Exhaled nitric oxide (NO) is reduced shortly after bronchoconstriction to direct and indirect stimuli in asthma

The Impact of Airway Obstruction on Feno Values in Asthma Patients

BACKGROUND

Exhaled nitric oxide (Feno) is used as a marker of type-2 airway inflammation in asthma management. Studies with airway challenges demonstrated that a reduction in airway caliber decreases Feno levels.

OBJECTIVE

To evaluate the impact of airway caliber reduction occurring spontaneously in patients with asthma on Feno values in daily clinical practice.

METHODS

In this post hoc analysis, Feno, FEV1, and asthma control questionnaire scores were recorded on each visit for 120 (1073 visits) adult patients with asthma. Blood eosinophils were measured intermittently. The intraindividual relationship between Feno and FEV1 was evaluated via a linear mixed model. The determinants of the individual mean Feno were measured by a stepwise multivariate linear model including individual mean FEV1, inhaled corticosteroid dose, asthma control questionnaire score, and blood eosinophils.

RESULTS

Variations in the negative Feno-FEV1 relationship within individuals at different times were significantly determined by the individual's mean FEV1. This relationship did not hold for individuals above the 75th and below the 25th quartiles. The best explanatory variables for individual mean Feno were FEV1 (+4.3 parts per billion/10%pred) and blood eosinophil count (+1 part per billion per 100 cells/mm3).

DISCUSSION

In the presence of variable degrees of heterogeneous patterns of airway inflammation, airway caliber is shown to be an independent and significant determinant of Feno when measured in patients with asthma. We would propose a +4-parts-per-billion correction factor to the measured Feno value for each 10% reduction below 100% predicted FEV1. Doing this should improve the rigor of interpretation of Feno as an indicator of type-2 inflammation in patients with low FEV1.

Effects of the salbutamol bronchodilator response on measurements of fractional exhaled nitric oxide in children with asthma: a prospective, observational study

BACKGROUND

Salbutamol bronchodilator response (BDR) test and fractional exhaled nitric oxide (FeNO) have been recommended for the diagnosis of asthma in children, but FeNO levels is affected by many factors. Nonetheless, data of the effect on the FeNO values throughout the bronchodilator test and the differences in FeNO values between BDR positive (BDR+) and negative (BDR-) children with asthma are still limited. We aimed to evaluate the effect of the BDR test on FeNO and the differences in FeNO levels between BDR+ and BDR- children with asthma.

METHODS

This was a prospective, observational study performed over a 5-month period (December 2018 to April 2019) and involved 57 children with asthma. The FeNO levels at pre-spirometry, post-spirometry, and post-salbutamol BDR testing were estimated. Finally, the children were divided into two groups i.e., BDR+ and BDR-, and differences in the FeNO levels were compared between the two groups.

RESULTS

The spirometry results were normal in 2 patients (3.5%). There were 53 (93%) patients with obstructive lung disease, including 40 (70.2%), 11 (19.3%), and 2 (3.5%) patients with mild, moderate, and severe obstruction, respectively. The remaining two patients had mixed lesions (3.5%), none of which were restrictive. The baseline median FeNO levels were significantly higher in the BDR+ group than in the BDR- group [33.00 (23.78, 46.73) vs. 23.00 (9.80, 37.80), (P=0.048)]. Following spirometry, there was a statistically significant decrease in median FeNO levels from baseline to post-spirometry (P=0.002). However, there was no significant difference between the median FeNO levels at baseline and following the BDR test (P=0.976). The impact of spirometry on FeNO was not statistically different in BDR+ versus BDR- children (Z=-0.186, P=0.853); however, the impact of bronchodilators on FeNO exhibited a statistically significant difference between the two groups (Z=3.160, P=0.002).

CONCLUSIONS

This study revealed dynamic changes in the FeNO levels during the BDR test. The use of a bronchodilator results in a statistically significant difference in FeNO levels between BDR+ and BDR- children with asthma. Moreover, spirometry leads to a marked decrease in the FeNO levels. Our results will allow clinicians to better interpret FeNO, BDR and pulmonary function outcomes and better develop clinical protocols.

Taiwanese dermatological association consensus for the definition, classification, diagnosis, and management of urticaria: A 2021 update

Urticaria is a prevalent disease with substantial physical, psychological, and economic impacts. With the advent of understandings of the disease and the emerging evidence of treatments, the international guidelines for treating urticaria have been updated in recent years. In order to update the 2014 edition of the Taiwanese Dermatological Association (TDA) consensus of urticaria, a total of 17 dermatologists with extensive experience in urticaria management were invited to and attended the TDA consensus meetings. All the specific aspects of the content were approved by at least 75% of the experts in attendance. Comparing to the former edition, several substantial modifications were made. For diagnosis, D-dimer was added as the recommended routine test in patients with chronic spontaneous urticaria. For pharmacological management, treatment suggestions were simplified. The approved-dosed, the up-dosed second-generation antihistamines, omalizumab, and cyclosporine were listed as the first-line to the fourth-line treatment, respectively. In addition, the management for patients of special considerations, such as the elderly, children, and pregnant women, were all discussed and mentioned in the consensus. We hope the updated TDA consensus can serve as a reference for all physicians and can help the physicians providing up-to-dated managements for these patients.

Exploring the sites and kinetics of bronchodilator response to -2 agonists in asthma

We previously documented, in patients with asthma, three different profiles of bronchodilation induced by short-acting β-2 mimetics (SABA), characterized by dilation up to central, preacinar, and intra-acinar airways assessed by ventilation distribution tests and associated with no change, increase, and decrease of fractional exhaled nitric oxide concentration (FENO), respectively. To investigate the dynamics of these profiles over the entire SABA action period, assuming that bronchodilation of proximal and peripheral airways could exhibit varying kinetics due to differences in the distribution of β-2 receptors in both the central and peripheral human airways. FENO, forced expired volume in one second (FEV₁), and the slope (S) of He and SF₆ phase III (single-breath test) were measured in asthma patients before, and up to 6 h after SABA inhalation (salbutamol 400 µg). S_He and S_SF6 decrease reflects pre- and intra-acinar obstruction relief, respectively. Thirty patients with asthma (12F/18M, aged 45 ± 18 yr) were divided into groups with positive (NO+, n = 9), negative (NO-, n = 11), and no (NO=, n = 10) FENO acute change. In the NO- group, FEV₁ increased for up to 4 h, whereas FENO, S_He, and S_F6 decreased in the early phase only. In stark contrast, in the NO+ group, FEV₁ increased in the early phase only whereas the FENO increase and the S_He decrease lasted for up to 4 h. This study documents various profiles of SABA-induced bronchodilation in patients with asthma, differing both by sites and dynamics of the bronchodilator process. So, detailed understanding of the bronchodilator effect of β2-agonists in asthma should not solely be limited to studying their impact on FEV₁.NEW & NOTEWORTHY FEV₁ increase usually observed after the inhalation of short-acting β2-agonists in asthma patients tends to involve peripheral airways. This study shows that the heterogeneity of responses to short-acting β2-agonists in asthma not only involves distinct sites of bronchodilation, but also distinct sequences between these sites. This indicates that a detailed understanding of the bronchodilator effect of β2-agonists in asthma should not be limited to studying its early impact on FEV₁.

An official JRS statement: The principles of fractional exhaled nitric oxide (FeNO) measurement and interpretation of the results in clinical practice

Nitric oxide (NO) is produced in the body and has been shown to have diverse actions in the abundance of research that has been performed on it since the 1970s, leading to Furchgott, Murad, and Ignarro receiving the Nobel Prize in Physiology or Medicine in 1998. NO is produced by nitric oxide synthase (NOS). NOS is broadly distributed, being found in the nerves, blood vessels, airway epithelium, and inflammatory cells. In asthma, inflammatory cytokines induce NOS activity in the airway epithelium and inflammatory cells, producing large amounts of NO. Measurement of fractional exhaled nitric oxide (FeNO) is a simple, safe, and quantitative method of assessing airway inflammation. The FeNO measurement method has been standardized and, in recent years, this noninvasive test has been broadly used to support the diagnosis of asthma, monitor airway inflammation, and detect asthma overlap in chronic obstructive pulmonary disease (COPD) patients. Since the normal upper limit of FeNO for healthy Japanese adults is 37 ppb, values of 35 ppb or more are likely to be interpreted as a signature of inflammatory condition presenting features with asthma, and this value is used in clinical practice. Research is also underway for clinical application of these measurements in other respiratory diseases such as COPD and interstitial lung disease. Currently, there remains some confusion regarding the significance of these measurements and the interpretation of the results. This statement is designed to provide a simple explanation including the principles of FeNO measurements, the measurement methods, and the interpretation of the measurement results.

COPD patients with peripheral airway obstruction reversibility identified by exhaled nitric oxide

RATIONALE

Besides its role as an inflammatory marker in asthma, fractional exhaled nitric oxide (F_ENO) provides information on the extent of the airway obstruction process through evaluating its change after bronchodilation.

OBJECTIVE

To investigate whether F_ENO change after bronchodilation can identify different sites of airway obstruction in COPD patients.

METHODS

F_ENO, FEV₁ and the slopes (S) of the alveolar plateau of the single breath washout test (SBWT) were measured in 61 stable COPD patients (FEV₁ 34.5% predicted) before and after the inhalation of 400 μg salbutamol. SBWT used Helium (He), and sulfur-hexafluoride (SF₆). Obstruction relief occurring in pre-acinar and intra-acinar small airways is expected to decrease S_He and S_SF6, respectively. Indices changes (Δ) after bronchodilation were expressed as a percentage of pre-bronchodilation values.

RESULTS

F_ENO stability (∣ΔF_ENO∣ ≤ 11%) was observed in 19 patients [-2.7(6.7)%] [mean (SD)] (NO = group); ΔF_ENO > 11% [+37.4(27.7)%] in 20 patients (NO+ group) and ΔF_ENO < -11% in 22 patients [-31.2(9.8)%] (NO- group). A similar ΔFEV₁ (p = 0.583; [+9.4(9.6)%]) was found in the three groups. In NO = and NO+ groups, neither S_He nor S_SF6 changed; in NO- both S_He [-12.4(27.5)%, p = 0.007] and S_SF6 [-20.2(20.4)%, p < 0.001] significantly decreased.

CONCLUSION

Different patterns of F_ENO response to β ₂-agonists were observed in COPD most likely depending on the extent of the dilation process. A profile of airway obstruction with an extensive β ₂-agonist response down to lung periphery is identified by F_ENO reduction after acute bronchodilation in 30% of COPD patients. The clinical relevance of this profile requires further investigation.

Pneumomediastinum, Tracheal Diverticulum, and Probable Asthma: Coincidence or Possible Association? A Case Report

Patient: Male, 25

Final Diagnosis: Spontaneous pneumomediastinum

Symptoms: Chest discomfort • exertional dyspnea • wheezing

Medication: —

Clinical Procedure: —

Specialty: Pulmonology

Ability of Exhaled Nitric Oxide to Discriminate for Airflow Obstruction Among Frequent Exacerbators of Clinically Diagnosed Asthma

OBJECTIVE

Fraction of exhaled nitric oxide (FE_NO) has been proposed as a non-invasive biomarker for allergic inflammation seen in asthma. Many asthmatics in clinical practice have never had spirometry and recent data report misdiagnoses in patients with physician diagnosed (PD) asthma. The aim of this study was to assess the ability of FE_NO to discriminate between those with and without airflow obstruction (AO) among patients with PD-asthma.

METHODS

Frequent exacerbators of PD-asthma (with 2 or more asthma exacerbations leading to emergency room visit or hospitalization within last 12 months) were enrolled. All patients underwent diagnostic evaluations including spirometry, FE_NO testing and serum immunoglobulin (IgE) and eosinophils. Serial spirometry and methacholine challenge testing (MCT) were performed as indicated. AO was defined by a decreased FEV1/FVC ratio (< 70% and/or < LLN), or a positive MCT.

RESULTS

Of the 222 patients with PD-asthma, AO was found in 136 (vs. 86 without AO). 81.6% of patients with AO and 66.2% without AO completed FE_NO testing. There was no significant difference in the mean FE_NO levels among patients with or without AO (40.8 vs. 30.4 ppb, P = 0.10). Likewise, there was no difference in the serum IgE levels and serum eosinophils.

CONCLUSIONS

Our analyses suggest that FE_NO levels do not help discriminate between those with and without AO in patients with PD-asthma. Patients who experience symptoms of asthma may have elevated FE_NO levels above the suggested cut points of 20-25 ppb. Objective confirmation of AO should be considered in all patients with PD-asthma, irrespective of FE_NO levels.

A new role for the exhaled nitric oxide as a functional marker of peripheral airway caliber changes: a theoretical study

Although considered as an inflammation marker, exhaled nitric oxide (FENO) was shown to be sensitive to airway caliber changes to such an extent that it might be considered as a marker of them. It is thus important to understand how these changes and their localization mechanically affect the total NO flux penetrating the airway lumen ( JawNO), and hence FENO, independently from any inflammatory status change. In this work, a new model was used. It simulates NO production, consumption, and diffusion inside the airway epithelium, NO excretion from the epithelial wall into the airway lumen and, finally, its axial transport by diffusion and convection in the airway lumen. This model may also consider the possible presence of a fluid layer coating the epithelial wall. Simulations were performed. They show the great sensitivity of JawNO to peripheral airway caliber changes. Moreover, FENO shows distinct behaviors, depending on the location of the caliber change. Considering a bronchodilation, absence of FENO change was associated with dilation of central airways, FENO increase with dilation down to pre-acinar small airways, and FENO decrease with intra-acinar dilation due to the amplification of the back diffusion flux. The presence of a fluid layer was also shown to play a significant role in FENO changes. Altogether, the present work theoretically supports that specific FENO changes in acute situations are linked to specifically located airway caliber changes in the lung periphery. This opens the way for a new role for FENO as a functional marker of peripheral airway caliber change.

NEW & NOTEWORTHY Using a new model of nitric oxide production and transport, allowing realistic simulation of airway caliber change, the present work theoretically supports that specific changes of the molar fraction of nitric oxide in the exhaled air, occurring without any change in the inflammatory status, are linked to specifically located airway caliber changes in the lung periphery. This opens the way for a new role for FENO as a functional marker of peripheral airway caliber change.

Airway calibre variation is a major determinant of exhaled nitric oxide's ability to capture asthma control

Changes in airway calibre have the potential to modify exhaled nitric oxide fraction (F_ENO) values and could hamper how F_ENO captures changes in asthma control. Here, our objective was to assess whether forced expiratory volume in 1 s (FEV₁) variations alter the ability of F_ENO to reflect asthma control.F_ENO, asthma control (Asthma Control Questionnaire (ACQ)) and FEV₁ were measured at least two times in 527 patients during 1819 pairs of visits. Determinants of F_ENO-ACQ discordance probability were evaluated through a logistic regression analysis. The effectiveness of F_ENO at capturing either asthma control worsening or improvement between two visits was then assessed by undertaking a stratified receiver operating characteristic curves analysis.When FEV₁ and F_ENO change in the same direction, the odds of F_ENO-ACQ being discordant are multiplied by 3 (p<0.001). The area under the curve values were 0.765 (95% CI 0.713-0.805) (improvement; p<0.001) and 0.769 (95% 0.706-0.810) (worsening; p<0.001) or 0.590 (95% 0.531-0.653) (improvement; p=0.001) and 0.498 (95% 0.416-0.567) (worsening; p=0.482) when FEV₁ and F_ENO changed in the opposite or same direction, respectively.The manner in which F_ENO and FEV₁ vary concomitantly when asthma control changes determines the ability of F_ENO to capture this change: parallel or opposite changes in FEV₁ and F_ENO either decrease or increase this ability to capture asthma control changes.

Military small arms fire in association with acute decrements in lung function

OBJECTIVE

After introduction of unleaded ammunition, Norwegian Armed Forces received reports of acute respiratory symptoms in soldiers after exposure to fumes from firing the standard weapon, HK416. The aim of the present study was to examine lung function before and after exposure to fumes from HK416 in a double-blinded standardised study design using three different types of ammunition.

METHODS

Fifty-four healthy, non-smoking male volunteers (19-62 years) fired the weapons for 60 min with either leaded, unleaded or 'modified' unleaded ammunition. Gaseous and particulate emissions were monitored. Spirometry and exhaled nitric oxide (eNO) were performed within 14 days before (T0), shortly after (T1) and 24 hours after (T2) shooting. Methacholine provocation and diffusing capacity of carbon monoxide (DLCO) were carried out at T0 and T2.

RESULTS

The mean forced expiratory volume in 1 s on a group level was significantly reduced both at T1 and T2 compared with T0, with means and 95% CI of 226 mL (158 to 294 mL) and 285 mL (218 to 351 mL), respectively. The same significant pattern was seen for DLCO, forced vital capacity and eNO. The methacholine test indicated a slight increase in bronchial hyper-reactivity. However, there were no significant differences between types of ammunition used.

CONCLUSION

Exposure to fumes from military weapons might be a respiratory hazard for soldiers who do live-fire training regularly or are in a closed combat environment.

Modeling of the Nitric Oxide Transport in the Human Lungs

In the human lungs, nitric oxide (NO) acts as a bronchodilatator, by relaxing the bronchial smooth muscles and is closely linked to the inflammatory status of the lungs, owing to its antimicrobial activity. Furthermore, the molar fraction of NO in the exhaled air has been shown to be higher for asthmatic patients than for healthy patients. Multiple models have been developed in order to characterize the NO dynamics in the lungs, owing to their complex structure. Indeed, direct measurements in the lungs are difficult and, therefore, these models are valuable tools to interpret experimental data. In this work, a new model of the NO transport in the human lungs is proposed. It belongs to the family of the morphological models and is based on the morphometric model of Weibel (1963). When compared to models published previously, its main new features are the layered representation of the wall of the airways and the possibility to simulate the influence of bronchoconstriction (BC) and of the presence of mucus on the NO transport in lungs. The model is based on a geometrical description of the lungs, at rest and during a respiratory cycle, coupled with transport equations, written in the layers composing an airway wall and in the lumen of the airways. First, it is checked that the model is able to reproduce experimental information available in the literature. Second, the model is used to discuss some features of the NO transport in healthy and unhealthy lungs. The simulation results are analyzed, especially when BC has occurred in the lungs. For instance, it is shown that BC can have a significant influence on the NO transport in the tissues composing an airway wall. It is also shown that the relation between BC and the molar fraction of NO in the exhaled air is complex. Indeed, BC might lead to an increase or to a decrease of this molar fraction, depending on the extent of the BC and on the possible presence of mucus. This should be confirmed experimentally and might provide an interesting way to characterize the extent of BC in unhealthy patients.

Effect of Inhaled β2-Agonist on Exhaled Nitric Oxide in Chronic Obstructive Pulmonary Disease

The fractional exhaled nitric oxide measured at an expiratory flow of 50mL/s (FE_NO50) is a marker of airway inflammation, and high levels are associated with greater response to steroid treatment. In asthma, FE_NO50 increases with bronchodilation and decreases with bronchoconstriction, the latter potentially causing an underestimate of the degree of airway inflammation when asthma worsens. It is unknown whether the same effect occurs in chronic obstructive lung disease (COPD). Likewise, it is not known whether changes in airway calibre in COPD patients alter flow-independent parameters describing pulmonary nitric oxide exchange, such as the maximal flux of nitric oxide (NO) from the proximal airway compartment (J’aw_NO) and the distal airway/alveolar concentration of NO (CA_NO). We recruited 24 patients with COPD and performed FE_NO analysis at multiple expiratory flows before and after treatment with inhaled β₂-agonist bronchodilator therapy. For the 21 patients analysed, FE_NO50 rose from 17.1 (1.4) ppb (geometric mean (geometric SD)) at baseline, to 19.3 (1.3) ppb after bronchodilator therapy, an increase of 2.2 ppb (95% CI, 0.7–3.6; P = 0.005). There were non-significant changes in flow-independent NO parameters. The change in FE_NO50 correlated positively with the change in J’aw_NO (r_s = 0.67, P < 0.001; r_s = 0.62, P = 0.002 before and after correction for axial back-diffusion respectively) following bronchodilation. Inhaled bronchodilator therapy can increase exhaled nitric oxide measurements in COPD. The standardisation of inhaled bronchodilator therapy before FE_NO analysis in COPD patients should therefore be considered in both research and clinical settings.

New strategies for the treatment of pulmonary hypertension in sickle cell disease : the rationale for arginine therapy

Nitric oxide (NO) is inactivated in sickle cell disease (SCD), while bioavailability of arginine, the substrate for NO synthesis, is diminished. Impaired NO bioavailability represents the central feature of endothelial dysfunction, and is a key factor in the pathophysiology of SCD. Inactivation of NO correlates with the hemolytic rate and is associated with erythrocyte release of cell-free hemoglobin and arginase during hemolysis. Accelerated consumption of NO is enhanced further by the inflammatory environment of oxidative stress that exists in SCD. Based upon its critical role in mediating vasodilation and cell growth, decreased NO bioavailability has also been implicated in the pathogenesis of pulmonary arterial hypertension (PHT). Secondary PHT is a common life-threatening complication of SCD that also occurs in most hereditary and chronic hemolytic disorders. Aberrant arginine metabolism contributes to endothelial dysfunction and PHT in SCD, and is strongly associated with prospective patient mortality. The central mechanism responsible for this metabolic disorder is enhanced arginine turnover, occurring secondary to enhanced plasma arginase activity. This is consistent with a growing appreciation of the role of excessive arginase activity in human diseases, including asthma and PHT. Decompartmentalization of hemoglobin into plasma consumes endothelial NO and thus drives a metabolic requirement for arginine, whose bioavailability is further limited by arginase activity. New treatments aimed at maximizing both arginine and NO bioavailability through arginase inhibition, suppression of hemolytic rate, or oral arginine supplementation may represent novel therapeutic strategies.

Different patterns of exhaled nitric oxide response to β2-agonists in asthmatic patients according to the site of bronchodilation

BACKGROUND

In asthmatic patients undergoing airway challenge, fraction of exhaled nitric oxide (FENO) levels decrease after bronchoconstriction. In contrast, model simulations have predicted both decreased and increased FENO levels after bronchodilation, depending on the site of airway obstruction relief.

OBJECTIVE

We sought to investigate whether β2-agonists might induce divergent effects on FENO values in asthmatic patients as a result of airway obstruction relief occurring at different lung depths.

METHODS

FENO, FEV1, and the slope of phase III of the single-breath washout test (S) of He (S(He)) and sulfur hexafluoride (S(SF6)) were measured in 68 asthmatic patients before and after salbutamol inhalation. S(He) and S(SF6) decreases reflected preacinar and intra-acinar obstruction relief, respectively. Changes (Δ) were expressed as a percentage from the baseline.

RESULTS

No FENO change (|ΔFENO| ≤ 10%) was found in 16 patients (mean [SD]: 2.5% [5.2%]; ie, FENO= group); a ΔFENO value of greater than 10% was found in 23 patients (31.7% [20.3%]; ie, the FENO+ group); and a ΔFENO value of less than -10% was found in 29 patients (-31.5% [17.3%]; ie, the FENO- group). All groups had similar ΔFEV1 values. In the FENO= group neither S(He) nor S(SF6) changed, in the FENO+ group only S(He) decreased significantly (-21.8% [SD 28.5%], P = .03), and in the FENO- group both S(He) (-29.8% [24.0%], P < .001) and S(SF6) (-27.2% [23.3%], P < .001) decreased.

DISCUSSION

Three FENO behaviors were observed in response to β2-agonists: a decrease likely caused by relief of an intra-acinar airway obstruction that we propose reflects amplification of nitric oxide back-diffusion, an increase likely associated with a predominant dilation up to the preacinar airways, and FENO stability when obstruction relief involved predominantly the central airways. In combination, these results suggest a new role for FENO in identifying the site of airway obstruction in asthmatic patients.

A pathophysiological approach for FeNO: A biomarker for asthma

The present review is focused on literature concerning the relevance of fractional exhaled nitric oxide (FeNO) in clinical practice from a pathophysiological point of view. There is increasing evidence that asthma is a heterogeneous pathological condition characterised by different phenotypes/endotypes related to specific biomarkers, including FeNO, helpful to predict therapeutic response in selected asthmatic populations. Nowadays FeNO, a non-invasive biomarker, appears to be useful to foresee asthma developing, to recognise specific asthma phenotypes, like the eosinophilic, to ameliorate asthma diagnosis and management in selected populations and to predict standard corticosteroid and biologic therapy efficacy. In addition, FeNO assessment may also be useful in patients with allergic rhinitis in order to detect the potential involvement of eosinophilic bronchial inflammation in "case finding" subjects at risk of asthma diagnosis. Therefore, it is possible to hypothesise a future with an appropriate use of FeNO by physicians dealing with worrisome clinical issues in specific asthma phenotypes.

Albuterol inhalation increases FeNO level in steroid-naive asthmatics but not COPD patients with reversibility

INTRODUCTION

Fractional exhaled nitric oxide (FeNO) has been used as a marker of airway inflammation. Airway caliber is related to the level of FeNO in asthmatics.

OBJECTIVES

This study aimed to investigate whether airway obstruction could interfere with real FENO levels and if different FeNO changes after albuterol inhalation could assist in distinguishing asthma from chronic obstructive pulmonary disease (COPD).

METHODS

FeNO and spirometry measurements were performed before and after albuterol inhalation in the following three patient groups: 30 steroid-naive asthmatics, 25 asthmatics inhaling corticosteroids/long-acting β(2)-adrenergic agonists for at least 1 month and 20 COPD patients. Bronchodilator test (BDT) results were positive in all patients enrolled. The correlations among FeNO levels, pulmonary function and sputum eosinophil counts were analyzed.

RESULTS

FeNO increased significantly after albuterol inhalation in steroid-naive asthmatics but not in ICS-treated asthmatics or COPD patients. The FeNO levels demonstrated no significant correlation with spirometry results or sputum eosinophil counts before or after inhaling bronchodilator in all three groups. Both the levels of FeNO and changes in FENO after albuterol inhalation in steroid-naive asthma patients were higher than those in ICS-treated asthmatics and COPD patients (P < 0.001). The differences remained after proper adjustment for confounding factors (gender, age, smoking pack-years, ICS-treated and pulmonary function index).

CONCLUSIONS

Our results support the role of FeNO in differentiating asthmatics from COPD patients with positive BDT. FeNO detection after albuterol inhalation should be encouraged in steroid-naive asthma patients with airway obstruction.

Advances in the diagnosis and management of asthma in older adults

Global estimates on aging predict an increased burden of asthma in the older population. Consequently, its recognition, diagnosis, and management in clinical practice require optimization. This review aims to provide an update for clinicians, highlighting advances in the understanding of the aging process and immunosenescence together with their applicability to asthma from a diagnostic and therapeutic perspective. Aging impacts airway responses and immune function, and influences efficacy of emerging phenotype-specific therapies when applied to the elderly patient. Differentiating eosinophilic and neutrophilic disease accounts for atopic illness and distinguishes long-standing from late-onset asthma. Therapeutic challenges in drug delivery, treatment adherence, and side-effect profiles persist in the older patient, while novel recording devices developed to aid detection of an adequate inhalation evaluate treatment effectiveness and compliance more accurately than previously attainable. Anticytokine therapies improve control of brittle asthma, while bronchial thermoplasty is an option in refractory cases. Multidimensional intervention strategies prove best in the management of asthma in the older adult, which remains a condition that is not rare but rarely diagnosed in this patient population.

Exhaled nitric oxide: a biomarker integrating both lung function and airway inflammation changes

BACKGROUND

The increased fraction of exhaled nitric oxide (Feno) values observed in asthmatic patients are thought to reflect increased airway inflammation. However, Feno values can be affected by airway caliber reduction, representing a bias when using Feno values to assess asthma control.

OBJECTIVE

We sought to determine the effect of changes in both airway caliber and inflammation on Feno values using the allergen challenge model.

METHODS

FEV1 and Feno values were measured during early airway responses (EARs) and late airway responses after challenge with house dust mite allergens in 15 patients with mild allergic asthma. Helium and sulfur hexafluoride (SF6) phase III expired concentration slopes (SHe and SSF6, respectively) from single-breath washout tests were measured to identify sites of airway constriction.

RESULTS

In EARs, FEV1 and Feno value decreases reached 36.8% and 22%, respectively (P < .001). ΔSHe was greater than ΔSSF6 (+189.4% vs +82.2%, P = .001). In late airway responses FEV1 and Feno value decreases reached 31.7% and 28.7%, respectively (P < .001), with the same ΔSHe and ΔSSF6 pattern (+155.8% vs +76%, P = .001). Eight hours after the EAR, FEV1 was still decreased (P < .001), whereas Feno values had returned to baseline. At 24 hours, FEV1 had returned to baseline, with Feno values increased by 38.7% (P = .04).

CONCLUSION

In patients with mild allergic asthma, airway caliber changes modulate changes in Feno values resulting from airway inflammation. Therefore Feno should no longer be considered solely an inflammation biomarker but rather a biomarker that integrates both airway inflammation and lung function changes. Furthermore, early and late phases resulting from allergen exposure were shown to involve similar lung regions.

Fractional exhaled nitric oxide in clinical trials: an overview

Designing clinical trials in asthma it is crucial to find the perfect primary endpoint for showing bioequivalence, especially when the investigational medicinal product is not a bronchodilator, but a substance, which suppresses the inflammatory process, e.g. inhalative corticosteroids (ICS). In the past, lung function parameters were used as the primary endpoint, which entails a long study duration and hundreds of patients. The measurement of fractional exhaled nitric oxide (FeNO) is established as a non-invasive marker for eosinophilic inflammation, and several guidelines focus on that diagnosis. FeNO is a surrogate measure of eosinophilic inflammation and at the same time, eosinophilic airway inflammation is usually steroid responsive. Thus, FeNO should be a part of the clinical management of asthma in ambulatory settings in conjunction with other conventional methods of asthma assessment. Furthermore, FeNO should be used to determine the presence or absence of eosinophilic airway inflammation, to determine the likelihood of steroid responsiveness, to measure response to steroid therapy, and level of inflammation control. In addition, FeNO is a useful tool to monitor patient ICS treatment adherence and allergen exposure. FeNO may be used to predict steroid responsiveness and as a measure to determine the optimal treatment of airway inflammation. FeNO has all characteristics of a good marker for bioequivalence measurements in the market approval process of generic ICS products. With a reliable study design in terms of patient population, concomitant medication, equipment and other factors, which can influence the measurement, efficient clinical trials can be performed, with a relatively short treatment time of 2-4 weeks and 50-100 patients.

Fractional exhaled nitric oxide in children with acute exacerbation of asthma

OBJECTIVE

To determine whether fractional exhaled nitric oxide (FENO) has a utility as a diagnostic or predictive maker in acute exacerbations of asthma in children.

DESIGN

Analysis of data collected in a pediatric asthma cohort.

SETTING

Pediatric Chest Clinic of a tertiary care hospital.

METHODS

A cohort of children with asthma was followed up every 3 months in addition to any acute exacerbation visits. Pulmonary function tests (PFT) and FENO were obtained at all visits. We compared the FENO values during acute exacerbations with those at baseline and those during the follow up.

RESULTS

243 asthmatic children were enrolled from August 2009 to December 2011 [mean (SD) follow up - 434 (227) days]. FENO during acute exacerbations was not different from FENO during follow up; however, FENO was significantly higher than personal best FENO during follow up (P < 0.0001). FENO during acute exacerbation did not correlate with the severity of acute exacerbation (P=0.29). The receiver operating characteristics curve for FENO as a marker for acute exacerbation had an area under the curve of 0.59. Cut-off of 20 ppb had a poor sensitivity (44%) and specificity (68.7%) for acute exacerbation.

CONCLUSIONS

FENO levels during acute exacerbation increase from their personal best levels. However, no particular cut off could be identified that could help in either diagnosing acute exacerbation or predicting its severity.

Mechanisms of decrease in fractional exhaled nitric oxide during acute bronchoconstriction

BACKGROUND

Fractional exhaled nitric oxide measured at expiratory flow of 50 mL/s (Feno50), a biomarker of airway inflammation, is affected by changes in airway caliber. Whether a lower Feno50 level during bronchoconstriction is only an artifact due to the strong flow dependence of this parameter is controversial.

METHODS

We aimed to evaluate the dynamics of airway and alveolar nitric oxide (NO) during acute bronchoconstriction induced by methacholine. Exhaled NO was measured at expiratory flows of 10, 50, 100, 150, and 250 mL/s before and after metacholine in 26 responders to methacholine and 37 nonresponders. Flow-independent parameters (airway wall NO flux, airway NO diffusing capacity, airway wall NO concentration, alveolar NO concentration) were calculated using a two-compartment model, and correction for NO axial back diffusion was applied.

RESULTS

Bronchoconstriction in responders was associated with a decrease in Feno50 (-28%, P &lt; .0001), in airway wall NO flux (-34%, P &lt; .0001), and in airway NO diffusing capacity (-15%, P &lt; .05). In contrast, alveolar NO concentration was not affected by bronchoconstriction. Postmethacholine changes in Feno50 were more strictly related to the ventilation distribution, assessed by single-breath carbon monoxide uptake, than to larger airways caliber, assessed by FEV1. When bronchoconstriction was reversed by salbutamol, airway wall NO flux and airway NO diffusing capacity returned to values comparable to those measured premethacholine.

CONCLUSIONS

The changes in airway caliber induced by noninflammatory stimuli alter NO transport in the lung. The changes in NO dynamics are limited to conductive airways and are characterized by a reduction of NO flow to luminal space.

Axial distribution of nitric oxide airway production in asthma patients

In healthy subjects, axial distribution of nitric oxide (NO) airway production is likely heterogeneous: notably a distal peak of production in terminal bronchioles and a quasi-nil NO production in the most of the conducting airways. In asthma, few information exists about the contributions of the proximal and distal airways to NO overproduction. In 18 asthma patients, sites of constriction after methacholine and adenosine 5'-monophosphate (AMP) challenges were assessed by ventilation distribution tests with He and SF(6). The resulting decreases in fractional exhaled NO (FENO) were measured. Changes in He and SF(6) slopes indicated a pre-acinar bronchoconstriction due to AMP and a more proximal action for methacholine. FENO decreased by 38.7% and 20.2% (p<0.001) after AMP and methacholine challenges, respectively. Significant FENO decreases after AMP and methacholine implies substantial pre-acinar but also, contrary to healthy subjects, more proximal airway production. In conclusion, nitric oxide overproduction in asthma patients appears to involve the most part of the conducting airways.

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.

Asthma in the elderly: Current understanding and future research needs--a report of a National Institute on Aging (NIA) workshop

Asthma in the elderly is underdiagnosed and undertreated, and there is a paucity of knowledge on the subject. The National Institute on Aging convened this workshop to identify what is known and what gaps in knowledge remain and suggest research directions needed to improve the understanding and care of asthma in the elderly. Asthma presenting at an advanced age often has similar clinical and physiologic consequences as seen with younger patients, but comorbid illnesses and the psychosocial effects of aging might affect the diagnosis, clinical presentation, and care of asthma in this population. At least 2 phenotypes exist among elderly patients with asthma; those with longstanding asthma have more severe airflow limitation and less complete reversibility than those with late-onset asthma. Many challenges exist in the recognition and treatment of asthma in the elderly. Furthermore, the pathophysiologic mechanisms of asthma in the elderly are likely to be different from those seen in young asthmatic patients, and these differences might influence the clinical course and outcomes of asthma in this population.

Spirometric maneuvers and inhaled salbutamol do not affect exhaled nitric oxide measurements among patients with allergic asthma

BACKGROUND

Exhaled nitric oxide (ENO) is used as a marker of airway inflammation. Factors such as spirometric maneuvers (SPM), β(2)-agonists, or tobacco smoking have been postulated to affect ENO measurements. Guidelines on measurement techniques have been published based on expert opinions. Nevertheless, there is no strong clinical evidence of many aspects because they have not been supported by research data.

OBJECTIVES

The aim of this study was to evaluate the influence of performing a spirometry or receiving inhaled salbutamol on ENO readings.

METHODS

One hundred forty-five adults and 62 children with allergic asthma were included with a mean age of 36 ± 13 years for adults and 13 ± 2 years for children. A control group comprised 30 healthy adults and 30 children with a mean age of 37 ± 14 years and 13 ± 2 years, respectively. ENO measurements were performed with a NIOX-MINO® electrochemical device. In 179 patients ENO was measured before and after performing SPM and in 88 patients before and 15 min after SPM plus 2 puffs of salbutamol (100 μg/puff).

RESULTS

There were no significant differences in mean ENO levels before and after SPM or before and after SPM plus 2 puffs of inhaled salbutamol in adults or children (asthmatic or healthy).

CONCLUSIONS

Levels of ENO are not significantly affected by SPM or salbutamol inhalation.

Effect of the influenza A (H1N1) live attenuated intranasal vaccine on nitric oxide (FE(NO)) and other volatiles in exhaled breath

For the 2009 influenza A (H1N1) pandemic, vaccination and infection control were the main modes of prevention. A live attenuated H1N1 vaccine mimics natural infection and works by evoking a host immune response, but currently there are no easy methods to measure such a response. To determine if an immune response could be measured in exhaled breath, exhaled nitric oxide (FE(NO)) and other exhaled breath volatiles using selected ion flow tube mass spectrometry (SIFT-MS) were measured before and daily for seven days after administering the H1N1 2009 monovalent live intranasal vaccine (FluMist®, MedImmune LLC) in nine healthy healthcare workers (age 35 ± 7 years; five females). On day 3 after H1N1 FluMist® administration there were increases in FE(NO) (MEAN±SEM: day 0 15 ± 3 ppb, day 3 19 ± 3 ppb; p < 0.001) and breath isoprene (MEAN±SEM: day 0 59 ± 15 ppb, day 3 99 ± 17 ppb; p = 0.02). MS analysis identified the greatest number of changes in exhaled breath on day 3 with 137 product ion masses that changed from baseline. The exhaled breath changes on day 3 after H1N1 vaccination may reflect the underlying host immune response. However, further work to elucidate the sources of the exhaled breath changes is necessary.

Exhaled nitric oxide levels during treatment of pediatric acute asthma exacerbations and association with the need for hospitalization

OBJECTIVES

To examine how exhaled nitric oxide (eNO) levels measured before and after treatment of asthma exacerbations relate to emergency department (ED) disposition.

METHODS

We enrolled children 6 to 17 years old treated for asthma exacerbations in a pediatric ED. Using an offline single-breath eNO sampling technique, we collected replicate initial samples before treatment and replicate final samples when disposition was decided. We determined correlations and coefficients of variability of eNO values (parts per billion, ppb) of samples and compared by disposition (hospitalization or discharge) mean initial and final eNO levels and initial-to-final change.

RESULTS

Eighty-one subjects had initial and final eNO values; 24 subjects with more severe presentations had final values only. Replicate eNO samples were correlated (initial r = 0.98, final r = 0.99) and had low coefficients of variability (initial, 0.059 ± 0.057; final, 0.061 ± 0.070). For subjects with initial and final values, initial eNO levels were similar by disposition (mean difference, -8.0 ppb; 95% confidence interval [CI], -24.8 to 8.9 ppb), as were final levels (mean difference, -2.8 ppb; 95% CI, -23.8 to 18.2 ppb). Overall, final eNO was higher than initial (36.3 ± 29.7 vs 31.5 ± 23.9 ppb), but only 63% of subjects had any increase. Change in eNO was similar by disposition (mean difference, 4.6 ppb; 95% CI, -3.4 to 12.6). For more severe subjects with final eNO only, eNO was similar by disposition (P = 0.47).

CONCLUSIONS

For children aged 6 to 17 years with asthma exacerbations, eNO levels can be reliably measured. However, eNO levels measured before treatment or when disposition was determined did not distinguish children needing hospitalization.

Breath profiles by electronic nose correlate with systemic markers but not ozone response

BACKGROUND

The evaluation of exhaled breath profiles by electronic nose (eNose) is considered as a promising non-invasive diagnostic tool, and the discrimination of breathprints between patients with COPD and asthma has been reported. The aim of this study was to assess, whether exhaled breath profile analysis can detect the inflammatory airway response induced by ozone inhalation.

METHODS

In a randomized double-blind, cross-over study 14 healthy ozone-responsive subjects were exposed to 250 ppb ozone and filtered room air for 3h with intermittent exercise. Blood biomarkers, exhaled NO, exhaled CO, and breathprints (Cyranose 320(®)) were assessed prior and at 3 time points up to 24h post exposure. Induced sputum was collected at baseline and 3h post exposure. Multivariate analysis of eNose data was performed using transformed and normalized datasets.

RESULTS

Significantly increased numbers of sputum and blood neutrophils were observed after ozone, whereas the eNose signals showed no differences between exposures and no correlation with neutrophilic airway inflammation. However, independent of ozone exposure, sensor data correlated with serum SP-D levels and to a smaller extent with blood neutrophil numbers.

CONCLUSIONS

Exhaled breath profiles as measured by the Cyranose 320(®) did not reflect airway responses to ozone. This suggests that exhaled volatiles did not change with ozone challenges or that the changes were below the detection limits. Conversely, the correlation of eNose signals with blood neutrophils and serum SP-D, i.e. markers of systemic inflammation and lung permeability, suggested that the Cyranose 320(®) can detect volatile organic compounds of systemic origin.

Relationship between exhaled nitric oxide and small airway lung function in normal and asthmatic children

BACKGROUND

In children, exhaled nitric oxide (eNO) is usually confounded by factors such as age and height. We evaluated the relationship between eNO and lung function by minimizing the effects of aging and height.

METHODS

In Study 1, the subjects comprised 738 elementary school children and junior high school children (aged 6 to 15 years, 366 males and 372 females). They were divided into two groups according to age (6-10 years and 11-15 years). A height range was determined by a histogram of height in each group. In Study 2, lung function, respiratory resistance and eNO level were measured in age- and height-limited groups.

RESULTS

In Study 1, total of 148 younger children ranging in height from 120 to 130 cm and 180 older children ranging in height from 148 to 158 cm participated in Study 2. The level of eNO among asthmatic children was higher than that of normal children in both the younger and the older groups. The decrease in forced expiratory volume in 1 second (FEV(1)) and other parameters of central airway resistance did not correlate with the eNO level. However, the small airway parameters of MMEF and V(25)/HT in older asthmatic children, and V(25)/HT and R(5)-R(20) in younger asthmatic children inversely correlated with eNO.

CONCLUSIONS

Our data suggest that eNO level inversely correlates with small airway narrowing, and airway inflammation has a significant effect on small airway lung function in asthmatic school children.

Electronic nose breathprints are independent of acute changes in airway caliber in asthma

Molecular profiling of exhaled volatile organic compounds (VOC) by electronic nose technology provides breathprints that discriminate between patients with different inflammatory airway diseases, such as asthma and COPD. However, it is unknown whether this is determined by differences in airway caliber. We hypothesized that breathprints obtained by electronic nose are independent of acute changes in airway caliber in asthma. Ten patients with stable asthma underwent methacholine provocation (Visit 1) and sham challenge with isotonic saline (Visit 2). At Visit 1, exhaled air was repetitively collected pre-challenge, after reaching the provocative concentration (PC(20)) causing 20% fall in forced expiratory volume in 1 second (FEV(1)) and after subsequent salbutamol inhalation. At Visit 2, breath was collected pre-challenge, post-saline and post-salbutamol. At each occasion, an expiratory vital capacity was collected after 5 min of tidal breathing through an inspiratory VOC-filter in a Tedlar bag and sampled by electronic nose (Cyranose 320). Breathprints were analyzed with principal component analysis and individual factors were compared with mixed model analysis followed by pairwise comparisons. Inhalation of methacholine led to a 30.8 ± 3.3% fall in FEV(1) and was followed by a significant change in breathprint (p = 0.04). Saline inhalation did not induce a significant change in FEV(1), but altered the breathprint (p = 0.01). However, the breathprint obtained after the methacholine provocation was not significantly different from that after saline challenge (p = 0.27). The molecular profile of exhaled air in patients with asthma is altered by nebulized aerosols, but is not affected by acute changes in airway caliber. Our data demonstrate that breathprints by electronic nose are not confounded by the level of airway obstruction.

Oxidative stress and airway inflammation after allergen challenge evaluated by exhaled breath condensate analysis

BACKGROUND

Allergen exposure may increase airway oxidative stress, which causes lipid membrane peroxidation and an increased formation of 8-isoprostane.

OBJECTIVE

The aim of the study was to investigate oxidative stress induced by allergen challenge in mild asthmatics, by measuring 8-isoprostane in exhaled breath condensate (EBC), and to examine their relationship with mediators derived from arachidonic acid. Methods 8-isoprostane, cysteinyl leukotrienes (cys-LTs) and prostaglandin E2 (PGE(2) ) concentrations in EBC were measured at baseline and after allergen challenge in 12 patients with mild allergic asthma sensitized to cat allergen.

RESULTS

At 24 h after allergen challenge, compared with baseline values, EBC 8-isoprostane increased [48.64 pg/mL (44.14-53.61) vs. 21.56 pg/mL (19.92, 23.35), P<0.001], cys-LTs increased [27.37 pg/mL (24.09-31.10) vs. 13.28 pg/mL (11.32, 15.57), P<0.001] and PGE(2) decreased [18.69 pg/mL (12.26, 28.50) vs. 39.95 pg/mL (34.37, 46.43), P<0.001]. The trend of increasing 8-isoprostane after allergen challenge was significantly correlated with the trend of increasing cys-LTs (R(2) =0.85, P<0.001) whereas the trend of decreasing PGE(2) after allergen challenge was significantly correlated with the trend of increasing cys-LTs (R(2) =0.52, P=0.001).

CONCLUSIONS AND CLINICAL RELEVANCE

The increase in EBC 8-isoprostane observed after allergen challenge indicates that allergen exposure increases airway oxidative stress in allergic asthma. The strict correlation between cys-LTs and 8-isoprostane underlines the relationship between allergic inflammation and oxidative stress. A shift of arachidonic acid metabolism towards lipoxygenase pathway is induced by the allergen challenge. Airway oxidative stress occurs after allergen challenge even in patients with mild intermittent allergic asthma.

Diagnostic value of outcome measures following allergen exposure in an environmental challenge chamber compared with natural conditions

BACKGROUND

Efficacy testing of drugs in seasonal allergic rhinitis (SAR) is often disturbed by seasonal variations of environmental allergens, and assessment of onset and duration of action is hardly possible under natural conditions. Allergen provocation in an environmental challenge chamber (ECC) can be of added value in this respect. However, the specificity, sensitivity, and reproducibility of outcome measures under both settings are unclear.

OBJECTIVE

The aim of this study was to investigate and compare the diagnostic value (specificity, sensitivity, and reproducibility) of clinical end-points and biomarkers both following allergen provocation in an ECC and under natural conditions.

METHODS

Sixty adult patients with SAR to grass and 60 healthy subjects were exposed twice to grass pollen in an ECC and observed twice during the pollen season. Symptoms, nasal flow, as well as exhaled and nasal nitric oxide (NO) were investigated.

RESULTS

The total nasal symptom score (TNSS) in the ECC had the best reproducibility (intraclass correlation coefficient ICC=0.86) and sensitivity/specificity [area under receiver operating characteristic curve (AUC)=0.99] of all measures. Symptoms in season also had good sensitivity/specificity but were far less reproducible. Nasal flow in the ECC had good sensitivity/specificity but reproducibility was limited. NO measurements showed good reproducibility but sensitivity/specificity were limited, except for exhaled NO in season (AUC=0.75).

CONCLUSION

The high reproducibility and sensitivity/specificity in the ECC suggests that TNSS is a valuable outcome measure. While exhaled NO can be considered to monitor airway inflammation, nasal NO appears to be unspecific.

Mediators in exhaled breath condensate after hypertonic saline challenge

BACKGROUND

Airway narrowing after hypertonic saline challenge (HSC) is postulated to be mediated by bronchoconstrictors and inflammatory mediators.

OBJECTIVE

To study the mechanism of this challenge by using exhaled breath condensate (EBC).

METHODS

Fifty-six subjects (9 to 72 years of age) performed an HSC, with EBC collection and exhaled nitric oxide (FENO) measurements before and after the challenge. Bronchial hyper-reactivity (BHR) was defined if forced expiratory volume in 1 second (FEV1) decreased by 10% compared with baseline (PD10). EBC volume was recorded and was analyzed for mucin, histamine, nitrite/nitrate, and pH.

RESULTS

Those with BHR had a significant rise in EBC volume/5-minute collection period after challenge (286.3 +/- 25.6 microl vs 402.2 +/- 31.3 microl, p = 0.0002), while BHR(-) subjects did not show this change (387.6 +/- 29.7 microl vs 364.1 +/- 30.1 microl, p = 0.55). FENO showed a significant decrease in both BHR(+) and BHR(-) groups after challenge (p = < 0.0001). In BHR(+) subjects histamine increased significantly (1.3 +/- 0.1 microM vs 1.5 +/- 0.1 microM, p = 0.006) compared with baseline, while EBC pH and mucin increased significantly after HSC in both groups. EBC nitrite did not change in either group.

CONCLUSION

EBC analysis suggests that HSC causes an increase in pH and mucin in both groups, but EBC volume and histamine only increased in the BHR(+) group. This suggests that mast cells are activated and fluid flux is associated with the positive response, while mucin release is independent of BHR in HSC.

Exhaled nitric oxide in diagnosis and management of respiratory diseases

The analysis of biomarkers in exhaled breath constituents has recently become of great interest in the diagnosis, treatment and monitoring of many respiratory conditions. Of particular interest is the measurement of fractional exhaled nitric oxide (FENO) in breath. Its measurement is noninvasive, easy and reproducible. The technique has recently been standardized by both American Thoracic Society and European Respiratory Society. The availability of cheap, portable and reliable equipment has made the assay possible in clinics by general physicians and, in the near future, at home by patients. The concentration of exhaled nitric oxide is markedly elevated in bronchial asthma and is positively related to the degree of esinophilic inflammation. Its measurement can be used in the diagnosis of bronchial asthma and titration of dose of steroids as well as to identify steroid responsive patients in chronic obstructive pulmonary disease. In primary ciliary dyskinesia, nasal NO is diagnostically low and of considerable value in diagnosis. Among lung transplant recipients, FENO can be of great value in the early detection of infection, bronchioloitis obliterans syndrome and rejection. This review discusses the biology, factors affecting measurement, and clinical application of FENO in the diagnosis and management of respiratory diseases.

Fractional exhaled nitric oxide in asthma: an update

In asthma, clinical symptoms and lung function are insensitive in reflecting the underlying airway inflammation, and monitoring of this process has only recently become available. Fractional exhaled nitric oxide (Fe(NO)) is now recognized as a reliable surrogate marker of eosinophilic airway inflammation and offers the advantage of being completely non-invasive and very easy to obtain. This review summarizes the clinical use of Fe(NO) in asthma. It covers the relationship between Fe(NO) and the underlying eosinophilic inflammation, the pathophysiology and production of Fe(NO), technical aspects of Fe(NO) measurement and potential confounding factors in interpreting levels. Fe(NO) reference values and the role of Fe(NO) in asthma assessment, diagnosis and management are also discussed.

Effect of bronchoconstriction on exhaled nitric oxide levels in healthy and asthmatic children

BACKGROUND

Exhaled nitric oxide (eNO) has recently been proposed to be a noninvasive marker of airway inflammation in asthma.

OBJECTIVE

To evaluate the effect of bronchoconstriction by means of methacholine inhalation challenge on levels of eNO in children.

METHODS

Spirometry, impulse oscillometry, and eNO measurements were performed before and after methacholine inhalation challenge (bronchoconstriction phase) and after beta2-agonist inhalation (bronchodilation phase) in 92 children (62 children with asthma, 13 wheezy children, and 17 healthy children).

RESULTS

A significant decrease occurred in the eNO level after methacholine inhalation challenge (P < .01). This decrease did not correlate with the percentage decrease in forced expiratory volume in 1 second or with the change in large airway resistance (R20), but it did correlate with the percentage decline in maximal expiratory flow at 50% vital capacity and with the change in small airway resistance (R5-R20). The eNO decrease lasted for 15 minutes after beta2-agonist inhalation in the group with a high percentage decrease in R5-R20 (>200%). On the other hand, in the group with a low percentage decrease in R5-R20 (< or =200%), eNO recovered to the previous level immediately after beta2-agonist inhalation.

CONCLUSIONS

The eNO level significantly decreases after methacholine inhalation challenge. This decrease primarily depends on bronchoconstriction of the small airways.

Exhaled nitric oxide and breath condensate ph in asthmatic reactions induced by isocyanates

BACKGROUND

We investigated the usefulness of measurements of fractional exhaled nitric oxide (FeNO) and pH of exhaled breath condensate (EBC) for monitoring airway response after specific inhalation challenges with isocyanates in sensitized subjects.

METHODS

Lung function (FEV(1)), FeNO, and pH in argon-deaerated EBC were measured before and at intervals up to 30 days after a specific inhalation challenge in 15 subjects with isocyanate asthma, in 24 not sensitized control subjects exposed to isocyanates, and in 3 nonasthmatic subjects with rhinitis induced by isocyanate. Induced sputum was collected before and 24 h after isocyanate exposure.

RESULTS

Isocyanate-induced asthmatic reactions were associated with a rise in sputum eosinophil levels at 24 h (p < 0.01), and an increase in FeNO at 24 h (p < 0.05) and 48 h (p < 0.005), whereas FeNO level did not vary with isocyanate exposure in subjects with rhinitis and in control subjects. FeNO changes at 24 h positively correlated with corresponding sputum eosinophil changes (rho = 0.66, p < 0.001). A rise in pH was observed in the afternoon samples of EBC, irrespective of the occurrence of isocyanate-induced asthmatic reactions.

CONCLUSIONS

We demonstrated that isocyanate-induced asthmatic reactions are associated with a consistent delayed increase in FeNO but not with the acidification of EBC.

Offline exhaled nitric oxide in emergency department and subsequent acute asthma control

BACKGROUND

Few studies have evaluated exhaled NO measurement during acute asthma.

OBJECTIVES

To evaluate exhaled NO fraction (FE(NO)) and peak expiratory flow (PEF) time-courses during acute asthma treatment (beta 2-agonist plus systemic steroid) and to assess whether FE(NO) time-course predicts subsequent asthma control.

METHODS

Sixty-five asthmatic patients (mean +/- SD, 34 +/- 10 years) were prospectively enrolled in three Emergency Departments.

RESULTS

Sixteen patients were excluded (failure of offline FE(NO) measurement at 100 mL/s [FE(NO 0.1)], n = 4, and early discharge). The 49 remaining patients performed FE(NO 0.1) and PEF on admission, at the 2nd (H2) and 6th hour (H6). Follow-up using an Asthma Control Diary was obtained in 27 of 49 patients, whether they were hospitalized (n = 9) or discharged (n = 18). All but 2 patients had elevated FE(NO) on admission (median [interquartile], 49 [26-78] ppb). Unlike PEF, mean FE(NO 0.1) of our sample was not significantly modified by treatment. No significant relationship was evidenced between exhaled NO and PEF variations. The variation of FE(NO 0.1) [H0 minus H6] was different in patients who were hospitalized (decrease of 8 +/- 20 ppb) versus discharged (increase of 5 +/- 20 ppb, p = 0.04). This variation of FE(NO 0.1) was correlated with the Diary score (control of subsequent week), an initial increase in FE(NO 0.1) being associated with better asthma control. Nevertheless, neither exhaled NO nor PEFR were good predictors of asthma control.

CONCLUSIONS

An increase in FE(NO) is observed in almost all patients with acute asthma, and its subsequent increase within 6 hours is associated with a better degree of asthma control in the subsequent week.

Exhaled nitric oxide measurements in hospitalized children with asthma

BACKGROUND

The reproducibility of exhaled nitric oxide (FE(NO)) measurements performed in pediatric hospitalized asthmatics has not been previously evaluated.

OBJECTIVE

To evaluate the reproducibility of FE(NO) measurements in the hospital; to look for differences between those who were and were not able to perform FE(NO) measurements; and to assess any factors correlated with FE(NO) measurements.

METHODS

89 hospitalized pediatric asthmatics performed FE(NO), FEV1, and peak expiratory flow rate (PEFR) maneuvers in triplicate at the time of discharge. Reproducibility was assessed using the intraclass correlation coefficient (ICC) and coefficient of variation (CV). Demographic and measured variables were compared between those who were and were not able to perform FE(NO) measurements. Correlation of FE(NO) with other variables was investigated.

RESULTS

FE(NO) measurements showed clinically acceptable ICC and CV values (0.973 and 5.59%, respectively). These values were superior to the values obtained for FEV1 and PEFR. Subjects who successfully performed the FE(NO) measurements were older, had higher PEFR readings, and had a lower asthma dyspnea score. No correlation was found between FE(NO) and traditional asthma factors, though multiple factors did trend towards significance.

CONCLUSION

FE(NO) measurements can be obtained in hospitalized pediatric patients with good reproducibility. While the majority of children will be able to provide such readings, those who are younger and with a more severe exacerbation may be unsuccessful in doing so. Further research is needed to determine how best to incorporate FE(NO) values into the hospital setting.

Evaluation of exhaled nitric oxide measurements in the emergency department for patients with acute asthma

BACKGROUND

Fraction of exhaled nitric oxide (FE(NO)) measurements performed on patients with acute asthma in the emergency department (ED) have previously shown poor reproducibility.

OBJECTIVES

To evaluate the reproducibility of FE(NO) measurements in the ED using a new monitoring device, to evaluate any factors that may correlate with FE(NO) measurements, and to investigate if FE(NO) levels predict the need for admission to the hospital.

METHODS

Thirty-five adult patients with asthma seen in the ED performed FE(NO), forced expiratory volume in 1 second, and peak expiratory flow rate maneuvers in triplicate. Reproducibility was evaluated using the intraclass correlation coefficient and the coefficient of variation. Associations between FE(NO), demographic, and traditional asthma measurements were investigated. The FE(NO) levels between patients admitted for further care and those discharged home were compared.

RESULTS

The FE(NO) measurements showed acceptable intraclass correlation coefficient and coefficient of variation values (0.98 and 9.42%, respectively) for reproducibility. These values were superior to the values obtained for forced expiratory volume in 1 second and peak expiratory flow rate. No correlation was found between FE(NO) and traditional asthma factors, although length of the asthma attack trended toward statistical significance (P = .08). The FE(NO) levels did not differ between those admitted and those discharged home (P = .53).

CONCLUSIONS

Fraction of exhaled nitric oxide measurements can be obtained in the ED setting with good reproducibility. These measurements may provide useful information not obtainable by other means. Further research is needed to determine how best to incorporate FE(NO) values into the ED setting.

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.