Effects of increasing tidal volume and end-expiratory lung volume on induced bronchoconstriction in healthy humans.

BACKGROUND: Increasing functional residual capacity (FRC) or tidal volume (VT) reduces airway resistance and attenuates the response to bronchoconstrictor stimuli in animals and humans. What is unknown is which one of the above mechanisms is more effective in modulating airway caliber and whether their combination yields additive or synergistic effects. To address this question, we investigated the effects of increased FRC and increased VT in attenuating the bronchoconstriction induced by inhaled methacholine (MCh) in healthy humans. METHODS: Nineteen healthy volunteers were challenged with a single-dose of MCh and forced oscillation was used to measure inspiratory resistance at 5 and 19 Hz (R5 and R19), their difference (R5-19), and reactance at 5 Hz (X5) during spontaneous breathing and during imposed breathing patterns with increased FRC, or VT, or both. Importantly, in our experimental design we held the product of VT and breathing frequency (BF), i.e, minute ventilation (VE) fixed so as to better isolate the effects of changes in VT alone. RESULTS: Tripling VT from baseline FRC significantly attenuated the effects of MCh on R5, R19, R5-19 and X5. Doubling VT while halving BF had insignificant effects. Increasing FRC by either one or two VT significantly attenuated the effects of MCh on R5, R19, R5-19 and X5. Increasing both VT and FRC had additive effects on R5, R19, R5-19 and X5, but the effect of increasing FRC was more consistent than increasing VT thus suggesting larger bronchodilation. When compared at iso-volume, there were no differences among breathing patterns with the exception of when VT was three times larger than during spontaneous breathing. CONCLUSIONS: These data show that increasing FRC and VT can attenuate induced bronchoconstriction in healthy humans by additive effects that are mainly related to an increase of mean operational lung volume. We suggest that static stretching as with increasing FRC is more effective than tidal stretching at constant VE, possibly through a combination of effects on airway geometry and airway smooth muscle dynamics.

Utility and efficiency of methacholine challenge testing in evaluating pediatric asthma: unraveling the diagnostic conundrum.

OBJECTIVE: Interpretation of methacholine challenge testing (MCT) results depends on the patient's pretest probability of asthma as well as the provocative concentration (PC20); however, ordering providers rarely understand the complexity associated with its interpretation. This study investigated the clinical utility and efficiency of MCT at a tertiary center in evaluating pediatric asthma. METHODS: Retrospective chart review was done for all MCT done at a tertiary center over a six year period (2011-2017). Demographics, referring provider, referral diagnosis, current symptoms with and without exercise, and baseline spirometry were collected. Pretest probability of asthma was assigned by author (RB) who was blinded to MCT results and PC20. Post-test probability of asthma was assigned based on pretest probability, MCT result (+/-), and PC20. Three assigned asthma probability categories were "unlikely" "likely", and "very likely". RESULTS: Of 172 subjects (91 Females, age range 5-21 years), 64.9% of MCT results (n = 111)) were negative and 35.1% (n = 60)) were positive. One was inconclusive. Those who tested positive were shorter, lighter, younger and had lower forced expiratory volume in one second/forced vital capacity (FEV1/FVC) ratio than those who tested negative (p < 0.05). Subjects with exercise symptoms only were less likely to test positive (OR 0.2, CI 0.1-0.5). In a majority of subjects (91.8%; 157/171), MCT increased the certainty of presence or absence of asthma. CONCLUSIONS: In our subject population, MCT could be useful in evaluating pediatric asthma if subject's pretest probability of asthma and PC20 was taken into account. It was not as useful for subjects with exercise symptoms only.

Diagnostic value of the hypertonic saline bronchial provocation test in children with asthma using the high-power aerosol provocation system.

Objective: This study aimed to evaluate the diagnostic value of the modified hypertonic saline bronchial provocation test (HS-BPT) for children with asthma by using the high-power Aerosol Provocation System (APS).Methods: A total of 330 children suspected of having asthma and receiving HS-BPT-APS were included in this prospective survey conducted in Guangzhou, China from February 2017 to September 2018. The positive rate of HS-BPT-APS and the volume and types of adverse reactions were observed. There was also a retrospective cohort of 123 children with suspected asthma who underwent a methacholine BPT from 2015 to 2017. Using the method of nearest neighbor matching, a comparison was made of the positive rate and adverse reaction between the methacholine BPT group and HS-BPT-APS group.Results: The total positive rate of HS-BPT-APS was 43.9%. Common adverse reactions included cough, wheezing and chest tightness. There were no serious adverse reactions. Results of nearest neighbor matching showed a difference in the positive rate between the methacholine BPT group and HS-BPT-APS group (8.1% vs 18.2%, p = 0.026), but there was no statistically significant difference between the age groups in patients who received the methacholine BPT or HS-BPT-APS. There was a similar adverse reaction rate in the two groups (p = 0.609).Conclusions: HS-BPT-APS is simple, safe, and time-saving, with few adverse reactions. The positive rate of HS-BPT-APS was higher than that of methacholine BPT in children with asthma. HS-BPT-APS may be a valuable tool in the diagnosis of children with asthma, and further study is required.

Baseline spirometry parameters as predictors of airway hyperreactivity in adults with suspected asthma.

BACKGROUND: Methacholine challenge tests (MCTs) are used to diagnose airway hyperresponsiveness (AHR) in patients with suspected asthma where previous diagnostic testing has been inconclusive. The test is time consuming and usually requires referral to specialized centers. Simple methods to predict AHR could help determine which patients should be referred to MCTs, thus avoiding unnecessary testing. Here we investigated the potential use of baseline spirometry variables as surrogate markers for AHR in adults with suspected asthma. METHODS: Baseline spirometry and MCTs performed between 2013 and 2019 in a large tertiary center were retrospectively evaluated. Receiver-operating characteristic curves for the maximal expiratory flow-volume curve indices (angle ß, FEV1, FVC, FEV1/FVC, FEF50%, FEF25-75%) were constructed to assess their overall accuracy in predicting AHR and optimal cutoff values were identified. RESULTS: A total of 2983 tests were analyzed in adults aged 18-40 years. In total, 14% of all MCTs were positive (PC20 ≤ 16 mg/ml). All baseline spirometry parameters were significantly lower in the positive group (p < 0.001). FEF50% showed the best overall accuracy (AUC = 0.688) and proved to be useful as a negative predictor when applying FEF50% ≥ 110% as a cutoff level. CONCLUSIONS: This study highlights the role of FEF50% in predicting AHR in patients with suspected asthma. A value of ≥ 110% for baseline FEF50% could be used to exclude AHR and would lead to a substantial decrease in MCT referrals.

Small airway dysfunction in patients with cough variant asthma: a retrospective cohort study.

BACKGROUND: Cough variant asthma (CVA) is one of the special populations of asthma. The aim of the study was to compare small airways, the degree of bronchial hyperresponsiveness (BHR) and airway inflammatory subtypes between CVA and classic asthma (CA), and investigate the relationship between these markers to determine the accuracy as indicators of CVA. METHODS: A total of 825 asthmatic patients participated in the study and 614 were included. 614 patients underwent spirometry and a bronchial challenge with methacholine and 459 patients performed induction sputum cell test. RESULTS: The number of CVA patients showed less small airway dysfunction than those of CA patients (p < 0.005). The degree of small airways dysfunction was higher in the CA group compared with the CVA group (p < 0.001). Small airways dysfunction was severer in the eosinophilic airway inflammatory subtype compared with other subtypes (p < 0.05).The area under curve of MMEF, FEF50 and FEF75 (% predicted) was 0.615, 0.621, 0.606, respectively. 0.17mcg of PD20 and 4.7% of sputum eosinophils was the best diagnostic value for CVA with an AUC of 0.582 and 0.575 (p = 0.001 and p = 0.005, respectively). CONCLUSIONS: The eosinophilic airway inflammatory subtype may be increased small airway dysfunction. The value of small airways, BHR and induction sputum cells in CVA prediction, which reflected significant, but not enough to be clinically useful.

Current Asthma Prevalence Using Methacholine Challenge Test in Korean Children from 2010 to 2014.

BACKGROUND: Most epidemiological studies depend on the subjects' response to asthma symptom questionnaires. Questionnaire-based study for childhood asthma prevalence may overestimate the true prevalence. The aim of this study was to investigate the prevalence of "Current asthma" using the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire and methacholine challenge test in Korean children. METHODS: Our survey on allergic disease included 4,791 children (age 7-12 years) from 2010 to 2014 in Korean elementary schools. Bronchial hyperresponsiveness (BHR) was defined as provocative concentration of methacholine causing a 20% fall in forced expiratory volume in one second (FEV1) (PC20) ≤ 16 mg/mL. "Current asthma symptoms" was defined as positive response to "Wheezing, current," "Treatment, current," or "Exercise, current." "Current asthma" was defined when the subjects with "Current asthma symptoms" showed BHR on the methacholine challenge test or had less than 70% of predicted FEV1 value. RESULTS: The prevalence of "Wheezing, ever," "Wheezing, current," "Diagnosis, ever," "Treatment, current," "Exercise, current," and "Current asthma symptoms" was 19.6%, 6.9%, 10.0%, 3.3%, 3.5%, and 9.6%, respectively, in our cross-sectional study of Korean elementary school students. The prevalence of BHR in elementary school students was 14.5%. The prevalence of BHR in children with "Wheezing, ever," "Wheezing, current," "Diagnosis, ever," "Treatment, current," and "Exercise, current" was 22.3%, 30.5%, 22.4%, 28.8%, and 29.9%, respectively. BHR was 26.1% in those with "Current asthma symptoms." The prevalence of "Current asthma" was 2.7%. CONCLUSIONS: Our large-scale study provides 2.7% prevalence of current asthma in Korean elementary school children. Since approximately one third of the children who have "Current asthma symptoms" present BHR, both subjective and objective methods are required to accurately predict asthma in subjects with asthma symptoms.

Effect of nintedanib on airway inflammation in a mouse model of acute asthma.

Objective: New treatments are needed for cases of asthma that are refractory to traditional therapies. In this study, we examined the effect of oral nintedanib, an intracellular inhibitor of tyrosine kinases, on airway hyper-responsiveness (AHR) and airway smooth muscle cells, using a mouse model of experimental asthma. Methods: Asthma was experimentally induced in mice via subcutaneous injection of ovalbumin (OVA). A group of saline-injected mice served as a control group. The OVA mice were then divided into four treatment groups according to the dose of nintedanib. AHR was examined via exposure to vaporized methacholine. Airway inflammation was assessed via bronchoalveolar lavage fluid (BALF) cell counts and Th2 cytokine concentrations. Results: Baseline levels of AHR and airway inflammation were higher in OVA mice than in the control group. Treatment with nintedanib lowered AHR, BALF cell counts and BALF cytokine levels in a dose-dependent fashion. The effect of nintedanib was comparable to that of dexamethasone. In particular, treatment with nintedanib lowered the expression of transforming growth factor-ß1 and inhibited the expression and phosphorylation of platelet-derived growth factor receptor-ß, vascular endothelial growth factor receptor 1 (VEGFR1), VEGFR2, fibroblast growth factor receptor 2 (FGFR2), FGFR3, and extracellular signal-regulated kinase. Conclusions: Nintedanib lowered AHR and the expression of factors associated with airway inflammation and remodeling in a mouse model of experimental asthma. Our results suggest that nintedanib may be useful in the treatment of asthma.

Dynamic airway constriction in rats: heterogeneity and response to deep inspiration.

Airway narrowing due to hyperresponsiveness severely limits gas exchange in patients with asthma. Imaging studies in humans and animals have shown that bronchoconstriction causes patchy patterns of ventilation defects throughout the lungs, and several computational models have predicted that these regions are due to constriction of smaller airways. However, these imaging approaches are often limited in their ability to capture dynamic changes in small airways, and the patterns of constriction are heterogeneous. To directly investigate regional variations in airway narrowing and the response to deep inspirations (DIs), we utilized tantalum dust and microfocal X-ray imaging of rat lungs to obtain dynamic images of airways in an intact animal model. Airway resistance was simultaneously measured using the flexiVent system. Custom-developed software was used to track changes in airway diameters up to generation 19 (~0.3-3 mm). Changes in diameter during bronchoconstriction were then measured in response to methacholine (MCh) challenge. In contrast with the model predictions, we observed significantly greater percent constriction in larger airways in response to MCh challenge. Although there was a dose-dependent increase in total respiratory resistance with MCh, the percent change in airway diameters was similar for increasing doses. A single DI following MCh caused a significant reduction in resistance but did not cause a significant increase in airway diameters. Multiple DIs did, however, cause significant increases in airway diameters. These measurements allowed us to directly quantify dynamic changes in airways during bronchoconstriction and demonstrated greater constriction in larger airways.

Comparison of multi-wall carbon nanotube and nitrogen-doped multi-wall carbon nanotube effects on lung function and airway reactivity in rats.

Incorporation of multi-wall carbon nanotubes (MWCNT) into materials has raised concerns about their potential hazards to manufacturing workers. In animal models, airway inflammation and lung fibrosis follow aspiration, instillation, and inhalation exposures to MWCNT. However, the effects of MWCNT on pulmonary function, airway reactivity and airway epithelium function following inhalation exposure has not been studied. We investigated whether inhaled MWCNT affects lung resistance (RL) and dynamic compliance (Cdyn), reactivity to inhaled methacholine (MCh), epithelial regulation of airway reactivity to MCh in vitro, and airway epithelial ion transport. Male rats were exposed by whole body inhalation for 6 h to air or aerosolized MWCNT (0.5, 1 or 5 mg/m3) for one or nine days. Eighteen h after 1 d exposure to 5 mg/m3 MWCNT, basal RL was increased and basal Cdyn was decreased; changes did not persist for 7 d. Reactivity to MCh (RL) was increased and Cdyn responses were decreased at 18 h, but not 7 d after exposure to 1 and 5 mg/m3 MWCNT. The effects of i.t.-instilled MWCNT and nitrogen-doped MWCNT (N-MWCNT) on pulmonary function and reactivity to MCh at doses comparable to deposition after inhalation of 5 mg/m3 at 1 d and 0.5, 1, and 5 mg/m3 MWCNT 9 d-exposures were compared. Both nanoparticles increased airway reactivity (RL); N-MWCNT did not affect Cdyn responses. Lung function and airway reactivity are altered following a single MWCNT inhalation and generally subside over time. Given i.t., MWCNT's and N-MWCNT's effects were comparable, but N-MWCNT evoke smaller changes in Cdyn responses.

Older age and obesity are associated with increased airway closure in response to methacholine in patients with asthma.

BACKGROUND AND OBJECTIVE: The reduction of forced expiratory volume in 1 s (FEV1 ) in response to methacholine challenge in asthma may reflect two components: airway narrowing, assessed by the change in FEV1 /forced vital capacity (FVC), and airway closure, assessed by the change in FVC. The purpose of this study was to determine the degree and determinants of airway closure in response to methacholine in a large group of asthmatic patients participating in studies conducted by the American Lung Association-Airways Clinical Research Centers (ALA-ACRC). METHODS: We used the methacholine challenge data from participants in five studies of the ALA-ACRC to determine the closing index, defined as the contribution of airway closure to the decrease in FEV1 , and calculated as %ΔFVC/%ΔFEV1 . RESULTS: There were a total of 936 participants with asthma, among whom the median closing index was 0.67 relative to that of a published healthy population of 0.54. A higher closing index was associated with increased age (10-year increments) (0.04, 95% CI = 0.02, 0.05, P < 0.005) and obesity (0.07, 95% CI = 0.03, 0.10, P < 0.001). There was no association between the closing index and asthma control. CONCLUSION: Our findings confirm that airway closure in response to methacholine occurs in a large, diverse population of asthmatic participants, and that increased airway closure is associated with older age and obesity. These findings suggest that therapies targeting airway closure may be important in patients with a high closing index.

Leukotriene E4 induces airflow obstruction and mast cell activation through the cysteinyl leukotriene type 1 receptor.

BACKGROUND: Leukotriene (LT) E4 is the final active metabolite among the cysteinyl leukotrienes (CysLTs). Animal studies have identified a distinct LTE4 receptor, suggesting that current cysteinyl leukotriene type 1 (CysLT1) receptor antagonists can provide incomplete inhibition of CysLT responses. OBJECTIVE: We tested this hypothesis by assessing the influence of the CysLT1 antagonist montelukast on responses induced by means of inhalation of LTE4 in asthmatic patients. METHODS: Fourteen patients with mild intermittent asthma and 2 patients with aspirin-exacerbated respiratory disease received 20 mg of montelukast twice daily and placebo for 5 to 7 days in a randomized, double-blind, crossover study (NCT01841164). The PD20 value was determined at the end of each treatment period based on an increasing dose challenge. Measurements included lipid mediators in urine and sputum cells 4 hours after LTE4 challenge. RESULTS: Montelukast completely blocked LTE4-induced bronchoconstriction. Despite tolerating an at least 10 times higher dose of LTE4 after montelukast, there was no difference in the percentage of eosinophils in sputum. Urinary excretion of all major lipid mediators increased after LTE4 inhalation. Montelukast blocked release of the mast cell product prostaglandin (PG) D2, as well as release of PGF2α and thromboxane (Tx) A2, but not increased excretion of PGE2 and its metabolites or isoprostanes. CONCLUSION: LTE4 induces airflow obstruction and mast cell activation through the CysLT1 receptor.

Bacterial respiratory tract inflammation in neonatal rat model is attenuated by benzofuran through inhibition of GATA3.

The current study was aimed to investigate the effect of benzofuran on asthma neonatal rat model. Twenty-five neonatal rats were assigned into five groups; Normal control, untreated, 1 mg/kg, 8 mg/kg and 10 mg/kg treatment groups. Methacholine was administered orally to the rats of untreated and treatment groups. Animals in the normal control group were given PBS as a vehicle. FlexiVent system employing a computer-controlled mouse ventilator along with respiratory mechanics was used for the analysis of airway resistance in the rats. Cytokine level and IFN-γ in the rat serum samples was performed by ELISA in accordance with the instructions of manufacturer. Methacholine administration into the rats caused a marked increase in lung airway resistance. However, treatment with 8 and 10 mg/kg doses of benzofuran led to marked decrease in the airway resistance. Benzofuran treatment prevented accumulation of macrophages and inflammatory cells in the lung airways. Inhibition of inflammation in methacholine administered rats by benzofuran was also confirmed by hematoxylin & eosin-staining. Examination of the rat serum showed significantly higher level of Th2 cytokines (IL-4, -5 and -13) in the untreated rats. However, treatment of methacholine administered rats with benzofuran significantly inhibited Th2 cytokine expression. The level of IFN-γ was increased by benzofuran treatment in methacholine administered rats. In methacholine administered rats the level of IgE was markedly higher however treatment of asthma rats with benzofuran inhibited up-regulation of IgE significantly. The expression of T-bet is decreased and that of GATA-3 is increased by methacholine administration in the rat lungs. Benzofuran treatment of methacholine administered rats prevented reduction in T-bet and up-regulation of GATA-3 expression in the rat lungs. The effect of benzofuran was significant at the doses of 8 and 10 mg/kg and non-significant at 1 mg/kg. These finding suggest that benzofuran inhibits expression of dominant T-helper 2 cytokines through targeting GATA-binding protein 3 transcription factor. Thus benzofuran can be of therapeutic importance for the treatment of asthma.

Realising the potential of various inhaled airway challenge agents through improved delivery to the lungs.

Inhaled airway challenges provoke bronchoconstriction in susceptible subjects and are a pivotal tool in the diagnosis and monitoring of obstructive lung diseases, both in the clinic and in the development of new respiratory medicines. This article reviews the main challenge agents that are in use today (methacholine, mannitol, adenosine, allergens, endotoxin) and emphasises the importance of controlling how these agents are administered. There is a danger that the optimal value of these challenge agents may not be realised due to suboptimal inhaled delivery; thus considerations for effective and reproducible challenge delivery are provided. This article seeks to increase awareness of the importance of precise delivery of inhaled agents used to challenge the airways for diagnosis and research, and is intended as a stepping stone towards much-needed standardisation and harmonisation in the administration of inhaled airway challenge agents.

Association of methacholine challenge test with diagnosis of chronic lung allograft dysfunction in lung transplant patients.

BACKGROUND: Chronic lung allograft dysfunction (CLAD) is a complication of lung transplantation. We sought to determine whether bronchial hyperresponsiveness detected by the methacholine challenge test (MCT) at 3 months after lung transplant (LT) predicts the development of CLAD. METHODS: We performed a retrospective cohort study of 140 LT patients between 1/2008 and 6/2014 who underwent MCT at 3 months after LT. Pearson's chi-squared test and Kruskal-Wallis test were used to compare categorical and continuous variables, respectively. Cox proportional hazards modeling was used to evaluate the association between CLAD and MCT. RESULTS: Methacholine challenge test+ was associated with the development of overall CLAD (adjusted hazards ratio [aHR]: 3.47; 95% confidence interval [95% CI]: 1.71, 7.03; P = 0.001) and CLAD within 3 years (aHR: 4.98; 95%CI: 1.84, 13.48; P = 0.002). Subgroup analysis showed that MCT (+) is associated with overall CLAD in single lung transplant (SLT) (aHR: 8.18; 95% CI: 2.22, 30.09; P = 0.002), double lung transplant (DLT) (aHR: 3.27; 95% CI: 1.22, 8.78; P = 0.02) and CLAD within 3 years in DLT patients (aHR: 6.76; 95% CI: 1.71, 26.74; P = 0.01). CONCLUSION: Methacholine challenge test+ at 3 months after LT is associated with the development of overall CLAD. Positive MCT could predict the development of early CLAD within 3 years in DLT patients.

Changes in the breath sound spectrum during methacholine inhalation in children with asthma.

BACKGROUND AND OBJECTIVE: An effort-independent breath sound analysis is expected to be a safe and simple method for clinical assessment of changes in airway function. The effects of bronchoconstriction and bronchodilation on novel breath sound parameters in asthmatic children were investigated. METHODS: The study population included 49 children with atopic asthma (male = 33; mean age: 10.2 years). We evaluated breath sound parameters of the highest frequency of the power spectrum (HFp), frequency limiting 50% and 99% of the power spectrum (F50 and F99 ) and roll-off from 600 Hz to the HFp (Slope). We also assessed new parameters obtained using the ratios of sound spectrum parameters (spectrum curve indices), such as the ratio of the third and fourth power area to the total power area (P3 /PT and P4 /PT ), the ratio of the third and fourth areas to the total area under the curve (A3 /AT and B4 /AT ) and the ratio of power and frequency at 75% of HFp and 50% of HFp (RPF75 and RPF50 ). This was measured before and after methacholine inhalation challenge and after ß2 agonist inhalation. RESULTS: The parameters, F50 and F99 , showed no changes after methacholine inhalation. Conversely, the A3 /AT (12.5-10.0%, P < 0.001), B4 /AT (7.6-5.5%, P < 0.001), RPF75 (6.7-4.0 dBm/Hz, P < 0.001) and RPF50 (5.8-4.3 dBm/Hz, P < 0.001) were significantly decreased. These values returned to the original level after ß2 agonist inhalation. CONCLUSION: Spectrum curve indices indicate bronchoconstriction and bronchodilation. These parameters may play a role in the assessment of airway narrowing in asthmatic children.

Measurement of tidal breathing flows in infants using impedance pneumography.

Tidal breathing flow volume (TBFV) profiles have been used to characterise altered lung function. Impedance pneumography (IP) is a novel option for assessing TBFV curves noninvasively. The aim of this study was to extend the application of IP for infants and to estimate the agreement between IP and direct pneumotachograph (PNT) measurements in assessing tidal airflow and flow-derived indices.Tidal flow profiles were recorded for 1 min simultaneously with PNT and uncalibrated IP at baseline in 44 symptomatic infants, and after methacholine-induced bronchoconstriction in a subgroup (n=20).The agreement expressed as the mean deviation from linearity ranged between 3.9 and 4.3% of tidal peak inspiratory flow, but was associated with specific airway conductance (p=0.002) and maximal flow at functional residual capacity (V'maxFRC) (p=0.004) at baseline. Acute bronchoconstriction induced by methacholine did not significantly affect the agreement of IP with PNT. TBFV indices derived from IP were slightly underestimated compared to PNT, but were equally well repeatable and associated with baseline V'maxFRC (p=0.012 and p=0.013, respectively).TBFV profiles were consistent between IP and PNT in most infants, but the agreement was affected by reduced lung function. TBFV parameters were not interchangeable between IP and PNT, but had a similar association with lung function in infants.

The effect of glycopyrronium and indacaterol, as monotherapy and in combination, on the methacholine dose-response curve of mild asthmatics: a randomized three-way crossover study.

BACKGROUND: Methacholine dose-response curves illustrate pharmacologic bronchoprotection against methacholine-induced airway hyperresponsiveness and can be used to quantitate changes in airway sensitivity (position), reactivity (slope), and maximal responsiveness following drug administration. Our objective was to determine the influence of single-dose glycopyrronium (long-acting muscarinic antagonist) and indacaterol (ultra-long acting ß2 agonist), as monotherapy and in combination, on the methacholine dose-response curve of mild asthmatics and to compare these findings with a non-asthmatic control curve. METHODS: This was a randomized, double blind, double dummy, three-way crossover study. For asthmatic participants (n = 14), each treatment arm included a baseline methacholine challenge, drug administration, and repeat methacholine challenges at 1, 24, and 48 h. Non-asthmatic control participants (n = 15) underwent a single methacholine challenge and did not receive any study treatment. Methacholine dose-response curves were graphed as the percent fall in forced expiratory volume in 1 s (FEV1) for each methacholine concentration administered. Best-fit curves were then generated. Differences in airway reactivity were calculated through linear regression. Changes in airway sensitivity were assessed as the shift in the provocative concentration of methacholine causing a 20% fall in FEV1. RESULTS: Compared to baseline, all treatments significantly reduced airway sensitivity to methacholine at 1 h post-dose (indacaterol ~1.5 doubling concentrations; glycopyrronium ~5 doubling concentrations; combination ~5 doubling concentrations). Bronchoprotection at 24 and 48 h remained significant with glycopyrronium and combination therapy only. Airway reactivity was not influenced by indacaterol whereas glycopyrronium significantly reduced airway reactivity at all time-points (p = 0.003-0.027). The combination significantly decreased slope at 1 (p = 0.021) and 24 (p = 0.039) hours only. The non-asthmatic control and 1-h glycopyrronium curves are nearly identical. Only the non-asthmatic control and 1-h post-combination therapy curves appeared to generate a true response plateau (three data points within 5%), which occurred at a 14% fall in FEV1. CONCLUSIONS: Methacholine dose-response curves differentiate the bronchoprotective mechanisms triggered by different classes of asthma medications. Assessment of bronchoprotection using methacholine dose-response curves may be useful during clinical development of respiratory medications when performing superiority, equivalence, or non-inferiority trials. TRIAL REGISTRATION: clinicaltrials.gov ( NCT02953041 ). Retrospectively registered on October 24th 2016.

Methacholine challenge tests to demonstrate therapeutic equivalence of terbutaline sulfate via different Turbuhaler® devices in patients with mild to moderate asthma: Appraisal of a four-way crossover design.

BACKGROUND/OBJECTIVE: To demonstrate therapeutic equivalence of terbutaline via two different Turbuhaler® devices by evaluating its protective effect against methacholine-induced bronchoconstriction in stable asthma. METHODS: In this double-blind, double-dummy, multicentre, single-dose, 4-way crossover study, patients with stable mild-to-moderate asthma (FEV1 ≥80% predicted) were randomised to 0.5 or 1.5 mg terbutaline via either Turbuhaler® M2 or Turbuhaler® M3 followed by a methacholine challenge test. The primary outcome variable was the concentration of methacholine causing a 20% drop in FEV1 (PC20). Patients had a PC20 methacholine <8 mg/mL that was reproducible after 2 weeks, and a stable baseline FEV1 at all visits (90-110% of enrolment value). RESULTS: 60 patients (mean age 31.1 years [range:18-64]; mean FEV1 92.1% predicted normal [78.4-120.6%]) were randomised to treatment; all completed the study. There was a clear dose-response for both devices. The within-device ratios (1.5 mg:0.5 mg) were 1.79 and 1.87 for Turbuhaler® M3 and M2, respectively (both p < 0.001). The between-device ratios (M3:M2) were 0.92 (95% CI: 0.75-1.13) for 0.5 mg and 0.88 (95% CI 0.72-1.08) for 1.5 mg. Both confidence intervals lie inside the interval 0.67-1.50, which was the pre-specified condition for equivalent effect. CONCLUSIONS: Bronchoprotection using a standardised methacholine challenge model proved to be an effective design to elucidate therapeutic equivalence between devices in patients with mild-to-moderate asthma. The findings indicate that patients may switch from one type of Turbuhaler® to the other without adjustment of therapy. Moreover, they show the robustness and utility of this study design and its suitability for investigating therapeutic equivalence. EUDRACT NUMBER: 2014-001457-16. CLINICALTRIALS. GOV IDENTIFIER: NCT02322788.

Comparison of diagnostic validity of mannitol and methacholine challenges and relationship to clinical status and airway inflammation in steroid-naïve asthmatic patients.

OBJECTIVES: The purpose of this study was to demonstrate and compare the diagnostic validity of two bronchial challenges and to investigate their correlation with patient clinical status, atopy and inflammation markers. METHODS: Eighty-eight patients, 47 women and 41 men, mean age 38.56 ± 16.73 years who presented with asthma related symptoms and were not on any anti-asthma medication, were challenged with mannitol and methacholine on separate days. Medical history regarding asthmatic symptoms, physical examination, skin prick tests and FeNO levels were also assessed. The clinical diagnosis of asthma was based on bronchodilator reversibility test. RESULTS: Sixty-seven patients were diagnosed with asthma and 21 without asthma. Both methacholine (P < 0.014) and mannitol (P < 0.000) challenges were significant in diagnosing asthma. The positive/negative predictive value was 93.33%/41.86% for methacholine, 97.72%/45.45% for mannitol and 97.05%/45.45%. for both methods assessed together. Worthy of note that 22% of asthmatics had both tests negative. There was a negative correlation between PC20 of methacholine and the FeNO level P < 0.001, and positive with the PD15 of mannitol P < 0.001 and the pre-test FEV1% pred P < 0.005, whereas PD15 of mannitol was negatively correlated with the FeNO level P < 0.001. Furthermore, dyspnea was the only asthmatic symptom associated with FeNO level P < 0.035 and the positivity of mannitol P < 0.014 and methacholine P < 0.04. CONCLUSIONS: Both challenge tests were equivalent in diagnosing asthma. Nevertheless, specificity appeared to be slightly higher in mannitol challenge.

Diagnostic accuracy of methacholine challenge tests assessing airway hyperreactivity in asthmatic patients - a multifunctional approach.

BACKGROUND: There are few studies comparing diagnostic accuracy of different lung function parameters evaluating dose-response characteristics of methacholine (MCH) challenge tests (MCT) as quantitative outcome of airway hyperreactivity (AHR) in asthmatic patients. The aim of this retrospectively analysis of our database (Clinic Barmelweid, Switzerland) was, to assess diagnostic accuracy of several lung function parameters quantitating AHR by dose-response characteristics. METHODS: Changes in effective specific airway conductance (sGeff) as estimate of the degree of bronchial obstruction were compared with concomitantly measured forced expiratory volume in 1 s (FEV1) and forced expiratory flows at 50% forced vital capacity (FEF50). According to the GINA Guidelines the patients (n = 484) were classified into asthmatic patients (n = 337) and non-asthmatic subjects (n = 147). Whole-body plethysmography (CareFusion, Würzburg, Germany) was performed using ATS-ERS criteria, and for the MCTs a standardised computer controlled protocol with 3 consecutive cumulative provocation doses (PD1: 0.2 mg; PD2: 1.0 mg; PD3: 2.2 mg) was used. Break off criterion for the MCTs were when a decrease in FEV1 of 20% was reached or respiratory symptoms occurred. RESULTS: In the assessment of AHR, whole-body plethysmography offers in addition to spirometry indices of airways conductance and thoracic lung volumes, which are incorporated in the parameter sGeff, derived from spontaneous tidal breathing. The cumulative percent dose-responses at each provocation step were at the 1st level step (0.2 mg MCH) 3.7 times, at the 2nd level step (1 mg MCH) 2.4 times, and at the 3rd level step (2.2 mg MCH) 2.0 times more pronounced for sGeff, compared to FEV1. A much better diagnostic odds ratio of sGeff (7.855) over FEV1 (6.893) and FEF50 (4.001) could be found. Moreover, the so-called dysanapsis, and changes of end-expiratory lung volume were found to be important determinants of AHR. CONCLUSIONS: Applying plethysmographic tidal breathing analysis in addition to spirometry in MCTs provides relevant advantages. The absence of deep and maximal inhalations and forced expiratory manoeuvres improve the subject's cooperation and coordination, and provide sensitive and differentiated test results, improving diagnostic accuracy. Moreover, by the combined assessment, pulmonary hyperinflation and dysanapsis can be respected in the differentiation between "asthmatics" and "non-asthmatics".