Expired nitric oxide as a marker for childhood asthma

Effects of montelukast on symptoms and eNO in children with mild to moderate asthma

BACKGROUND

Asthma is a chronic inflammatory airway disease. Exhaled nitric oxide (eNO) is a marker reflecting airway inflammation. This study was conducted to investigate whether montelukast, a leukotriene receptor antagonist, could be used for the management of asthma and how fast the montelukast sodium decreased airway inflammation as demonstrated by eNO levels.

METHODS

Twenty children aged 6-14 years (mean age: 9.2 +/- 2.4 years; mean weight 30 +/- 4.6 kg) with mild to moderate asthma were recruited for the study. They received montelukast plus an inhaled short-acting beta2 agonist as open and uncontrolled therapy. Asthma score (AS) and peak expiratory flow rate (PEFR) and eNO concentrations were measured at pretreatment (0 week) and post-treatment (1 and 2 weeks) as well as 2 weeks after withdrawal of therapy.

RESULTS

In one week, the eNO levels (33.3 +/- 15.5 p.p.b. vs 14.8 +/- 8.6 p.p.b.; P < 0.05), and AS (4.2 +/- 1.3 vs 1.8 +/- 1.3; P < 0.05) decreased rapidly, and PEFR (206.9 +/- 69.7 L/min vs 236.2 +/- 69.8 L/min; P < 0.05) increased. Concurrent beta2 agonist use decreased from a mean +/- SD of 2.2 +/- 0.4-1.3 +/- 0.3 puffs per weeks (P < 0.05). After the withdrawal of treatment for 2 weeks, the eNO levels (29.2 +/- 16.1 p.p.b) rebounded again, although the improvements in AS (1.1 +/- 1.3) and PEFR (245.0 +/- 91.3 L/min) persisted.

CONCLUSION

Oral montelukast sodium treatment of these children with mild to moderate asthma effectively improved asthmatic symptoms and suppressed airway inflammation in 1 week, suggesting that this leukotriene antagonist combined with short-acting beta2 agonists may provide effective treatment option in mild to moderate childhood asthma. Larger, controlled, and double-blinded studies are needed to confirm these preliminary open uncontrolled observations.

Methodological issues related to exhaled nitric oxide measurement in children aged four to six years

This study was designed to test five methodological issues related to measurement of fractional exhaled nitric oxide (FE(NO)) in children aged 4-6 years using commercially available apparatus. Participants attended two randomly selected schools. A respiratory questionnaire was completed. Measurements of FE(NO) were made on successive days, using a NIOX analyzer employing standard or modified methodologies. Ninety-one children participated in the study (mean age, 5.3 years; 46 boys). Using a standard methodology (n = 61), FE(NO) was successfully measured in 28 (46%) children, 1/12 aged 4 years, 12/25 aged 5 years, and 15/24 aged 6 years (trend test P = 0.01). On the first assessment, FE(NO) could be determined in more boys than girls (64% vs. 30%, respectively, P = 0.008), but this gender difference was not apparent on the second assessment. Exhaled NO was reproducible over a 24-hr period; the mean difference between repeated measurements of natural log (ln) FE(NO) was 0.016 parts per billion (ppb) (95% confidence limits, -0.479, 0.511), n = 20. Data from 35 assessments showed that values of FE(NO) did not alter over nine individual, successive measurements. Use of a modified methodology in 30 children increased success in obtaining FE(NO), but these values were unreliable. In conclusion, measurements of FE(NO) can be obtained in the majority of 5- and 6-year-old but not 4-year-old children. Exhaled NO measurements were reproducible over a 24-hr interval, and did not change over up to nine expiratory maneuvers in these young children.

Titrating steroids on exhaled nitric oxide in children with asthma: a randomized controlled trial

RATIONALE

Corticosteroids are the antiinflammatory treatment of choice in asthma. Treatment guidelines are mainly symptom-driven but symptoms are not closely related to airway inflammation. The fraction of nitric oxide in exhaled air (FENO) is a marker of airway inflammation in asthma.

OBJECTIVE

We evaluated whether titrating steroids on FENO improved asthma management in children.

METHODS

Eighty-five children with atopic asthma, using inhaled steroids, were allocated to a FENO group (n=39) in which treatment decisions were made on both FENO and symptoms, or to a symptom group (n=46) treated on symptoms only. Children were seen every 3 months over a 1-year period.

MEASUREMENTS

Symptoms were scored during 2 weeks before visits and 4 weeks before the final visit. FeNO was measured at all visits, and airway hyperresponsiveness and FEV1 were measured at the start and end of the study. Primary endpoint was cumulative steroid dose.

RESULTS

Changes in steroid dose from baseline did not differ between groups. In the FENO group, hyperresponsiveness improved more than in the symptom group (2.5 vs. 1.1 doubling dose, p=0.04). FEV1 in the FENO group improved, and the change in FEV1 was not significantly different between groups. The FENO group had 8 severe exacerbations versus 18 in the symptom group. The change in symptom scores did not differ between groups. FENO increased in the symptom group; the change in FENO from baseline differed between groups (p=0.02).

CONCLUSION

In children with asthma, 1 year of steroid titration on FENO did not result in higher steroid doses and did improve airway hyperresponsiveness and inflammation.

Measurement of exhaled nitric oxide in young children during tidal breathing through a facemask

Measurement of exhaled nitric oxide (eNO) offers a non-invasive means for assessment of airway inflammation. The currently available methods are difficult to apply in preschool children. We evaluated four methods potentially applicable for eNO measurement during tidal breathing in young children. eNO was assessed during tidal breathing in 24 children, 2-7 yr old, using a facemask which separated nasal and oral airflow. Facemasks with and without a one-way valve allowing exhalation through the nose were used. Expiratory flow control was not attempted. Measurements of eNO were performed both on-line and off-line. In 11 children, 8-12 yr old, measurements were compared with the standard single breath on-line method. eNO was significantly lower applying the one-way valve in on-line and off-line measurements in comparison with measurements without the valve [4.6 and 3.9 parts per billion (ppb) vs. 6.9 ppb and 6.5 ppb]. The mean within subject coefficient of variation (CV) was significantly lower in on-line measurements with the one-way valve (9.6%) compared with the other three methods (18.8, 27.7 and 29.3% respectively). Measurements with a facemask fitted with a one-way valve yielded similar eNO levels as the standard single breath method (7.0 ppb vs. 6.9 ppb) and reproducibility (9.8% vs. 7.1%). In conclusion, reproducible measurements of eNO can be obtained without control of expiration flow using a facemask fitted with a one-way valve on the nasal compartment. The likely explanation to this is that the one-way valve reduces the admixture of nasal NO, thereby improving the reliability of eNO measurements.

Minimal exhaled nitric oxide production in the lower respiratory tract of healthy children aged 2 to 7 years

BACKGROUND

Exhaled nitric oxide (eNO) is elevated in inflammatory airway conditions, e.g. asthma. We measured eNO levels in normal preschool children for whom there is little data available and in whom the prevalence of asthma is high.

SUBJECTS AND METHODS

Fifty children, 2-7 years old, undergoing elective surgery, excluding airway procedures, were recruited. Children with known respiratory disease or acute viral infections were excluded. Gas for eNO measurement was collected in a non-diffusion bag via 1) the mask after inhalation induction of anesthesia, 2) endotreacheal tube (ETT) or laryngeal mask airway (LMA), and 3) during emergence. Measurement was off-line by chemiluminescent analyzer.

RESULTS

Mean eNO level by mask was 10.23 ppb (mean value+/-SD of 8.8-11.1 ppb) after induction and 8.35 ppb (mean value+/-SD of 5.9-10.8 ppb) on emergence. Mean eNO for the intubated group (n=25) was 0.75 ppb (mean value+/-SD of 0.4-1 ppb) (P<0.0001 vs mask); mean eNO for the LMA group (n=25) was 2.6 ppb (mean value+/-SD of 2-3.2 ppb), which differed from the mask (P<0.0001), and from ETT values (P<0.0001).

CONCLUSIONS

Most eNO is produced by the upper airway in healthy pre-school children. The lower airway constitutive eNO production is very low. The LMA does not completely isolate the upper airway and current mask collection techniques allow significant contamination of samples by sino-nasal eNO production in young children.

Measuring exhaled nitric oxide levels in adults: the importance of atopy and airway responsiveness

BACKGROUND

Raised exhaled nitric oxide (Feno) levels have been associated with asthma. However, we have found that in children, Feno was increased in atopic children with increased airway responsiveness (AR), and this was independent of a diagnosis of asthma.

STUDY OBJECTIVES

The current study was designed to test the hypothesis that in adults there is no association between Feno and asthma after controlling for atopy and AR.

MEASUREMENTS

One hundred fifteen adults (77 women; mean age, 41 years) underwent an assessment that included Feno measurements, spirometry, skin-prick testing, blood eosinophil count, and inhaled histamine challenge (results are expressed as a dose-response slope [DRS]).

RESULTS

When only atopic individuals were considered (n = 73), Feno was positively associated with the DRS (p = 0.003), male gender (0.02), and negatively associated with current smoking (p = 0.09). Only male gender (p = 0.03) was associated with Feno among nonatopic individuals (n = 36). In multivariate analysis, there was no association between Feno and current asthma, current wheeze, or asthma ever.

CONCLUSIONS

We conclude that in adult subjects, elevated Feno measurements are associated with a phenotype characterized by atopy and increased AR regardless of the presence of asthma or asthma-like symptoms.

Nitric oxide synthase inhibition: therapeutic potential in asthma

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

Phenotype specific treatment of asthma in childhood

The term "asthma syndrome" encompasses a range of disorders, all characterised clinically by combinations of cough, wheeze and breathlessness. In older children, evidence of variable airway obstruction is manifest by change in peak flow over time or with treatment, reduction in peak flow on exercise, and a positive methacholine challenge. The underlying pathology includes combinations of bronchial hyperreactivity (BHR), airway inflammation and alterations in underlying baseline airway calibre or compliance. This is not merely of academic importance, but is fundamental to organizing appropriate treatment. In children with symptoms with viral colds and also between colds, and in particular if they are atopic, the underlying abnormality is likely to be T-cell driven, eosinophil-mediated airway inflammation. There is compelling evidence that early treatment with inhaled corticosteroids is essential if airway remodelling is to be avoided and optimum long-term lung function is to be achieved. The pathophysiology of wheezing with viral colds in the non-atopic infant is completely different; such infants have evidence of abnormal lung function soon after birth and before their first episode of viral wheeze, and no evidence of either bronchial hyperreactivity or airflow inflammation. Response to inhaled steroids is very poor. For most infants with wheeze, it is currently not possible to predict whether they will go on to the picture of established asthma. Post-bronchiolitic asthma syndrome also does not respond to inhaled steroids, because prolonged symptoms are likely due to abnormal pre-morbid airway function, albeit worsened by atopy. Phenotype-specific treatment is also important in older children who have severer asthma and do not respond to high dose inhaled steroids. We have delineated a group with marked BHR but no evidence of inflammation who respond to subcutaneous terbutaline, and a second group with steroid resistant inflammation who may do better with cyclosporin. A phenotype-specific treatment approach may also help to delineate which add on therapy (long-acting beta agonist, leukotriene receptor antagonist, theophylline) is best for children with moderate asthma not controlled by moderate dose (400 mcg/day) inhaled corticosteroids. Asthma is not one disease but many, and attention to delineating clinical phenotypes, rather than being obsessed with guidelines based on large heterogeneous groups, may allow rational individual treatment.

Biological markers in diagnosing, monitoring, and treating asthma: a focus on noninvasive measurements

Asthma is a major concern for society, healthcare professionals, and individuals and families directly affected by asthma due to rising morbidity rates and costs associated with the disease. The pathological hallmark of asthma is airway inflammation that is considered to be a major cause of exacerbations and persistent structural alterations of the airways. Assessing airway inflammation is important for investigating the underlying mechanisms of the disease and possibly for following the progression and resolution of the disease. The presence and type of airway inflammation can be difficult to detect clinically, and may result in delays in initiating appropriate therapy. The purpose of this article is to review noninvasive methods for assessing biological markers of airway inflammation and their potential role in the future for diagnosing, monitoring, and treating asthma. The article reviews the noninvasive measurements of induced sputum and exhaled nitric oxide as indicators of airway inflammation.

Decreased arginine bioavailability and increased serum arginase activity in asthma

Recent studies suggest that a nitric oxide (NO) deficiency and elevated arginase activity may play a role in the pathogenesis of asthma. Although much attention has been directed toward measurements of exhaled NO in asthma, no studies to date have evaluated levels of plasma arginase or arginine, the substrate for NO production, in patients with asthma. This study, therefore, measured amino acid levels, arginase activity, and nitric oxide metabolites in the blood of patients with asthma, as well as NO in exhaled breath. Although levels of virtually all amino acids were reduced, patients with asthma exhibited a striking reduction in plasma arginine levels compared with normal control subjects without asthma (45 +/- 22 vs. 94 +/- 29 microM, p < 0.0001), and serum arginase activity was elevated (1.6 +/- 0.8 vs. 0.5 +/- 0.3 micromol/ml/hour, asthma vs. control, p < 0.0001). High arginase activity in patients with asthma may contribute to low circulating arginine levels, thereby limiting arginine bioavailability and creating a NO deficiency that induces hyperreactive airways. Addressing the alterations in arginine metabolism may result in new strategies for treatment of asthma.

Evaluation of the long-term pancreatic effects of constitutive nitric oxide synthase inhibition in dogs

Constitutive and inducible isoforms of nitric oxide synthase (NOS) catalyze the synthesis of nitric oxide (NO) from L-arginine in various tissues and in different pathophysiologic states. Short-term treatment with NOS inhibitors has been associated with pancreatic enzyme elevations and pancreatic acinar cell degeneration; however, long-term pancreatic effects of NOS inhibition are not known. The purpose of this study was to evaluate the subchronic pancreatic effects of L-nitro-arginine (LNA), a compound that preferentially inhibits constitutive NOS isoforms. LNA was administered orally at doses of 10 and 30 mg/kg per day to 6 female dogs/group for 4 weeks. To differentiate whether the pancreatic effects of LNA may be related to its arginine structure, an additional group was given L-arginine (L-Arg) at plasma concentrations similar to the high dose of LNA (30 mg/kg per day). Pancreatic effects were monitored by changes in serum levels of pancreatic enzymes at regular intervals and by microscopic examinations at the end of the study. Both LNA and L-Arg were systematically available throughout the 4-week study period. LNA produced dose-related elevations (1.3-10-fold above concurrent control) in serum levels of pancreatic enzymes (amylase, lipase and trypsin-like immunoreactivity) during the 4-week treatment period with peak elevations occurring during the first week. Histologic assessments of the pancreas conducted at the end of the 4-week dosing period were unremarkable. Additionally, LNA treatment resulted in reduction in heart rate (40%), gastric distension and gastric mucosal erosion and ulceration. No pancreatic, cardiac, or gastric effects were seen with L-Arg, indicating that above effects were likely due to NOS inhibition. Results of this study confirmed previous observations of acute pancreatic alterations following the inhibition of constitutive NOS isoforms. However, these pancreatic alterations appear to be only transient effects as elevations in serum enzymes declined over time and no structural acinar cell damage was seen after continuous treatment with LNA for 4 weeks, suggesting an adaptation to NOS inhibition over time.

Exhaled nitric oxide is age-dependent in asthma

We determined whether the exhaled nitric oxide (eNO) level in asthmatics is age-dependent. Eighty-seven asthmatic patients aged 2-41 years were studied. Hyperreactivity to adenosine 5'-monophosphate (AMP) was used to confirm asthma (</= 200 mg/ml). In the younger group of children (2-5 years), AMP challenge was performed by the provocation concentration causing wheeze (PCW) method, while in the older groups of patients (6-41 years), regular spirometry was used. Exhaled NO was measured in the younger group by the tidal breathing method (TBm) and in the older subjects by the slow vital capacity method (SVCm). TBm and SVCm were compared in 21 other subjects, and there was a significant correlation between the two values (r = 0.96, P < 0.0001). The equation of correlation between the two methods was eNOTBm = 0.78eNOSVCm - 0.51. Within asthmatic patients, we found a significant increase in eNO with age (P < 0.0001), while there was no significant difference in AMP reactivity (P = 0.35). We conclude that eNO in asthmatic patients is age-dependent, with lower values in young children.

Flow dependency and off-line measurement of exhaled NO in children

Levels of exhaled nitric oxide (eNO) are flow-dependent, and the choice of an optimal flow rate for off-line and on-line eNO measurement has raised much debate. Recently, a flow rate of 50 ml/s was recommended, but children younger than 5-6 years are not capable of stabilizing their expiratory flow at low flow rates. The power of off-line eNO values to discriminate between normal and atopic children was therefore evaluated at different exhalation flow rates. At flow rates of both 8.3 ml/s and of 350 ml/s, children (8-12 years) sensitive to house dust mite have two-fold higher eNO values (p < 0.001) as compared with children lacking such a sensitivity. The power of eNO to discriminate between normal and atopic subjects was similar at the two flow rates (no difference in AUC of receiver operation curves, p = 0.89). All children from 4.5 to 5 years of age (n = 29) could perform a single off-line exhalation manoeuvre at high (>350 ml/s) but not at low (8.3 ml/s) flow rates. At high exhalation flow rate, eNO was 7.1 +/- 2.4 (mean +/- SD) median, 6.5 p.p.b. with a mean variation coefficient of 5.5%. Depending on their developmental level, about half of the younger children (35-46 months of age) could perform an off-line exhalation manoeuvre at high flow rate with good reproducibility (mean variation coefficient of 6.6%). It is concluded that an exhalation flow rate of 350 ml/s is feasible to determine off-line eNO-values in children from 3.5 years of age, and that this high flow rate does not compromise the power of eNO to detect allergic disease.

Hydroxyurea and arginine therapy: impact on nitric oxide production in sickle cell disease

PURPOSE

Recent data suggest that hydroxyurea (HU) increases the production of nitric oxide (NO), a potent vasodilator. NO is normally metabolized from l-Arginine (Arg). However, in vitro and animal experiments suggest that HU is the NO donor itself. In contrast, a recent study indicates that nitric oxide synthase (NOS) may play a role. Since adults with sickle cell disease (SCD) are Arg-deficient, Arg availability may limit the ability of HU to maximally impact NO production if an NOS mechanism is involved. The authors have previously shown that Arg supplementation alone induces a paradoxical decrease in NO metabolite (NO(x)) production.

METHODS

The authors studied the effects of HU and Arg supplementation on NO(x) production. HU alone or HU + Arg was administered to patients with SCD at steady state, and sequential levels of Arg, serum NO(x) and exhaled NO were followed over 4 hours.

RESULTS

After HU + Arg, all patients demonstrated a significant increase in serum NO(x) production within 2 hours. When the same patients were treated with HU alone (5.1 +/- 2 micromol/L), a mixed response occurred. NO(x) levels increased in four patients and decreased in one patient (-23.3 micromol/L).

CONCLUSIONS

While Arg alone does not increase serum NO(x) production in SCD patients at steady state, it does when given together with HU. Hence, co-administration of Arg with HU may augment the NO(x) response in SCD and improve utilization of Arg in patients at steady state.

Experimental rhinovirus challenges in adults with mild asthma: response to infection in relation to IgE

BACKGROUND

Although most children and young adults with asthma are atopic, exacerbations of asthma are frequently associated with viral respiratory tract infections, especially those caused by rhinovirus (HRV).

OBJECTIVE

Young atopic adults with mild asthma were evaluated before and during an experimental HRV infection to test the hypothesis that airway inflammation before virus inoculation may be a risk factor for an adverse response to HRV.

METHODS

Experimental HRV infections were evaluated in 16 allergic volunteers with mild asthma and 9 nonatopic control patients (age, 18 to 30 years). Before virus inoculation, each participant was screened with tests for lung function, prick skin tests for sensitization to common aeroallergens, measurements of total serum IgE, and serum neutralizing antibody to rhinovirus-16 (the serotype used for inoculation). The response to infection was monitored for 21 days by using symptom diary cards, tests for lung function, and markers of airway inflammation in nasal washes, blood, and expired air.

RESULTS

During the infection, asthmatic patients had cumulative upper and lower respiratory tract symptom scores that were significantly greater over the course of 21 days than scores from the control patients. At baseline, the asthmatic patients also had increased sensitivity to methacholine and significantly lower values for FEV(1) (percent predicted) than the control patients (geometric mean and intraquartile values: 87% [79% to 91%] for the asthmatic patients and 101% [90% to 104%] for the control patients, P <.03). Among the patients with mild asthma, 6 had levels of total serum IgE that were substantially elevated (range, 371 to 820 IU/mL) compared with 10 who had lower levels (range, 29 to 124 IU/mL). Those with high levels of IgE had significantly greater lower respiratory tract symptom scores during the initial 4 days of the infection than the low IgE group. They also had higher total blood eosinophil counts at baseline, increased eosinophil cationic protein in their nasal washes (>200 ng/mL), and augmented levels of expired nitric oxide at baseline and during peak cold symptoms. In contrast, levels of soluble intracellular adhesion molecule-1 in nasal wash supernatants from the asthmatic patients with high IgE were diminished, both at baseline and during the infection.

CONCLUSIONS

The reduced lung function and increased markers of inflammation observed before virus inoculation in the asthmatic patients who had high levels of total serum IgE may be risk factors for an adverse response to infections with HRV.

Effectiveness of pharmacotherapy in asthmatic preschool children

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

Sinus computed tomography scan and markers of inflammation in vocal cord dysfunction and asthma

BACKGROUND

The inappropriate closure of the vocal cords is characteristic of vocal cord dysfunction (VCD). These patients present with wheezing and frequently receive a misdiagnosis of asthma.

OBJECTIVE

To demonstrate the ability of computed tomography (CT) scored for the presence and extent of sinus disease and markers of inflammation to distinguish patients with VCD from patients with asthma.

METHODS

Comparisons of 13 patients with VCD were made to 77 patients presenting to the emergency room with acute asthma, 31 non-acute asthmatic patients, and 65 nonasthmatic controls. Evaluation consisted of exhaled nitric oxide gas (eNO), circulating eosinophils, and total serum immunoglobulin (Ig)E, as well as the sinus CT scan.

RESULTS

Extensive sinus CT changes were present in 23 of 74 acute asthmatic patients, 5 of 29 non-acute asthmatic patients, and 2 of 59 nonasthmatic controls. In addition, absolute eosinophil counts, eNO, and total IgE were significantly elevated among the asthmatic patients. Sinus symptoms reported by questionnaire did not predict sinus CT findings. Among the patients with VCD, none had extensive sinus disease. They also had normal eNO, low IgE, and normal eosinophil count. Five of the patients presenting to the emergency room who were identified as acute asthmatic were identified with VCD by laryngoscopy and were all characterized by the absence of significant inflammation on their sinus CT scan, low IgE, and normal eosinophil count.

CONCLUSIONS

Among patients presenting with intermittent or reversible airway obstruction, patients with VCD can be distinguished from asthma by minimum or absence of inflammation in their sinuses as shown by CT scan. Clinical symptom scores are not predictive of presence or extent of sinus disease in most cases.

Influence of ventilatory settings and sampling position on measurements of simulated exhaled nitric oxide levels

Chronic lung disease is a common adverse outcome of prematurely born infants and is associated with an early inflammatory response, which persists over weeks. As a consequence, it is possible that exhaled nitric oxide levels might be raised in affected infants. The majority of such infants will be ventilated in the first weeks of birth and thus it is important to determine the influence of mechanical ventilation on nitric oxide levels. As a consequence, our aim was to determine whether, during mechanical ventilation, simulated exhaled nitric oxide levels were influenced by changes in ventilator settings or the sampling catheter position. A lung model was created consisting of a rubber bag inside a 11 jar. An endotracheal tube (ETT) was fixed securely within the neck of the bag. Nitric oxide was delivered into the bag at a constant rate to simulate production and sampled from within the ETT and the bag. The sampled nitric oxide was analysed using a Sievers chemiluminescence analyser. The ETT was attached to a neonatal ventilator and a nitric oxide scavenger placed in the ventilator's inspiratory limb to ensure nitric oxide free gas was delivered. Comparison of different sampling positions revealed that the highest peak nitric oxide level within the ETT was at the tip. Increasing peak inflating pressure and ventilator rate resulted in a decrease in the peak nitric oxide levels. Increasing the inspired oxygen concentration also was associated with a reduction in the peak nitric oxide levels, the effect being more pronounced when larger volume lung models were examined. The results emphasized that the conditions of measurement must be standardized in infants receiving respiratory support, if exhaled nitric oxide results are to be appropriately interpreted.

Increased leukotrienes in exhaled breath condensate in childhood asthma

Cysteinyl leukotrienes (cys-LTs; LTC4, LTD4, and LTE4) are generated predominantly by mast cells and eosinophils and induce airway smooth muscle contraction, microvascular leakage, and mucous hypersecretion whereas leukotriene B4 (LTB4) is a potent chemoattractant of neutrophils. We measured cys-LTs and LTB4 in exhaled breath condensate from children aged 7-14 years including healthy nonatopic children (n = 11) and children with mild intermittent asthma (steroid naive, n = 11), mild persistent asthma (low-dose inhaled steroid treatment, n = 13), or moderate to severe persistent asthma (high-dose inhaled steroid treatment, n = 13). Exhaled LTB4 levels were increased in patients with mild and moderate to severe persistent asthma compared with patients with mild intermittent asthma (126.0 +/- 8.8 and 131.9 +/- 7.1 versus 52.7 +/- 3.8 pg/ml, p < 0.001 and p < 0.0001) and normal subjects (126.0 +/- 8.8 and 131.9 +/- 7.1 versus 47.9 +/- 4.1 pg/ml, p < 0.0001). Elevated exhaled cys-LT levels were found in patients with mild and moderate to severe persistent asthma compared with normal subjects (27.9 +/- 2.8 and 31.5 +/- 4.5 versus 18.5 +/- 0.5 pg/ml, p < 0.01 and p < 0.05). There was an inverse correlation between exhaled cys-LTs and LTB4 in patients with mild persistent asthma. We conclude that exhaled cys-LTs and LTB4 may be noninvasive markers of airway inflammation in pediatric asthma.

Evaluation of exhaled nitric oxide in schoolchildren at different exhalation flow rates

Nitric oxide (NO) in exhaled air is believed to reflect allergic inflammation in the airways. Measured levels of exhaled NO vary with the exhaled flow rate, which therefore must be standardized. The aim of this study was to estimate the optimal exhalation flow rate when measuring NO in exhaled air. We studied 15 asthmatic children (8-18 y) with elevated NO levels and 15 age-matched controls and focused on how the quality of the NO curve profile, the discriminatory power, and the reproducibility were influenced by the exhalation flow rate. We used an on-line system for NO measurements at six different exhalation flow rates in the interval of 11-382 mL/s. The fraction of exhaled nitric oxide (FENO) was highly flow-dependent as was expected. Intermediate flow rates yielded a flat and stable NO plateau and were considerably easier to interpret than those obtained at the highest and lowest flow rates. The ratio of FENO between asthmatics and controls was lower at higher flow rates and a considerable overlap in NO values was demonstrated at all flow rates except 50 mL/s. The reproducibility was much lower at more extreme flow rates and was best at 50 mL/s. We conclude that a target exhalation flow rate of approximately 50 mL/s is to be preferred using the single-breath method for on-line NO measurements in schoolchildren.

Exhaled NH3 and excreted Nh4+ in children in unpolluted or urban environments

Exhaled ammonia (NH3ex) was measured by chemiluminescence in a group of healthy children (n = 20) and in two groups of asthmatic children, one (Group 1) residing in a National Park in the mountains (n = 68) and other (Group 2) in an urban area (n = 52). We also determined urinary ammonia, nitrates, urea, sodium and potassium normalized to osmolarity. Unlike exhaled nitric oxide (NOex), NH3ex was not specific to asthma as the children in Group 2 and the controls exhaled more ammonia that did the children in Group 1 (14.3 +/- 10.2 and 14.8 +/- 10.3 vs. 5.6 +/- 4.7 ppb; P < .001, respectively). In the urban environment, all children, including the healthy controls, excreted more ammonia (P < .001) and potassium (P < .001) but less urea (P < .02) than did the children residing in the National Park. These manifestations of moderate metabolic acidosis would favor excretion of ammonia at the expense of urea. In the children residing in the National Park, positive correlations were observed between NH3ex and urinary ammonia, and nitrates, age and morphological parameters. The relationship with the morphological parameters is a reflection of the normal physiological formation of NH3ex. In the children residing in the urban area, the other endogenous source of NH3ex was attributed to a slight disturbance in acid-base balance. In conclusion, the measurement of NH3ex appeared of limited interest, although the higher urinary urea/NH4+ ratio in Group 1 (P < .0001), especially in the treated children, appeared to be linked to the lack of atmospheric pollutants in the National Park. Further experimentation is in progress to confirm these findings.

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.

Exhaled nitric oxide at school age in prematurely born infants with neonatal chronic lung disease

Prematurely born infants with neonatal chronic lung disease (CLD) have increased respiratory morbidity and bronchial obstruction at school age. To evaluate the possible inflammatory basis of lung function abnormalities, we studied 40 children, 7.5-9.6 years of age, born very prematurely (birth weights, 600-1,575 g) and 14 nonatopic term-born controls, using flow-volume spirometry and exhaled nitric oxide (eNO) measurements. In children born prematurely, eNO was significantly higher in atopics than in nonatopics (respective means, 14.8 vs. 6.3 ppb, P = 0.02). Nonatopic prematurely born infants did not differ significantly from controls (means, 6.3 vs. 6.4 ppb, P = ns). Of the 27 nonatopic children not on regular glucocorticoid inhalations, 9 had a history of CLD. Spirometry indicated bronchial obstruction and values that were significantly lower in prematurely born infants with or without CLD than in controls, and they were lower in the CLD than the non-CLD group. However, no significant differences were observed in eNO levels between CLD, non-CLD, and control groups (means, 6.8, 5.9, and 6.4 ppb, P = ns). In nonatopic schoolchildren born very prematurely and with a history of CLD, we found no evidence of airway inflammation associated with increased eNO concentrations. Neither were eNO levels associated with severity of chronic lung disease, as determined by conventional lung function tests. eNO levels were higher in atopic children born prematurely than in controls.

Exhaled nitric oxide concentrations: online versus offline values in healthy children

Exhaled nitric oxide (FE(NO)) is a noninvasive and practical method to assess airway inflammation. We conducted this investigation to determine the most appropriate flow rate to measure FE(NO) and to obtain reference values for FE(NO) in children. FE(NO) was measured in 112 healthy 6-18 year olds (60 males) at 4 expiratory flow rates (46, 31, 23, and 15 mL/sec) using a chemiluminescent nitric oxide analyzer. Offline and online analyses were done to determine FE(NO) intraclass correlation coefficients, the relationship between FE(NO) and expiratory flow rates, and the effects of age and gender on these measurements. The major findings were: 1) intraclass correlation coefficients for FE(NO) and flow rates ranged from 0.92-0.99 for offline values, and 0.99 for all online values; 2) variation at an expiratory flow rate of 46 mL/sec (SD, 9.39) was considerably less than at other flows, especially at 15 mL/sec (SD, 26.55); 3) FE(NO) increased as flow rates decreased for both offline and online values; 4) there were no significant differences and good agreement between offline bag and online FE(NO) values at 31 and 46 mL/sec expiratory flows; and 5) using multiple regression, significant predictors of FE(NO) were flow, body surface area, age, and FEF(25-75). We have provided FE(NO) values in healthy children and propose that the ideal expiratory flow rate for FE(NO) measurements in children using the single breath technique is between 30-50 mL/sec.

Acute effects of aerosolized S-nitrosoglutathione in cystic fibrosis

S-nitrosoglutathione (GSNO), a naturally occurring constituent of airway lining fluid, enhances ciliary motility, relaxes airway smooth muscle, inhibits airway epithelial amiloride-sensitive sodium transport, and prevents pathogen replication. Remarkably, airway levels of GSNO are low in patients with cystic fibrosis (CF). We hypothesized that replacement of airway GSNO would improve gas exchange in CF. In a double-blind, placebo controlled study, we administered 0.05 ml/kg of 10 mM GSNO or phosphate buffered saline by aerosol to patients with CF and followed oxygen saturation, spirometry, respiratory rate, blood pressure, heart rate, and expired nitric oxide (NO). Nine patients received GSNO and 11 placebo. GSNO inhalation was associated with a modest but sustained increase in oxygen saturation at all time points. Expired NO increased in the low ppb range with GSNO treatment, peaking at 5 minutes but remaining above baseline at 30 minutes. There were no adverse effects. We conclude that GSNO is well tolerated in patients with CF and improves oxygenation through a mechanism that may be independent of free NO. Further, GSNO breakdown increases expired NO. We suggest that therapy aimed at restoring endogenous GSNO levels in the CF airway may merit study.

Nitrogen redox balance in the cystic fibrosis airway: effects of antipseudomonal therapy

Denitrifying bacteria metabolize nitrogen oxides through assimilatory and dissimilatory pathways. These redox reactions may affect lung physiology. We hypothesized that airway colonization with denitrifying bacteria could alter nitrogen balance in the cystic fibrosis (CF) airway. We measured airway nitrogen redox species before and after antimicrobial therapy for Pseudomonas aeruginosa in patients with CF. We also studied ammonium (NH(4)(+)) and nitric oxide (NO) metabolism in clinical strains of P. aeruginosa in vitro and in CF sputum ex vivo. Ammonium concentrations in both sputum and tracheal aspirates decreased with therapy. Nitric oxide reductase (NOR) was present in clinical strains of P. aeruginosa, which both produced NH(4)(+) and consumed NO. Further, NO consumption by CF sputum was inhibited by tobramycin ex vivo. We conclude that treatment of pseudomonal lung infections is associated with decreased NH(4)(+) concentrations in the CF airways. In epithelial cells, NH(4)(+) inhibits chloride transport, and nitrogen oxides inhibit amiloride-sensitive sodium transport and augment chloride transport. We speculate that normalization of airway nitrogen redox balance could contribute to the beneficial effects of antipseudomonal therapy on lung function in CF.

One-year treatment with different dosing schedules of fluticasone propionate in childhood asthma. Effects on hyperresponsiveness, lung function, and height

Dose-dependent effects of inhaled corticosteroids have been described. Although it has been advised to start treatment with inhaled corticosteroids with a high dose tapering off subsequently (stepdown approach), no clinical studies have assessed this strategy. We compared two different dosage schedules of inhaled fluticasone propionate (FP) in chronic persistent childhood asthma with respect to efficacy (airways hyperresponsiveness [PD(20)], lung function, exhaled nitric oxide [eNO]) and safety (height). During this double-blind study, children with asthma (aged 6-10 yr) were randomized to receive either FP 200 microg/d (constant dose approach) or to start with 1000 microg/d with two monthly reductions to 500, 200, and 100 microg/d (stepdown approach). PD(20) improved in both approaches during treatment with FP, with a significantly better PD(20) after 2 mo of 1000 microg/d followed by 500 microg/d in the stepdown approach versus 200 microg/d in the constant dose approach. No significant differences in PD(20) or other efficacy parameters were found after 1 yr. Changes in standing height were similar in both treatment approaches. This study showed no superior clinical effect of a stepdown approach compared with a constant dose strategy of FP for 1 yr in children with chronic persistent asthma.

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.

Exhaled nitric oxide levels in non-allergic and allergic mono- or polysensitised children with asthma

BACKGROUND

Increased fractional exhaled NO concentrations (FENO) and blood/tissue eosinophilia are frequently reported in allergic children with mild asthma and are thought to reflect the intensity of the inflammation characterising the disease. The aim of this study was to investigate possible differences in FENO levels or in the intensity of the blood eosinophilia in allergic and non-allergic asthmatic children.

METHODS

112 children with stable, mild, intermittent asthma with a positive bronchial challenge to methacholine were consecutively enrolled in the study; 56 were skin prick test and RAST negative (non-sensitised) while 56 were sensitised to house dust mites (23 only to house dust mites (monosensitised) and 33 were sensitised to mites and at least another class of allergens (pollens, pet danders, or moulds)). Nineteen sex and age matched healthy children formed a control group.

RESULTS

Compared with non-allergic patients, allergic children had a significantly higher rate of blood eosinophilia (p=0.0001) with no differences between mono- and polysensitised individuals. Forced expiratory volume in 1 second (FEV(1)), forced vital capacity (FVC), forced expiratory flow at 25-75% of vital capacity (FEF(25-75%)), and the degree of bronchial reactivity to methacholine were similar in non-atopic and atopic children, with no differences between mono- and polysensitised individuals. FENO levels measured by chemiluminescence analyser were higher in asthmatic children (15.9 (14.3) ppb) than in the control group (7.6 (1.6) ppb, p=0.04) and higher in allergic patients (23.9 (2.1) ppb) than in non-allergic patients (7.9 (0.8) ppb, p=0.0001), but there were no differences between mono- and polysensitised individuals (p>0.1). Significant correlations between blood eosinophilia and FENO levels were seen only in allergic (r=0.35, p<0.01) and in polysensitised individuals (r=0.45, p<0.05).

CONCLUSIONS

In children with mild asthma, a similar degree of functional disease severity may be associated with a higher inflammatory component in allergic than in non-allergic subjects.

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.

Time-dependent changes in orally exhaled nitric oxide and pulmonary functions induced by inhaled corticosteroids in childhood asthma

Exhaled nitric oxide levels are elevated in asthmatic children and decrease after inhaled steroid treatment. We evaluated the time-dependent changes in fractional exhaled nitric oxide concentration (FENO) and pulmonary function parameters following inhaled steroid therapy. Thirty-nine steroid-naive atopic patients (age 11.92+/-0.48 years) with mild intermittent asthma and 22 age-matched healthy controls were enrolled in the study; pulmonary functions and FE(NO) levels were measured. Low doses of inhaled steroids were prescribed to all asthmatic patients who were reevaluated in a second visit (between 10 and 40 days after the beginning of the treatment). At the enrolment, asthmatic patients had similar forced expiratory volume in 1 sec (FEV1) and forced vital capacity (FVC) values (p > 0.05) but reduced forced expiratory flows at 25-75% of the vital capacity (FEF(25-75%)) values, as compared to controls (p < 0.05). In addition, FE(NO) levels were significantly higher in asthmatics with respect to control subjects (30.8+/-3.0 and 4.0+/-0.5 ppb, respectively; p < 0.01). All asthmatics had FE(NO) levels higher than 8.8 ppb (i.e., > 2 standard deviations of the mean in controls). After steroid treatment, patients showed significant improvement of FEV1, FVC, and FEF(25-75%) (p = 0.0001; each comparison) and a reduction of FE(NO) levels (p = 0.0001). A weak significant correlation was found between percent decrease in FE(NO) levels and percent increase in FEV1 (r = 0.33, p = 0.04) or in FEF(25-75%) (r = 0.4, p = 0.01) after treatment. When changes in FE(NO) levels and in pulmonary function parameters were corrected for days of treatment, significant correlations were still present between percent decrease in FE(NO) levels and percent increase in FEV1 (r = 0.57, p = 0.0004) or percent increase in FEF(25-75%) (r = 0.45, p = 0.006). Sixteen of the 39 asthmatic patients were evaluated on two occasions after the beginning of treatment, at days 10 and 40. The significant reduction in FE(NO) levels (p < 0.01) and the significant increase in FEV1 and FEF(25-75%) values observed (p < 0.05) after 10 days did not further improve at day 40. These data show that it is possible to demonstrate early effects of low-dose inhaled steroids in asthmatic children using objective measurements of airway caliber and inflammation.

A single dose of nebulized budesonide decreases exhaled nitric oxide in children with acute asthma

This study was conducted to investigate whether a single dose of nebulized budesonide effectively decreased airway inflammation as demonstrated by exhaled nitric oxide (eNO) levels. A single dose of nebulized budesonide, but not nebulized terbutaline, rapidly decreased eNO levels in 6 hours. The decrease in eNO levels induced by nebulized budesonide was correlated to an increase in peak expiratory flow rate.

Budesonide but not nedocromil sodium reduces exhaled nitric oxide levels in asthmatic children

Exhaled nitric oxide (ENO) has been proposed as a marker of airway inflammation in asthma and could be useful to evaluate the response to anti-inflammatory treatment. We investigated the effect of budesonide and nedocromil sodium on ENO levels and lung function in asthmatic children. Twenty stable steroid-naïve asthmatic children were randomized in a single blind, cross-over study to receive inhaled budesonide (group A) or nedocromil sodium (group B) for 6 weeks. ENO was measured with a chemiluminescence analyser at baseline and at the end of each treatment period. Repeated-measures ANOVA was carried out. In asthmatic baseline ENO levels [mean 32.5 ppb, 95% confidence interval (CI) 26.4 to 38.7] were significantly higher compared to reference values (8.7 ppb, 95% CI 8.1 to 9.2, P<0.001). There were no treatment-order effect, no carry-over effect and in both groups the response pattern was the same: budesonide significantly lowered ENO levels from 41.0 ppb to 22.8 ppb in group A (mean, P<0.01) and from 22.6 ppb to 13.0 ppb in group B, (mean, P<0.05), while nedocromil did not reduce ENO values (from 24.4 ppb to 22.6 ppb in group B and from 22.8 ppb to 38.0 ppb in group A, mean, P = NS and P<0.01 respectively). After budesonide treatment ENO values of asthmatics were still significantly higher than in healthy children The baseline values of FEV1 and FEF(25-75) were normal in both groups and no significant changes were observed during the study. In conclusion, our study shows that budesonide, but not nedocromil sodium, significantly reduces ENO levels in stable asthmatic children even in absence of changes in the lung function.

Off-line exhaled nitric oxide measurements in children

The concentration of exhaled nitric oxide (eNO) is a useful marker of asthmatic bronchial inflammation. eNO can now be measured away from the laboratory (off-line), even in children. Short exhalation maneuvers (8 sec) and small samples (1 L) of exhaled gas are probably sufficient in children, but more information is needed about the effect of different measurement conditions. As a preliminary step before conducting epidemiological studies in schoolchildren, we investigated the effects of expiratory flow, dead space, and expiratory time on eNO concentrations collected in 1-L mylar collection bags. We studied 101 cooperative subjects (62 males) aged 5-18 years (30 healthy volunteers, 51 asthmatics, and 20 children with various other respiratory diseases) in our pulmonary function laboratory. On-line and off-line eNO were compared in a single session, and analyzed with a Sievers NOA 280 nitric oxide analyzer. For both methods of collecting expired gas, subjects did a single exhalation without breath-holding against an expiratory pressure 10 cm H(2)O. We investigated the effects of expiratory flow, dead space, and exhalation time on eNO; we also compared on-line and off-line eNO measurements, and the repeatability of both techniques at a given flow rate. Expiratory flows of 58 mL/sec provided more reproducible data than lower flows (coefficient of repeatability 1.1 ppb for 58 mL/sec vs. 2.8 for 27 mL/sec vs. 5.7 for 18 mL/sec). eNO concentrations were about 25% higher in off-line than in on-line recordings if the initial 250 mL of exhaled gas were not eliminated, and 37% higher if exhalation lasted longer (16 sec vs. 8 sec). Eliminating 250 mL of dead space and shortening the filling time to 8 sec yielded off-line eNO values close to those on-line (geometric mean off-line eNO 14.4 ppb, 95% confidence interval: 12.2-17.0) vs. on-line eNO 13.8 ppb (95% confidence interval: 11.6-16.5). On-line and off-line results were highly correlated (r = 0.996, P = 0.000) and had similar coefficients of variation (on-line eNO 2.6%, off-line 2.8%). Neither agreement nor repeatability of eNO measurements were affected by disease status or baseline FEV(1) (% predicted values). Once standardized, the off-line eNO technique using 1-L gas collection bags will provide results similar to those recorded on-line.

Off-line sampling of exhaled air for nitric oxide measurement in children: methodological aspects

Measurement of nitric oxide in exhaled air is a noninvasive method to assess airway inflammation in asthma. This study was undertaken to establish the reference range of exhaled NO in healthy school-aged children and to determine the influence of ambient NO, noseclip and breath-holding on exhaled NO, using an off-line balloon sampling method. All children attending a primary school (age range 8-13 yrs) underwent NO measurements on two occasions with high and low ambient NO. Each time, the children performed four expiratory manoeuvres into NO-impermeable balloons, with and without 10 s of breath-holding and with and without wearing a noseclip. Exhalation flow and pressure were not controlled. NO was measured within 4 h after collection, by means of chemiluminescence. All children completed a questionnaire on respiratory and allergic disorders, and performed flow/volume spirometry. With low ambient NO, the mean exhaled NO value of 72 healthy children with negative questionnaires and normal lung function was 5.1 +/- 0.2 parts per billion (ppb) versus a mean of 6.8 +/- 0.3 ppb in the remaining 49 children with positive questionnaires for asthma and allergy, and/or recent symptoms of cold (p=0.001). Exhaled and ambient NO were significantly related, especially with ambient NO > 10 ppb (r = 0.86, p=0.0001 versus r=0.34, p=0.004 for ambient values <10 ppb). The use of a noseclip, with low ambient NO and without breath-holding, caused a small decrease in exhaled NO values (p=0.001). The effect of breath-holding on exhaled NO depended on ambient NO. With ambient NO > 10 ppb, exhaled NO decreased, whereas with ambient NO < 10 ppb, exhaled NO increased after 10 s breath-hold. It is concluded that off-line sampling in balloons is a simple and, hence, attractive method for exhaled nitric oxide measurements in children which differentiates between groups with and without self-reported asthma, allergy and colds, when ambient nitric oxide is < 10 parts per billion. Wearing a noseclip and breath-holding affected measured values and should, therefore be standardized or, preferably, avoided.

Controlled low flow off line sampling of exhaled nitric oxide in children

BACKGROUND

The aim of this study was to validate exhaled nitric oxide (eNO) values obtained with an alternative off line, single breath, low flow balloon sampling method against on line sampling according to ERS and ATS guidelines in children who could perform both methods.

METHODS

One hundred and twenty seven white children of median age 14.1 years, all pupils of a secondary school, participated in the study. They performed the two different sampling techniques at three different flows of 50, 100, 150 ml/s. Additional measurements were done in random subgroups to determine the influence of the dead space air on eNO values obtained off line by excluding the first 220 ml of exhaled air. All children completed a questionnaire on respiratory and allergic disorders and underwent spirometric tests.

RESULTS

The off line eNO values were significantly higher than the on line values at all flows. At 50 ml/s the geometric mean (SE) off line eNO was 18.7 (1.1) ppb and the on line eNO was 15.1 (1.1) ppb (p<0.0001). However, when dead space air was discarded, off line and on line values were similar: at 50 ml/s off line eNO was 17.7 (1.0) ppb and on line eNO 16.0 (1.2) ppb. There was a good agreement between off line eNO values without dead space air and on line eNO: for 50 ml/s the mean on/off line ratio was 0.95 (95% agreement limits 0.63 to 1.27). The off line eNO level at 50 ml/s in 80 children with negative questionnaires for asthma, rhinitis, and eczema was 13.6 (1.0) ppb compared with 33.3 (1.1) ppb in the remaining children with positive questionnaires on asthma and allergy and/or recent symptoms of cold (p<0.0001).

CONCLUSIONS

In children, off line assessment of eNO using constant low flow sampling and excluding dead space air is feasible and produces similar results as on line assessment with the same exhalation flow rate. Both sampling methods are sufficiently sensitive to differentiate between groups of otherwise healthy school children with and without self-reported asthma, allergy, and/or colds. We propose that, for off line sampling, similar low flow rates should be used as are recommended for on line measurements.

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.

Acute asthma

OBJECTIVE: Asthma is the most common medical emergency in children. It is associated with significant morbidity and mortality rates and poses a tremendous societal burden worldwide. Management of the acute attack involves a stepwise approach that includes beta-agonist and steroid therapy, the mainstay of emergency treatment. Most patients will respond to this regime and can be discharged from the emergency department. Failure to respond to treatment necessitates hospital admission and sometimes admission to the intensive care unit (ICU). Management in the ICU involves intensification of pharmacologic therapy, including nonstandard therapies, in an attempt to avoid intubation and ventilation. When needed, mechanical ventilatory support can be rendered fairly safe with little morbidity if the likely cardiorespiratory physiologic derangements are appreciated and if appropriate ventilatory strategies are used. In the past two decades, the availability of newer potent medications and changes in approach to monitoring and ventilatory strategies have resulted in a decrease in ICU morbidity and mortality rates. Research endeavors are presently underway to further characterize the underlying mechanisms of the disease and are likely to lead to novel therapies. This article reviews the approach to management of acute severe asthma.

FeNO measured at fixed exhalation flow rate during controlled tidal breathing in children from the age of 2 yr

We have outlined a new method to measure exhaled nitric oxide on-line at fixed flow rate during controlled tidal breathing (FeNO [controlled]) in young children aged 2 yr and older. FeNO(controlled) measures NO on-line during operator-controlled tidal breathing. The operator targets the exhaled flow of the child within preset limits of 0.4-0.6 L/s by continuously adjusting an expiratory resistance. FeNO(controlled) is estimated during end exhalation. We have validated this method against the reference method of the single breath on-line (SBOL) maneuvre (FeNO[SBOL]) and compared it with NO in mixed exhaled air collected in a bag (FeNO [mixed]). Sixty-seven children were studied: 16 school children and 51 children aged 2-5 yr; 14 of the young children were healthy, 22 had asthma treated with regular inhaled budesonide, and 15 had mild episodic wheeze treated with inhaled terbutaline as necessary. FeNO (controlled) showed good agreement with FeNO(SBOL) (factor difference 0.7-1.4), whereas FeNO(mixed) showed poor agreement with FeNO(SBOL) (factor difference 0.51-5.37). FeNO(controlled) (mean [95% confidence interval]) was 6 ppb (4-8 ppb) in young children with asthma, 5 ppb (3-7 ppb) in young children with mild episodic wheeze, and 3 ppb (2-4 ppb) in healthy control subjects (asthma versus control subjects: p = 0.006; episodic wheeze versus control subjects: p = 0.057). FeNO(controlled) increased from 4 ppb (2-7 ppb) to 13 ppb (10-18 ppb) (p < 0.0001) when the mean daily maintenance dose of budesonide was tapered in nine young children with asthma. FeNO(controlled) is feasible in young children from age 2 and shows better agreement with FeNO(SBOL) than FeNO(mixed). FeNO(controlled) covaries with asthma disease severity and steroid dose. FeNO(controlled) is therefore suggested as a noninvasive diagnostic tool for monitoring asthma disease activity in young children with asthma from the age of 2 yr.

Correlation between reversibility of airway obstruction and exhaled nitric oxide levels in children with stable bronchial asthma

Recent trials measuring exhaled nitric oxide (eNO) concentrations have suggested that it may be a useful measure of ongoing airway inflammation in patients with asthma. The purpose of this study was to examine the relationship between eNO levels and baseline as well as postbronchodilator spirometry, a measurement commonly used in the clinical setting to determine the severity of asthma and as a guide to therapeutic decisions. Forty-nine patients between the ages of 5-16 years with physician-diagnosed asthma who attended the pediatric pulmonary clinic for a routine asthma visit with spirometric evaluation were recruited for the study. eNO levels prior to spirometry were obtained before and after receiving inhaled beta(2) agonist. eNO samples were collected in impermeable bags (Tedlar) and assayed within 24 hr by chemiluminescence. Regression analysis was used to assess the relationships between pre- and postbronchodilator eNO and spirometric variables. eNO was also compared in patients receiving and not receiving inhaled corticosteroids (ICS), as well as those whose therapy had been increased after evaluation by a pediatric pulmonologist or allergist. We found no significant difference between the levels of eNO before and after inhalation of beta(2) agonist (P = 0.60 paired t-test). Positive correlation was found between eNO vs. percentage change in FEV(1) (r = 0.35, P = 0.01) and percentage change in FEF(25-75% )(r = 0.29, P = 0.04). A negative correlation was found between prebronchodilator FEV(1) and eNO (r = -0.29, P = 0.03). Patients on ICS had lower mean eNO levels (29.9 vs. 47.6 parts per billion (ppb), P = 0.053) than those not receiving ICS. Patients whose ICS therapy was increased had higher mean eNO levels (47.2 vs. 26.9 ppb, P = 0.018) than those not having ICS therapy increased. We suggest that eNO levels could be a clinically useful measurement of asthma severity and could be used as an adjunct to spirometry to determine appropriate treatment plans. Longitudinal clinical trials are needed to determine if eNO can enhance therapeutic decisions for asthmatic children.

A simple flow-driven method for online measurement of exhaled NO starting at the age of 4 to 5 years

NO is increased in exhaled air of asthmatic patients, and may be used as a marker of airway inflammation. The online method is a standardized technique for measuring exhaled nitric oxide (ENO). However, this method has proven difficult for some children, who may have trouble maintaining a constant expiratory flow. The aim of this study was to validate a modified technique for online ENO measurement that utilizes a flow regulator to overcome the patient problem of having to actively maintain a constant expiratory flow. We measured ENO levels with two methods in 105 asthmatic and 10 healthy subjects, comparing the standardized (ST) single-breath method with a modified single-breath, flow-driven (FD) method. With the ST method and visual monitoring, the subjects inhaled NO-free air to TLC, and exhaled with a target flow of 50 ml/s. With the FD method, the subjects exhaled from TLC and flow was kept constant (50 ml/s) by the operator, using a flow regulator. The subjects were divided into two groups, one consisting of children aged 4 to 8 yr (n = 74) and the other of children aged 9 to 16 yr (n = 41). In the group aged 4 to 8 yr, 38 children (51%) were unable to perform the ST method, whereas only five children (7%) failed to perform the FD technique. In the group aged 9 to 16 yr, only four children (10%) were unable to perform the ST maneuver, and all successfully performed the FD maneuver. The mean concentrations of ENO in the 73 children who performed both types of maneuver were similar (36.1 +/- 3.4 [mean +/- SEM] ppb with the ST method and 33.8 +/- 3.3 ppb with the FD technique, p = NS) and were highly correlated with one another (r = 0.99, p < 0.0001). ENO values were significantly higher in steroid-naive than in steroid-treated asthmatic children. In conclusion, we describe a modified online method for measuring ENO that is simple, does not require active cooperation to maintain a constant expiratory flow, and can be easily performed by children from 4 to 5 yr of age onward.

S-nitrosoglutathione breakdown prevents airway smooth muscle relaxation in the guinea pig

Airway levels of the endogenous bronchodilator S-nitrosoglutathione (GSNO) are low in children with near-fatal asthma. We hypothesized that GSNO could be broken down in the lung and that this catabolism could inhibit airway smooth muscle relaxation. In our experiments, GSNO was broken down by guinea pig lung homogenates, particularly after ovalbumin sensitization (OS). Two lung protein fractions had catabolic activity. One was NADPH dependent and was more active after OS. The other was NADPH independent and was partially inhibited by aurothioglucose. Guinea pig lung tissue protein fractions with GSNO catabolic activity inhibited GSNO-mediated guinea pig tracheal ring relaxation. The relaxant effect of GSNO was partially restored by aurothioglucose. These observations suggest that catabolism of GSNO in the guinea pig 1) is mediated by lung proteins, 2) is partially upregulated after OS, and 3) may contribute to increased airway smooth muscle tone. We speculate that enzymatic breakdown of GSNO in the lung could contribute to asthma pathophysiology by inhibiting the beneficial effects of GSNO, including its effect on airway smooth muscle tone.

Salmeterol in paediatric asthma

BACKGROUND

The addition of long acting inhaled beta(2) agonists is recommended at step 3 of the British guidelines on asthma management but a recent study suggested no additional benefit in children with asthma.

METHODS

The aim of this study was to compare, in a double blind, three way, crossover study, the effects of the addition of salmeterol 50 microg bd, salmeterol 100 microg bd, and salbutamol 200 microg qds in asthmatic children who were symptomatic despite treatment with inhaled corticosteroids in a dose of at least 400 microg/day over a one month period. Symptom scores, morning and evening peak expiratory flow (PEF) rates, use of rescue medication, spirometric indices, and histamine challenge were measured.

RESULTS

Forty five children aged 5-14 years were enrolled. All three treatments improved asthma control, morning and evening PEF rates, and spirometric indices with no change in bronchial hyperreactivity. Mean morning PEF was significantly better during the salmeterol treatment periods than with salbutamol treatment (p<0.05). The analysis of mean morning PEF gave an estimated treatment difference of 9.6 l/min for salmeterol 50 microg bd versus salbutamol 200 microg qds (95% confidence interval (CI) 2.1 to 17.1), and an estimated treatment difference of 13.8 l/min for salmeterol 100 microg bd versus salbutamol 200 microg qds (95% CI 6.0 to 21.5). There were no significant differences between the two doses of salmeterol and all treatments were well tolerated.

CONCLUSIONS

In this population of moderate to severe asthmatic children on inhaled corticosteroids, salmeterol in a dose of either 50 microg bd or 100 microg bd is significantly more effective at increasing the morning PEF rate over a one month period than salbutamol 200 microg qds. The data provided no significant evidence of a difference in efficacy between the two doses of salmeterol, 50 microg and 100 microg. A trial of salmeterol 100 microg bd may be worth considering in those still symptomatic on the lower dose.

Issues and unmet needs in pediatric asthma

Asthma is common and becoming more so in childhood. Although mild asthma may incur low average annual costs per child, these estimates need to be viewed in the context of the very large numbers of affected individuals. Whereas asthma and wheezing illness in childhood had in the past been broadly subdivided into asthma (often associated with atopy) and wheezy bronchitis (wheeze only, with associated upper respiratory tract infection), this distinction was lost during the 1970s in view of the demonstrated underdiagnosis and undertreatment of symptomatic school-age children. The acceptance of asthma as a chronic inflammatory disease and evidence for airway remodeling and progressive deterioration in airway function in association with symptoms and atopy have led to earlier use of topical steroids at higher starting doses delivered by improved age-appropriate devices. Treating all children as if they were destined to become atopic asthmatics and at risk of airway remodeling may not be rational, particularly in those whose symptoms will subsequently resolve. However, there are as yet no screening tests which can clearly identify individuals at risk of long-term chronic airway inflammation and airway remodeling. The large number of infants and young children with current symptoms suggestive of asthma and in whom resolution is likely in the majority poses problems for the clinician in deciding the best initial therapy. There is an urgent need to develop simple and reliable measures that can identify the early manifestations of atopic airway sensitisation and to establish the place of early intervention with nonsteroidal drugs, including leukotriene antigonists.

Exhaled nitric oxide as an indicator of severity of asthmatic inflammation

Traditional assessment of severity of asthma relies on an evaluation of signs and symptoms and pulmonary function tests. These pulmonary function tests, such as peak expiratory flow rates, forced vital capacity, and forced expiratory flow rates, are indirect measures of airway caliber only, and not inflammation. Since asthma is an inflammatory disease, a measure of the degree of inflammation would be helpful in quantitating severity and titrating of anti-inflammatory therapy. A noninvasive method for measuring pulmonary inflammation would therefore be helpful to assist the emergency physician in initial treatment and assist in titration of anti-inflammatory therapy during repeat visits. Exhaled nitric oxide (NO) assays are convenient and practical and may fulfill this role. In this review, we discuss the role of NO in asthmatic inflammation and the role that exhaled NO values may play in the emergency management of asthma.

FE(NO): relationship to exhalation rates and online versus bag collection in healthy adolescents

Measurement of exhaled nitric oxide (FE(NO)) is a noninvasive and practical method for assessing airway inflammation. We conducted this investigation to determine the most appropriate flow rate for FE(NO) measurement and to obtain normal values for FE(NO). We determined which expiratory flow was easy to sustain, generated reproducible values, and provided good correlation between offline and online measurements. Thirty-two healthy subjects (15- 18 yr old) underwent spirometry and FE(NO) measurements, using a chemiluminescent NO analyzer at expiratory flow rates of 46, 31, 23, 15, 10, 7, 5, and 4 ml/s. The major findings were as follows: (1) FE(NO) increased as flow rates decreased, with strong correlation between FE(NO) values and flow rates at the four highest flows (0. 85- 0.93, p < 0.001); (2) there were no significant differences and good agreement between offline bag and online FE(NO) values for the four highest flows (p < 0.09-0.83); (3) online FE(NO) values increased with age 15-17 yr at all flow rates, but decreased at age 18 yr; and (4) using multiple regression, significant predictors of FE(NO) were flow, body surface area, age, and FEF(25-75). On the basis of these results, we provide FE(NO) values for healthy adolescents and propose that the ideal flow rate for children is between 30 and 50 ml/s.