Exhaled nitric oxide levels in asthma: Personal best versus reference values

Assessment of an exhaled breath test using ultraviolet photoionization time-of-flight mass spectrometry for the monitoring of kidney transplant recipients

Continuous monitoring for immunosuppressive status, infection and complications are a must for kidney transplantation (KTx) recipients. Traditional monitoring including blood sampling and kidney biopsy, which caused tremendous medical cost and trauma. Therefore, a cheaper and less invasive approach was urgently needed. We thought that a breath test has the potential to become a feasible tool for KTx monitoring. A prospective-specimen collection, retrospective-blinded assessment strategy was used in this study. Exhaled breath samples from 175 KTx recipients were collected in West China Hospital and tested by online ultraviolet photoionization time-of-flight mass spectrometry (UVP-TOF-MS). The classification models based on breath test performed well in classifying normal and abnormal values of creatinine, estimated glomerular filtration rate (eGFR), blood urea nitrogen (BUN) and tacrolimus, with AUC values of 0.889, 0.850, 0.849 and 0.889, respectively. Regression analysis also demonstrated the predictive ability of breath test for clinical creatinine, eGFR, BUN, tacrolimus level, as the predicted values obtained from the regression model correlated well with the clinical true values (p < 0.05). The findings of this investigation implied that a breath test by using UVP-TOF-MS for KTx recipient monitoring is possible and accurate, which might be useful for future clinical screenings.

The effects of oral corticosteroids on lung function, type-2 biomarkers and patient-reported outcomes in stable asthma: A systematic review and meta-analysis

BACKGROUND

Several studies have investigated the physiological effect of OCS in stable asthma, however these have included heterogeneous populations and outcomes. This paper is the first to combine their results.

METHODS

We searched Medline, Embase and Web of Science databases for studies reporting the impact of OCS on FEV₁, FVC, blood eosinophils, fractional exhaled nitric oxide (FeNO), Asthma Control Questionnaire (ACQ) score or Asthma Quality Of Life Questionnaire (AQLQ) score in stable asthma. We extracted data on the correlates of OCS response.

RESULTS

61 studies, comprising 1608 patients, were included. FEV₁ was improved by 9% (95% CI: 7, 11). There were stronger increases in FEV₁ among those with a mean baseline FEV₁<60% predicted (19%, 95% CI: 13, 24). Despite these improvements, substantial residual impairment remained after treatment. Blood eosinophils were reduced by 76% (95% CI: 63, 88) with larger decreases in studies of corticosteroid-naïve patients (93%, 95% CI: 73,100). Sputum eosinophils were reduced by 89% (95% CI: 79, 98) while FeNO was decreased by 35% (95% CI: 28, 41). ACQ scores were reduced by 20% (95% CI: 11, 29). Patients with higher baseline lung function impairment, sputum eosinophils, blood eosinophils and FeNO had improved OCS response.

INTERPRETATION

OCS consistently improves lung function, reduces markers of type-2 inflammation, and alleviates asthma symptoms. However, substantial residual impairment remained following treatment and mean improvements were below the minimally important clinically difference. Patients with increased markers of type-2 inflammation are more responsive to treatment, suggesting these should be used to better target OCS use.

Measurement of nitric oxide and assessment of airway diseases in children: an update

INTRODUCTION

Nitric oxide (NO) is a gas synthesized by the inducible NO synthase enzyme in airway cells and it is thought to make important functions in the airway inflammation of several respiratory diseases.

EVIDENCE ACQUISITION

This current study is a review of the literature from 1990 to present about NO and its use in clinical practice. The databases used were PubMed, Scopus, and Cochrane Library.

EVIDENCE SYNTHESIS

At the respiratory level there are three different measurements sites of NO: nNO (nasal nitric oxide), FeNO (exhaled fraction of nitric oxide), CaNO (alveolar nitric oxide). Each of them is produced at different levels of the respiratory tract and is involved in various diseases. nNO finds its use, principally, in the allergic rhinitis in fact it can be used as a measure of therapeutic efficacy, but not for the evaluation of the severity; also in primary ciliary dyskinesia (PCD), where high levels exclude the disease, and in chronic rhinosinusitis, but it is not currently used as a diagnostic or prognostic marker. FeNO has a greatest use in bronchial asthma, particularly, it is considered a non-invasive biomarker to identify and to monitor airway inflammation but currently, there is not a consensus on the use of the FeNO in the management of asthma treatment. Finally, CaNO is the least used in clinical practice, because lack of standardization of measurement techniques.

CONCLUSIONS

Nitric oxide is a sensitive indicator of the presence of airway inflammation and ciliary dysfunction, although some studies have shown varying or conflicting results.

Exhaled NO reference limits in a large population-based sample using the Lambda-Mu-Sigma method

Absolute values are used in the interpretation of the fraction of exhaled nitric oxide (FeNO), but it has been suggested that equations to calculate reference values may be a practical and clinically useful approach. We hypothesize that the application of the Lambda-Mu-Sigma (LMS) method may improve FeNO reference equations and their interpretation. Our aims were to develop FeNO reference equations with the LMS method and to describe the difference between this method and the absolute fixed cut-offs of the current recommendations. We utilized the United States National Health and Nutrition Examination Surveys 2007-2012 and included healthy individuals with no respiratory diseases and blood eosinophils <300/mm³ ( n = 8,340). Natural log-transformed FeNO was modeled using the LMS method, imbedded in the generalized additive models for location, scale, and shape models. A set of FeNO reference equations was developed. The explanatory variables were sex, age, height, smoking habits, and race/ethnicity. A significant proportion of individuals with normal FeNO given by the equations were classified as having intermediate levels by the current recommendations. Further lower predicted FeNO compared with previous linear models was seen. In conclusion, we suggest a novel model for the prediction of reference FeNO values that can contribute to the interpretation of FeNO in clinical practice. This approach should be further validated in large samples with an objective measurement of atopy and a medical diagnosis of asthma and rhinitis. NEW & NOTEWORTHY Novel reference equations and fraction of exhaled nitric oxide (FeNO)-predicted values to improve interpretation of FeNO in clinical practice are presented. These may increase the accuracy of ruling out airway inflammation in patients with asthma or suspected asthma.

A Review of Pulmonary Toxicity of Electronic Cigarettes in the Context of Smoking: A Focus on Inflammation

The use of electronic cigarettes (e-cigs) is increasing rapidly, but their effects on lung toxicity are largely unknown. Smoking is a well-established cause of lung cancer and respiratory disease, in part through inflammation. It is plausible that e-cig use might affect similar inflammatory pathways. E-cigs are used by some smokers as an aid for quitting or smoking reduction, and by never smokers (e.g., adolescents and young adults). The relative effects for impacting disease risk may differ for these groups. Cell culture and experimental animal data indicate that e-cigs have the potential for inducing inflammation, albeit much less than smoking. Human studies show that e-cig use in smokers is associated with substantial reductions in blood or urinary biomarkers of tobacco toxicants when completely switching and somewhat for dual use. However, the extent to which these biomarkers are surrogates for potential lung toxicity remains unclear. The FDA now has regulatory authority over e-cigs and can regulate product and e-liquid design features, such as nicotine content and delivery, voltage, e-liquid formulations, and flavors. All of these factors may impact pulmonary toxicity. This review summarizes current data on pulmonary inflammation related to both smoking and e-cig use, with a focus on human lung biomarkers. Cancer Epidemiol Biomarkers Prev; 26(8); 1175-91. ©2017 AACR.

Setting reference values for exhaled nitric oxide: a systematic review

BACKGROUND

The values obtained when the fraction of exhaled nitric oxide (FeNO) is measured are affected by several factors that are specific to the individual patient, making interpretation difficult, especially in the initial assessment of patients with respiratory symptoms.

METHODS

Systematic review of studies on FeNO reference values and individual-specific factors that influence them.

RESULTS

From 3739 references, 15 studies were included. Four studies included children and adolescents. In nine studies, samples were selected from the general population. Most studies reported objective measures for atopy (nine studies), but not for smoking status (one). Significant determinants of FeNO values reported were age and height (seven studies), atopy (six), smoking (four), weight (four), sex (three) and race (three). Additional factors were included in eight studies. R2 was reported in only five studies. The logarithmic transformation of FeNO was inadequately described in seven studies.

CONCLUSION

There are several equations for FeNO reference values that may be used in clinical practice, although the factors they include and the statistical methods they use vary considerably. We recommend the development of standard methods for the evaluation of normal FeNO data and that reference equations should be formulated based on a predetermined physiological model.

A systematic review of fractional exhaled nitric oxide in the routine management of childhood asthma

BACKGROUND

Fractional exhaled nitric oxide (FeNO) is a non-invasive biomarker of eosinophilic inflammation which may be used to guide the management of asthma in childhood.

OBJECTIVES

To synthesise the available evidence on the efficacy of FeNO-guided management of childhood asthma.

METHODS

Databases including MEDLINE and the Cochrane Library were searched, and randomised controlled trials (RCTs) comparing FeNO-guided management with any other monitoring strategy were included. Study quality was assessed using the Cochrane risk of bias tool for RCTs, and a number of outcomes were examined, including: exacerbations, medication use, quality of life, adverse events, and other markers of asthma control. Meta-analyses were planned if multiple studies with suitable heterogeneity were available. However, due to wide variations in study characteristics, meta-analysis was not possible.

RESULTS

Seven RCTs were identified. There was some evidence that FeNO-guided monitoring results in improved asthma control during the first year of management, although few results attained statistical significance. The impact on severe exacerbations was unclear. Similarly, the impact on use of anti-asthmatic drugs was unclear, and appears to depend on the step up/down protocols, and the clinical characteristics of patients.

CONCLUSIONS

The potential benefit of FeNO monitoring is equivocal. Trends toward reduced exacerbation and increased medication use were seen, but typically failed to reach statistical significance. There are a number of issues that complicate data interpretation, including differences in the likely severity of included cohorts and variations in treatment algorithms. Further work is needed to systematically explore the impact of these parameters.

Management based on exhaled nitric oxide levels adjusted for atopy reduces asthma exacerbations in children: A dual centre randomized controlled trial

While several randomized control trials (RCTs) have evaluated the use of fractional exhaled nitric oxide (FeNO) to improve asthma outcomes, none used FeNO cut-offs adjusted for atopy, a determinant of FeNO levels. In a dual center RCT, we assessed whether a treatment strategy based on FeNO levels, adjusted for atopy, reduces asthma exacerbations compared with the symptoms-based management (controls). Children with asthma from hospital clinics of two hospitals were randomly allocated to receive an a-priori determined treatment hierarchy based on symptoms or FeNO levels. There was a 2-week run-in period and they were then reviewed 10 times over 12-months. The primary outcome was the number of children with exacerbations over 12-months. Sixty-three children were randomized (FeNO = 31, controls = 32); 55 (86%) completed the study. Although we did achieve our planned sample size, significantly fewer children in the FeNO group (6 of 27) had an asthma exacerbation compared to controls (15 of 28), P = 0.021; number to treat for benefit = 4 (95% CI 3-24). There was no difference between groups for any secondary outcomes (quality of life, symptoms, FEV1 ). The final daily inhaled corticosteroids (ICS) dose was significantly (P = 0.037) higher in the FeNO group (median 400 µg, IQR 250-600) compared to the controls (200, IQR100-400). Taking atopy into account when using FeNO to tailor asthma medications is likely beneficial in reducing the number of children with severe exacerbations at the expense of increased ICS use. However, the strategy is unlikely beneficial for improving asthma control. A larger study is required to confirm or refute our findings.

Evolution of exhaled nitric oxide levels throughout development and aging of healthy humans

It is not fully understood how the fraction of exhaled nitric oxide (FeNO) varies with age and gender in healthy individuals. We aim to describe the evolution of FeNO with age, giving special regard to the effect of gender, and to relate this evolution to natural changes in the respiratory tract.We studied 3081 subjects from NHANES 2007-08 and 2009-10, aged 6-80 years, with no self-reported diagnosis of asthma, chronic bronchitis or emphysema, and with normal values of blood eosinophils and C-reactive protein. The relationship of the mean values of FeNO to age, in all participants and divided by gender, was computed, and compared with changes in anatomic dead space volume and forced vital capacity. A change-point analysis technique and subsequent piecewise regression was used to detect breakpoints in the evolution of FeNO with age.Three distinct phases in the evolution of FeNO throughout the age range 6-80 years can be seen. FeNO values increase linearly between 6-14 years of age in girls and between 6-16 years of age in boys, in parallel with somatic growth. After that, FeNO levels plateau in both genders until age 45 years in females and age 59 years in males, when they start to increase linearly again. This increase continues until age 80.Our data clearly show a triphasic evolution of FeNO throughout the human age range in healthy individuals. This should be accounted for in development of reference equations for normal FeNO values.

Revisiting the role of exhaled nitric oxide in asthma

PURPOSE OF REVIEW

This review focuses on the most recent studies investigating fractional nitric oxide concentration in exhaled breath (FeNO) as a useful biomarker for identifying specific phenotypes in asthma and as a tool for asthma diagnosis, monitoring and clinical decision-making.

RECENT FINDINGS

On the basis of the current literature, it has been highlighted that FeNO is a clinically relevant marker in various clinical aspects of asthma: FeNO is a predictor for developing asthma in persistent rhinitis or in infants with respiratory symptoms; FeNO contributes to identification of asthma phenotypes in both children and adults, also in relation to severity; FeNO is useful in monitoring the effectiveness of inhaled corticosteroids (including compliance) and biologic treatments like omalizumab; FeNO, in conjunction with symptom registration and lung function measurements, contributes to asthma diagnosis and optimizes asthma management.

SUMMARY

FeNO provides further information in distinguishing different phenotypes in asthma, allowing a much more appropriate control of the disease, especially in patients with difficult/severe asthma. In the future, it would be interesting to shed light on the hidden biological mechanisms responsible for low or normal FeNO values in symptomatic asthmatic patients.

Fraction of exhaled nitric oxide (FeNO ) norms in healthy Tunisian adults

Aims. To establish Fe_NO norms for healthy Tunisian adults aged 18–60 years and to prospectively assess their reliability. Methods. This was a cross-sectional analytical study. A convenience sample of healthy Tunisian adults was recruited. Subjects responded to a medical questionnaire, and then Fe_NO levels were measured by an online method (Medisoft, Sorinnes (Dinant), Belgium). Clinical, anthropometric, and plethysmographic data were collected. All analyses were performed on natural logarithm values of Fe_NO. Results. 257 adults (145 males) were retained. The proposed reference equation to predict Fe_NO value is lnFe_NO (ppb) = 3.47−0.56× height (m). After the predicted Fe_NO value for a given adult was computed, the upper limit of normal could be obtained by adding 0.60 ppb. The mean ± SD (minimum-maximum) of Fe_NO (ppb) for the total sample was 13.54 ± 4.87 (5.00–26.00). For Tunisian and Arab adults of any age and height, any Fe_NO value greater than 26.00 ppb may be considered abnormal. Finally, in an additional group of adults prospectively assessed, we found no adult with a Fe_NO higher than 26.00 ppb. Conclusion. The present Fe_NO norms enrich the global repository of Fe_NO norms that the clinician can use to choose the most appropriate norms.

Health effects of daily airborne particle dose in children: direct association between personal dose and respiratory health effects

Air pollution is a widespread health problem associated with respiratory symptoms. Continuous exposure monitoring was performed to estimate alveolar and tracheobronchial dose, measured as deposited surface area, for 103 children and to evaluate the long-term effects of exposure to airborne particles through spirometry, skin prick tests and measurement of exhaled nitric oxide (eNO). The mean daily alveolar deposited surface area dose received by children was 1.35 × 10(3) mm(2). The lowest and highest particle number concentrations were found during sleeping and eating time. A significant negative association was found between changes in pulmonary function tests and individual dose estimates. Significant differences were found for asthmatics, children with allergic rhinitis and sensitive to allergens compared to healthy subjects for eNO. Variation is a child's activity over time appeared to have a strong impact on respiratory outcomes, which indicates that personal monitoring is vital for assessing the expected health effects of exposure to particles.

Inhaled and systemic corticosteroid response in severe asthma assessed by alveolar nitric oxide: a randomized crossover pilot study of add-on therapy

AIMS

Alveolar nitric oxide (CA(NO)) is a potential biomarker of small airway inflammation. We investigated effects on CA(NO) of the addition of coarse and fine particle inhaled corticosteroids to standard therapy in severe asthma.

METHODS

Severe asthmatics taking ≥1600 µg day(-1) budesonide or equivalent performed a randomized open-label crossover study. Subjects with FEV(1) < 80%, gas trapping and CA(NO) ≥2 ppb entered a 6 week dose-ramp run-in of fluticasone/salmeterol(FPSM) 250/50 µg twice daily for 3 weeks, then 500/50 µg twice daily for 3 weeks. Patients then received additional HFA-beclomethasone diproprionate (BDP) 200 µg twice daily or FP 250 µg twice daily for 3 weeks in a crossover. Participants then received prednisolone(PRED) 25 mg day(-1) for 1 week. Nitric oxide, lung function, mannitol challenge, systemic inflammatory markers and urinary cortisol were measured.

RESULTS

Fifteen completed per protocol: mean (SD) age 51 (12) years, FEV(1) 58 (13)% predicted, residual volume 193 (100)% predicted and mannitol(PD10) 177 (2.8) µg. There was no significant difference between FPSM and add-on therapy for CA(NO). FPSM/BDP and FPSM/PRED suppressed broncial flux (Jaw(NO)) and FE(NO) compared with FPSM alone, but there was no significant difference between FPSM/BDP and FPSM/FP. ECP, e-selectin and ICAM-1 were suppressed by FPSM/PRED compared with FPSM and FPSM/FP but not FPSM/BDP. Plasma cortisol was significantly suppressed by FPSM/PRED.

CONCLUSION

In severe asthma, CA(NO) is insensitive to changes in dose and delivery of inhaled corticosteroids and is not suppressed by systemic corticosteroids. Additional inhaled HFA-BDP reduced FE(NO) and Jaw(NO) without adrenal suppression. There was a trend to reduction in FE(NO) and Jaw(NO) with additional FP but this did not reach statistical significance. PRED reduced FE(NO) and Jaw(NO) with suppression of systemic inflammatory markers and urinary cortisol.

The value of FeNO measurement in childhood asthma: uncertainties and perspectives

Asthma is considered an heterogeneous disease, requiring multiple biomarkers for diagnosis and management. Fractional exhaled nitric oxide in exhaled breath (FeNO) was the first useful non-invasive marker of airway inflammation in asthma and still is the most widely used. The non-invasive nature and the relatively easy use of FeNO technique make it an interesting tool to monitor airway inflammation and rationalize corticosteroid therapy in asthmatic patients, together with the traditional clinical tools (history, physical examination and lung function tests), even if some controversies have been published regarding the use of FeNO to support the management of asthma in children. The problem of multiple confounding factors and overlap between healthy and asthmatic populations preclude the routine application of FeNO reference values in clinical practice and suggest that it would be better to consider an individual "best", taking into account the context in which the measurement is obtained and the clinical history of the patient. Besides, there is still disagreement about the role of FeNO as a marker of asthma control, due to the complexity of balance among the different items involved in its determination and the lack of homogeneity in the population groups studied in the few studies conducted so far. Heterogeneity of problematic severe asthma greatly limits utility of FeNO alone as a biomarker of inflammation to optimize the disease management on an individual basis. None of the studies conducted so far demonstrated that the use of FeNO was better than current asthma guidelines in controlling asthma exacerbations. In summary, there is a large variation in FeNO levels between individuals, which may reflect the natural heterogeneity in baseline epithelial nitric oxide synthase activity and/or the contribution of other noneosinophilic factors to epithelial nitric oxide synthase activity. FeNO is a promising biomarker, but at present some limits are highlighted. We would recommend that further research can be carried out by organizing studies aimed to obtain reliable reference values of FeNO and in order to better interpret FeNO measurements in clinical settings, taking also into account the influence of genetic and environmental factors.

Guidance for a personal target value of F(E)NO in allergic asthma: case report and theoretical example

In clinically stable asthma the exhaled NO values (F(E)NO) are generally higher than in control subjects. Therefore, reference values are of limited importance in clinical practice. This is demonstrated in this case report, but it is also shown that NO parameters from non-linear modelling do have a clinical value. A subject with asthma was treated with inhaled corticosteroids for 1 week. The non-linear NO model was used to measure the response to treatment. The NO parameters from subjects with atopic rhinitis and asthma were fed into a computer program to generate theoretical F(E)NO₀.₀₅ values, i.e. target values. There was a dramatic decrease in F(E)NO₀.₀₅ due to treatment, from 82 to 34 ppb, but it remained higher than in healthy controls. This is due to the elevated diffusion rate of NO, unchanged by treatment. When the NO parameters are known, a personal best value of F(E)NO₀.₀₅ (fractional concentration of exhaled NO in the gas phase, 0.05 L/s) can be calculated, which can be the target value when only F(E)NO₀.₀₅ can be monitored. In conclusion, reference values for NO parameters are shown to be clinically useful. It is essential that every patient receives his/her target value of F(E)NO₀.₀₅, when only a single NO measurement is available. In our opinion, this is the reason why there are few successful studies of trying to target the NO value with inhaled corticosteroids.

Association of asthma education with asthma control evaluated by asthma control test, FEV1, and fractional exhaled nitric oxide

BACKGROUND

Asthma education is an important adjunct for asthma control although the way asthma education affects asthma outcomes is poorly understood. The asthma control test (ACT), forced expiratory volume in 1 s (FEV(1)), and fractional exhaled nitric oxide (FeNO) have all been used as markers of asthma control. However, the use of FeNO as a surrogate marker remains controversial.

OBJECTIVES

(i) To examine whether asthma education is associated with asthma control; (ii) to compare absolute levels and changes of ACT, FEV(1), and FeNO over a year; and (iii) to evaluate whether FeNO can be used as an additional marker of asthma control.

METHODS

Fifty asthmatics with poor adherence (12 mild, 21 moderate, and 17 severe) received asthma education at study entry. Medications were unchanged for the first 3 months, and ACT, FEV(1), and FeNO measurements were recorded at entry, 3, 6, and 12 months. Asthma control was assessed at each visit and patients were categorized as either "stable" or "unstable" asthmatics according to the global initiative for asthma (GINA) guidelines.

RESULTS

A significant decrease in FeNO and increase in ACT score were noted in the stable asthmatic group at 3 months (p < .001), and this persisted over 12 months. Significant correlations were seen between changes (Δ) in FeNO, ACT, and FEV(1) over time. However, significant correlations between the absolute levels were not maintained over 12 months. A decrease of ≥18.6% in FeNO and a ≥3-point increase in ACT score (sensitivity: 80% and 73.3% and specificity: 83.3% and 87.5%, respectively) were associated with stable asthma control although the absolute levels were not.

CONCLUSIONS

Asthma education may be useful to achieve stable control. In addition, changes rather than absolute levels of FeNO and ACT may be better markers of asthma control.

Update on exhaled nitric oxide in pulmonary disease

The ability to assess the inflammatory status of a patient's airway using a noninvasive method is the ideal situation for clinicians. Owing in part to the relationship between the levels of exhaled nitric oxide to inflammation and the ease of the technique, the measurement of the fraction of exhaled nitric oxide (F(E)NO) has achieved considerable attention, particularly with respect to asthma. A multitude of studies have shown that when measured in exhaled air, this unique molecule has the potential to have both diagnostic and therapeutic roles in the clinical setting for many pulmonary diseases. The incorporation of F(E)NO into asthma management and treatment algorithms may help shed further insight on the current control and future risk of patients. Research is ongoing to determine the biology and the benefits of the use of F(E)NO in respiratory conditions in addition to asthma. This review will briefly outline the pathophysiology of nitric oxide, the measurement of F(E)NO and the potential clinical uses of F(E)NO in asthma and a number of other respiratory diseases. Despite its promise, until further research is conducted, the use of F(E)NO cannot be recommended for routine clinical management of respiratory diseases at present, but should be considered as an adjuvant to help guide therapy in certain patients with asthma and in those with eosinophilic bronchitis.

Exhaled nitric oxide in pediatrics: what is new for practice purposes and clinical research in children?

Fractional exhaled NO (FeNO) is universally considered an indirect marker of eosinophilic airways inflammation, playing an important role in the physiopathology of childhood asthma. Advances in technology and standardization have allowed a wider use of FeNO in clinical practice in children from the age of four years. FeNO measurements add a new dimension to the traditional clinical tools (symptoms scores, lung function tests) in the assessment of asthma. To date a number of studies have suggested a possible use of FeNO in early identification of exacerbation risk and in inhaled corticosteroids titration. The aim of this paper is to address practical issues of interest to paediatric clinicians who are attempting to use FeNO measurements as an adjunctive tool in the diagnosis and management of childhood airway diseases.

An official ATS clinical practice guideline: interpretation of exhaled nitric oxide levels (FENO) for clinical applications

BACKGROUND

Measurement of fractional nitric oxide (NO) concentration in exhaled breath (Fe(NO)) is a quantitative, noninvasive, simple, and safe method of measuring airway inflammation that provides a complementary tool to other ways of assessing airways disease, including asthma. While Fe(NO) measurement has been standardized, there is currently no reference guideline for practicing health care providers to guide them in the appropriate use and interpretation of Fe(NO) in clinical practice.

PURPOSE

To develop evidence-based guidelines for the interpretation of Fe(NO) measurements that incorporate evidence that has accumulated over the past decade.

METHODS

We created a multidisciplinary committee with expertise in the clinical care, clinical science, or basic science of airway disease and/or NO. The committee identified important clinical questions, synthesized the evidence, and formulated recommendations. Recommendations were developed using pragmatic systematic reviews of the literature and the GRADE approach.

RESULTS

The evidence related to the use of Fe(NO) measurements is reviewed and clinical practice recommendations are provided.

CONCLUSIONS

In the setting of chronic inflammatory airway disease including asthma, conventional tests such as FEV(1) reversibility or provocation tests are only indirectly associated with airway inflammation. Fe(NO) offers added advantages for patient care including, but not limited to (1) detecting of eosinophilic airway inflammation, (2) determining the likelihood of corticosteroid responsiveness, (3) monitoring of airway inflammation to determine the potential need for corticosteroid, and (4) unmasking of otherwise unsuspected nonadherence to corticosteroid therapy.

Approaches to stepping up and stepping down care in asthmatic patients

The variability in symptom control is a challenging feature of asthma that necessitates careful monitoring and the need to step up and step down individualized therapeutic regimens over time. This stepwise concept in asthma therapy can be considered in at least 3 contexts. For lack of control that is persistent over long periods of time, an increase in the overall medication or a step-up long-term strategy is indicated. A second approach, the step-up short-term strategy, can be used during a temporary loss of acceptable control, such as at the onset of a viral respiratory tract illness. In these cases a step-up in therapy is usually terminated in 3 to 10 days once asthma control has been satisfactorily achieved. Finally, for treating symptoms related to the variability of asthma on a day-to-day basis, inhaled corticosteroids used concomitantly with a β-agonist have been evaluated, although this treatment is not currently approved in the United States. We will term this particular intervention a step-up intermittent strategy. Here we summarize the existing data regarding these 3 approaches to step up care and step down management, as well as to identify areas where more comparative studies are necessary to provide further guidance to clinicians regarding proper step-up and step-down strategies in the care of asthma.

Fractional exhaled nitric oxide measurement with a handheld device

A sensing system for fractional exhaled nitric oxide (FeNO) measurement is presented, which is characterized by a compact setup and a cost potential to be made available for the patient at home. The sensing is based on the work function measurement of a phthalocyanine-type sensing material, which is shown to be sufficiently sensitive for NO(2) in the ppb range. The transducer used to measure the work function is a field effect transistor with a suspended gate electrode. Selectivity is given with respect to other breath components including typically metabolic by-products. The measurement system includes breath treatments in a simple setup, which essentially are dehumidification and a quantitative conversion of NO to NO(2) with a conversion rate of approx. 95%, using a disposable oxidation catalyst. The accomplishment of the correct exhalation maneuver and feeding of the suited portion of exhaled air to the sensor is provided by breath sampling means. The sensor is not gas consuming. This allows us to fill the measurement chamber once, instead of establishing a gas flow for the measurement. This feature simplifies the device architecture. In this paper, we report on sensor characteristics, system architecture and measurement with artificial breath-gas as well as with human breath with the device.

Using biomarkers in the assessment of airways disease

A biomarker provides a window on underlying disease activity. This is helpful when the pathology, treatment response, or both are heterogeneous or when trying to interpret nonspecific respiratory symptoms in patients with comorbidities. The successful application of a biomarker result is critically dependent on the specific question being addressed and the performance characteristics of the biomarker in relation to that question in the context of pretest probabilities. Negative prediction might be the best way to use a biomarker, such as a D-dimer, pro-brain natriuretic peptide, and exhaled nitric oxide. In this review the role of biomarkers in airways disease (notably induced sputum eosinophils and exhaled nitric oxide) is considered in relation to risk stratification, identification of treatment responders, identification of a clinical phenotype, monitoring of disease, and new drug development.

Hand-held nitric oxide sensor NIOX MINO® for the monitoring of respiratory disorders

Measurements of exhaled nitric oxide have been proposed as a tool to improve the control of asthma and inflammatory airways disease, including the patient's response to anti-inflammatory treatment and to predict loss of control and to monitor compliance with treatment. Several techniques have been used to assess exhaled nitric oxide gas and the majority of studies have used the chemiluminescence method. More recently, a new hand-held electrochemical sensor NIOX MINO(®) has been developed. Here, we will review the use of the NIOX MINO for the study of respiratory disorders.

Exhaled nitric oxide in pulmonary diseases: a comprehensive review

The upregulation of nitric oxide (NO) by inflammatory cytokines and mediators in central and peripheral airway sites can be monitored easily in exhaled air. It is now possible to estimate the predominant site of increased fraction of exhaled NO (FeNO) and its potential pathologic and physiologic role in various pulmonary diseases. In asthma, increased FeNO reflects eosinophilic-mediated inflammatory pathways moderately well in central and/or peripheral airway sites and implies increased inhaled and systemic corticosteroid responsiveness. Recently, five randomized controlled algorithm asthma trials reported only equivocal benefits of adding measurements of FeNO to usual clinical guideline management including spirometry; however, significant design issues may exist. Overall, FeNO measurement at a single expiratory flow rate of 50 mL/s may be an important adjunct for diagnosis and management in selected cases of asthma. This may supplement standard clinical asthma care guidelines, including spirometry, providing a noninvasive window into predominantly large-airway-presumed eosinophilic inflammation. In COPD, large/central airway maximal NO flux and peripheral/small airway/alveolar NO concentration may be normal and the role of FeNO monitoring is less clear and therefore less established than in asthma. Furthermore, concurrent smoking reduces FeNO. Monitoring FeNO in pulmonary hypertension and cystic fibrosis has opened up a window to the role NO may play in their pathogenesis and possible clinical benefits in the management of these diseases.

Consistently high levels of exhaled nitric oxide in children with asthma

BACKGROUND

Exhaled nitric oxide (eNO) levels in children are unstable because they are regulated by many potent factors. The purpose of the current study was to evaluate the reliability of eNO levels between a long interval and other lung functions in normal and asthmatic children.

METHODS

Eighty-three elementary school children (aged 11-12 years; male : female, 39 : 44) participated in this study. Lung function, airway resistance and eNO levels were measured twice: the first measurement was in autumn 2007, and the second was one year later.

RESULTS

There were 62 non-asthmatic control children (male : female, 31 : 31) and 21 asthmatic children (male : female, 8 : 13). In both the first and the second examination, the levels of eNO in children with asthma were higher than those in children without asthma. The parameters of lung function and the respiratory resistance in children without asthma showed a good correlation between the results of the first and second examinations. The eNO level in non-asthmatic children showed a good correlation between the two. On the other hand, the peripheral airway parameters of lung function and the respiratory resistance in children with asthma were not correlated between the first and the second examinations. The eNO level in these patients was well correlated between the two examinations.

CONCLUSIONS

These data suggest that the eNO level showed good reproducibility in children with and without asthma. The eNO level is therefore considered to be a useful marker for reproducibly evaluating a subject's airway condition.

Advances in pediatric asthma in 2009: gaining control of childhood asthma

This year's summary will focus on recent advances in pediatric asthma as reported in Journal of Allergy and Clinical Immunology publications in 2009. New National Asthma Education and Prevention Program asthma guidelines were released in 2007, with a particular emphasis on asthma control. Now that we have worked with the principals of the guidelines for 2 years, new insights are reported on how to implement the guidelines into clinical practice. This year's report will focus on gaps in management that need to be addressed, including health disparities, methods to improve asthma management through opportunities available in school-based asthma programs, and more information on the development of asthma in childhood. This information brings us closer to the point of managing children with controllable asthma and understanding reasons why asthma is not controlled in the remaining children. If we can close these gaps through better communication, improvements in the health care system, and new insights into treatment, we will move closer to better methods to intervene early in the course of the disease and induce clinical remission as quickly as possible in most children.

Advances in adult asthma diagnosis and treatment in 2009

There is a growing need to standardize and validate outcomes for asthma research. In this review of asthma-related publications from the Journal in 2009, efforts to standardize methodology and reporting of translational research, the influence of the environment, therapeutics, and management of asthma are highlighted.