial NO output in asthma was studied. Alveolar NO concentration and bronchial NO flux were assessed in 16 patients with asthma before and during treatment with inhaled fluticasone for 8 weeks and in 16 healthy controls. Before the treatment, asthmatics had increased bronchial NO flux (mean+/-SEM: 3.6+/-0.4 versus 0.7+/-0.1 nL x s(-1), p<0.001) but normal alveolar NO concentration (1.2+/-0.5 versus 1.0+/-0.2 parts per billion (ppb), p>0.05) compared with controls. Inhaled fluticasone decreased bronchial NO flux from 3.6+/-0.4 to 0.7+/-0.1 nL x s(-1) (p<0.01) but had no effect on alveolar NO concentration (before: 1.2+/-0.5; after: 1.2+/-0.1 ppb, p>0.05). The forced expiratory volume in one second improved, whereas asthma symptom score and serum levels of eosinophil cationic protein and eosinophil protein X decreased during the treatment. In conclusion, inhaled fluticasone decreases bronchial but not alveolar nitric oxide output simultaneously with clinical improvement in patients with asthma.

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

Exhaled nitric oxide (eNO) levels are increased in untreated or unstable asthma and measurements can be made easily. Our aim was to assess the usefulness of eNO for diagnosing and predicting loss of control (LOC) in asthma following steroid withdrawal. Comparisons were made against sputum eosinophils and airway hyperresponsiveness (AHR) to hypertonic saline (4.5%). Seventy-eight patients with mild/moderate asthma had their inhaled steroid therapy withdrawn until LOC occurred or for a maximum of 6 wk. Sixty (77.9%) developed LOC. There were highly significant correlations between the changes in eNO and symptoms (p < 0.0001), FEV(1) (p < 0.002), sputum eosinophils (p < 0.0002), and saline PD(15) (p < 0.0002), and there were significant differences between LOC and no LOC groups. Both single measurements and changes of eNO (10 ppb, 15 ppb, or an increase of > 60% over baseline) had positive predictive values that ranged from 80 to 90% for predicting and diagnosing LOC. These values were similar to those obtained using sputum eosinophils and saline PD(15) measurements. We conclude that eNO measurements are as useful as induced sputum analysis and AHR in assessing airway inflammation, with the advantage that they are easy to perform.

Markers of airway inflammation and airway hyperresponsiveness in patients with well-controlled asthma

In steroid-naive asthmatics, airway hyperresponsiveness correlates with noninvasive markers of airway inflammation. Whether this is also true in steroid-treated asthmatics, is unknown. In 31 stable asthmatics (mean age 45.4 yrs, range 22-69; 17 females) taking a median dose of 1,000 microg inhaled corticosteroids (ICS) per day (range 100-3,600 microg x day(-1)), airway responsiveness to the "direct" agent histamine and to the "indirect" agent mannitol, lung function (forced expiratory volume in one second (FEV1), forced vital capacity (FVC), peak expiratory flow (PEF)), exhaled nitric oxide (eNO), and number of inflammatory cells in induced sputum as a percentage of total cell count were measured. Of the 31 subjects, 16 were hyperresponsive to mannitol and 11 to histamine. The dose-response ratio (DRR: % fall in FEV1/cumulative dose) to both challenge tests was correlated (r=0.59, p=0.0004). However, DRR for histamine and DRR for mannitol were not related to basic lung function, eNO, per cent sputum eosinophils and ICS dose. In addition, NO was not related to basic lung function and per cent sputum eosinophils. In clinically well-controlled asthmatics taking inhaled corticosteroids, there is no relationship between markers of airway inflammation (such as exhaled nitric oxide and sputum eosinophils) and airway responsiveness to either direct (histamine) or indirect (mannitol) challenge. Airway hyperresponsiveness in clinically well-controlled asthmatics appears to be independent of eosinophilic airway inflammation.

Effect of nebulised l- and d-arginine on exhaled nitric oxide in steroid naive asthma

BACKGROUND

Nitric oxide (NO) is a product of the enzyme nitric oxide synthase (NOS) and is found in normal and asthmatic human airways. The administration ofl-arginine results in an increase in airway NO production in asthmatic subjects. This is thought to occur becausel-arginine is the substrate for NOS. However, studies in the systemic vasculature suggest that other mechanisms may be responsible.

METHODS

Eight patients with steroid naive asthma each received 2.5 g l-arginine, 2.5 g d-arginine, and 2.0% saline by ultrasonic nebuliser on separate days in a randomised, single blind manner. Exhaled NO was measured by chemiluminescence and spirometric tests were performed before and for 3 hours after each administration. The mean concentration of NO after exposure was calculated from the area under the curve.

RESULTS

l-arginine,d-arginine, and 2.0% saline induced a mean (95% CI) maximal bronchoconstriction of 11.9% (–1.7 to 25.4), 10.0% (2.8 to 17.2), and 8.5% (–2.5 to 19.5) of the starting forced expiratory volume in one second (FEV1), respectively. Exhaled NO declined in proportion to the degree of bronchoconstriction (r=0.60, p<0.01). Bronchoconstriction and the acute reduction in exhaled NO resolved within 15 minutes. The mean post-exposure concentration of NO was 15.75 parts per billion (ppb) after l-arginine, 15.16 ppb after d-arginine, and 12.74 ppb after 2.0% saline. The mean (95% CI) difference between l-arginine and placebo was 3.01 (0.32 to 5.7) ppb, between d-arginine and placebo 2.42 (0.10 to 4.74) ppb, and between l- and d-arginine 0.59 (–1.56 to 2.74) ppb.

CONCLUSIONS

Exhaled NO decreased with acute bronchoconstriction and returned to baseline with the resolution of bronchoconstriction. Exhaled NO increased following the administration of both l-arginine andd-arginine. Since NOS is stereospecific, this finding suggests that the increase in exhaled NO is not entirely mediated through an increase in NOS enzyme activity. We suggest that arginine may react in a non-stereospecific fashion with reactive oxygen species present in asthmatic airways.

Effect of nebulised L- and D-arginine on exhaled nitric oxide in steroid naive asthma

BACKGROUND

Nitric oxide (NO) is a product of the enzyme nitric oxide synthase (NOS) and is found in normal and asthmatic human airways. The administration of L-arginine results in an increase in airway NO production in asthmatic subjects. This is thought to occur because L-arginine is the substrate for NOS. However, studies in the systemic vasculature suggest that other mechanisms may be responsible.

METHODS

Eight patients with steroid naive asthma each received 2.5 g L-arginine, 2.5 g D-arginine, and 2.0% saline by ultrasonic nebuliser on separate days in a randomised, single blind manner. Exhaled NO was measured by chemiluminescence and spirometric tests were performed before and for 3 hours after each administration. The mean concentration of NO after exposure was calculated from the area under the curve.

RESULTS

L-arginine, D-arginine, and 2.0% saline induced a mean (95% CI) maximal bronchoconstriction of 11.9% (-1.7 to 25.4), 10.0% (2.8 to 17.2), and 8.5% (-2.5 to 19.5) of the starting forced expiratory volume in one second (FEV(1)), respectively. Exhaled NO declined in proportion to the degree of bronchoconstriction (r=0.60, p<0.01). Bronchoconstriction and the acute reduction in exhaled NO resolved within 15 minutes. The mean post-exposure concentration of NO was 15.75 parts per billion (ppb) after L-arginine, 15.16 ppb after D-arginine, and 12.74 ppb after 2.0% saline. The mean (95% CI) difference between L-arginine and placebo was 3.01 (0.32 to 5.7) ppb, between D-arginine and placebo 2.42 (0.10 to 4.74) ppb, and between L- and D-arginine 0.59 (-1.56 to 2.74) ppb.

CONCLUSIONS

Exhaled NO decreased with acute bronchoconstriction and returned to baseline with the resolution of bronchoconstriction. Exhaled NO increased following the administration of both L-arginine and D-arginine. Since NOS is stereospecific, this finding suggests that the increase in exhaled NO is not entirely mediated through an increase in NOS enzyme activity. We suggest that arginine may react in a non-stereospecific fashion with reactive oxygen species present in asthmatic airways.

Total nitrite/nitrate in expired breath condensate of patients with asthma

Production of nitric oxide (NO) is generally increased during inflammatory diseases including asthma. The eventual fate of NO is oxidation to nitrite (NO2) and nitrate (NO3), both of which are end-products of NO metabolism. Hydrogen Peroxide (H2O2) is increased in exhaled breath condensate of asthmatic subjects and may be used as a non-invasive marker of oxidative stress. NO has in some cases been shown to attenuate oxidant-induced lung injury. Total NO2/NO3 concentration and H2O2 levels were measured in expired breath condensate in 50 clinically stable asthmatics [all males, all atopics, mean age 22 (3) SD yrs, forced expiratory volume in 1 sec (FEV1) 91 (10)% predicted, PD20 to histamine 0.262 (0.16) mg 20 on inhaled steroids, 20 smokers, all steroid-naive] and in 10 normal, non-atopic subjects [all males, age 23 (4) yrs, FEV1 101 (14)% predicted, PD20 to histamine 1.3 (0.55) mg]. NO2/NO3 levels were significantly higher in patients with asthma than in normal subjects (1.08, 95% CI 0.86-1.3 microM vs. 0.6; 95% CI 0.46-0.8, P < 0.001). Patients who were on inhaled steroids had significantly ower values compared to steroid-naive (0.71, 95% CI 0.55-0.87 microM vs. 133, 95% CI 1-1.65 microM, P < 0.001). Similar results were observed between smokers and non-smokers (1.11, 95% CI 0.74-1.47 microM vs. 1.77, 95% CI 1.1-24 microM, P < 0.0001). There was a significant positive correlation between NO2/NO3 levels and H2O2 concentration in expired breath condensate (r = 0.48, P < 0.0001). No correlation was observed between NO2/NO3 levels, airway obstruction and bronchial hyper-reactivity as assessed by PD20 to histamine. Total NO2/NO3 levels in expired breath condensate are raised in patients with stable asthma and are significantly related to oxidative stress as assessed by H2O2 concentration. Measurement of expired breath NO2/NO3 and H2O2 levels may be clinically useful in the management of oxidation and inflammation mediated lung injury.

Low-dose theophylline reduces eosinophilic inflammation but not exhaled nitric oxide in mild asthma

Theophylline is well-established in the management of asthma, and there is some evidence of an antiinflammatory effect in asthma. It is not known whether theophylline affects inflammatory markers such as sputum eosinophils and exhaled nitric oxide (NO) in patients with mild asthma not receiving inhaled steroid therapy. In a double-blind, placebo-controlled, cross-over study of 15 patients with mild asthma, we assessed the effect of low-dose theophylline therapy (250 mg twice per day) on eosinophils in induced sputum, bronchoalveolar lavage (BAL) and airway biopsies at the end of both the treatment and placebo periods. Measurements of exhaled nitric oxide (NO) were made at the end of the active and placebo treatment periods of 5 wk each. Low-dose theophylline (mean serum level, 6.1 mg/L) led to a significant reduction in mean (95% confidence interval [CI]) sputum eosinophils from 11.3% (7.80-14.76%) to 8.0% (5.46-10.44%), BAL eosinophils from 3.4% (2.4-4.4%) to 1.7% (1.1-2.3%) and biopsy eosinophils from 1.83% (0.76-2.89%) to 1.20% (0.27-2.13%) compared with placebo (all p < 0.05). There was no significant change in levels of exhaled NO or improvement in lung function and bronchial responsiveness. Low-dose theophylline induced antiinflammatory effects in asthma, reflected by a fall in airway eosinophils with no change in exhaled NO or changes in lung function.

Asthma severity and inflammation markers in children

The relationship of airway inflammation with asthma severity remains unclear. Our aim was to correlate the results of recommended methods of assessment of inflammation with measures of asthma control, in children with a wide range of asthma severity. The study was a cross-sectional investigation of 58 children receiving a wide range of treatment, including 10 treated without regular maintenance therapy and 29 treated with high-dose inhaled corticosteroids (CS). Exhaled nitric oxide (NO), serum eosinophil cationic protein (ECP), and induced sputum (processed for eosinophil count and ECP level) were related to recent symptoms, lung function, and bronchial responsiveness. There was no significant correlation between the results of any

METHOD

Neither did any marker of airway inflammation relate to recent symptoms, unlike PC20, which did. There was a significant, inverse correlation between the forced expiratory volume in 1 s (FEV1) and both NO and sputum ECP (r=-0.46, p=<0.001; r=-0.48, p=0.004, respectively). Sputum eosinophils were inversely related to the dose of methacholine that corresponded to a 20% fall in FEV1 (PC20) (r=-0.57, p=0.02). Serum ECP did not relate to any measure of asthma control. There was no association of any recommended inflammation markers with current symptoms and only a weak relationship between them and physiological measures. The place of these markers remains unclear and their use in clinical practice needs further investigation by long-term longitudinal studies.

PC(20) adenosine 5'-monophosphate is more closely associated with airway inflammation in asthma than PC(20) methacholine

Inhalation of a direct stimulus such as histamine or methacholine is generally used to measure bronchial hyperresponsiveness (BHR). Provocation with adenosine 5'-monophosphate (AMP), an indirect airway challenge, has been suggested to be a better marker of airway inflammation than direct challenges. However, so far little information on this subject is available. The aim of our study was to assess whether the concentration of AMP causing the FEV(1) to drop by 20% (PC(20)) is more closely associated with inflammatory parameters in asthma than PC(20) methacholine. In 120 patients with atopic asthma (median FEV(1) 81% predicted [pred], median age 27 yr), PC(20) methacholine and PC(20) AMP as well as sputum induction, blood sampling, and measurement of nitric oxide in exhaled air were performed. PC(20) methacholine was predominantly predicted by FEV(1) %pred (explained variance [ev] = 18%) with the percentage of peripheral blood monocytes being a weak additional independent predictor (total ev = 23%). By contrast, PC(20) AMP was predominantly predicted by the percentage of eosinophils in sputum (ev = 25%), while FEV(1) %pred was only an additional independent predictor (total ev = 36%). PC(20) AMP reflects more closely the extent of airway inflammation due to asthma than PC(20) methacholine.

Role of exhaled nitric oxide in asthma

Nitric oxide (NO), an evanescent atmospheric gas, has recently been discovered to be an important biological mediator in animals and humans. Nitric oxide plays a key role within the lung in the modulation of a wide variety of functions including pulmonary vascular tone, nonadrenergic non-cholinergic (NANC) transmission and modification of the inflammatory response. Asthma is characterized by chronic airway inflammation and increased synthesis of NO and other highly reactive and toxic substances (reactive oxygen species). Pro- inflammatory cytokines such as TNFalpha and IL-1beta are secreted in asthma and result in inflammatory cell recruitment, but also induce calcium- and calmodulin-independent nitric oxide synthases (iNOS) and perpetuate the inflammatory response within the airways. Nitric oxide is released by several pulmonary cells including epithelial cells, eosinophils and macrophages, and NO has been shown to be increased in conditions associated with airway inflammation, such as asthma and viral infections. Nitric oxide can be measured in the expired air of several species, and exhaled NO can now be rapidly and easily measured by the use of chemiluminescence analysers in humans. Exhaled NO is increased in steroid-naive asthmatic subjects and during an asthma exacerbation, although it returns to baseline levels with appropriate anti-inflammatory treatment, and such measurements have been proposed as a simple non-invasive method of measuring airway inflammation in asthma. Here the chemical and biological properties of NO are briefly discussed, followed by a summary of the methodological considerations relevant to the measurement of exhaled NO and its role in lung diseases including asthma. The origin of exhaled NO is considered, and brief mention made of other potential markers of airway inflammation or oxidant stress in exhaled breath.

Drug treatment of airway inflammation in asthma

Several methods are available for assessing drug effects on airway inflammation and the antiinflammatory effects of drugs for asthma. Cromolyn and theophylline are well-established drugs for the treatment of asthma, and each has antiinflammatory properties. Drugs in development include those aimed at inhibiting inflammatory mediators and immunoglobulin E function; clinical studies, however, have been conducted largely in patients with moderate to severe asthma.

Allergic airway hyperresponsiveness and eosinophil infiltration is reduced by a selective iNOS inhibitor, 1400W, in mice

Nitric oxide (NO) hyperproduction has been reported in asthmatic airways and may contribute to airway inflammatory responses. The purpose of this study was to examine the role of NO via inducible NO synthase (iNOS) in allergic airway inflammation using a selective iNOS inhibitor, N-[3-(aminomethyl)benzyl] acetamidine (1400W), in ovalbumin (OVA)-sensitized Balb/c mice. Sensitized animals were challenged with aerosolized 0.5% OVA for 1 h on two occasions 4 h apart. 1400W or the vehicle was administered by osmotic mini-pump from 2 h before to 24 h after OVA challenge. Twenty-four hours after OVA challenge, the vehicle-treated mice showed a significant airway hyperresponsiveness to intravenous methacholine (P<0.05) as well as an influx of eosinophils into the airways (P<0.05). iNOS immunoreactivity was obvious in the epithelial and, to a lesser extent, the infiltrated inflammatory cells. iNOS protein in the airway assessed by Western blotting also increased. Pretreatment with 1400W almost completely abolished the OVA-induced airway hyperresponsiveness and to a lesser extent eosinophil accumulation into the airways. These results suggest that NO synthesized by iNOS may participate in airway hyperresponsiveness and eosinophil infiltration into the airways after allergic reaction.

In patients with chronic bronchitis a four week trial with inhaled steroids does not attenuate airway inflammation

Systemic corticosteroids have been recommended as a therapeutic option in patients with moderate to severe COPD. In an early stage of the disease, i.e. chronic bronchitis with mild or no airflow obstruction, a trial with inhaled steroids could reveal potential benefits, particularly in terms of a modulation of airway inflammation. We therefore investigated the effect of inhaled fluticasone (1000 microg day(-1)) on markers of airway inflammation in 19 patients with chronic bronchitis (mean+/-SEM FEV1, 83.4+/-3.0% predicted; FEV1/VC, 67.5+/-2.4%) in a double-blind, cross-over, placebo-controlled manner. Visits were performed before and after two 4-week treatment periods. separated by a 4-week washout period. Lung function, the concentration of exhaled nitric oxide, differential cell counts in induced sputum and the number of cells positive for iNOS, as well as the levels of LDH, ECP, neutrophil elastase and IL-8 in sputum supernatants were determined. Although the total cell number decreased significantly after fluticasone (geometric mean 12.3 vs. 7.7 x 10(6)/ml; P<0.05) it was not significantly different from the change observed after placebo (14.2 vs. 10.6 x 10(6)/ml; n.s.). None of the other parameters showed statistically significant changes after fluticasone or placebo and the results did not depend on the presence of airway hyperresponsiveness. We conclude that in patients with chronic bronchitis short-term treatment with inhaled corticosterids did not improve lung function or inflammatory parameters to an extent which was statistically significant as compared to spontaneous variability.

Predictive markers of asthma exacerbation during stepwise dose reduction of inhaled corticosteroids

To determine predictors for failed reduction of inhaled corticosteroids (ICS), in 50 subjects with well-controlled asthma (age 43.7 [18-69]; 22 males) taking a median dose of 1,000 microg ICS/d (100-3,600 microg/d), ICS were halved every 8 wk. Airway hyperresponsiveness (AHR) to a bronchial provocation test (BPT) with histamine was measured at baseline. AHR to BPT with mannitol, spirometry, exhaled nitric oxide (eNO), and, in 31 subjects, sputum inflammatory cells were measured at baseline and at monthly intervals. Thirty-nine subjects suffered an asthma exacerbation. Seven subjects were successfully weaned off ICS. Using a Kaplan- Meier survival analysis, the significant predictors of a failure of ICS reduction were being hyperresponsive to both histamine and mannitol at baseline (p = 0.039), and being hyperresponsive to mannitol during the dose-reduction phase of the study (p = 0.02). Subjects older than 40 yr of age tended to be at greater risk of ICS reduction failure (p = 0.059). Response to mannitol and percentage sputum eosinophils were significantly greater before a failed ICS reduction than before the last successful ICS reduction, whereas there were no significant differences in symptoms, spirometry, or eNO. These findings suggest that documentation of patient's AHR or sputum eosinophils may be useful in guiding the reduction of ICS doses.

Surrogate markers of airway inflammation: inflammometry in paediatric respiratory medicine

Until recently, there has not been any practical way to assess airway inflammation non-invasively in paediatrics. Surrogate markers of airway inflammation are potentially of great importance in the diagnosis and monitoring of inflammatory airways disease in children. A large number of substances in blood, urine and exhaled air or induced sputum are currently under study to evaluate their possible usefulness as markers of airway inflammation. To be useful, a marker should be valid, preferably non-invasive, quick, reproducible, repeatable and cheap. In addition, markers should be studied in relation to their specific purpose because different markers may be useful for different types of airway inflammation. Few, if any, markers will fulfill all these requirements. Most research has focused on applications of markers in asthma, some data refer to cystic fibrosis, infections and ciliary dyskinesia. Of all surrogate markers, exhaled nitric oxide has been studied the most and seems to offer information that should be evaluated for its relevance to clinical practice. Before introducing markers of inflammation into daily practice, analysis of benefits and costs are needed. There is little doubt that 'inflammometry' will be a major step forward and will be useful in differentiating airways diseases and improving treatment.

Therapeutic ratio of inhaled corticosteroids in adult asthma. A dose-range comparison between fluticasone propionate and budesonide, measuring their effect on bronchial hyperresponsiveness and adrenal cortex function

Inhaled corticosteroids have become the mainstay treatment of bronchial asthma. However, simultaneous evaluations of efficacy and side effects are few. This study aimed to compare the relative effect of fluticasone propionate (FP) and budesonide (BUD) on bronchial responsiveness and endogenous cortisol secretion in adults with asthma. The study was double-blind and included 66 adults with asthma, who were randomized to FP (n = 33) or BUD (n = 33). Prestudy, all participants were clinically stable, using inhaled corticosteroids and hyperresponsive to methacholine. Eligible patients were randomized to three consecutive 2-wk periods with either FP 250 microg twice daily, FP 500 microg twice daily, and FP 1,000 microg twice daily, or BUD 400 microg twice daily, BUD 800 microg twice daily, and BUD 1,600 microg twice daily, delivered by Diskhaler and Turbuhaler, respectively. Before randomization and at the end of each treatment, bronchial methacholine PD(20), 24-h urinary cortisol excretion (24-h UC), plasma cortisol, serum osteocalcin, and blood eosinophils were determined. The relative PD(20) potency between FP and BUD was 2.51 (95% CI, 1.05-5.99; p < 0. 05), while the relative 24-h UC potency was 0.60 (95% CI, 0.44-0.83; p < 0.01). The differential therapeutic ratio (FP/BUD) based on PD(20) potency and 24-h UC was 4.18 (95% CI, 1.16-15.03; p < 0.05). The difference in systemic potency was also seen for plasma cortisol, serum osteocalcin, and blood eosinophils. Therapeutic ratio over a wide dose range, determined by impact on bronchial responsiveness and endogenous corticosteroid production, seems to favor FP.

Partial reversibility of airflow limitation and increased exhaled NO and sputum eosinophilia in chronic obstructive pulmonary disease

We investigated the relationship between the reversibility of airflow limitation, the concentration of nitric oxide (NO) in exhaled air, and the inflammatory cells in the sputum of patients with stable chronic obstructive pulmonary disease (COPD). We examined nine normal healthy control subjects and 20 nonatopic patients with COPD. Ten patients had no reversibility of airflow limitation (increase in FEV(1) of < 12% and < 200 ml after 200 microg of inhaled salbutamol), and 10 patients had partial reversibility of airflow limitation (increase in FEV(1) of < 12% but > 200 ml after 200 microg of inhaled salbutamol). Exhaled NO levels were higher in COPD patients with partial reversibility of airflow limitation than in those with no reversibility of airflow limitation (median 24 [interquartile range 15.3 to 32] ppb versus 8.9 [4.6 to 14.7] ppb; p < 0.01). Compared with healthy control subjects, only COPD patients with partial reversibility of airflow limitation had increased concentrations of sputum eosinophils. We conclude that, in patients with stable COPD, even a partial bronchodilator response to inhaled salbutamol is associated with increased exhaled NO and sputum eosinophilia, suggesting that these patients may have a different response to treatment than do those without reversible airflow limitation.

Atopy influences exhaled nitric oxide levels in adult asthmatics

STUDY OBJECTIVE

To examine whether atopy influences exhaled nitric oxide (NO) levels in adults with established asthma.

SETTING

Specialist respiratory unit in a university teaching hospital.

PATIENTS

Twenty-eight asthmatics (mean FEV(1), 85.7%) receiving short-acting inhaled bronchodilators and a range of inhaled steroids (0 to 4,000 microg/d).

INTERVENTIONS

Subjects were studied on two occasions, 5 to 7 days apart, between September and March.

MEASUREMENTS AND RESULTS

On the first day, FEV(1), exhaled NO, and histamine challenge were performed. On the second day, exhaled NO, total IgE, and skin-prick testing to six common allergens were conducted. Exhaled NO was measured with the single exhalation method. We found exhaled NO levels to correlate positively with total IgE (r = 0.43, p = 0.02) and number of positive skin-prick tests (p = 0. 002). By contrast, there was no significant correlation between exhaled NO and FEV(1) or the provocative concentration causing a 20% fall in FEV(1). Subanalyses of steroid-treated and steroid-naive patients in this group revealed the same findings.

CONCLUSION

Exhaled NO levels in asthmatics correlate more closely with atopy than with bronchial hyperreactivity and lung function.

Exhaled nitric oxide following leukotriene E(4) and methacholine inhalation in patients with asthma

Nitric oxide (NO) is a molecular gas that can be recovered in higher levels from the exhaled gas of subjects with asthma than from subjects without asthma. However, the precise mechanisms responsible of promoting increased fraction of expired nitric oxide (FE(NO)) in asthma are unknown. As leukotriene antagonism has been shown to reduce FE(NO) in patients with asthma, we hypothesized that leukotrienes mediate the increased FE(NO) encountered in this condition. Furthermore, because leukotriene antagonism stabilizes serum eosinophil markers during reductions in inhaled corticosteroid doses, and FE(NO) has been shown to correlate with sputum eosinophils in asthma, we reasoned that the effect of leukotrienes on FE(NO) might be mediated by eosinophils recruited to the airway by leukotrienes. To test this hypothesis, we performed methacholine and leukotriene (LT) E(4) bronchoprovocation challenges in 16 subjects with atopic asthma and measured FE(NO) and sputum differential counts before and after bronchoprovocation. We then compared FE(NO) in the seven subjects who developed increased sputum eosinophils following LTE(4) inhalation with values measured after methacholine inhalation in these seven subjects. Following LTE(4) inhalation, eosinophils rose from 4.01 +/- 0.89% pre-LTE(4) to 8.33 +/- 1.52% post-LTE(4). The mean change in sputum eosinophils from baseline after LTE(4) inhalation was larger than that after methacholine inhalation (+4.31 +/- 1.25% versus -1.14 +/- 0.93%). After LTE(4) inhalation, FE(NO) levels did not differ from prechallenge baseline or from levels following methacholine inhalation (ANOVA p > 0.05). These data indicate that neither LTE(4) nor recruitment of eosinophils into the airway by LTE(4) is a sufficient stimulus to acutely increase FE(NO) in subjects with asthma.

Increased nitrotyrosine in exhaled breath condensate of patients with asthma

The reaction of nitric oxide (NO) and superoxide anions (O(2)(-)) in the airway results in the formation of peroxynitrite, a highly reactive oxidant species. Peroxynitrite reacts with tyrosine residues in proteins to form the stable product nitrotyrosine. We investigated whether nitrotyrosine in exhaled breath condensates may be increased in patients with asthma. Four groups of nonsmoking subjects were studied. We measured exhaled NO, nitrotyrosine, and leukotrienes concentrations in breath condensate in healthy nonatopic subjects (n = 15) and in patients with mild asthma (steroid naive, n = 15), moderate asthma (inhaled steroid treatment, n = 12), and severe asthma (oral steroid treatment, n = 12). Exhaled NO was increased significantly in patients with mild (19.2 +/- 2.7 ppb, p < 0.01) and moderate asthma (14.0 +/- 1.53 ppb, p < 0.05), as compared with normal control (6.58 +/- 0.61 ppb). The levels of LTC(4)/D(4)/E(4) and LTB(4) were increased significantly in patients with moderate and severe asthma treated with steroids. Nitrotyrosine concentrations were detectable (6.3 +/- 0.8 ng/ml) in breath condensate of normal subjects, and were increased significantly in patients with mild asthma (15.3 +/- 2.0 ng/ml, p < 0.01). However, the levels of nitrotyrosine in exhaled condensate were lower in patients with moderate (5.0 +/- 0.6 ng/ml) and severe asthma (3.3 +/- 0.6 ng/ml, p < 0.05). There was a significant correlation between nitrotyrosine in breath condensate and exhaled NO in patients with mild asthma (r = 0.65, p < 0.05). We conclude that nitrotyrosine formation in exhaled breath condensates may be a marker of oxidative stress in airways of asthma.

Effects of once-daily formoterol and budesonide given alone or in combination on surrogate inflammatory markers in asthmatic adults

OBJECTIVES

We wished to evaluate the effects of once-daily combination therapy on surrogate inflammatory markers.

METHODS

Fifteen patients with atopic persistent asthma were evaluated (mean age, 32.4 years; FEV(1), 75.2% predicted) in a randomized, double-blind, double-dummy, placebo-controlled crossover study with a 1-week placebo washout period, comparing the following once-daily nighttime treatments: (1) formoterol (FM), 12 microg, for 2 weeks and FM, 24 microg, for 2 weeks; or (2) budesonide (BUD), 400 microg, for 2 weeks and BUD, 800 microg, for 2 weeks; or (3) FM, 12 microg, plus BUD, 400 microg, for 2 weeks and FM, 24 microg, plus BUD, 800 microg, for 2 weeks. Adenosine monophosphate (AMP) bronchial challenge, exhaled nitric oxide (NO), and serum eosinophilic cationic protein (ECP) were evaluated at 12 h postdosing after administration of each placebo and after 2 and 4 weeks of each treatment.

RESULTS

The results of AMP challenge (provocative concentration causing a 20% fall in FEV(1)) at 4 weeks showed significant (p<0.05) improvements after patients had received all active treatments compared to placebo (20 mg/mL), with FM plus BUD, 261 mg/mL, being superior (p<0.05) to FM alone, 82 mg/mL, but not to BUD, 201 mg/mL. NO and ECP showed significant (p<0.05) reductions compared to placebo with FM plus BUD or BUD alone but not with FM alone. Combination therapy was associated with optimal patient preference (rank order, FM plus BUD > FM > BUD; p<0.0005), highest domiciliary peak expiratory flow, and lowest rescue inhaler usage. All three treatments produced equivalent improvements in spirometry.

CONCLUSIONS

Patients preferred once-daily combination therapy, but this had no greater effect on inflammatory markers than therapy with BUD alone. FM alone had no anti-inflammatory activity but exhibited bronchoprotection. This emphasizes the importance of first optimizing anti-inflammatory control with inhaled corticosteroids before considering adding a regular long-acting beta(2)-agonist.

Screening for bronchial hyperresponsiveness using methacholine and adenosine monophosphate. Relationship to asthma severity and beta(2)-receptor genotype

Bronchial hyperresponsiveness (BHR) is a key feature of asthma and may be measured by direct methacholine challenge or indirect adenosine monophosphate (AMP) challenge. We performed a retrospective analysis of our database (n = 487) of patients with asthma with the aim first, to compare methacholine and AMP challenge as screening tools, and second, to identify any relationships between BHR and disease severity markers or beta(2)-adrenoceptor genotype. Of these subjects, 258 had a methacholine challenge, 259 an AMP challenge and 185 both. Of subjects having both, 140 (76%) were methacholine responsive with PD(20) < 500 microgram (PC(20) < 5 mg/ml) and 92 (50%) were AMP responsive with PC(20) < 200 mg/ ml. For those who were AMP unresponsive 57% were methacholine responsive, whereas for the methacholine nonresponders 11% were AMP responsive. Methacholine (but not AMP)-responsive patients had a significantly (p < 0.05) lower % predicted FEV(1) and FEF(25-75) and higher inhaled corticosteroid dose than unresponsive patients. Finally, subjects with a glycine allele at codon 16 had significantly (p < 0.05) increased BHR to methacholine but not AMP. Our results suggest that methacholine is a more appropriate screening tool for BHR than AMP as it was more sensitive in our population and was also related to asthma severity. In addition, we have demonstrated an association between the glycine allele (codon 16) and increased BHR to methacholine.

A comparison of exhaled nitric oxide and induced sputum as markers of airway inflammation

BACKGROUND

Exhaled nitric oxide (ENO) has been proposed as a noninvasive marker of airway inflammation in asthma.

OBJECTIVE

We investigated the relationships among ENO, eosinophilic airway inflammation as measured by induced sputum, and physiologic parameters of disease severity (spirometry and methacholine PC(20)). We also examined the effect of corticosteroid treatment and atopy on ENO levels and eosinophil counts in induced sputum.

METHODS

Measurements were taken on one day in 22 healthy nonatopic subjects, 28 healthy atopic subjects, 38 asthmatic subjects not taking inhaled steroids, 35 asthmatic subjects taking inhaled steroids, and 8 subjects with eosinophilic bronchitis without asthma.

RESULTS

ENO levels showed significant but weak correlations with eosinophil differential counts in the steroid-naive asthmatic and healthy atopic groups (r (s) < 0.05). ENO levels were significantly lower in the asthmatic subjects taking steroids compared with the asthmatic subjects not taking steroids, despite there being no difference in the sputum cell counts, and a tendency to increased airflow limitation. ENO levels and sputum eosinophil counts were equally good at differentiating from steroid-naive asthmatic subjects. ENO levels were consistently raised in subjects with eosinophilic bronchitis without asthma. Atopy had no effect on ENO levels in the healthy subjects.

CONCLUSION

We conclude that ENO is likely to have limited utility as a surrogate clinical measurement for either the presence or severity of eosinophilic airway inflammation, except in steroid-naive subjects.

Adolescents in clinical remission of atopic asthma have elevated exhaled nitric oxide levels and bronchial hyperresponsiveness

Symptoms of atopic asthma often decrease or even seem to disappear around puberty. The aim of this study was to investigate whether this so-called clinical remission is accompanied by remission of airway inflammation, since symptoms relapse in a substantial proportion of subjects later in life. To assess indicators of inflammation and/or structural damage of the airways, exhaled nitric oxide (eNO) and bronchial responsiveness to adenosine-5'-monophosphate (AMP) and methacholine (MCh) were determined in 21 subjects in clinical remission of atopic asthma. Clinical remission was defined as complete absence of symptoms of asthma without the use of any medication in the year preceding the study. Results were compared with those of 21 patients with current asthma and 18 healthy control subjects. We found significantly higher eNO values in the remission group than in healthy controls (geometric mean, 18.9 and 1.0 ppb, respectively; p < 0.001) whereas eNO values of the remission group and those of the subjects with current asthma (geometric mean, 21.9 ppb) were similar (p = 0.09). The responsiveness to both AMP and MCh of subjects in clinical remission was significantly higher as compared with responsiveness of healthy controls, and lower than responsiveness of subjects with current asthma. A significant correlation could be established between eNO and responsiveness to AMP, but not between eNO and responsiveness to MCh. The results of this study are suggestive of persistent airway inflammation during clinical remission of atopic asthma. We speculate that subclinical inflammation is a risk factor for asthma relapse later in life, and that eNO and responsiveness to both AMP and MCh can be used as different, noninvasive indices of the inflammatory process of the airways.