Exhaled nitric oxide; relationship to clinicophysiological markers of asthma severity

Possible pathogenic roles of nitric oxide in asthma

Nitric oxide (NO) has broad physiologic functions, including vasodilation, bronchodilatation, neurotransmission, inflammation, and host defense. Fraction of exhaled NO (FeNO) is used as a biomarker of eosinophilic airway inflammation for asthma control. However, the role of NO in the pathogenesis and progression of asthma is not well understood. Additionally, the absence of bronchial eosinophilic inflammation, mucus hypersecretion, and increased Th2 cytokine levels in mice lacking NO synthase isoforms (n/i/eNOS^-/-), suggests that NO has an essential role in the promoting the pathogenesis of asthma. Recent clinical data investigating antibodies for interleukin (IL)-4 receptor α, which inhibits both IL-4 and IL-13 signaling, and anti-IL-13 antibody suggest a unique association between NO and the pathogenesis and progression of asthma. Antibody therapies targeting several cytokines may provide clues to elucidate the mechanisms underlying the pathogenesis and progression of asthma.

Exhaled NO as a predictor of exercise-induced asthma in cold air

PURPOSE

Physical activity is an important part of life, and exercise-induced asthma (EIA) can reduce the quality of life. A standardized exercise challenge is needed to diagnose EIA, but this is a time consuming, effortful and expensive method. Exhaled nitric oxide (eNO) as a marker of eosinophil inflammation is determined rapidly and easily. The aim of this study was to investigate eNO as surrogate marker for predicting a positive reaction in an exercise challenge in a cold chamber (ECC).

METHODS

A total of 143 subjects aged 6-45 years with suspected EIA were recruited for the study. The subjects underwent an eNO measurement, an ECC and a skin prick test (SPT). To define the sensitivity and specificity of eNO as predictor, a receiver-operating characteristic (ROC) curve was plotted. The individual probability of the occurrence of a positive reaction after ECC based on an eNO value was calculated using a logistic regression model.

RESULTS

An eNO cut-off value of 18.5 ppb (area under the curve (AUC) 0.71, p < 0.001) showed the best combination of sensitivity and specificity for a positive reaction (forced expiratory volume in 1 s (FEV₁) decrease ≥ 10% after ECC) for the whole group. An eNO cut-off value of 46.0 ppb had a specificity of 100.0% to predict a significant FEV₁ decrease and may save exercise testing in 22.4% of patients. A negative predictive level with a high sensitivity and negative predictive value (NPV) could not be defined. In the subgroup that was house dust might (HDM) allergy positive (HDM pos; n = 68, 45.5% of all subjects), an eNO cut-off value of 35.5 ppb (AUC 0.79, p < 0.01) showed the best combination of sensitivity and specificity for a positive reaction after the ECC with a specificity 100.0% and may save exercise testing in 45.6% of HDM pos patients. Using logistic regression, a 95% probability for a positive FEV₁ decrease after ECC was estimated at 53 ppb for the whole group and at 47 ppb for the HDM pos subgroup.

CONCLUSIONS

Exhaled NO measurement is a screening tool for EIA, especially in HDM pos subjects. In a real-life setting, a cut-off value of 46.0 ppb detects EIA at 100% in all suspected patients, and a cut-off level of 35.5 ppb is valuable marker of EIA in patients with an HDM allergy. These levels can save time and costs in a large proportion of patients and will be helpful for clinicians.

Importance of fractional exhaled nitric oxide in the differentiation of asthma-COPD overlap syndrome, asthma, and COPD

Background

Fractional exhaled nitric oxide (FeNO) is an easy, sensitive, reproducible, and noninvasive marker of eosinophilic airway inflammation. Accordingly, FeNO is extensively used to diagnose and manage asthma. Patients with COPD who share some of the features of asthma have a condition called asthma–COPD overlap syndrome (ACOS). The feasibility of using FeNO to differentiate ACOS patients from asthma and COPD patients remains unclear.

Methods

From February 2013 to May 2016, patients suspected with asthma and COPD through physician’s opinion were subjected to FeNO measurement, pulmonary function test (PFT), and bronchial hyperresponsiveness or bronchodilator test. Patients were divided into asthma alone group, COPD alone group, and ACOS group according to a clinical history, PFT values, and bronchial hyperresponsiveness or bronchodilator test. Receiver operating characteristic (ROC) curves were obtained to elucidate the clinical functions of FeNO in diagnosing ACOS. The optimal operating point was also determined.

Results

A total of 689 patients were enrolled in this study: 500 had asthma, 132 had COPD, and 57 had ACOS. The FeNO value in patients with ACOS was 27 (21.5) parts per billion (ppb; median [interquartile range]), which was significantly higher than that in the COPD group (18 [11] ppb). The area under the ROC curve was estimated to be 0.783 for FeNO. Results also revealed an optimal cutoff value of >22.5 ppb FeNO for differentiating ACOS from COPD patients (sensitivity 70%, specificity 75%).

Conclusion

FeNO measurement is an easy, noninvasive, and sensitive method for differentiating ACOS from COPD. This technique is a new perspective for the management of COPD patients.

Importance of fractional exhaled nitric oxide in diagnosis of bronchiectasis accompanied with bronchial asthma

BACKGROUND

Fractional exhaled nitric oxide (FeNO) measurement is a simple, rapid, highly reproducible, and noninvasive method of airway inflammation assessment. Therefore, FeNO is extensively used for the diagnosis and management of asthma. The feasibility of using FeNO as an alternative to conventional pulmonary function test to differentiate patients with bronchiectasis (BE) and bronchial asthma from those with BE only remains unclear.

METHODS

From February 2013 to February 2015, 99 patients diagnosed with BE through high-resolution computed tomography (HRCT) were subjected to FeNO measurement, bronchial challenge test (BCT), or bronchodilator test. Bronchial hyperreactivity and/or reversible airway obstruction was used to define asthma. The receiver operating characteristic (ROC) curves were obtained to elucidate the clinical functions of FeNO in the diagnosis of asthmatic patients with BE, and the optimal operating point was also determined.

RESULTS

Of 99 patients with BE, 20 patients presented asthma, and 12 of these patients received regular treatment, which were given with budesonide (200 µg, bid) for 12 weeks to evaluate changes in the concentration and assess the role of FeNO in the treatment. The area under the ROC curve was estimated as 0.832 for FeNO. Results also revealed a cut off value of >22.5 part per billion (ppb) FeNO for differentiating asthmatic from non-asthmatic (sensitivity, 90.0%; specificity, 62.5%) patients with BE. FeNO and forced expiratory volume for 1 second significantly improved after the treatment.

CONCLUSIONS

Clinical FeNO measurement is a simple, noninvasive, and rapid method used to differentiate asthmatic from nonasthmatic patients with BE. This technique exhibits potential for asthma management.

No direct association between asthma and the microbiome based on currently available techniques

Current uses of culture-independent tools in previous studies have shown a significant relationship between microbiota and asthma. Although these studies are relatively new, there is also evidence of the possibility of new therapeutic strategies for the treatment or prevention of asthma. This article retrospectively examines the possible association between microorganisms and asthma. Data on all patients with different types of asthma were collected from hospital charts from the Department of Internal Medicine, Saarland University Medical Center, Germany, within the study period of 2011 to 2012. The tracheal secretions of asthmatics obtained by bronchoalveolar lavage, bronchial aspirates through flexible bronchoscopy, and directly in sputum were examined microbiologically for microorganisms. Thirty-one (10.47%, 95% CI, 6.98-13.96) of a total of 296 patients were found to have asthma microorganisms in their airways. We could not establish a causal relationship between microorganisms and asthma based on the results of our study (P = 0.893). Additionally, acute respiratory infections did not affect the microbiological colonization in asthmatics' airways (P = 0.472). We were unable to find a direct association between asthma and the microbiome based on existing diagnostic techniques.

Exhaled nitric oxide levels in childhood asthma: a more reliable indicator of asthma severity than lung function measurement?

The level of exhaled nitric oxide (NO) has been demonstrated to reflect the degree of airway inflammation in patients with asthma and to be related to the severity of asthma, as well as to the efficacy of treatment. In contrast, lung function tests provide information about airway volumes and flows reflecting the level of airway obstruction, but do not allow any direct information about the degree of airway inflammation. Several studies have evaluated the relationships between the level of airway inflammation assessed by exhaled NO and the levels of airway obstruction and/or bronchial hyperresponsiveness in asthmatic adults and children. These studies highlight the complex pathophysiology of asthma and suggest that exhaled NO may have a promising role in addition to lung function measurement in the evaluation of asthma severity in children.

Increased parasympathetic tone as the underlying cause of asthma: a hypothesis

Asthma is a chronic inflammatory disease of airways that is characterized by increased responsiveness of the tracheo-bronchial tree to multiple number of stimuli. Immunological theory does not explain all features in asthma, for example hyper-reactivity of the airways. Neurogenic theory also fails to explain the pathogenesis of asthma comprehensively. Higher parasympathetic tone has been reported in asthmatics but has never been suggested as a major underlying cause of asthma. This article attempts to explain the occurrence of hyper-responsiveness, inflammatory/allergic reactions and broncho-constriction in asthma on a common basis of inherent higher parasympathetic tone in asthmatics. The higher background parasympathetic firing leads to increased nitric oxide (NO) production owing to its co-localization with acetylcholine (ACh) in inhibitory non-adrenergic and non-cholinergic (i-NANC) nerves. NO is a neurotransmitter of i-NANC system and it mediates bronchodilation. Increased NO release has been found to be responsible for hyper-responsiveness and increased inflammation in the airways. The authors suggest that an inherently higher background parasympathetic tone in concert with inflammation or a specific genetic background could modify the effects of NO on lung homeostasis in humans leading to increased susceptibility to an asthmatic state.

Effect of oral magnesium supplementation on measures of airway resistance and subjective assessment of asthma control and quality of life in men and women with mild to moderate asthma: a randomized placebo controlled trial

BACKGROUND

Epidemiological data shows low dietary magnesium(Mg) may be related to incidence and progression of asthma.

OBJECTIVE

To determine if long term(6.5 month) treatment with oral Mg would improve asthma control and increase serum measures of Mg status in men and women with mild-to-moderate asthma.

SUBJECTS

55 males and females aged 21 to 55 years with mild to moderate asthma according to the 2002 National Heart, Lung, and Blood Institute(NHLBI) and Asthma Education and Prevention Program(NAEPP) guidelines and who used only beta-agonists or inhaled corticosteroids(ICS) as asthma medications were enrolled.

DESIGN

Subjects were randomly assigned to consume 340 mg(170 mg twice a day) of Mg or a placebo for 6.5 months.

MEASUREMENTS

Multiple measures of Mg status including serum, erythrocyte, urine, dietary, ionized and IV Mg were measured.

OBJECTIVE

markers of asthma control were: methacholine challenge test(MCCT) and pulmonary function test(PFT) results. Subjective validated questionnaires on asthma quality of life(AQLQ) and control(ACQ) were completed by participants. Markers of inflammation, including c-reactive protein(CRP) and exhaled nitric oxide(eNO) were determined.

RESULTS

The concentration of methacholine required to cause a 20% drop in forced expiratory volume in in minute(FEV(1)) increased significantly from baseline to month 6 within the Mg group. Peak expiratory flow rate(PEFR) showed a 5.8% predicted improvement over time(P = 0.03) in those consuming the Mg. There was significant improvement in AQLQ mean score units(P < 0.01) and in overall ACQ score only in the Mg group(P = 0.05) after 6.5 months of supplementation. Despite these improvements, there were no significant changes in any of the markers of Mg status.

CONCLUSION

Adults who received oral Mg supplements showed improvement in objective measures of bronchial reactivity to methacholine and PEFR and in subjective measures of asthma control and quality of life.

The clinical significance of exhaled nitric oxide in asthma

Asthma is an inflammatory disease of the airways, for which many therapeutic options are available. Guidelines for the management of asthma suggest a stepwise approach to pharmacotherapy based on assessment of asthma severity and control. However, the assessment of asthma control presently relies on surrogate measures, such as the frequency of symptoms or the frequency of use of short-acting beta2-adrenergic agonists. There is no simple, noninvasive technique for the assessment of severity of actual airway inflammation in asthma. The collection and analysis of nitric oxide (NO) levels in exhaled breath has recently become feasible in humans. Based on increased exhaled NO (eNO) levels in patients with asthma, eNO analysis has been proposed as a novel, noninvasive approach to the assessment and monitoring of airway inflammation, and as a basis for adjustments in asthma therapy. In the present paper, the relationship of elevated eNO levels in asthma with inflammatory, physiological and clinical markers of asthma in adults was reviewed. Use of eNO is a promising tool for diagnosing asthma, for monitoring asthma control and for guiding optimal anti-inflammatory asthma therapy. However, because of many unresolved questions, eNO cannot be recommended at present for routine clinical management of adults with asthma.

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

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

Exhaled nitric oxide in asthma: variability, relation to asthma severity, and peripheral blood lymphocyte cytokine expression

Exhaled nitric oxide has been used as a means of indirectly measuring the underlying inflammation in asthma. The objectives of the study were to measure exhaled nitric oxide levels in asthma patients and healthy volunteers, to study peripheral blood lymphocyte cytokine expression, and to study the relationship between exhaled nitric oxide and intracellular cytokine expression. Exhaled nitric oxide was elevated in patients with moderate to severe asthma and with treatment decreased in the first week reaching to a near normal level by 4 weeks. Elevated exhaled nitric oxide was associated with decreased IL-4 and IL-13 cytokine expression by CD8 lymphocytes.

Modulation of nitric oxide pathways: therapeutic potential in asthma and chronic obstructive pulmonary disease

Nitric oxide (NO) is present in the exhaled breath of humans and other mammalian species. It is generated in the lower airways by enzymes of the nitric oxide synthase (NOS) family, although nonenzymatic synthesis and consumptive processes may also influence levels of NO in exhaled breath. The biological properties of NO in the airways are multiple, complex, and bidirectional. Under physiological conditions, NO appears to play a homeostatic bronchoprotective role. However, its proinflammatory properties could also potentially cause tissue injury and contribute to airway dysfunction in disease states such as asthma and chronic obstructive pulmonary disease (COPD). This article will review the physiological and pathophysiological roles of NO in the airways, discuss the rationale for the use of drugs that modulate NO pathways--nitric oxide synthase inhibitors and NO donors--to treat inflammatory airway diseases, and attempt to predict the likely therapeutic benefit of such agents.

Exhaled nitric oxide in the diagnosis of asthma: comparison with bronchial provocation tests

BACKGROUND

Bronchial provocation tests such as exercise, methacholine (MCH), and adenosine-5'-monophosphate (AMP) challenges are used extensively in the diagnosis of asthma. A study was undertaken to determine whether exhaled nitric oxide (eNO) can be used to diagnose asthma in patients with non-specific respiratory symptoms and to compare this test with conventional provocation tests.

METHODS

Patients with non-specific respiratory symptoms and normal spirometric parameters were included in the study. eNO was measured and exercise, MCH and AMP challenges performed in all subjects. Patients were defined as asthmatic based on clinical follow up 24 months after testing.

RESULTS

Forty patients were considered asthmatic and 45 were not. The area under receiver operating characteristic curves gave values of 0.896 for eNO, 0.781 for exercise, 0.924 for MCH, and 0.939 for AMP (p = 0.033, 0.575 and 0.085 for eNO v exercise, MCH and AMP respectively). From our data, a cut off value of NO > 7 ppb at a flow rate of 250 ml/s best differentiates between asthmatics and non-asthmatics (sensitivity 82.5%, specificity 88.9%). Optimal cut off values for other tests were exercise: deltaFEV1 > or = 10% (sensitivity 57.9%, specificity 100%); PC20-MCH: < or = 3 mg/ml (sensitivity 87.5%, specificity 86.7%); and PC20-AMP: < or = 150 mg/ml (sensitivity 89.5%, specificity 95.6%).

CONCLUSIONS

Measurement of eNO can be used as a safe, simple and rapid test for the diagnosis of asthma and is as good as bronchial provocation tests.

Evaluation of oxidative-antioxidative status and the L-arginine-nitric oxide pathway in asthmatic patients

BACKGROUND

Reactive nitrogen, oxygen species and oxidative stress are related to many pulmonary diseases. Nitric oxide (NO) may be involved in either the protection against or the induction of oxidative stress within various tissues. It is derived from the amino acid L-arginine by the action of NO synthase (NOS). L-arginine can also be metabolized by arginase with the production of ornithine and urea. Because of the competition between NOS and arginase for the same substrate, their activities are regulated reciprocally. Therefore, the rate of NO generation associated with oxidative stress is dependent on the relative activities of both NOS and arginase. The objective of this study is to investigate the L-arginine-NO pathway, evaluate oxidative-antioxidative status in the patients with asthma and demonstrate their reciprocal regulation.

METHODS

30 voluntary asthmatic patients and 30 healthy control subjects with similar age range and sex were included in the study. A total of 10 ml venous blood was drawn, plasma and packed erythrocytes were prepared for the biochemical analyses. Plasma arginase activities and NO levels, and erythrocyte malondialdehyde and reduced glutathione levels were detected.

RESULTS

Plasma malondialdehyde levels were significantly higher and glutathione levels were lower in patients with asthma than those of the control subjects (P < 0.001 and P < 0.01, respectively). Arginase activities were significantly lower and NO levels were higher in the patients than those of the controls (P < 0.001 for both). The negative correlation between arginase and NO levels in the patients was significant (r = -0.47; P < 0.01). There was also a positive correlation between malondialdehyde and NO levels in the patients (r = 0.51; P < 0.01).

CONCLUSIONS

The results suggest that the L-arginine-NO pathway is involved in the pathophysiology of asthma; the arginase activities decrease which causes an increase in the L-arginine levels thereby up-regulation of NO production may contribute to the increase of oxidative stress in asthma.

Exhaled nitric oxide in relation to the clinical features of childhood asthma

BACKGROUND

Exhaled nitric oxide (ENO) has been shown to be a noninvasive marker of eosinophilic inflammation in asthmatic children. Few studies have evaluated the relationship between ENO levels and the clinical features of children with asthma. The aim of this study was to examine children attending a routine asthma clinic and evaluate the relationship between ENO levels and clinical parameters including decision making.

METHODS

Asthmatic children (n= 133, aged 5 to 14 years) attending a hospital asthma clinic were studied. ENO levels were measured and compared between subgroups of subjects according to recent symptoms, asthma control and treatment, and the clinician's decision (blinded to ENO levels) regarding further management.

RESULTS

ENO levels (median [IQR] ppb) were significantly elevated in children who had recent symptoms compared to those without recent symptoms (14.6 [6.5 to 45.3] vs. 6.0 [3.2 to 17.4], difference between medians 8.6, 95% confidence interval [CI] (1.8 to 13.9, p=0.004). ENO levels differed significantly between the controlled and uncontrolled subgroups (8.5 [4.2 to 26.4] vs. 26.4 [5.0 to 62.0], difference between medians 17.9, 95% CI 0.1 to 22.8, p=0.03) and between the three treatment decision subgroups (up, down, or unchanged; p < 0.001).

CONCLUSIONS

ENO levels are strongly related to the clinical features of childhood asthma and the clinical decision making process. To fully evaluate the role of ENO in the clinical management of asthma, this "proof of concept" study paves the way for prospective randomized trials of the inclusion of ENO levels in the decision making process in childhood asthma.

Nitric oxide synthase inhibition: therapeutic potential in asthma

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

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Heterogeneity of FeNO response to inhaled steroid in asthmatic children

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Relationship among pulmonary function, bronchial reactivity, and exhaled nitric oxide in a large group of asthmatic patients

BACKGROUND

Bronchial reactivity and exhaled nitric oxide (eNO) are not often used to monitor control and severity of asthma in clinical practice.

OBJECTIVE

To evaluate the relationship among different physiologic measures (pulmonary function, nonspecific bronchial reactivity, and eNO) in asthmatic patients.

METHODS

Cross-sectional, hospital-based study conducted in patients with varied asthma severity.

RESULTS

A total of 392 patients participated in the study. There was no difference in eNO levels between patients taking inhaled corticosteroids (ICS group) and patients not receiving inhaled corticosteroids (NICS group). However, the percentage of predicted forced expiratory volume in 1 second (FEV1) and the provocative dose of methacholine causing a 20% decrease in FEV1 were significantly lower in the ICS group compared with the NICS group (mean, 83.2%; 95% confidence interval [CI], 80.4%-86.0%; vs mean, 94.1%; 95% CI, 91.1%-97.1%; P = .001; and geometric mean, 0.32 mg; 95% CI, 0.23-0.45 mg; vs geometric mean, 0.58 mg; 95% CI, 0.42-0.81 mg; P = .01; respectively). Patients with more severe bronchial hyperresponsiveness had a lower percentage of predicted FEV1 values (P < .001) and levels of eNO were significantly increased with increasing bronchial hyperresponsiveness (P < .001). There was no relationship between the percentage of predicted FEV1 and eNO. Atopic patients had significantly higher eNO levels than nonatopic patients (geometric mean, 11.21 ppb; 95% CI, 10.07-12.49 ppb; vs geometric mean, 7.76 ppb; 95% CI, 6.11-9.85 ppb; P = .006; respectively).

CONCLUSIONS

eNO values are not related to the degree of airway obstruction but are related to airway reactivity and atopic status independent of inhaled corticosteroid use. Higher values of eNO are seen with increased airway reactivity.

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.

Nitric oxide airway diffusing capacity and mucosal concentration in asthmatic schoolchildren

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

Effect of Montelukast on Exhaled Nitric Oxide and Nonvolatile Markers of Inflammation in Mild Asthma

STUDY OBJECTIVES

Leukotriene receptor antagonists appear to exert anti-inflammatory activity in asthma. We undertook the present study to evaluate the effect of montelukast on levels of exhaled nitric oxide (ENO) and two inflammatory markers, hydrogen peroxide (H(2)O(2)), and cysteinyl leukotrienes (cys-LTs), in the exhaled breath condensate of subjects with mild asthma.

PATIENTS

Twenty stable subjects with mild asthma (15 women and 5 men; mean [+/- SD] age, 34.8 +/- 12.6 years) were included in the study.

INTERVENTION

A 1-week run-in period was followed by 2 weeks of treatment (with montelukast or placebo) that was administered in randomized, double-blind, crossover fashion. One week of washout followed each treatment arm.

RESULTS

Montelukast significantly reduced the levels of ENO from baseline (median, 52.5 parts per billion [ppb]; 25th to 75th percentile, 37.8 to 101.8 ppb) during the entire treatment period (ie, day 1 to day 14), with the effect measurable as early as day 1 (median, 45.9 ppb; 25th to 75th percentile, 29.3 to 92.5 ppb) and with the maximal effect being observed on day 7 (median, 35.7 ppb; 25th to 75th percentile, 27.6 to 66.6 ppb). The levels of ENO did not change significantly with placebo therapy. Montelukast improved symptom score and reduced peak expiratory flow (PEF) variability. Changes in PEF variability correlated positively with changes in ENO (r = 0.46; p = 0.04). No significant changes in FEV(1) or concentration of H(2)O(2) in the exhaled breath condensate were observed. Levels of cys-LTs were undetectable in the exhaled breath condensate.

CONCLUSIONS

We concluded that montelukast reduces the levels of ENO in patients with mild asthma, a finding that is compatible with an anti-inflammatory effect of montelukast, and that ENO appears to be more sensitive in detecting this effect than FEV(1) and H(2)O(2) levels in the exhaled breath condensate.

Assessment of inhaled BDP-dose dependency of exhaled nitric oxide and local and serum eosinophilic markers in steroids-naive nonatopic asthmatics

The aim of the present study was to assess the dose-dependency from inhaled steroids of changes of airways inflammation [eosinophils count and eosinophil cationic protein (ECP)] measures in induced sputum and in serum, as well as that of exhaled nitric oxide. Twenty steroid-naive patients with nonatopic asthma of mild to moderate degree [forced expiratory volume in 1 s (FEV1) = 70% of predicted] and with negative response to the standard tests for allergy were selected; after a 1-week run-in period they were randomized to receive a 12-week treatment period of inhaled beclomethasone dipropionate dry powder given with the Pulvinal inhaler (Clenil P, Chiesi Farmaceutici S.p.A., Parma, Italy) in two different dose regimens, 400 microg bid (high dose) or 200 microg bid (low dose), over a double blind, parallel groups design. The following outcome measures were assessed in baseline and after 1, 6 and 12 weeks of treatment: FEV1 (l), eosinophils count in sputum (%), is ECP (microg/l), serum eosinophils count (%), serum ECP (microg/l) and exhaled NO (ppb). The results showed that all the considered parameters improved in both groups: the increase over baseline of FEV1 and the decrease of NO were significant at any time in the high-dose group and only at week 12 in the low-dose group (NS between groups), whereas the markers of eosinophilic activity showed more consistent reductions in the high-dose than in the low-dose group when measured in induced sputum (P < 0.05 between groups after 6 and 12 weeks for eosinophils count and after 12 weeks for ECP). Decreases over baseline of markers measured in serum were more rapid in the high-dose group, without differences between groups. A marked trend towards a negative correlation was found between FEV1 and ECP, (r = -0.72, P < 0.05), between FEV1 and eosinophils in sputum (r = -0.31, NS) and between FEV1 and exhaled NO (r = -0.38, NS), all of them only in the high-dose group. The results of the study demonstrate that changes of levels of eosinophilic activity in the airways are dependent from the daily dose of inhaled steroids when measured in induced sputum and that the local assessment can therefore represent a practical and noninvasive method to monitor the extent of airways inflammation.

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

OBJECTIVE

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

STUDY DESIGN

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

RESULTS

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

CONCLUSIONS

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

Prevalence of endothelial nitric oxide synthase gene polymorphisms in patients with atopic asthma

BACKGROUND

Asthma is a common multifactorial disease, the aetiology of which is attributable to both environmental and genetic factors. The endothelial nitric oxide synthase (NOS3) gene has been implicated in asthma pathogenesis.

OBJECTIVE

This study investigated associations of 27 base-pair tandem repeat polymorphism in intron 4 and the Glu298Asp (G894T) variant of the NOS3 gene with atopic asthma in a Czech population.

METHODS

Polymerase chain reaction was used to determine the NOS3 genotypes in subjects with atopic asthma (n = 163) and random controls (n = 209).

RESULTS

The NOS3 allele or genotype distributions did not differ significantly between the control and asthma groups. However, the common genotype (bb) of the NOS3 polymorphism in intron 4 was found to be significantly associated with total IgE levels (P = 0.006), specific IgE levels for feathers (P = 0.0002) and a positive skin prick test for hay (P = 0.004). In one atopic patient, we identified an additional 27-bp repeat in the NOS3 gene (NOS3c), which occurred in heterozygous combination with the NOS3b allele (NOS3b/c genotype). In addition, we describe a new polymorphism (A5495G) in the NOS3 gene, which was in almost complete linkage disequilibrium with the NOS3 repeat polymorphism in intron 4. The Glu298Asp variant was not associated with asthma and/or related atopic phenotypes in our study.

CONCLUSION

Neither the NOS3 'b' allele nor the NOS3 'b/b' genotype showed any general association with atopic asthma, but they were associated with atopy-related phenotypes. We conclude that the NOS3 gene polymorphisms may act as disease modifiers in atopic asthma phenotype in our population.

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 monoxides as a pulmonary function test: use of exhaled nitric oxide and carbon monoxide

Although there has been tremendous improvement in the technologic ability to measure exhaled gases and monitor biologic processes in the lung, it has not yet found a clinical role outside the research laboratory. Common themes seem to be significant overlap in the amount of exhaled gases in clinically distinct populations, confounding variables such as infection, smoking, and environmental exposure, and lack of consistent change with disease management. If these tests are ever to be used by the general pulmonologist, consistent links between the measurements and the response to disease modification will need to be demonstrated at the very least and, ideally, the clinician would like to see improved outcomes when these noninvasive tests are employed regularly.

Nitric oxide and asthma: a review

Nitric oxide (NO) is synthesized from the amino acid arginine by enzymes called nitric oxide synthases. NO has an important physiologic role in the regulation of vascular tone, response to vascular injury, and hemostasis. It also acts as a neurotransmitter for the nonadrenergic noncholinergic nerves and has important antimicrobial, immunologic, and proinflammatory activities. The lung is rich in nitric oxide synthases, and NO is normally present in the exhaled air. Use of NO in the treatment of asthma has not withstood the test of time and is not recommended. With the advent of analyzers capable of measuring NO rapidly and reliably, however, the analysis of NO in exhaled air is being increasingly recognized as a potential noninvasive test for the evaluation of the inflammatory component of the pathology of patients with asthma. An increase in the exhaled NO has been shown to accompany eosinophilic inflammation and to correlate with other indices of inflammation in asthma. Exhaled NO increases during exacerbation and decreases with recovery in patients with asthma. As exhaled NO is not increased during bronchospasm in the absence of coexisting inflammation, it could serve to differentiate between the inflammatory and bronchospastic components in asthma, thereby guiding therapy with steroids and other anti-inflammatory medications. Levels of NO also can be increased in certain other conditions, for example, allergic rhinitis and adult respiratory distress syndrome, but these can be clinically differentiated from asthma and do not lessen the diagnostic value of exhaled NO. Measurements of exhaled NO are influenced by several physiologic and technical variables, which results in a wide variation in the levels reported from the different laboratories. Standardization of technique, a better understanding of the confounding effects of physiologic and environmental variables, and establishment of the normal range and variability of exhaled NO are needed before its measurement could gain wide acceptance as a clinically useful test. Development of less expensive NO analyzers is also an important consideration.