Reproducibility and comparison of responses to inhaled histamine and methacholine

Changes in Small Airway Physiology Measured by Impulse Oscillometry in Subjects with Allergic Asthma Following Methacholine and Inhaled Allergen Challenge

Background: Small airway dysfunction (SAD) is associated with impaired asthma control, but small airway physiology is not routinely assessed in clinical practice. Previously, we demonstrated impulse oscillometry (IOS)-defined small airway dysfunction (SAD) in dual responders (DRs) upon bronchoprovocation with various allergens. Aim: To compare lung physiology using spirometry and IOS following bronchoprovocation with methacholine (M) and inhaled house dust mite (HDM) extract in corticosteroid-naïve asthmatic subjects. Methods: Non-smoking, clinically stable HDM-allergic asthmatic subjects (18-55 years, FEV1 > 70% of pred.) underwent an M and inhaled HDM challenge on two separate days. Airway response was measured by IOS and spirometry, until a drop in FEV1 ≥ 20% (PC20) from post-diluent baseline (M), and up to 8 h post-allergen (HDM). Early (EAR) and late asthmatic response (LAR) to HDM were defined as ≥20% and ≥15% fall in FEV1 from post-diluent baseline during 0-3 h and 3-8 h post-challenge, respectively. IOS parameters (Rrs5, Rrs20, Rrs5-20, Xrs5, AX, Fres) were compared between mono-responders (MRs: EAR only) and dual responders (EAR + LAR). Correlations between maximal % change from baseline after the two airway challenges were calculated for both FEV1 and IOS parameters. Results: A total of 47 subjects were included (11 MRs; 36 DRs). FEV1 % predicted did not differ between MR and DR at baseline, but DR had lower median PC20M (0.84 (range 0.07-7.51) vs. MR (2.15 (0.53-11.29)); p = 0.036). During the LAR, DRs had higher IOS values than MRs. For IOS parameters (but not for FEV1), the maximal % change from baseline following M and HDM challenge were correlated. PC20M was inversely correlated with the % change in FEV1 and the % change in Xrs5 during the LAR (r= -0.443; p = 0.0018 and r= -0.389; p = 0.0075, respectively). Conclusions: During HDM-induced LAR, changes in small airway physiology can be non-invasively detected with IOS and are associated with increased airway hyperresponsiveness and changes in small airway physiology during methacholine challenge. DRs have a small airways phenotype, which reflects a more advanced airway disease.

Discrepancy in the suppressive function of regulatory T cells in allergic asthmatic vs. allergic rhinitis subjects upon low-dose allergen challenges

Background

Regulatory T cells (Tregs) contribute to the maintenance of immunological tolerance. There is evidence of impaired function of these cells in people with asthma and allergy. In this study, we evaluated and compared the function of Tregs in allergic asthmatic and allergic non-asthmatic patients, both before and after low-dose allergen challenges.

Methods

Three groups of subjects were recruited for a baseline evaluation: healthy controls without allergy or asthma, allergic asthmatic subjects, and allergic non-asthmatic subjects. All of them were subjected to expiratory flow measurements, sputum induction, and blood sampling. In addition, both groups of allergic subjects underwent low-dose allergen challenges. Tregs were isolated from whole blood using CD4+CD25high and CD127low staining. The suppression function was measured by flow cytometry. The levels of IL-10, IFN-γ, IgG4, IgA, and TGF-β were measured using ELISA, and sputum Foxp3 was evaluated using qRT-PCR.

Results

The suppressive function of Tregs in healthy controls was significantly higher than in allergic asthmatic or allergic non-asthmatic subjects. Repeated exposure to low doses of allergen increased the suppressor function of Tregs in allergic non-asthmatic subjects but decreased it in allergic asthmatic subjects. Foxp3 gene expression was increased in induced sputum in allergic non-asthmatic subjects, whereas it did not change in asthmatic subjects. Serum IL-10 level was decreased in allergic asthmatic subjects after allergen challenge but not in allergic non-asthmatic subjects. IFN-γ level increased upon allergen challenge in allergic non-asthmatic subjects. IgG4 level was higher in allergic non-asthmatic subjects than in allergic asthmatic subjects.

Conclusions

Low-dose allergen challenges stimulate the suppressor function of Tregs in non-asthmatic allergic subjects but not in allergic asthmatic subjects.

The cumulative effect of methacholine on large and small airways when deep inspirations are avoided

BACKGROUND AND OBJECTIVE

The effect of serial incremental concentrations of methacholine is only slightly cumulative when assessed by spirometry. This limited cumulative effect may be attributed to the bronchodilator effect of deep inspirations that are required between concentrations to measure lung function. Using oscillometry, the response to methacholine can be measured without deep inspirations. Conveniently, oscillometry can also dissociate the contribution of large versus small airways. Herein, oscillometry was used to assess the cumulative effect of methacholine in the absence of deep inspirations on large and small airways.

METHODS

Healthy and asthmatic volunteers underwent a multiple-concentration methacholine challenge on visit 1 and a single-concentration challenge on visit 2 using the highest concentration of visit 1. The maximal response was compared between visits to assess the cumulative effect of methacholine. The lung volume was also measured after the final concentration to assess hyperinflation.

RESULTS

In both healthy and asthmatic subjects, increases in resistance at 19 Hz (R_rs19 ), reflecting large airway narrowing, did not differ between the multiple- and the single-concentration challenge. However, increases in resistance at 5 Hz (R_rs5 ) minus R_rs19 , reflecting small airway narrowing, were 117 and 270% greater in the multiple- than the single-concentration challenge in healthy (p = 0.006) and asthmatic (p < 0.0001) subjects, respectively. Hyperinflation occurred with both challenges and was greater in the multiple- than the single-concentration challenge in both groups.

CONCLUSION

Without deep inspirations, the effect of methacholine is cumulative on small airways but not on large airways. Lung hyperinflation and derecruitment may partially explain these different responses.

Sounding the alarmins-The role of alarmin cytokines in asthma

The alarmin cytokines thymic stromal lymphopoietin (TSLP), interleukin (IL)-33, and IL-25 are epithelial cell-derived mediators that contribute to the pathobiology and pathophysiology of asthma. Released from airway epithelial cells exposed to environmental triggers, the alarmins drive airway inflammation through the release of predominantly T2 cytokines from multiple effector cells. The upstream positioning of the alarmins is an attractive pharmacological target to block multiple T2 pathways important in asthma. Blocking the function of TSLP inhibits allergen-induced responses including bronchoconstriction, airway hyperresponsiveness, and inflammation, and subsequent clinical trials of an anti-TSLP monoclonal antibody, tezepelumab, in asthma patients demonstrated improvements in lung function, airway responsiveness, inflammation, and importantly, a reduction in the rate of exacerbations. Notably, these improvements were observed in patients with T2-high and with T2-low asthma. Clinical trials blocking IL-33 and its receptor ST2 have also shown improvements in lung function and exacerbation rates; however, the impact of blocking the IL-33/ST2 axis in T2-high versus T2-low asthma is unclear. To date, there is no evidence that IL-25 blockade is beneficial in asthma. Despite the considerable overlap in the cellular functions of IL-25, IL-33, and TSLP, they appear to have distinct roles in the immunopathology of asthma.

In mice of both sexes, repeated contractions of smooth muscle in vivo greatly enhance the response of peripheral airways to methacholine

BALB/c mice from both sexes underwent one of two nebulized methacholine challenges that were preceded by a period of 20 min either with or without tone induced by repeated contractions of the airway smooth muscle. Impedance was monitored throughout and the constant phase model was used to dissociate the impact of tone on conducting airways (R_N - Newtonian resistance) versus the lung periphery (G and H - tissue resistance and elastance). The effect of tone on smooth muscle contractility was also tested on excised tracheas. While tone markedly potentiated the methacholine-induced gains in H and G in both sexes, the gain in R_N was only potentiated in males. The contractility of female and male tracheas was also potentiated by tone. Inversely, the methacholine-induced gain in hysteresivity (G/H) was mitigated by tone in both sexes. Therefore, the tone-induced muscle hypercontractility impacts predominantly the lung periphery in vivo, but also promotes further airway narrowing in males while protecting against narrowing heterogeneity in both sexes.

Bronchial hyperresponsiveness is common in Hanoi, Vietnam: Asthma probably underdiagnosed

BACKGROUND

Bronchial hyperresponsiveness (BHR) is a key pathophysiological feature of asthma. Methacholine challenge test (MCT) is a common bronchoprovocation test useful for confirming a diagnosis of asthma. Studies of BHR in the general population of Asian countries are rare.

AIM

To estimate prevalence and determinants of BHR in Hanoi, Vietnam, and to study the association between BHR and symptoms common in asthma and previously diagnosed asthma.

METHODS

1500 out of 5872 randomly selected adults in urban and rural Hanoi, who had participated in a questionnaire survey (83% participated), were randomly selected and invited to clinical examinations. Totally 684 subjects (46%) participated. MCT was performed in 366 subjects. BHR was defined as a FEV₁-decrease of ≥20% from baseline following methacholine inhalations (PC₂₀). Cut offs used in the analyses were PC₂₀ ≤ 1 mg/ml, ≤2 mg/ml and ≤8 mg/ml.

RESULTS

The prevalence of BHR was 16.4% at doses ≤8 mg/ml, while 9.6% reacted on doses ≤2 mg/ml. PC₂₀ ≤ 2 mg/ml was associated with FEV₁ <80% of predicted. PC₂₀ ≤ 2 mg/ml, but not PC₂₀ ≤ 8 mg/ml, was associated with multi-sensitization to airborne allergens. BHR defined as PC₂₀ ≤ 8 mg/ml was associated with age >45y. The combination of asthmatic wheeze (wheezing with breathlessness apart from colds) and BHR, irrespectively of magnitude of BHR, was more common than the combination of BHR with previously diagnosed asthma.

CONCLUSIONS

The results indicate BHR to be more common in Hanoi than previously found in south-east Asia. Although the prevalence of physician diagnosed asthma has increased in Vietnam, our results indicate that asthma still may be underdiagnosed in Vietnam.

Measurement of bronchial hyperreactivity: comparison of three Nordic dosimetric methods

Clinical testing of bronchial hyperreactivity (BHR) provides valuable information in asthma diagnostics. Nevertheless, the test results depend to a great extent on the testing procedure: test substance, apparatus and protocol. In Nordic countries, three protocols predominate in the testing field: Per Malmberg, Nieminen and Sovijärvi methods. However, knowledge of their equivalence is limited. We aimed to find equivalent provocative doses (PD) to obtain similar bronchoconstrictive responses for the three protocols. We recruited 31 patients with suspected asthma and health care workers and performed BHR testing with methacholine according to Malmberg and Nieminen methods, and with histamine according to Sovijärvi. We obtained the individual response-dose slopes for each method and predicted equivalent PD values. Applying a mixed-model, we found significant differences in the mean (standard error of mean) response-dose (forced expiratory volume in one second (FEV₁)%/mg): Sovijärvi 7.2 (1.5), Nieminen 13.8 (4.2) and Malmberg 26 (7.3). We found that the earlier reported cut-point values for moderate BHR and marked BHR between the Sovijärvi (PD₁₅) and Nieminen (PD₂₀) methods were similar, but with the Malmberg method a significant bronchoconstrictive reaction was measured with lower PD₂₀ values. We obtained a relationship between slope values and PD (mg) between different methods, useful in epidemiological research and clinical practice.

Use of a vibrating mesh nebulizer for allergen challenge

Background

Allergen inhalation tests are a valuable research tool. The allergen dose producing an early asthmatic response (EAR) can be predicted from methacholine responsiveness and allergen skin test endpoint (STE). The Wright^® jet nebulizer, which is both inefficient and increasingly difficult to obtain, has been used historically. We assessed the Solo^® vibrating mesh nebulizer as an alternative for allergen and methacholine challenges.

Methods

Eighteen mild atopic asthmatics completed the study. Doubling concentration allergen prick skin tests were performed to determine the STE in allergen units/mL. The Wright^® protocol was used to measure the methacholine provocation dose causing a 20% forced expired volume in one second (FEV₁) fall (PD₂₀) (μg) and the allergen PD₂₀ (units). The Solo^® protocol (0.5 mL nebulized to completion, tidal breathing inhalation) was used to determine both methacholine PD₂₀ and allergen PD₂₀. The nebulizer order was randomized and separated by ≥ 2 weeks.

Results

All data were log transformed. The allergen PD₂₀, predicted from the methacholine PD₂₀ and the STE, was within 2 doubling doses of the PD₂₀ measured with the Wright^® and 2.64 doubling doses of that measured with Solo^®. The Wright^® allergen PD₂₀ correlated with the Wright^® methacholine PD₂₀ (r = 0.74) and the STE (r = 0.78) and more strongly with the product of the two (Wright^® methacholine PD₂₀ × STE, r = 0.91, p < 0.00001). The Solo^® allergen PD₂₀ showed similar relationships with the Solo^® methacholine PD₂₀ (r = 0.61), the STE (r = 0.75) and the product of the two (Solo^® methacholine PD₂₀ × STE, r = 0.83, p < 0.00002). The Wright^® and the Solo^® methacholine geometric mean PD₂₀s were not significantly different (49.3 and 54.5 μg respectively, p = 0.62). The Wright^® allergen PD₂₀ was slightly but significantly lower than the Solo^® allergen PD₂₀ (geometric means 6.7 and 10.5 units respectively, p = 0.003).

Conclusion

The Solo^® allergen PD₂₀ showed the same relationship with methacholine responsiveness and STE as did the Wright^®. The Solo^® allergen PD₂₀ was slightly but significantly higher than the Wright^® allergen PD₂₀. The Solo^® vibrating mesh nebulizer was well tolerated and is an acceptable alternative for allergen challenge.

Trial registration clinicaltrials.gov: NCT03491358

Predictive factors for a shortened methacholine challenge protocol in children

RATIONALE

Although the methacholine challenge test is useful in the diagnosis of asthma, it is time-consuming in children. While protocols that quadruple methacholine concentrations are widely used in adults to shorten testing time, this has not been evaluated in children. Studies have not identified predictors associated with the safe use of a quadrupled concentration protocol.

OBJECTIVES

To identify clinical predictors associated with the preclusion of a quadrupled concentration protocol in children.

METHODS

We included subjects <18 years who performed a methacholine challenge tests between April 2016 to February 2017 (derivation cohort) and March 2017 to September 2017 (validation cohort). We determined the eligibility of a subject to omit the 0.5 mg/ml and 2.0 mg/ml concentrations based on their PC20 and identified baseline characteristics that are associated with the preclusion of the quadrupled protocol using bivariate analysis. The derived algorithm was applied to the validation cohort.

RESULTS

We included 399 and 195 patients in the derivation and validation cohorts, respectively. A baseline FEV₁ ≤90% predicted, FEV₁/FVC ≤0.8, FEF_25-75 ≤70% predicted, and a decrease in FEV₁ ≥10% with the previous concentration significantly precluded the omission of the 0.5 mg/ml concentration. A baseline FEF_25-75 ≤70% predicted and a drop in FEV₁ ≥10% with the previous concentration significantly precluded the omission of the 2.0 mg/ml concentration. Applying these 4 criteria to the validation cohort resulted in an overall sensitivity and specificity of 74.0% and 84.6%, respectively.

CONCLUSIONS

We identified objective pulmonary function measures that may personalize and shorten the methacholine challenge protocol in children by quadrupling concentrations.

Bronchoprovocation Testing in Asthma: An Update

Bronchial hyperresponsiveness (BHR) is defined as a heightened bronchoconstrictive response to airway stimuli. It complements the cardinal features in asthma, such as variable or reversible airflow limitation and airway inflammation. Although BHR is considered a pathophysiologic hallmark of asthma, it should be acknowledged that this property of the airway is dynamic, because its severity and even presence can vary over time with disease activity, triggers or specific exposure, and with treatment. In addition, it is important to recognize that there is a component that is not reflective of a specific disease entity.

Direct bronchoprovocation test methods: history 1945-2018

INTRODUCTION

Bronchoprovocation inhalation challenge tests with direct acting stimuli (e.g. methacholine) are widely used clinically to aid in the diagnosis of asthma. Areas covered: The history of direct challenges with histamine and muscarinic agonists is reviewed. This began with parenteral administration of stimuli with responses monitored clinically and by VC, progressing to inhalation dose-response challenges monitored by FEV₁ and FEV₁/VC ratio, both (the challenge method and the technology to measure FEV₁) developed by Robert Tiffeneau in the mid-1940s. Careful standardization of methods has become appreciated albeit after-the-fact. Recent guidelines recommend standardizing the methacholine PD₂₀ at 400 μg above which a methacholine challenge is considered negative.

CONCLUSIONS

The methacholine inhalation test is highly sensitive for a diagnosis of current asthma when symptoms under evaluation are clinically current and when methacholine is inhaled without deep inhalations. Under these circumstances, a methacholine PD₂₀ > 400 μg excludes current asthma with reasonable certainty. PD₂₀ values >25 μg and ≤400 μg will have a variable specificity and positive predictive value for asthma which increases the lower the PD₂₀ and the higher the pre-test probability for a diagnosis of asthma. A PD₂₀ ≤25 μg has high specificity and low sensitivity for asthma.

Bronchial hyper-responsiveness after preterm birth

Being born preterm often adversely affects later lung function. Airway obstruction and bronchial hyperresponsiveness (BHR) are common findings. Respiratory symptoms in asthma and in lung disease after preterm birth might appear similar, but clinical experience and studies indicate that symptoms secondary to preterm birth reflect a separate disease entity. BHR is a defining feature of asthma, but can also be found in other lung disorders and in subjects without respiratory symptoms. We review different methods to assess BHR, and findings reported from studies that have investigated BHR after preterm birth. The area appeared understudied with relatively few and heterogeneous articles identified, and lack of a pervasive understanding. BHR seemed related to low gestational age at delivery and a neonatal history of bronchopulmonary dysplasia. No studies reported associations between BHR after preterm birth and the markers of eosinophilic inflammatory airway responses typically found in asthma. This should be borne in mind when treating preterm born individuals with BHR and airway symptoms.

Calcium channel blockers for lung function improvement in asthma: A systematic review and meta-analysis

BACKGROUND

For decades, calcium channel blockers (CCBs) have been believed to play a role in asthma treatment. However, the clinical efficacy of CCBs for lung function improvement in patients with asthma has not been qualitatively evaluated.

OBJECTIVE

To assess the effect of CCBs vs placebo on lung function test results in adults with asthma.

METHODS

Various databases were systematically searched to identify all randomized clinical trials with adults with asthma. We aimed to assess the influence of CCBs on forced expiratory volume in 1 second (FEV₁), forced vital capacity (FVC), peak expiratory flow rate (PEFR), and provocative concentration of bronchoconstrictive agents causing a 20% decrease in FEV₁ (PC₂₀) compared with a placebo. All effect estimates were pooled by the generic inverse variance method with random-effects meta-analysis. Subgroup analysis, sensitivity analysis, and heterogeneity investigation were performed.

RESULTS

Thirty eligible articles with 301 patients were included in this meta-analysis. Our results revealed that in a standard exercise test CCBs could produce a mean maximal percentage decrease in FEV₁ of 11.56% (95% confidence interval, 8.97%-14.16%; P < .001) and an increase in postdose FEV₁ by 80 mL (95% confidence interval, 0.02-0.15 mL; P = .01). However, there was no statistical significance for CCBs in postdose FVC, PEFR, or PC₂₀ of histamine and methacholine.

CONCLUSION

CCBs may be beneficial for lung function improvement in asthma, especially in exercise-induced asthma. However, there is a lack of evidence for CCBs protecting asthma patients from chemical irritation.

Methacholine Challenge: Comparison of Airway Responsiveness Produced by a Vibrating Mesh Nebulizer Versus a Jet Nebulizer

BACKGROUND

The latest methacholine challenge testing (MCT) guidelines published by the European Respiratory Society recommend the characterization of nebulizers before their use in clinics and research. Such investigations are necessary for accurately determining the provocative dose of methacholine causing a 20% fall in FEV₁ (PD₂₀) delivered by a given device. The standard English Wright (Wright) jet nebulizer recommended in the 1999 guidelines by the American Thoracic Society has become difficult to obtain and possesses some characteristics that complicate the calculation of dose delivery from this device (e.g. evaporation). Our objective was to determine if the Aerogen^® Solo (Solo) vibrating mesh nebulizer provides similar methacholine challenge test results compared to the currently used Wright jet nebulizer.

METHODS

Sixty mild-to-moderate asthmatics were studied across three research sites in a randomized crossover study. Both methacholine challenges were completed at least 24 hours apart within a 2-week period. Testing with the Wright device was performed as per the 2-minute tidal breathing protocol. The Solo study arm followed the same procedure except for a shorter inhalation time of 1 minute. The provocative concentration of methacholine causing a 20% fall in FEV₁ (PC₂₀) and the methacholine PD₂₀ were calculated following each methacholine challenge.

RESULTS

The geometric mean methacholine PC₂₀ values for the Solo and the Wright differed statistically (0.65 mg/mL vs. 2.58 mg/mL, respectively, p < 0.00001) and clinically. Between-nebulizer geometric mean methacholine PD₂₀ results are comparable by clinical standards [81.7 μg (Solo) vs. 64.7 μg (Wright)], although the slight difference in dose was statistically significant (p = 0.018).

CONCLUSIONS

The comparability of PD₂₀ values between the Solo and the Wright validates the importance of reporting airway responsiveness to methacholine in terms of dose and not concentration, as stressed in the latest testing guidelines. This finding along with several benefits associated with the Solo make it a promising nebulizer for performing MCT.

ERS technical standard on bronchial challenge testing: general considerations and performance of methacholine challenge tests

This international task force report updates general considerations for bronchial challenge testing and the performance of the methacholine challenge test. There are notable changes from prior recommendations in order to accommodate newer delivery devices. Rather than basing the test result upon a methacholine concentration (provocative concentration (PC20) causing a 20% fall in forced expiratory volume in 1 s (FEV1)), the new recommendations base the result upon the delivered dose of methacholine causing a 20% fall in FEV1 (provocative dose (PD20)). This end-point allows comparable results from different devices or protocols, thus any suitable nebuliser or dosimeter may be used, so long as the delivery characteristics are known. Inhalation may be by tidal breathing using a breath-actuated or continuous nebuliser for 1 min (or more), or by a dosimeter with a suitable breath count. Tests requiring maximal inhalations to total lung capacity are not recommended because the bronchoprotective effect of a deep breath reduces the sensitivity of the test.

Acute effects of nicotine-free and flavour-free electronic cigarette use on lung functions in healthy and asthmatic individuals

We designed a crossover and placebo-controlled trial to investigate the impact of a 1-h acute vaping session of nicotine-free and flavour-free e-liquid on the pulmonary functions and respiratory mechanics of healthy and asthmatic individuals. This study shows that a 1-h vaping session of a high-grade and contaminant-free mixture of propylene glycol and glycerol using a commercially available electronic cigarette performed in a controlled environment does not significantly impact pulmonary functions, respiratory mechanics or symptoms in healthy or asthmatic subjects.

Airway Hyperresponsiveness in Asthma: Measurement and Clinical Relevance

Airway hyperresponsiveness is a characteristic feature of asthma, and its measurement is an important tool in its diagnosis. With a few caveats, methacholine bronchial provocation by a 2-minute tidal breathing method is highly sensitive; a negative test result (PC₂₀ > 16 mg/mL, PD₂₀ > 400 μg) rules out current asthma with reasonable certainty. A PC₂₀ value of less than 1 mg/mL/PD₂₀ value of less than 25 μg is highly specific (ie, diagnostic) but quite insensitive for asthma. For accurate interpretation of the test results, it is important to control and standardize technical factors that have an impact on nebulizer performance. In addition to its utility to relate symptoms such as cough, wheeze, and shortness of breath to variable airflow obstruction (ie, to diagnose current asthma), the test is useful to make a number of other clinical assessments. These include (1) evaluation of patients with occupational asthma, (2) evaluation of patients with exercise-induced respiratory symptoms, (3) evaluation of novel asthma medications, (4) evaluation of relative potency of inhaled bronchodilators, (5) as a biomarker to adjust anti-inflammatory therapy to improve clinical outcomes, and (6) in the evaluation of patients with severe asthma to rule out masqueraders such as laryngeal dysfunction. The actual mechanism of altered smooth muscle behavior in asthma that is assessed by direct (eg, methacholine) or indirect (eg, allergen) bronchial provocation remains one of the most fundamental questions related to asthma that needs to be determined. The test is underutilized in clinical practice.

Comparison of the provocative concentration of methacholine causing a 20% fall in FEV1 between the AeroEclipse II breath-actuated nebulizer and the wright nebulizer in adult subjects with asthma

RATIONALE

The American Thoracic Society guidelines for methacholine testing for the diagnosis of asthma recommends the 2-minute tidal breathing protocol with the Wright nebulizer, which produces more aerosol than required, generates a small particle size, and requires cleaning between tests.

OBJECTIVES

To evaluate methacholine testing using a disposable, breath-actuated AeroEclipse II, which produces aerosol during inspiration and was developed for single-patient use.

METHODS

Forty-six adult subjects with asthma (19 men), aged 27.3 (SD, 9.5) years, with FEV1 98.5 (SD, 18.1) % predicted participated in a randomized, crossover, observational study. Subjects were first screened using the Wright nebulizer, then assigned to 2 minutes of tidal breathing from the Wright or 20 seconds of tidal breathing from the AeroEclipse nebulizer on 2 separate days, in random order. Provocative concentration of methacholine causing a 20% fall in FEV1 (PC20) values were calculated by linear interpolation of log dose-versus-response curves, log-transformed, and compared using paired Student t test and Pearson correlation.

MEASUREMENTS AND MAIN RESULTS

The 38 subjects demonstrating reproducible PC20 measurements of within 1.5 doubling concentrations were included in the comparison. The geometric mean methacholine PC20 measured with the AeroEclipse nebulizer was approximately 1 doubling concentration lower than the geometric mean methacholine PC20 of the Wright nebulizer (P < 0.05). The Pearson correlation coefficient between the two nebulizers was 0.86 (P < 0.05).

CONCLUSIONS

The PC20 measurements using the two nebulizers were highly correlated; however, the PC20 determined with the AeroEclipse nebulizer was significantly lower than those determined using the Wright nebulizer. Clinical trial registered with www.clinicaltrials.gov (NCT 01919424).

Provocative dose of methacholine causing a 20% drop in FEV1 should be used to interpret methacholine challenge tests with modern nebulizers

RATIONALE

The American Thoracic Society guidelines (1999) for methacholine challenge tests (MCTs) using the 2-minute tidal breathing protocol were developed for the now-obsolete English-Wright (EW) nebulizer. In addition, the guideline recommendation to use the provocative concentration of methacholine causing a 20% drop in FEV1 (PC20) rather than the provocative dose of methacholine causing a 20% drop in FEV1 (PD20) for determining the level of bronchial hyperresponsiveness has been challenged.

OBJECTIVES

To determine if cumulative dose or concentration of methacholine delivered to the airways is the determinant for airway responsiveness and to validate use of the AeroEclipse* II BAN (Aero; Trudell Medical International, London, ON, Canada) nebulizer compared with use of the reference standard EW nebulizer.

METHODS

Subjects with asthma (10-18 yr old) participated in randomized, controlled cross-over experiments comparing four MCT protocols using standard methacholine concentrations, but varying: (1) methacholine starting concentration (testing for cumulative effect); (2) nebulizer (EW versus Aero); and (3) inhalation time. PD20 was calculated using nebulizer output rate, inhalation time, and preceding doses delivered. ANOVA analyses were used to compare geometric means of PC20 and PD20 between protocols.

RESULTS

A total of 32 subjects (17 male) participated. PC20 differed when starting concentration varied (0.46 vs. 0.80 mg/ml; P<0.0001), whereas PD20 did not (0.06 vs. 0.08 mg). PC20 differed with the EW versus the Aero nebulzer with 30-second inhalation (1.19 vs. 0.43 mg/ml; P=0.0006) and the EW versus the Aero nebulizer with 20-second inhalation (1.91 vs. 0.89 mg/ml; P=0.0027), whereas PD20 did not (0.07 vs. 0.06 mg and 0.11 vs. 0.09 mg, respectively).

CONCLUSIONS

In MCTs, the cumulative dose (PD20), not the PC20, determines bronchial responsiveness. Modern nebulizers may be used for the test if clinical interpretation is based on PD20. Clinical trial registered with www.clinicaltrials.gov (NCT01288482).

Airway response to methacholine following eucapnic voluntary hyperpnea in athletes

Aim

To evaluate the changes in airway responsiveness to methacholine inhalation test (MIT) when performed after an eucapnic voluntary hyperpnea challenge (EVH) in athletes.

Methods

Two MIT preceded (visit 1) or not (visit 2) by an EVH, were performed in 28 athletes and 24 non-athletes. Twelve athletes and 13 non-athletes had airway hyperresponsiveness (AHR) to methacholine, and 11 athletes and 11 non-athletes had AHR to EVH (EVH+).

Results

The MIT PC₂₀ post-EVH was significantly lower compared to baseline MIT PC₂₀ by 1.3±0.7 doubling-concentrations in EVH+ athletes only (p<0.0001). No significant change was observed in EVH- athletes and EVH+/EVH- non-athletes. A significant correlation between the change in MIT PC₂₀ post-EVH and EVH+/EVH- status and athlete/nonathlete status was found (Adjusted R²=0.26 and p<0.001). Three (11%) athletes and one (4%) non-athlete had a change in the diagnosis of AHR when MIT was performed consecutively to EVH.

Conclusion

The responsiveness to methacholine was increased by a previous indirect challenge in EVH+ athletes only. The mechanisms for such increase remain to be determined. MIT and EVH should ideally be performed on separate occasions as there is a small but possible risk to obtain a false-positive response to methacholine when performed immediately after the EVH.

Trial Registration

ClinicalTrials.gov NCT00686491

T helper 17 cells and related cytokines after allergen inhalation challenge in allergic asthmatics

BACKGROUND

T helper (Th)17 cells may play a role in allergic asthma. This study assessed the effect of allergen inhalation challenge on circulating Th17 cells and related cytokines in allergic asthmatics.

METHODS

Peripheral blood mononuclear cells were collected from 16 atopic asthmatics before and 24 h after allergen challenge, as well as from 10 atopic nonasthmatics and 10 normal controls. Cells were stained for Th17 cytokines and their receptors (IL-17A, IL-17F, IL-21, IL-22, IL-17R, and IL-23R) using flow cytometry. Cytokine concentrations from cell culture supernatants were quantified using a multiplex assay for IL-17A, IL-17F, IL-21, IL-22, and IL-23.

RESULTS

At baseline, asthmatics had a higher percentage of circulating Th17 cells (1.2 ± 0.5%) compared to normal controls (0.9 ± 0.66%, p < 0.001) but not compared to atopic nonasthmatics (1.13 ± 0.5%). There was a significant increase in Th17 cells in asthmatics after allergen challenge to 1.55 ± 0.4% (p < 0.05) and a trend toward significance in IL-17R expression from 3.4 ± 4.3 to 6.86 ± 6.84% after allergen challenge (p = 0.06). There was also a significant reduction in IL-21-positive cells following allergen challenge from 3.46 ± 1.85 to 2.33 ± 1.37% (p < 0.001). There were no significant differences in IL-17F, IL-22 and IL-23R expression. The concentration of IL-17A in culture supernatant was significantly higher in asthmatics compared to normal controls and IL-17A significantly increased 24 h after allergen challenge.

CONCLUSIONS

The increase of Th17 cells and IL-17A in atopic asthma after allergen inhalation challenge suggests a possible role for Th17 in allergen-induced airway responses.

Pharmacogenomics: novel loci identification via integrating gene differential analysis and eQTL analysis

Nearly one-half of asthmatic patients do not respond to the most commonly prescribed controller therapy, inhaled corticosteroids (ICS). We conducted an expression quantitative trait loci (eQTL) analysis using >300 expression microarrays (from 117 lymphoblastoid cell lines) in corticosteroid (dexamethasone) treated and untreated cells derived from asthmatic subjects in the Childhood Asthma Management Program (CAMP) clinical trial. We then tested the associations of eQTL with longitudinal change in airway responsiveness to methacholine (LnPC20) on ICS. We identified 2484 cis-eQTL affecting 767 genes following dexamethasone treatment. A significant over-representation of lnPC20-associated cis-eQTL [190 single-nucleotide polymorphisms (SNPs)] among differentially expressed genes (odds ratio = 1.76, 95% confidence interval: 1.35-2.29) was noted in CAMP Caucasians. Forty-six of these 190 clinical associations were replicated in CAMP African Americans, including seven SNPs near six genes meeting criteria for genome-wide significance (P < 2 × 10(-7)). Notably, the majority of genome-wide findings would not have been uncovered via analysis of untreated samples. These results indicate that identifying eQTL after relevant environmental perturbation enables identification of true pharmacogenetic variants.

Respiratory disorders in endurance athletes - how much do they really have to endure?

Respiratory disorders are often a cause of morbidity in top level endurance athletes, more often compromising their performance and rarely being a cause of death. Pathophysiological events occurring during exercise, such as bronchospasm, are sometimes followed by clear pathological symptoms represented by asthma related to physical exertion or rarely by pulmonary edema induced by a strenuous effort. Both bronchospasm and the onset of interstitial edema induced by exercise cannot be considered pathological per se, but are more likely findings that occur in several healthy subjects once physical exhaustion during exertion has been reached. Consequently, we get a vision of the respiratory system perfectly tailored to meet the body's metabolic demands under normal conditions but which is limited when challenged by strenuous exercise, in particular when it happens in an unfavorable environment. As extreme physical effort may elicit a pathological response in healthy subjects, due to the exceeding demand in a perfectly functional system, an overview of the main tools both enabling the diagnosis of respiratory impairment in endurance athletes in a clinical and preclinical phase has also been described.

Advances in the diagnosis of exercise-induced bronchoconstriction

Exercise-induced bronchoconstriction (EIB) describes the post exercise phenomenon of acute airway narrowing in association with physical activity. A high prevalence of EIB is reported in both athletic and recreationally active populations. Without treatment, EIB has the potential to impact upon both health and performance. It is now acknowledged that clinical assessment alone is insufficient as a sole means of diagnosing airway dysfunction due to the poor predictive value of symptoms. Furthermore, a broad differential diagnosis has been established for EIB, prompting the requirement of objective evidence of airway narrowing to secure an accurate diagnosis. This article provides an appraisal of recent advances in available methodologies, with the principle aim of optimising diagnostic assessment, treatment and overall clinical care.

Challenging the two-minute tidal breathing challenge test

BACKGROUND

In the adenosine 5'-monophosphate (AMP) bronchial challenge test, AMP is usually administered according to dosing protocols for methacholine. We investigated whether the 2-min tidal breathing challenge test for methacholine is applicable to AMP. Parameters known to affect nebulizer output were studied. Our aim was to determine whether control of additional parameters is needed for currently standardized protocols.

METHODS

The study was performed with the Sidestream nebulizer from the APS Pro Aerosol Provocation System (CareFusion Respiratory). The effects of AMP concentration, jet pressure, and suction flow rate on nebulizer output rate and aerosol droplet size distribution were determined.

RESULTS

The volume median diameter for water increased from 5.10 μm to 8.49 μm when the jet pressure was reduced to obtain the prescribed output rate of 0.13 mL/min. The output rate was increased when a suction flow rate was used to remove the aerosol. Increasing the AMP concentration resulted in smaller droplets and a lower output rate when a suction flow was applied.

CONCLUSIONS

The effects of AMP concentration on nebulizer performance may result in changes in the administered dose and site of deposition of AMP at dose escalation. All of the investigated parameters influence nebulizer performance, hence the outcome of a bronchial challenge test. Therefore, these parameters should not only be specified in challenge testing, but be actively controlled as well.

A cross-sectional study of patterns of airway dysfunction, symptoms and morbidity in primary care asthma

BACKGROUND

Most patients with asthma are managed exclusively in primary care. Little is known about the patterns of airway dysfunction in these patients and how these relate to other aspects of the disease.

AIMS

We set out to assess this in a cross-sectional study of 262 patients.

METHODS

Symptoms, spirometry, airway responsiveness, reversibility, and airway inflammation were all assessed. Exacerbations requiring oral corticosteroids in the preceding year were enumerated.

RESULTS

Patients had heterogeneous patterns of airway dysfunction. Those with a post-bronchodilator forced expiratory volume in 1 sec/ forced vital capacity ratio of <0.7 had more exacerbations in the previous year (2.2 vs. 0.8; mean difference 1.4; 95% CI 0.4 to 2.4; p=0.007). Patients with normal results had less inflammation (proportion with a sputum eosinophil count of >1.9%, 20% vs. 48%, χ²=14.8, df=3; p<0.001) and fewer exacerbations (0.5 vs. 1.4; mean difference -0.9; 95% CI -1.4 to -0.4; p=0.001) but similar symptom scores (6.2 vs. 6.9; p=0.2) compared with patients with any abnormality.

CONCLUSIONS

Patients with a diagnosis of asthma have mixed patterns of physiological impairment; many have no airflow obstruction or airway hyper-responsiveness. The physiological characterisation of asthma is not related to symptoms and is of little value in predicting exacerbations or eosinophilic airway inflammation.

Obesity in asthma: more neutrophilic inflammation as a possible explanation for a reduced treatment response

BACKGROUND

The incidence of asthma and obesity is increasing worldwide, and reports suggest that obese patients have more severe asthma. We investigated whether obese asthma patients have more severe airway obstruction and airway hyper-responsiveness and a different type of airway inflammation than lean asthmatics. Furthermore, we assessed the effect of obesity on corticosteroid treatment response.

METHODS

Patient data from four well-documented asthma cohorts were pooled (n = 423). We evaluated FEV(1) , bronchial hyper-responsiveness (PC(20) ) to either methacholine/histamine or adenosine 5'-monophosphate (AMP) (differential) cell counts in induced sputum and blood and corticosteroid treatment response in 118 patients.

RESULTS

At baseline, FEV(1) , PC(20) methacholine or histamine, and PC(20) AMP values were comparable in 63 obese (BMI ≥ 30 kg/m(2) ) and 213 lean patients (BMI <25 kg/m(2) ). Obese patients had significantly higher blood neutrophils. These higher blood neutrophils were only seen in obese women and not in obese men. After a two-week treatment with corticosteroids, we observed less corticosteroid-induced improvement in FEV(1) %predicted in obese patients than in lean patients (median 1.7% vs 6.3% respectively, P = 0.04). The percentage of sputum eosinophils improved significantly less with higher BMI (P = 0.03), and the number of blood neutrophils increased less in obese than in lean patients (0.32 x10(3) /μl vs 0.57 x10(3) /μl, P = 0.046).

CONCLUSIONS

We found no differences in asthma severity between obese and nonobese asthmatics. Interestingly, obese patients demonstrated more neutrophils in sputum and blood than nonobese patients. The smaller improvement in FEV(1) and sputum eosinophils suggests a worse corticosteroid treatment response in obese asthmatics.

Bronchoprovocation testing in asthma

This article covers the relationships between BHR and airway inflammation. Recent evidence suggests that various commonly used bronchoprovocation challenges (BPCs) differ in their potential to serve as inflammatory biomarkers. The response to direct stimuli depends on the smooth muscle's response to the chemical, whereas in indirect challenges, the reaction is caused by the smooth muscle's responsiveness to the mediators induced by the stimuli. The information obtained from studies with BPC has provided insights into the pathogenesis and pathophysiology of asthma, and the relationships between airway inflammation and bronchial hyper-responsiveness.

A case of histamine fish poisoning in a young atopic woman

Histamine fish poisoning, also known as scombroid poisoning, is a histamine toxicity syndrome that results from eating specific types of spoiled fish. Although typically a benign syndrome, characterized by self-limited flushing, headache, and gastrointestinal symptoms, we describe a case unique in its severity and as a precipitant of an asthma exacerbation. A 25-year-old woman presented to the emergency department (ED) with one hour of tongue and face swelling, an erythematous pruritic rash, and dyspnea with wheezing after consuming a tuna sandwich. She developed abdominal pain, diarrhea and hypotension in the ED requiring admission to the hospital. A diagnosis of histamine fish poisoning was made and the patient was treated supportively and discharged within 24 hours, but was readmitted within 3 hours due to an asthma exacerbation. Her course was complicated by recurrent admissions for asthma exacerbations.

Asthma outcomes: pulmonary physiology

BACKGROUND

Outcomes of pulmonary physiology have a central place in asthma clinical research.

OBJECTIVE

At the request of National Institutes of Health (NIH) institutes and other federal agencies, an expert group was convened to provide recommendations on the use of pulmonary function measures as asthma outcomes that should be assessed in a standardized fashion in future asthma clinical trials and studies to allow for cross-study comparisons.

METHODS

Our subcommittee conducted a comprehensive search of PubMed to identify studies that focused on the validation of various airway response tests used in asthma clinical research. The subcommittee classified the instruments as core (to be required in future studies), supplemental (to be used according to study aims and in a standardized fashion), or emerging (requiring validation and standardization). This work was discussed at an NIH-organized workshop in March 2010 and finalized in September 2011.

RESULTS

A list of pulmonary physiology outcomes that applies to both adults and children older than 6 years was created. These outcomes were then categorized into core, supplemental, and emerging. Spirometric outcomes (FEV(1), forced vital capacity, and FEV(1)/forced vital capacity ratio) are proposed as core outcomes for study population characterization, for observational studies, and for prospective clinical trials. Bronchodilator reversibility and prebronchodilator and postbronchodilator FEV(1) also are core outcomes for study population characterization and observational studies.

CONCLUSIONS

The subcommittee considers pulmonary physiology outcomes of central importance in asthma and proposes spirometric outcomes as core outcomes for all future NIH-initiated asthma clinical research.

Effect of bariatric surgery on airway response and lung function in obese subjects with asthma

BACKGROUND

Obesity is a risk factor for self-reported asthma and makes asthma management more difficult. The effects of bariatric surgery on asthma in severely obese subjects remain to be documented.

METHODS

In this prospective study, 12 asthmatic patients with severe obesity were evaluated before, 6 and 12 months after bariatric surgery. Each had methacholine inhalation tests, measures of expiratory flows and lung volumes, measurements of C-reactive protein and questionnaires on asthma medication, asthma symptoms and co-morbid conditions. Eleven severely obese patients with asthma (considered as controls) underwent the same evaluations. Primary endpoint was airway responsiveness to methacholine and secondary endpoints were lung volumes and markers of systemic inflammation.

RESULTS

Mean body mass index decreased from 51.2 to 34.4 kg/m(2) twelve months post-surgery. Mean PC(20) methacholine improved from 0.84 to 6.2 mg/ml (P < 0.001); FEV(1), FVC, FRC, FRC/TLC and ERV all improved (P ≤ 0.006). C-reactive protein decreased from 8.6 to 1.7 mg/L (P < 0.001) Asthma symptoms total score was significantly reduced (P = 0.03) and asthma medication needs decreased, ten patients being able to stop all asthma drugs. No significant changes of these parameters from baseline were observed in asthmatic controls. Improvements in airway responsiveness and lung volumes happened in parallel and correlated with reductions of body mass index (r = 0.58, P = 0.049), C-reactive protein levels (r = -0.74, P = 0.004).

CONCLUSION

Airway responsiveness, lung volumes and asthma severity/control markedly improved with weight loss following bariatric surgery in severely obese patients.

The effect of caffeinated coffee on airway response to methacholine and exhaled nitric oxide

BACKGROUND

The bronchoprotective effect of caffeine on histamine challenge testing (HCT) has been studied with equivocal results. Current guidelines for bronchoprovocation testing recommend exclusion of caffeine the day of testing. The effects of caffeine on methacholine challenge testing (MCT), now more commonly performed than histamine challenge, are unknown.

METHODS

Sixteen well-controlled asthmatics with a forced expiratory volume in 1 s (FEV(1)) > 65% predicted and methacholine provocation concentration causing a 20% fall in FEV(1) (PC(20)) ≤ 16 mg/ml participated in a randomized single-blind crossover study. The two treatments included 16 ounces of caffeinated and decaffeinated coffee given on two separate days. The fraction of exhaled nitric oxide (eNO) and FEV(1) were measured before and 1 h after each treatment. One hour post treatment blood was drawn for serum caffeine level and the MCT was done.

RESULTS

Fourteen subjects completed the study; there were no adverse events. No significant bronchodilation was seen between the mean FEV(1) values before and after the caffeinated treatment (3.31 ± 0.75 L and 3.36 ± 0.74 L, respectively). No significant bronchoprotection was seen between the caffeinated and decaffeinated treatment's geometric mean PC(20) values (1.35 mg/ml and 1.36 mg/ml, respectively). Mean eNO values before and after caffeinated treatment were not significantly different (31.2 ± 19.6 ppb and 31.5 ± 20.4 ppb).

CONCLUSION

The amount of caffeine in a normal dietary serving of a 16 oz cup of coffee is not enough to cause significant bronchoprotection, bronchodilation, or decrease eNO values. Registered at http://clinicaltrials.gov: NCT01057875.

Allergen inhalation challenge in smoking compared with non-smoking asthmatic subjects

BACKGROUND

Smoking asthmatics experience more severe symptoms, require more rescue medication and have more asthma-related hospitalizations than non-smoking asthmatics. However, studies in mice suggest that mainstream cigarette smoke may reduce airway inflammation and may attenuate airway hyperresponsiveness. A comparison of allergen-induced airway inflammatory responses of smoking and non-smoking atopic asthmatics has not been examined previously.

OBJECTIVES

To determine whether allergen-induced airway responses and inflammatory profiles are attenuated in smoking when compared with non-smoking mild allergic asthmatic subjects.

METHODS

Allergen inhalation challenges were performed in 13 smoking and 19 non-smoking mild allergic asthmatic subjects. The forced expired volume in 1 s (FEV(1) ) was measured up to 7 h after allergen inhalation. Methacholine airway responsiveness was measured before and at 24 h after allergen and sputum was induced before and at 7 and 24 h after allergen.

RESULTS

Both the smoking and non-smoking groups developed similar allergen-induced falls in FEV(1) during the early and late asthmatic responses and similar increases in allergen-induced airway eosinophils. The mean maximum fall in FEV(1) during the late response was 16.3 ± 4.3% in non-smokers and 12.9 ± 7.2% in smokers. The smoking asthmatics, however, did not develop allergen-induced methacholine airway hyperresponsiveness, whereas the non-smoking controls developed a 1.18 doubling dose shift in methacholine PC(20) (P < 0.05).

CONCLUSIONS AND CLINICAL RELEVANCE

Mild allergic asthmatic subjects, who were current smokers with a mean 6-year pack history, develop allergen-induced eosinophilic airway inflammation and late responses, similar in magnitude to non-smoking asthmatics, but do not develop methacholine airway hyperresponsiveness associated with the allergen-induced airway eosinophilia.

Introduction: Airway hyperresponsiveness in asthma: its measurement and clinical significance

This supplement to CHEST, titled "Airway Hyperresponsiveness in Asthma: Its Measurement and Clinical Significance," resulted from a symposium that brought together experts from Canada, the United States, and Australia to discuss the progress in the understanding of measurements of airway hyperresponsiveness. There was an additional focus on the indirect measurement of airway inflammation and its interaction with airway hyperresponsiveness, as well as the role of measuring airway inflammation in the management of asthma.

Bronchial hyperresponsiveness to histamine correlates with airway remodelling in adults with asthma

BACKGROUND

Chronic eosinophilic inflammation may promote bronchial hyperresponsiveness (BHR), which involves reversible reduction of airflow and airway remodelling such as a thickening of the reticular basement membrane (RBM) and hypertrophy and hyperplasia of airway smooth muscle (ASM). BHR to histamine (Hist) and acetylcholine (ACh) cannot differentiate airway inflammation and remodelling.

OBJECTIVE

To examine the correlations between eosinophilic inflammation or airway remodelling and BHR to Hist or ACh in adults with severe asthma.

METHODS

We examined eosinophils in the sputum of 50 adult patients with severe asthma before inhaled corticosteroid (ICS) treatment. Airway responses to ACh and Hist were measured on separate days after the first hospital visit and before bronchofiberscopy. Bronchial specimens were obtained by bronchofibrescopy for evaluation of RBM and ASM thickening after systemic corticosteroid treatment.

RESULTS

Eosinophil scores in the sputum before ICS treatment were correlated with BHR to ACh but not to Hist. Asthma duration was inversely correlated with % forced expiratory volume in 1 s, %V(50), %V(25), BHR to Hist, and ASM thickness, but not BHR to ACh or RBM. A multivariate logistic regression model showed that Long duration of asthma affected ASM thickness more than it affected %V(50). ASM thickness was inversely correlated with BHR to Hist but not to ACh.

CONCLUSION

In adult patients with severe asthma, BHR to ACh is related to the degree of eosinophilic airway inflammation, whereas BHR to Hist indicates airway remodeling, particularly ASM hypertrophy.

Asthmatics without rhinitis have more fixed airway obstruction than those with concurrent rhinitis

PURPOSE

Rhinitis and asthma usually occur together. There are increasing evidences that allergic rhinitis (AR) may influence the clinical course of asthma. The aim of this study is to evaluate clinical parameters and therapeutic response in patients with between asthma and asthma with AR.

METHODS

Four-hundred eighty-five patients with asthma and 428 asthmatics with AR, who had lesser than 50 years old and smoked less than 10 pack-years were recruited. We compared FEV1 and FEV1/FVC following bronchodilator, atopy, IgE, emphysema on HRCT, and aspirin intolerance between two groups. Also we compared physiologic fixed airway obstruction defined using FEV1/FVC and FEV1 less than 75% following anti-asthmatic drug for 1 year.

RESULTS

46.8% (428/913) asthmatics suffered from AR. There were no differences of total IgE, body mass index, PC20, sputum eosinophils and emphysema on HRCT between two groups. The age in asthmatics was higher than that in those with AR. FEV1/FVC was lower in asthmatics than in those with AR. The prevalence of atopy was higher in asthmatics with AR than in asthmatics. Aspirin intolerance was higher in asthmatics with AR than in asthmatics (42/218 vs 13/109, P=0.001). Fixed airway obstruction were more observed in asthmatics than in those with AR (39/319 vs 28/355, P=0.001) after anti-asthmatic drug for 1 year.

CONCLUSIONS

Asthmatics with AR had more atopy and aspirin intolerance than asthmatics, and asthmatics had poor response to anti-inflammatory drugs than those with concurrent rhinitis, indicating that asthmatics have more fixed airway obstruction than those with concurrent rhinitis.

Effects of budesonide and formoterol on allergen-induced airway responses, inflammation, and airway remodeling in asthma

BACKGROUND

Combining inhaled corticosteroids with long-acting beta(2)-agonists results in improved asthma symptom control and fewer asthma exacerbations compared with those seen after inhaled corticosteroids alone. However, there are limited data as to whether these beneficial effects are due to enhanced anti-inflammatory actions or whether such combination therapies affect airway remodeling in patients with asthma.

OBJECTIVE

We sought to determine the effects of inhaled budesonide/formoterol combination therapy versus inhaled budesonide alone or inhaled placebo on allergen-induced airway responses, airway inflammation, and airway remodeling.

METHODS

Fourteen asthmatic subjects with dual responses after allergen inhalation were included in this prospective, randomized, double-blind, 3-period crossover study. Outcomes included early and late asthmatic responses, changes in airway responsiveness, sputum eosinophilia measured before and after allergen challenge, numbers of airway submucosal myofibroblasts, and smooth muscle area measured before and after study treatment.

RESULTS

Allergen-induced sputum eosinophilia was significantly reduced by combination treatment to a greater extent than by budesonide alone. Allergen inhalation resulted in a significant increase in submucosal tissue myofibroblast numbers and produced a significant decrease in percentage smooth muscle area. Combination therapy, but not budesonide monotherapy, significantly attenuated these changes in myofibroblast numbers and smooth muscle area.

CONCLUSIONS

The effects on allergen-induced changes in sputum eosinophils, airway myofibroblast numbers, and smooth muscle seen with combination therapy suggest that the benefits associated with this treatment might relate to effects on airway inflammation and remodeling. The attenuation of early asthmatic responses and airway hyperresponsiveness by combination treatment was likely due to the known functional antagonistic effect of formoterol.

The impact of smoking on clinical and therapeutic effects in asthmatics

Smoking is associated with poor symptom control and impaired therapeutic responses in asthma. A total of 843 patients with asthma were recruited. The patients received treatment for 1 yr according to the severity of their asthma. We compared the forced expiratory volume in 1 sec (FEV1), the ratio of FEV1 to forced vital capaity (FVC), atopy, total IgE, emphysema on high-resolution computed tomography (HRCT), the number of near-fatal asthma attacks, and physiological fixed airway obstruction between the smoking and nonsmoking groups. The study population consisted of 159 (18.8%) current smokers, 157 (18.7%) ex-smokers, and 525 (62.5%) nonsmokers. Although the prevalence of atopy was not different between the smoking and nonsmoking groups, the total IgE was higher among the smokers than the nonsmokers. Compared with the nonsmoking group, the smokers had a lower FEV1 % predicted and forced expiratory flow between 25 and 75% of FVC. A greater prevalence of emphysema and a significantly higher number of asthmatic patients with fixed airway obstruction were detected in the smoking versus nonsmoking group. The 37.5% of asthmatic patients who were former or current smokers showed decreased pulmonary function and increased IgE, emphysema on HRCT, and fixed airway obstruction, indicating that smoking can modulate the clinical and therapeutic responses in asthma.

Provoked models of asthma: what have we learnt?

Asthma is a chronic inflammatory disease of the airways characterized by physiological abnormalities of variable airflow obstruction and airway hyperresponsiveness (AHR) to a wide variety of physical and inhaled chemical stimuli and the presence of symptoms. AHR is measured by challenging the airways with a variety of agonists and naturally occurring stimuli, which results in constriction of the airway smooth muscle, leading to airway narrowing and airflow limitation. There are two distinct mechanisms by which the airways can narrow to a constrictor stimulus and these are defined by the pathways they take to induce AHR. Direct stimuli are pharmacological agents administered exogenously (such as histamine or methacholine) that act 'directly' on specific receptors on the bronchial smooth muscle to cause constriction. The other mechanism by which the airway can narrow is via the inhalation of indirect stimuli, which include natural stimuli, such as allergen or exercise, and pharmacological agents such as adenosine monophosphate and hyper-osmotic agents (e.g. hypertonic saline or dry powder mannitol). These stimuli induce airway narrowing 'indirectly' by causing the endogenous release of mediators of bronchoconstriction from airway inflammatory cells. Provoked models of asthma have been extremely valuable in understanding the pathobiology of asthma, in aiding diagnosis, in helping to clarify the mechanisms of actions of effective drugs and in the development of new entities to treat asthma. Some provoked models are valuable clinically, particularly those that measure direct AHR, while others, particularly allergen challenge, have been used in animal models and in humans to study the mechanisms of allergen-induced airway inflammation and the associated physiological changes, as well in the development of new drugs for asthma. An emerging role for measurements of AHR is in the evaluation of the optimal treatment for patients with asthma.

Bronchoprovocation testing

Airway smooth muscles of asthmatics tend to be hyperresponsive when provoked. The exaggerated bronchial constriction can be measured by the airflow limitation seen following bronchial provocation. Measuring bronchial hyperresponsiveness by broncho provocation testing is helpful in diagnosing and optimizing therapy. While numerous agents have been used to provoke a measurable airflow limitation, standardized protocols are available for only a few. This article aims to discuss the various methods that have been reported for bronchoprovocation testing.

Bronchial hyperresponsiveness in a population of north Finland with no previous diagnosis of asthma or chronic bronchitis assessed with histamine and methacholine tests

OBJECTIVES

To assess the prevalence of bronchial hyperresponsiveness (BHR) in a population of north Finland among subjects with no previous diagnosis of asthma or chronic bronchitis by using histamine and methacholine challenges. The agreement between the methods was also evaluated.

STUDY DESIGN

An epidemiological study assessing the prevalence of BHR measured with 2 direct dosimetric challenge methods. METHODS; Seventy-nine randomly selected subjects (21-73 years) were studied; 67% had respiratory or allergic symptoms. The baseline spirometry was normal or showed mild obstruction. Bronchial challenges to methacholine and histamine were performed on each subject in a randomized order. Provocative doses inducing the decrease of FEV1 by 15% and 20% (PD15FEV1 and PD20FEV1) and dose response ratios (DDR) were calculated for both tests. RESULTS; BHR with the methacholine test (PD20FEV1 < or = 2.6 mg) was found in 20% and with the histamine test (PD15FEV1 < or = 1.6 mg) in 28% of subjects; the agreement was 80% (kappa 0.45; 95% CI 0.23-0.68). In staging the severity of BHR the methods had a good agreement (weighted kappa 0.64; CI 95% 0.46-0.82). Prevalence of BHR fulfilling the criteria of the both methods was 14%.

CONCLUSIONS

The findings suggest that the prevalence of BHR in the population of north Finland with no previous diagnosis of asthma or chronic bronchitis is at least 14%, probably around 20%, assessed by histamine and methacholine challenge methods. The methods have a good agreement to be used for classifying the severity of BHR.