Inhibition of mast cell PGD2 release protects against mannitol-induced airway narrowing

Defining the contractile prostanoid component in hyperosmolar-induced bronchoconstriction in human small airways

Exercise-induced bronchoconstriction (EIB) is thought to be triggered by increased osmolarity at the airway epithelium. The aim of this study was to define the contractile prostanoid component of EIB, using an ex vivo model where intact segments of bronchi (inner diameter 0.5-2 mm) isolated from human lung tissue and subjected to mannitol. Exposure of bronchial segments to hyperosmolar mannitol evoked a contraction (64.3 ± 3.5 %) which could be prevented either by elimination of mast cells (15.8 ± 4.3 %) or a combination of cysteinyl leukotriene (cysLT1), histamine (H1) and thromboxane (TP) receptor antagonists (11.2 ± 2.3 %). Likewise, when antagonism of TP receptor was exchanged for inhibition of either cyclooxygenase-1 (8 ± 2.5 %), hematopoietic prostaglandin (PG)D synthase (20.7 ± 5.6 %), TXA synthase (14.8 ± 4.9 %), or the combination of the latter two (12.2 ± 4.6 %), the mannitol-induced contraction was prevented, suggesting that the TP-mediated component is induced by PGD2 and TXA2 generated by COX-1 and their respective synthases.

Diagnosis and management of allergy and respiratory disorders in sport: An EAACI task force position paper

Allergy and respiratory disorders are common in young athletic individuals. In the context of elite sport, it is essential to secure an accurate diagnosis in order to optimize health and performance. It is also important, however, to consider the potential impact or consequences of these disorders, in recreationally active individuals engaging in structured exercise and/or physical activity to maintain health and well-being across the lifespan. This EAACI Task Force was therefore established, to develop an up-to-date, research-informed position paper, detailing the optimal approach to the diagnosis and management of common exercise-related allergic and respiratory conditions. The recommendations are informed by a multidisciplinary panel of experts including allergists, pulmonologists, physiologists and sports physicians. The report is structured as a concise, practically focussed document, incorporating diagnostic and treatment algorithms, to provide a source of reference to aid clinical decision-making. Throughout, we signpost relevant learning resources to consolidate knowledge and understanding and conclude by highlighting future research priorities and unmet needs.

Management of Exercise-Induced Bronchoconstriction in Athletes

Exercise-induced bronchoconstriction (EIB) is a phenomenon observed in asthma but is also seen in healthy individuals and frequently in athletes. High prevalence rates are observed in athletes engaged in endurance sports, winter sports, and swimming. The pathophysiology of EIB is thought to be related to hyperventilation, cold air, and epithelial damage caused by chlorine and fine particles in inspired air. Several diagnostic procedures can be used; however, the diagnosis of EIB based on self-reported symptoms is not reliable and requires an objective examination. The hyperosmolar inhalation test and eucapnic voluntary hyperpnea test, which involve indirect stimulation of the airway, are useful for the diagnosis of EIB. A short-acting β-agonist is the first choice for prevention of EIB, and an inhaled corticosteroid is essential for patients with asthma. Furthermore, treatment should accommodate antidoping requirements in elite athletes. Tailoring of the therapeutic strategy to the individual case and the prognosis after cessation of athletic activity are issues that should be clarified in the future.

Bronchial Provocation Testing for the Identification of Exercise-Induced Bronchoconstriction

Exercise-induced bronchoconstriction (EIB) occurs in patients with asthma, children, and otherwise healthy athletes. Poor diagnostic accuracy of respiratory symptoms during exercise requires objective assessment of EIB. The standardized tests currently available are based on the assumption that the provoking stimulus to EIB is dehydration of the airway surface fluid due to conditioning large volumes of inhaled air. "Indirect" bronchial provocation tests that use stimuli to cause endogenous release of bronchoconstricting mediators from airway inflammatory cells include dry air hyperpnea (eg, exercise and eucapnic voluntary hyperpnea) and osmotic aerosols (eg, inhaled mannitol). The airway response to different indirect tests is generally similar in patients with asthma and healthy athletes with EIB. Furthermore, the airway sensitivity to these tests is modified by the same pharmacotherapy used to treat asthma. In contrast, pharmacological agents such as methacholine, given by inhalation, act directly on smooth muscle to cause contraction. These "direct" tests have been used traditionally to identify airway hyperresponsiveness in clinical asthma but are less useful to diagnose EIB. The mechanistic differences between indirect and direct tests have helped to elucidate the events leading to airway narrowing in patients with asthma and elite athletes, while improving the clinical utility of these tests to diagnose and manage EIB.

Asthma and Lung Mechanics

This article will discuss in detail the pathophysiology of asthma from the point of view of lung mechanics. In particular, we will explain how asthma is more than just airflow limitation resulting from airway narrowing but in fact involves multiple consequences of airway narrowing, including ventilation heterogeneity, airway closure, and airway hyperresponsiveness. In addition, the relationship between the airway and surrounding lung parenchyma is thought to be critically important in asthma, especially as related to the response to deep inspiration. Furthermore, dynamic changes in lung mechanics over time may yield important information about asthma stability, as well as potentially provide a window into future disease control. All of these features of mechanical properties of the lung in asthma will be explained by providing evidence from multiple investigative methods, including not only traditional pulmonary function testing but also more sophisticated techniques such as forced oscillation, multiple breath nitrogen washout, and different imaging modalities. Throughout the article, we will link the lung mechanical features of asthma to clinical manifestations of asthma symptoms, severity, and control. © 2020 American Physiological Society. Compr Physiol 10:975-1007, 2020.

Airway hyperresponsiveness to mannitol improves in both type 2 high and type 2 low asthma after specialist management

OBJECTIVES

Type 2 low (T2-low) asthma is reported to respond less to anti-inflammatory treatment compared with Type 2 high (T2-high) asthma. Airway hyperresponsiveness (AHR) to mannitol, a marker of airway mast cell activation, may be indicative of response to treatment in patients with T2-low disease. We investigated whether AHR to mannitol improves in patients with T2-low asthma after specialist management.

METHODS

Patients with asthma or suspected asthma, referred to our specialist outpatient clinic, were enrolled consecutively and assessed with FeNO, asthma control, blood eosinophils, mannitol and methacholine tests and induced sputum. T2-low asthma was defined in patients with FeNO < 25ppb and sputum eosinophils < 3% and blood eosinophils < 300µl^-1 at inclusion. Patients with asthma and AHR to mannitol (PD15 ≤ 635 mg) were followed and reassessed after 12 months of specialist management.

RESULTS

Thirty-two patients (Females: 56%, age: 22 years (15-59)) were followed. Fourteen (44%) with T2-high and 18 (56%) with T2-low asthma. Baseline AHR to mannitol was comparable: G_mean PD15: 150 mg (95% CI 61-368) and 214 mg (95% CI 106-432) for T2-high and T2-low asthma respectively (P = 0.51). Both groups improved equally: G_mean PD15: 488 mg (95% CI 311-767) and 507 mg (95% CI 345-746); corresponding to a doubling-dose of: 3.00 (95% CI 1.58-5.74, P = 0.003) and 2.28 (95% CI 1.47-3.53, P = 0.001) respectively. There were no concomitant improvements in AHR to methacholine.

CONCLUSION

Patients with asthma and AHR to mannitol improve similarly in responsiveness to mannitol after 12 months of specialist management regardless of Type 2 inflammatory biomarker levels. Mechanisms driving AHR in T2-low asthma need to be further elucidated.

Mast Cells in Cardiac Fibrosis: New Insights Suggest Opportunities for Intervention

Mast cells (MC) are innate immune cells present in virtually all body tissues with key roles in allergic disease and host defense. MCs recognize damage-associated molecular patterns (DAMPs) through expression of multiple receptors including Toll-like receptors and the IL-33 receptor ST2. MCs can be activated to degranulate and release pre-formed mediators, to synthesize and secrete cytokines and chemokines without degranulation, and/or to produce lipid mediators. MC numbers are generally increased at sites of fibrosis. They are potent, resident, effector cells producing mediators that regulate the fibrotic process. The nature of the secretory products produced by MCs depend on micro-environmental signals and can be both pro- and anti-fibrotic. MCs have been repeatedly implicated in the pathogenesis of cardiac fibrosis and in angiogenic responses in hypoxic tissues, but these findings are controversial. Several rodent studies have indicated a protective role for MCs. MC-deficient mice have been reported to have poorer outcomes after coronary artery ligation and increased cardiac function upon MC reconstitution. In contrast, MCs have also been implicated as key drivers of fibrosis. MC stabilization during a hypertensive rat model and an atrial fibrillation mouse model rescued associated fibrosis. Discrepancies in the literature could be related to problems with mouse models of MC deficiency. To further complicate the issue, mice generally have a much lower density of MCs in their cardiac tissue than humans, and as such comparing MC deficient and MC containing mouse models is not necessarily reflective of the role of MCs in human disease. In this review, we will evaluate the literature regarding the role of MCs in cardiac fibrosis with an emphasis on what is known about MC biology, in this context. MCs have been well-studied in allergic disease and multiple pharmacological tools are available to regulate their function. We will identify potential opportunities to manipulate human MC function and the impact of their mediators with a view to preventing or reducing harmful fibrosis. Important therapeutic opportunities could arise from increased understanding of the impact of such potent, resident immune cells, with the ability to profoundly alter long term fibrotic processes.

Mechanisms and Biomarkers of Exercise-Induced Bronchoconstriction

Exercise is a common trigger of bronchoconstriction. In recent years, there has been increased understanding of the pathophysiology of exercise-induced bronchoconstriction. Although evaporative water loss and thermal changes have been recognized stimuli for exercise-induced bronchoconstriction, accumulating evidence points toward a pivotal role for the airway epithelium in orchestrating the inflammatory response linked to exercise-induced bronchoconstriction. Overproduction of inflammatory mediators, underproduction of protective lipid mediators, and infiltration of the airways with eosinophils and mast cells are all established contributors to exercise-induced bronchoconstriction. Sensory nerve activation and release of neuropeptides maybe important in exercise-induced bronchoconstriction, but further research is warranted.

ERS technical standard on bronchial challenge testing: pathophysiology and methodology of indirect airway challenge testing

Recently, this international task force reported the general considerations for bronchial challenge testing and the performance of the methacholine challenge test, a "direct" airway challenge test. Here, the task force provides an updated description of the pathophysiology and the methods to conduct indirect challenge tests. Because indirect challenge tests trigger airway narrowing through the activation of endogenous pathways that are involved in asthma, indirect challenge tests tend to be specific for asthma and reveal much about the biology of asthma, but may be less sensitive than direct tests for the detection of airway hyperresponsiveness. We provide recommendations for the conduct and interpretation of hyperpnoea challenge tests such as dry air exercise challenge and eucapnic voluntary hyperpnoea that provide a single strong stimulus for airway narrowing. This technical standard expands the recommendations to additional indirect tests such as hypertonic saline, mannitol and adenosine challenge that are incremental tests, but still retain characteristics of other indirect challenges. Assessment of airway hyperresponsiveness, with direct and indirect tests, are valuable tools to understand and to monitor airway function and to characterise the underlying asthma phenotype to guide therapy. The tests should be interpreted within the context of the clinical features of asthma.

Exhaled nitric oxide and mannitol test to predict exercise-induced bronchoconstriction

BACKGROUND

Exercise-induced bronchoconstriction (EIB) is diagnosed via exercise challenge on a treadmill, but such testing requires complex equipment and sufficient health-care resources. The fraction of exhaled nitric oxide (FeNO) test and mannitol bronchial provocation test (BPT) may serve as a surrogate for exercise testing.

METHODS

We compared the diagnostic utilities of the FeNO test and mannitol BPT in predicting EIB in asthmatic children. We retrospectively analyzed data from 60 asthmatic children aged 6-16 years. We compared the exercise BPT results, FeNO levels, and mannitol BPT data.

RESULTS

All subjects were divided into exercise-positive (n = 41) or -negative (n = 19) BPT groups. Of the 41 exercise-positive patients, 32 were mannitol BPT positive and nine were mannitol BPT negative. Of the 19 exercise-negative patients, nine and 10, respectively, were mannitol BPT positive and BPT negative. The maximum % forced expiratory volume in 1 s (FEV₁ ) decrease after exercise was positively correlated with FeNO (r = 0.556, P < 0.001), and with mannitol response-dose ratio (RDR; r = 0.416, P = 0.001). The receiver operating characteristic (ROC) curve for FeNO to discriminate between asthmatic subjects with and without EIB had an area under the curve (AUC) of 0.771 (95%CI: 0.643-0.870). The discriminatory ROC curve for mannitol RDR had an AUC of 0.763 (95%CI: 0.633-0.864). The AUC of FeNO and mannitol RDR did not differ significantly.

CONCLUSIONS

EIB significantly correlated with both FeNO and mannitol BPT data. Given that both methods similarly predicted EIB in asthmatic children, the simpler and safer FeNO test alone may be a clinically useful diagnostic tool.

Repurposing drugs as inhaled therapies in asthma

For the first 40 years of the 20th century treatment for asthma occurred in response to an asthma attack. The treatments were given by injection or orally and included the adrenergic agonists adrenalin/epinephrine and ephedrine and a phosphodiesterase inhibitor theophylline. Epinephrine became available as an aerosol in 1930. After 1945, isoprenaline, a non-selective beta agonist, became available for oral use but it was most widely used by inhalation. Isoprenaline was short-acting with unwanted cardiac effects. More selective beta agonists, with a longer duration of action and fewer side-effects became available, including orciprenaline in 1967, salbutamol in 1969 and terbutaline in 1970. The inhaled steroid beclomethasone was available by 1972 and budesonide by 1982. Spirometry alone and in response to exercise was used to assess efficacy and duration of action of these drugs for the acute benefits of beta₂ agonists and the chronic benefits of corticosteroids. Early studies comparing oral and aerosol beta₂ agonists found equivalence in bronchodilator effect but the aerosol treatment was superior in preventing exercise-induced bronchoconstriction. Inhaled drugs are now widely used including the long-acting beta₂ agonists, salmeterol and formoterol, and the corticosteroids, fluticasone, ciclesonide, mometasone and triamcinolone, that act locally and have low systemic bio-availability. Repurposing drugs as inhaled therapies permitted direct delivery of low doses of drug to the site of action reducing the incidence of unwanted side-effects and permitting the prophylactic treatment of asthma.

Repurposing excipients as active inhalation agents: The mannitol story

The story of how we came to use inhaled mannitol to diagnose asthma and to treat cystic fibrosis began when we were looking for a surrogate for exercise as a stimulus to identify asthma. We had proposed that exercise-induced asthma was caused by an increase in osmolarity of the periciliary fluid. We found hypertonic saline to be a surrogate for exercise but an ultrasonic nebuliser was required. We produced a dry powder of sodium chloride but it proved unstable. We developed a spray dried preparation of mannitol and found that bronchial responsiveness to inhaling mannitol identified people with currently active asthma. We reasoned that mannitol had potential to replace the 'osmotic' benefits of exercise and could be used as a treatment to enhance mucociliary clearance in patients with cystic fibrosis. These discoveries were the start of a journey to develop several registered products that are in clinical use globally today.

Hypertonic saline inhibits airway smooth muscle contraction by inhibiting Ca2+ sensitization

The effects of hypertonic solution on airway smooth muscle (ASM) contraction and the underlying mechanisms are largely unknown. We found that hypertonic saline (HS) inhibited acetylcholine (ACh)-induced contraction of ASM from the mouse trachea and human bronchi. In single mouse ASM cells (ASMCs), ACh induced an increase in intracellular Ca²⁺ that was further enhanced by 5% NaCl, indicating that the HS-induced inhibition of ASM contraction was not mediated by a decrease in cytosolic Ca²⁺ . The Rho-associated kinase (ROCK) inhibitor Y-27632 relaxed ACh-induced precontraction of mouse tracheal rings. However, such inhibition was not observed after the relaxation induced by 5% NaCl. Moreover, the incubation of mouse tracheal rings with 5% NaCl decreased ACh-induced phosphorylation of myosin light chain 20 and myosin phosphatase target subunit 1. These data indicate that HS inhibits the contraction of ASM by inhibiting Ca²⁺ sensitization, not by decreasing intracellular Ca²⁺ .

Airway hyperresponsiveness to mannitol and methacholine and exhaled nitric oxide in children with asthma

OBJECTIVE

Asthma is characterized by airway hyperresponsiveness (AHR), inflammation, and obstruction. AHR to stimuli that indirectly cause bronchial smooth muscle (BSM) contractions via release of endogenous mediators is thought to better reflect airway inflammation than AHR to stimuli that act directly on BSM. Fractional exhaled nitric oxide (FeNO) is a useful parameter for noninvasive clinical airway inflammation assessments. Accordingly, this study aimed to examine the relationships of mannitol and methacholine challenge test outcomes with FeNO and the influence of inhaled corticosteroid treatment in children with asthma.

METHODS

One hundred thirty-four asthmatic children (89 males; ages: 5-17 years, median: 9 years) underwent spirometry, FeNO measurement, serum total/specific IgE testing, and blood eosinophil count. All subjects were challenged with mannitol dry powder (MDP; AridolH, Pharmaxis, Australia) and methacholine at 7-day intervals. Data of steroid-treated and steroid-naïve children were compared.

RESULTS

Positive responses to MDP and methacholine challenge tests were observed in 74.6% and 67.2% of total subject group, respectively, and 72 children had positive response to both challenge tests. The median FeNO level, response-dose ratio (RDR) of PC₂₀ methacholine, and RDR of PD₁₅ MDP were significantly higher in the steroid-treated group than in the steroid-naïve group (p < 0.001, 0.226, and 0.004, respectively). FeNO levels associated significantly with PD₁₅ MDP and RDR PD₁₅ MDP in total subject populations (p = 0.016 and 0.003, respectively); however, a significant correlation between FeNO and RDR PD₁₅ MDP was observed only in the steroid-naïve group.

CONCLUSIONS

Compared with AHR to methacholine, AHR to MDP more closely reflected the level of FeNO in steroid-naïve asthmatic children.

Exercice-induced bronchoconstriction among athletes: Assessment of bronchial provocation tests

Diagnosis of exercise-induced bronchoconstriction (EIB) requires the use of bronchial provocation tests (BPTs). We assessed exercise-induced respiratory symptoms (EIRS), EIB and asthma in athletes and evaluated the validity of BPTs in the diagnosis of EIB. Rhinitis and atopy were also assessed. Athletes with (n=55) and without previous asthma diagnosis (n=145) were tested by skin prick tests, lung function and eNO measurements. EIRS were recorded and EIB was assessed by methacholine (Mch), eucapnic voluntary hyperpnoea (EVH), mannitol and exercise test. EIRS were highly reported and history of asthma was common among athletes. A high prevalence of atopy (48.7%) and allergic rhinitis (30.5%) was found. Athletes with asthma had a higher response rate to Mch and to EVH, as compared with athletes without a previous asthma diagnosis (P=0.012 and P=0.017 respectively). Report of EIRS, rhinitis and atopy were not associated with a positive BPT response. Screening athletes for EIB using BPTs is suggested, irrespective of reported EIRS or a previous asthma diagnosis.

Exercise-induced bronchoconstriction update-2016

The first practice parameter on exercise-induced bronchoconstriction (EIB) was published in 2010. This updated practice parameter was prepared 5 years later. In the ensuing years, there has been increased understanding of the pathogenesis of EIB and improved diagnosis of this disorder by using objective testing. At the time of this publication, observations included the following: dry powder mannitol for inhalation as a bronchial provocation test is FDA approved however not currently available in the United States; if baseline pulmonary function test results are normal to near normal (before and after bronchodilator) in a person with suspected EIB, then further testing should be performed by using standardized exercise challenge or eucapnic voluntary hyperpnea (EVH); and the efficacy of nonpharmaceutical interventions (omega-3 fatty acids) has been challenged. The workgroup preparing this practice parameter updated contemporary practice guidelines based on a current systematic literature review. The group obtained supplementary literature and consensus expert opinions when the published literature was insufficient. A search of the medical literature on PubMed was conducted, and search terms included pathogenesis, diagnosis, differential diagnosis, and therapy (both pharmaceutical and nonpharmaceutical) of exercise-induced bronchoconstriction or exercise-induced asthma (which is no longer a preferred term); asthma; and exercise and asthma. References assessed as relevant to the topic were evaluated to search for additional relevant references. Published clinical studies were appraised by category of evidence and used to document the strength of the recommendation. The parameter was then evaluated by Joint Task Force reviewers and then by reviewers assigned by the parent organizations, as well as the general membership. Based on this process, the parameter can be characterized as an evidence- and consensus-based document.

'Indirect' challenges from science to clinical practice

Indirect challenges act to provoke bronchoconstriction by causing the release of endogenous mediators and are used to identify airway hyper-responsiveness. This paper reviews the historical development of challenges, with exercise, eucapnic voluntary hyperpnoea (EVH) of dry air, wet hypertonic saline, and with dry powder mannitol, that preceded their use in clinical practice. The first challenge developed for clinical use was exercise. Physicians were keen for a standardized test to identify exercise-induced asthma (EIA) and to assess the effect of drugs such as disodium cromoglycate. EVH with dry air became a surrogate for exercise to increase ventilation to very high levels. A simple test was developed with EVH and used to identify EIA in defence force recruits and later in elite athletes. The research findings with different conditions of inspired air led to the conclusion that loss of water by evaporation from the airway surface was the stimulus to EIA. The proposal that water loss caused a transient increase in osmolarity led to the development of the hypertonic saline challenge. The wet aerosol challenge with 4.5% saline, provided a known osmotic stimulus, to which most asthmatics were sensitive. To simplify the osmotic challenge, a dry powder of mannitol was specially prepared and encapsulated. The test pack with different doses and an inhaler provided a common operating procedure that could be used at the point of care. All these challenge tests have a high specificity to identify currently active asthma. All have been used to assess the benefit of treatment with inhaled corticosteroids. Over the 50 years, the methods for testing became safer, less complex, and less expensive and all used forced expiratory volume in 1 sec to measure the response. Thus, they became practical to use routinely and were recommended in guidelines for use in clinical practice.

A standard, single dose of inhaled terbutaline attenuates hyperpnea-induced bronchoconstriction and mast cell activation in athletes

This study provides the first in vivo evidence for a mast cell stabilizing effect of the short-acting inhaled β₂-adrenoceptor agonist terbutaline, when administered prophylactically at a clinically recommended dose (0.5 mg) before bronchial provocation with dry air. Our data therefore support the proposal that β₂-adrenoceptor agonist-mediated mast cell stabilization is a major contributor to bronchoprotection in individuals with exercise-induced bronchoconstriction.

Release of bronchoactive mediators from mast cells during exercise hyperpnea is a key factor in the pathophysiology of exercise-induced bronchoconstriction (EIB). Our aim was to investigate the effect of a standard, single dose of an inhaled β₂-adrenoceptor agonist on mast cell activation in response to dry air hyperpnea in athletes with EIB. Twenty-seven athletes with EIB completed a randomized, double-blind, placebo-controlled, crossover study. Terbutaline (0.5 mg) or placebo was inhaled 15 min prior to 8 min of eucapnic voluntary hyperpnea (EVH) with dry air. Pre- and postbronchial challenge, urine samples were analyzed by enzyme immunoassay for 11β-prostaglandin F_2α (11β-PGF_2α). The maximum fall in forced expiratory volume in 1 s of 14 (12–20)% (median and interquartile range) following placebo was attenuated to 7 (5–9)% with the administration of terbutaline (P < 0.001). EVH caused a significant increase in 11β-PGF_2α from 41 (27–57) ng/mmol creatinine at baseline to 58 (43–72) ng/mmol creatinine at its peak post-EVH following placebo (P = 0.002). The rise in 11β-PGF_2α was inhibited with administration of terbutaline: 39 (28–44) ng/mmol creatinine at baseline vs. 40 (33–58) ng/mmol creatinine at its peak post-EVH (P = 0.118). These data provide novel in vivo evidence of mast cell stabilization following inhalation of a standard dose of terbutaline prior to bronchial provocation with EVH in athletes with EIB.

Air quality and temperature effects on exercise-induced bronchoconstriction

Exercise-induced bronchoconstriction (EIB) is exaggerated constriction of the airways usually soon after cessation of exercise. This is most often a response to airway dehydration in the presence of airway inflammation in a person with a responsive bronchial smooth muscle. Severity is related to water content of inspired air and level of ventilation achieved and sustained. Repetitive hyperpnea of dry air during training is associated with airway inflammatory changes and remodeling. A response during exercise that is related to pollution or allergen is considered EIB. Ozone and particulate matter are the most widespread pollutants of concern for the exercising population; chronic exposure can lead to new-onset asthma and EIB. Freshly generated emissions particulate matter less than 100 nm is most harmful. Evidence for acute and long-term effects from exercise while inhaling high levels of ozone and/or particulate matter exists. Much evidence supports a relationship between development of airway disorders and exercise in the chlorinated pool. Swimmers typically do not respond in the pool; however, a large percentage responds to a dry air exercise challenge. Studies support oxidative stress mediated pathology for pollutants and a more severe acute response occurs in the asthmatic. Winter sport athletes and swimmers have a higher prevalence of EIB, asthma and airway remodeling than other athletes and the general population. Because of fossil fuel powered ice resurfacers in ice rinks, ice rink athletes have shown high rates of EIB and asthma. For the athlete training in the urban environment, training during low traffic hours and in low traffic areas is suggested.

Airway Hyperresponsiveness to Mannitol in Obesity Before and After Bariatric Surgery

BACKGROUND

The relationship between airway hyperresponsiveness (AHR) and obesity, a low-grade systemic inflammatory condition, remains largely unknown. It is established that AHR to indirect stimuli is associated with active airway inflammation. The objectives were to investigate the rate of AHR to mannitol in obese subjects and its changes 1 year after bariatric surgery (BS).

METHODS

We enrolled 58 candidates to BS severely obese (33 nonsmokers and 25 smokers) without history of asthma and 20 healthy, nonobese participants and related AHR to functional findings and serum and exhaled biomarkers.

RESULTS

Before surgery, AHR was observed in 16 (28 %) obese with the provocation doses of mannitol to induce a 15 % fall in FEV1 (PD15) of (geometric mean [95 % CI]) 83 (24-145) mg. Compared to control participants, obese participants had lower spirometric values and higher serum and exhaled biomarkers (p < 0.05 each). After surgery, AHR was abolished (p < 0.01) in all but four obese subjects.

CONCLUSIONS

Weight loss induced by BS was the key independent factor associated to AHR improvement. AHR to mannitol is highly prevalent in obesity, and it is largely abolished by BS.

Airway hyper-responsiveness to mannitol provides a good evaluation of atopy in childhood asthma

AIM

The relationship between airway hyper-responsiveness (AHR) and atopy has been previously investigated, but there are still some issues to be clarified. The aim of this study was to assess the link between AHR and mannitol and atopy in asthmatic children.

METHODS

We evaluated 44 children with asthma, aged 6-16 years of age, using skin prick tests (SPTs), serum total and specific immunoglobulin E (IgE) levels and the mannitol challenge test (MCT).

RESULTS

We found a good correlation between AHR to mannitol and specific IgE against Dermatophagoides pteronissinus (r = -0.66, p < 0.001) and a weak correlation with specific IgE against dog dander (r = -0.33, p = 0.01) and Aspergillus fumigatus (r = -0.23, p = 0.02). Furthermore, we found a weak correlation between AHR to mannitol and serum total IgE (r = -0.30; p = 0.03), the sum of specific IgE to aeroallergens (r = -0.37, p = 0.01) and the number of positive SPTs (r = -0.31, p = 0.02).

CONCLUSION

Measuring AHR with MCT might provide an accurate evaluation of the degree of atopy in children. The patients with a higher degree of atopy were significantly more reactive to mannitol. In clinical practice, these results indicate that children with asthma who are more atopic may require more intensive treatment strategies to reduce AHR.

The effect of omega-3 fatty acids on bronchial hyperresponsiveness, sputum eosinophilia, and mast cell mediators in asthma

BACKGROUND

Omega-3 fatty acid supplements have been reported to inhibit exercise-induced bronchoconstriction (EIB). It has not been determined whether omega-3 supplements inhibit airway sensitivity to inhaled mannitol, a test for bronchial hyperresponsiveness (BHR) and model for EIB in people with mild to moderate asthma.

METHODS

In a double-blind, crossover trial, subjects with asthma who had BHR to inhaled mannitol (n = 23; 14 men; mean age, 28 years; one-half taking regular inhaled corticosteroids) were randomized to omega-3 supplements (4.0 g/d eicosapentaenoic acid and 2.0 g/d docosahexaenoic acid) or matching placebo for 3 weeks separated by a 3-week washout. The primary outcome was the provoking dose of mannitol (mg) to cause a 15% fall in FEV1 (PD15). Secondary outcomes were sputum eosinophil count, spirometry, Asthma Control Questionnaire (ACQ) score, serum triacylglyceride level, and lipid mediator profile in urine and serum.

RESULTS

PD15 (geometric mean, 95% CI) to mannitol following supplementation with omega-3s (78 mg, 51-119 mg) was not different from placebo (88 mg, 56-139 mg, P = .5). There were no changes in sputum eosinophils (mean ± SD) in a subgroup of 11 subjects (omega-3, 8.4% ± 8.2%; placebo, 7.8% ± 11.8%; P = .9). At the end of each treatment period, there were no differences in FEV1 % predicted (omega-3, 85% ± 13%; placebo, 84% ± 11%; P = .9) or ACQ score (omega-3, 1.1% ± 0.5%; placebo, 1.1% ± 0.5%; P = .9) (n = 23). Omega-3s caused significant lowering of blood triglyceride levels and expected shifts in serum fatty acids and eicosanoid metabolites, confirming adherence to the supplements; however, no changes were observed in urinary mast cell mediators.

CONCLUSIONS

Three weeks of omega-3 supplements does not improve BHR to mannitol, decrease sputum eosinophil counts, or inhibit urinary excretion of mast cell mediators in people with mild to moderate asthma, indicating that dietary omega-3 supplementation is not useful in the short-term treatment of asthma.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT00526357; URL: www.clinicaltrials.gov.

Combining the Mannitol Test and FeNO in the Assessment of Poorly Controlled Asthma

BACKGROUND

International guidelines recommend up-titration of anti-inflammatory treatment in asthmatic patients with poor symptom control, but patients without eosinophilic airway inflammation are less likely to benefit from this. The mannitol bronchoprovocation test and fractional exhaled nitric oxide (FeNO) are increasingly used in the diagnostic assessment of asthma, but the utility of combining these tests has not been evaluated.

AIM

The aim of this study was to determine the value of combining FeNO and the mannitol test to assess patients with asthma referred for specialist assessment because of poor symptom control.

METHODS

All patients referred consecutively over a 12-month period for the assessment of asthma at the Respiratory Outpatient Clinic at Bispebjerg Hospital in Copenhagen were examined with bronchial provocation to mannitol, FeNO, and induced sputum.

RESULTS

Among asthmatic patients with partly controlled or uncontrolled symptoms according to Global Initiative for Asthma criteria, only 23% had sputum eosinophilia (eosinophils >2.99%). A positive mannitol test did not increase the likelihood of airway eosinophilia significantly (positive test: 32% vs negative test: 18%, P = .12). However, a positive mannitol test combined with a FeNO > 25 ppb indicated a high likelihood of airway eosinophilia (73%), compared with FeNO > 25 ppb and a negative mannitol test (29%) (P < .05). In contrast, in patients with FeNO < 25 ppb, a positive mannitol test was not associated with airway eosinophilia (sputum eosinophils > 2.99%: positive mannitol test: 0%, negative test: 11%, ns).

CONCLUSION

Combining the mannitol test and FeNO may aid in the differentiation between eosinophilic and noneosinophilic asthma in patients referred for specialist management because of poorly controlled asthma symptoms.

Bronchoprovocation tests in asthma: direct versus indirect challenges

PURPOSE OF REVIEW

This review describes different bronchoprovocation tests and their merits in diagnosing asthma.

RECENT FINDINGS

A new indirect challenge test using dry powder mannitol has been made available and has been systematically validated and tested in different populations.

SUMMARY

Airway hyperresponsiveness (AHR) is a characteristic feature of asthma, and its measurement using direct inhalation challenges, particularly with inhaled methacholine or histamine, or indirect challenges using stimuli such as exercise, dry air hyperpnea, distilled water, hypertonic saline and mannitol, and the pharmacological agent adenosine monophosphate is important in establishing a correct diagnosis. Direct challenge tests are sensitive and have a high negative predictive value to exclude asthma. This is particularly true in excluding asthma as a diagnosis in patients with symptoms that suggest asthma, but are caused by another condition. Indirect AHR correlates better with eosinophilic airway inflammation. Therefore, indirect challenge tests are seen as more specific. A newer indirect challenge test that uses a kit containing prepacked capsules of dry powder mannitol in different doses is safe and efficient to use. Indirect challenge tests are superior to direct challenge tests to confirm the presence of asthma.

Pulmonary function assessment in the early phase of patients with smoke inhalation injury from fire

OBJECTIVES

Fire smoke contains toxic gases and numerous chemical compounds produced by incomplete combustion, and may cause injury to the airways. Increased airway reactivity, as well as a decrease in lung function, has been reported as a sequela of smoke inhalation injury. This study was undertaken to assess lung functions in the early phase of patients with smoke inhalation damage from fires.

METHODS

A total of 15 patients with fire smoke inhalation (fire smoke group) and 15 subjects with chronic cough but no previous history of lung disease (chronic cough group) were enrolled. For diagnosis of inhalation injury, we performed bronchoscopy, high-resolution computed tomography (HRCT), as well as arterial carboxyhemoglobin (COHb) at admission. Clinical characteristics, pulmonary function tests (PFTs) and mannitol bronchial provocation tests (BPTs) were analyzed and compared between the two groups.

RESULTS

In fire smoke group, initial COHb levels and the PaO2/FiO2 ratio were (14.8±18.49)% and 425.7±123.68, respectively. Of seven patients performing HRCT, 4 (57.1%) showed the CT findings compatible with lung involvement of inhalation injury. Post bronchodilator value of the percent of forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) were (76.0±24.27)% and (79.8±27.82)%, respectively. Pre-and post- bronchodilator forced expiratory flow between 25% and 75% of the FVC (FEF25-75) and the percent predicted FEF25-75 were 2.41±1.47 vs. 2.65±1.45 L (P=0.045), and (68.7±37.29)% vs. (76.4±36.70)% (P=0.031), respectively. Two patients (13.3%) had positive bronchodilator response (BDR). In fire smoke and chronic cough group, all the subjects showed mannitol BPTs within normal limits.

CONCLUSIONS

Fire smoke inhalation leads to mild obstructive small airway disease pattern of pulmonary function in the early phase of patients with fire smoke damage. Further studies, however, need to be followed to identify the relationship between airway narrowing to inhaled mannitol and smoke inhalation injury.

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.

Response to add-on inhaled corticosteroids in COPD based on airway hyperresponsiveness to mannitol

BACKGROUND

The use of inhaled corticosteroids in mild to moderate COPD is controversial. The aim of this study was to determine whether airway hyperresponsiveness to mannitol might identify patients who are likely to respond to add-on inhaled corticosteroids.

METHODS

Ninety subjects with mild to moderate COPD were recruited and 68 subsequently randomized in a double-blind manner to receive inhaled budesonide (1,600 μg/d, n = 31) or placebo (n = 37) for 3 months. Thirty-eight subjects had airway hyperresponsiveness to mannitol (17 received budesonide, 21 placebo). All subjects received tiotropium throughout the study, including 4 weeks before randomization. Spirometry, quality of life (St. George Respiratory Questionnaire), degree of dyspnea, airway responsiveness to mannitol, and exhaled nitric oxide were assessed at week 0 (recruitment), week 4 (baseline prior to randomization), and week 16 (posttreatment).

RESULTS

Compared with placebo, budesonide was associated with improved quality of life in subjects showing airway hyperresponsiveness to mannitol (difference of changes in quality of life score between randomization and study completion, −9.1; 95% CI, −15.8 to −2.3; P < .01). Treatment with inhaled budesonide also led to a reduction in airway responsiveness to mannitol compared with placebo (difference in log10 response-dose ratio, −0.3; 95% CI, −0.6 to −0.04; P < .01). However, postrandomization changes in FEV1 % predicted, quality of life, and exhaled nitric oxide showed no difference between budesonide and placebo.

CONCLUSIONS

In subjects with mild to moderate COPD and airway hyperresponsiveness to mannitol, quality of life and airway responsiveness improved after treatment with inhaled corticosteroids added to long-acting bronchodilator therapy.

Assessment of EIB: What you need to know to optimize test results

Respiratory symptoms and asthma control questionnaires are poor predictors of the presence or severity of exercise-induced bronchoconstriction (EIB), and objective measurement is recommended. To optimize the chance of a positive test result, there are several factors to consider when exercising patients for EIB, including the ventilation achieved and sustained during exercise, water content of the inspired air, and the natural variability of the response. The high rate of negative exercise test results has led to the development of surrogates to identify EIB in laboratory or office settings, including eucapnic voluntary hyperpnea of dry air and inhalation of hyperosmolar aerosols.

Pathogenesis of exercise-induced bronchoconstriction

This article presents the various potential mechanisms responsible for the development of exercise-induced bronchoconstriction (EIB). Although the etiology of EIB is multifactorial, and the physiologic processes involved may vary between individuals (especially between those with and without asthma), drying of the small airways with an associated inflammatory response seems prerequisite for EIB. Dysregulated repair processes following exercise-induced airway epithelial injury may also serve as basis for EIB development/progression.

Where to from here for exercise-induced bronchoconstriction: the unanswered questions

The role of epithelial injury is an unanswered question in those with established asthma and in elite athletes who develop features of asthma and exercise-induced bronchorestriction (EIB) after years of training. The movement of water in response to changes in osmolarity is likely to be an important signal to the epithelium that may be central to the onset of EIB. It is generally accepted that the mast cell and its mediators play a major role in EIB and the presence of eosinophils is likely to enhance EIB severity.

Refractoriness to exercise challenge: a review of the mechanisms old and new

This article discusses the available literature on refractoriness in exercise-induced bronchoconstriction, namely, a decrease in airway responsiveness with repeated exercise challenges. The mechanisms of this naturally occurring protective feature is unknown. Reviewing previous studies together with findings in more recent studies, the authors propose desensitization of the G protein-coupled cysteinyl leukotriene receptor1 as the mechanism of refractoriness and that this desensitization occurs as a result of interplay between leukotrienes and prostaglandins.

[Inhalation therapy: provocation tests, infectious risks, acute bronchiolitis and ENT diseases. GAT aerosolstorming, Paris 2011]

Communications from the 2011 meeting of the GAT are reported in this second article on the practical management of bronchial provocation tests and infectious risks associated with the use of nebulization. Recent advances on the role of nebulized hypertonic saline in the treatment of acute bronchiolitis in infants and of the nebulization in sinusal diseases are also reported.

Airway hyperresponsiveness in asthma: mechanisms, clinical significance, and treatment

Airway hyperresponsiveness (AHR) and airway inflammation are key pathophysiological features of asthma. Bronchial provocation tests (BPTs) are objective tests for AHR that are clinically useful to aid in the diagnosis of asthma in both adults and children. BPTs can be either “direct” or “indirect,” referring to the mechanism by which a stimulus mediates bronchoconstriction. Direct BPTs refer to the administration of pharmacological agonist (e.g., methacholine or histamine) that act on specific receptors on the airway smooth muscle. Airway inflammation and/or airway remodeling may be key determinants of the response to direct stimuli. Indirect BPTs are those in which the stimulus causes the release of mediators of bronchoconstriction from inflammatory cells (e.g., exercise, allergen, mannitol). Airway sensitivity to indirect stimuli is dependent upon the presence of inflammation (e.g., mast cells, eosinophils), which responds to treatment with inhaled corticosteroids (ICS). Thus, there is a stronger relationship between indices of steroid-sensitive inflammation (e.g., sputum eosinophils, fraction of exhaled nitric oxide) and airway sensitivity to indirect compared to direct stimuli. Regular treatment with ICS does not result in the complete inhibition of responsiveness to direct stimuli. AHR to indirect stimuli identifies individuals that are highly likely to have a clinical improvement with ICS therapy in association with an inhibition of airway sensitivity following weeks to months of treatment with ICS. To comprehend the clinical utility of direct or indirect stimuli in either diagnosis of asthma or monitoring of therapeutic intervention requires an understanding of the underlying pathophysiology of AHR and mechanisms of action of both stimuli.

Inhaled mannitol as a test for bronchial hyper-responsiveness

Bronchial provocation tests (BPTs) are useful for identifying one of the key features of asthma: bronchial hyper-responsiveness (BHR). The symptoms of asthma are not always reflective of the underlying pathophysiology of asthma and there is a need for objective tests to identify the presence and severity of BHR. A new BPT, involving the inhalation of dry powder mannitol, has recently been approved to identify BHR and is now in use as a diagnostic tool for currently active asthma. Airway sensitivity to mannitol identifies BHR that is dependent upon the presence of airway inflammation and would probably benefit from treatment with inhaled corticosteroids. The mannitol BPT is available commercially as a (single-use) test kit (Aridol/Osmohale), with the only additional requirement to perform the test being a spirometer. Accordingly, the mannitol BPT provides a point-of-need tool to identify BHR to assist in the diagnosis of asthma.

Prostaglandin D2 induces apoptosis of human osteoclasts by activating the CRTH2 receptor and the intrinsic apoptosis pathway

Prostaglandin D(2) (PGD(2)) is a lipid mediator synthesized from arachidonic acid that directly activates two specific receptors, the D-type prostanoid (DP) receptor and chemoattractant receptor homologous molecule expressed on T-helper type 2 cells (CRTH2). PGD(2) can affect bone metabolism by influencing both osteoblast and osteoclast (OC) functions, both cells involved in bone remodeling and in in vivo fracture repair as well. The objective of the present study was to determine the effects of PGD(2), acting through its two specific receptors, on human OC apoptosis. Human OCs were differentiated in vitro from peripheral blood mononuclear cells in the presence of receptor activator for nuclear factor κB ligand (RANKL) and macrophage-colony stimulating factor (M-CSF), and treated with PGD(2), its specific agonists and antagonists. Treatment with PGD(2) for 24hours in the presence of naproxen (10μM) to inhibit endogenous prostaglandin production increased the percentage of apoptotic OCs in a dose-dependent manner, as did the specific CRTH2 agonist compound DK-PGD(2) but not the DP agonist compound BW 245C. In the absence of naproxen, the CRTH2 antagonist compound CAY 10471 reduced OC apoptosis rate but the DP antagonist BW A868C had no effect. The induction of PGD(2)-CRTH2 dependent apoptosis was associated with the activation of caspase-9, but not caspase-8, leading to caspase-3 cleavage. These data show that PGD(2) induces human OC apoptosis through activation of CRTH2 and the apoptosis intrinsic pathway.

Feasibility and acceptability of using bronchial hyperresponsiveness to manage asthma in primary care: a pilot study

AIMS

To determine if indirect testing for bronchial hyperresponsiveness (BHR) to monitor inhaled corticosteroid (ICS) treatment in asthma is feasible and acceptable in primary care.

METHODS

Fourteen adult patients with asthma aged 22-70 years (4M:10F, forced expiratory volume in 1 s >70% predicted) taking ICS performed a test for BHR using mannitol on three visits 6 weeks apart. ICS dose adjustments were made based on the presence of BHR. The Asthma Quality of Life Questionnaire (AQLQ) and the Asthma Control Questionnaire were used at each visit. A semi structured interview at study exit assessed subject acceptability.

RESULTS

BHR did not return in those with no BHR at study entry (n=9) with decreasing ICS dose. Improvements in BHR with increasing ICS dose (n=5) were observed with clinically significant improvements in AQLQ (mean score increase >0.5, p=0.02). Feasibility and acceptability of BHR testing was demonstrated.

CONCLUSIONS

It is feasible and acceptable to perform BHR testing using mannitol to help identify patients with asthma who would benefit from ICS dose increases and those with no BHR who could have a dose reduction.

TRIAL REGISTRATION

Australia New Zealand Clinical Trial Registry ACTRN12610000807055.

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.

The use of inhaled mannitol in the diagnosis and management of asthma

INTRODUCTION

Airway hyperresponsiveness (AHR) is a key feature of asthma and can be assessed by the use of bronchial provocation tests. A test using inhaled dry powder mannitol for diagnosing asthma is now regulatory approved in 20 countries.

AREAS COVERED

This paper reviews the literature on inhaled mannitol from the first publication in 1997 until present (October 2011). It discusses the current knowledge on the clinical usefulness as a tool for diagnosing and managing asthma.

EXPERT OPINION

Inhaled mannitol can be regarded as a safe, standardized, specific, but less sensitive, tool for the diagnosis of asthma in both children and adults. Discomfort, in terms of cough, during the test occurs in 85.3% of subjects, but rarely (1.3%) leads to discontinuation. Headache (6.1%), pharyngolaryngeal pain (2.6%) and cough (1.3%) are the most frequent adverse events that occur on the day of the test. The test holds several advantages compared with existing tests; there is no need for additional equipment (i.e., a nebulizer) besides a spirometer; it requires no cleaning and has only one standard operating protocol. In a new study using mannitol for monitoring mild and moderate persistent asthma in primary care, the number of mild exacerbations was reduced.

Cough response to isocapnic hyperpnoea of dry air and hypertonic saline are interrelated

Background

Mechanisms behind asthmatic cough are largely unknown. It is known that hyperosmolar challenges provoke cough in asthmatic but not in the healthy subjects. It has been postulated that isocapnic hyperpnea of dry air (IHDA) and hypertonic aerosols act via similar mechanisms in asthma to cause bronchoconstriction. We investigated whether there is an association between cough response induced by IHDA and hypertonic saline (HS) challenges.

Methods

Thirty-six asthmatic and 14 healthy subjects inhaled HS solutions with increasing osmolalities administered via ultrasonic nebuliser until 15 cumulative coughs were recorded. The IHDA consisted of three three-minute ventilation steps: 30%, 60% and 100% of maximal voluntary ventilation with an end-point of 30 cumulative coughs. The challenges were performed on separate days at least 48 hours between them and within one week. Inhaled salbutamol (400 mcg) was administered before the challenges to prevent bronchoconstriction. The cough response was expressed as the cough-to-dose ratio (CDR) which is the total number of coughs divided by the maximal osmolality inhaled or the maximal ventilation achieved.

Results

Cough response to IHDA correlated with the HS challenge (Rs = 0.59, p < 0.001). Cough response to IHDA was at its strongest during the first minute after the challenge. IHDA induced more cough among asthmatic than healthy subjects CDR being (mean ± SD) 0.464 ± 0.514 and 0.011 ± 0.024 coughs/MVV%, p < 0.001, respectively. Salbutamol effectively prevented bronchoconstriction to both challenges.

Conclusions

Asthmatic patients are hypersensitive to the cough-provoking effect of hyperpnoea, as they are to hypertonicity. Cough response induced by IHDA and HS correlated well suggesting similar mechanisms behind the responses.

Airway refractoriness to inhaled mannitol after repeated challenge

Exercise and inhaled mannitol are thought to cause bronchoconstriction through a similar mechanism in asthma. The response to exercise becomes refractory with repeated challenges. This study aimed to investigate whether repeated challenge with mannitol induces refractoriness, as with exercise. Forty-one children with asthma underwent two consecutive dose-response mannitol challenges (Phase 1); the second challenge proceeded after recovery (FEV(1) : 95% or more of baseline value) from the first. The response to mannitol was expressed as a provocative dose causing a 15% fall in FEV(1) (PD(15) ) and the response-dose ratio (RDR) (% fall in FEV(1) /cumulative dose). In 18 subjects who were deemed to have mannitol refractoriness in Phase 1, a mannitol challenge was performed before and after a methacholine challenge (Phase 2). In Phase 1, the time taken for the FEV(1) to recover after the first mannitol challenge ranged from 20 to 100 min with a median of 50 min. In the 23 subjects with a measurable mannitol PD(15) in both challenges, the geometric mean (95%CI) PD(15) in the second challenge (163 mg [114-232]) was significantly higher than that in the first challenge (66 mg [50-88], P < 0.001). The geometric mean (95%CI) RDR decreased from the value of 0.083%/mg (0.055-0.125) in the first challenge to 0.029%/mg (0.017-0.048) in the second challenge (P < 0.001). In Phase 2, prior challenge with methacholine or mannitol did not significantly alter subsequent bronchoconstriction to the opposite challenge. Repeated challenge with mannitol resulted in less bronchoconstriction when compared with the initial challenge. This refractoriness seems not to be attributable to functional loss of responsiveness or non-specific effect of prior bronchoconstriction.

Accuracy of eucapnic hyperpnea or mannitol to diagnose exercise-induced bronchoconstriction: a systematic review

BACKGROUND

Exercise challenge testing is the typical method for diagnosing exercise induced bronchoconstriction; however, alternate tests have been developed.

OBJECTIVE

The purpose of this paper was to summarize the current literature comparing eucapnic voluntary hyperpnea and mannitol with standard exercise challenge testing to determine whether either test is a suitable alternative to standard exercise testing for the diagnosis of exercise-induced bronchoconstriction.

METHODS

Using valid systematic review methods, a comprehensive search strategy to avoid publication bias, we identified 10 studies that compared exercise challenge testing with either eucapnic voluntary hyperpnea or mannitol.

RESULTS

For the 7 diagnostic cross-sectional studies that examined eucapnic voluntary hyperpnea, the sensitivity and specificity values were heterogeneous, ranging from 25 to 90% for sensitivity and 0 to 71% for specificity. In the 3 diagnostic cross-sectional studies that evaluated mannitol, the sensitivity and specificity ranged from 58 to 96% and 65 to 78%, respectively. For most studies, a representative spectrum of participants being tested was not used.

CONCLUSION

Given the heterogeneity in sensitivity and specificity of eucapnic voluntary hyperpnea studies and the relatively small number of studies that have examined mannitol, insufficient evidence is available to conclude that either of these tests are suitable alternatives to exercise challenge testing to detect exercise-induced bronchoconstriction. Additional research is required.

Have inadequate delivery systems hampered the clinical success of inhaled disodium cromoglycate? Time for reconsideration

IMPORTANCE OF THE FIELD

Disodium cromoglycate (DSCG) fits with the perception of a safe drug, but conclusions from questionable meta-analyses reduced its use. In addition, drug delivery aspects, such as hygroscopicity and the poor performance of delivery systems, were not considered to be important determinants of therapeutic failures.

AREAS COVERED IN THIS REVIEW

Drug delivery aspects and parameters affecting lung deposition and distribution, important parameters for therapeutic efficacy, are addressed. In addition, the distribution and ratio of mast cell tryptase and chymase-positive phenotypes in the lungs and their role in the prostaglandin and leukotriene pathway are discussed.

WHAT THE READER WILL GAIN

Information on why in vitro data are an excellent tool to understand better therapeutic failures associated with the moisture sensitivity of DSCG and the difficulty in handling and operating DSCG delivery systems in a therapeutically reliable way.

TAKE HOME MESSAGE

Pharmacological efficacy of DSCG has been demonstrated in animals and humans. If the drug is delivered to the site of inflammation in an effective dose, a reliable therapeutic effect can be expected. DSCG has extra properties and potential unspecific antiviral properties and may offer new therapeutic treatment aspects for asthma and viral-induced bronchiolitis in early childhood.

Bronchial provocation testing: the future

PURPOSE OF REVIEW

Performing a bronchial provocation test (BPT) using a direct or indirect stimulus to identify bronchial hyper-responsiveness (BHR) reduces the possibility of over and under-diagnosis of asthma based on history and symptoms. This review discusses some long-held beliefs of BPTs to include or exclude a diagnosis of asthma or exercise-induced bronchoconstriction (EIB).

RECENT FINDINGS

A high frequency of negative methacholine tests has been reported in 240 patients given a diagnosis of asthma at the end of the study, many of whom had documented EIB. This suggests that a negative methacholine test should not be relied upon to rule out asthma. Further, a positive methacholine test alone should be interpreted with caution as it may reflect airway injury rather than asthma or EIB. Mannitol, an indirect stimulus, identified a similar prevalence of BHR to methacholine and identified more patients than a single exercise test in three studies. However, neither mannitol nor methacholine identified all patients with EIB. Mannitol has a higher specificity for a physician diagnosis of asthma than methacholine.

SUMMARY

It is likely that both a direct test and an indirect test result may be required in some patients in order to confirm or exclude a diagnosis of asthma with certainty.

The occurrence of refractoriness and mast cell mediator release following mannitol-induced bronchoconstriction

For several hours after exercise-induced bronchoconstriction, there is diminished responsiveness to repeated challenge. The mechanism causing this refractoriness is unclear. Inhalation of dry powder mannitol is a new bronchial provocation test that has been suggested as a surrogate for an exercise challenge. Refractoriness to repeated mannitol challenge has however not been established. Our objective was to investigate if repeated challenge with mannitol is associated with refractoriness and diminished release of mast cell mediators of bronchoconstriction. Sixteen subjects with asthma underwent repeated inhalation of mannitol 90 min apart. Lung function was assessed by forced expiratory volume in 1 s (FEV₁). The urinary excretion (ng/mmol creatinine) of the mediators 9α,11β-prostaglandin (PG) F₂ and leukotriene (LT) E₄ were measured. The group mean fall in FEV₁ after the second challenge was 48.5 ± 5.8% of the first (P < 0.001). The protection afforded by the initial challenge, however, varied considerably between subjects (range 88-0%). Furthermore, the urinary excretion of the two mediators was increased after both challenges. The average excretion of mediators after the challenges was significantly higher for the six most refractory subjects. This was observed both for LTE₄ (95.6 ± 5.2 vs. 58.0 ± 2.4 for the 6 least refractory) (P < 0.001) and for 9α,11β-PGF₂ (137.6 ± 6.7 vs. 50.1 ± 1.1 for the 6 least refractory) (P = 0.002). As occurs with exercise-induced bronchoconstriction, repeated inhalation of mannitol induced refractoriness. We propose that refractoriness is due to tachyphylaxis at the level of the airway smooth muscle responsiveness to mediators of bronchoconstriction rather than due to fatigue of their release from mast cells.

Airway inflammation and mannitol challenge test in COPD

Background

Eosinophilic airway inflammation has successfully been used to tailor anti-inflammatory therapy in chronic obstructive pulmonary disease (COPD). Airway hyperresponsiveness (AHR) by indirect challenges is associated with airway inflammation. We hypothesized that AHR to inhaled mannitol captures eosinophilia in induced sputum in COPD.

Methods

Twenty-eight patients (age 58 ± 7.8 yr, packyears 40 ± 15.5, post-bronchodilator FEV₁ 77 ± 14.0%predicted, no inhaled steroids ≥4 wks) with mild-moderate COPD (GOLD I-II) completed two randomized visits with hypertonic saline-induced sputum and mannitol challenge (including sputum collection). AHR to mannitol was expressed as response-dose-ratio (RDR) and related to cell counts, ECP, MPO and IL-8 levels in sputum.

Results

There was a positive correlation between RDR to mannitol and eosinophil numbers (r = 0.47, p = 0.03) and level of IL-8 (r = 0.46, p = 0.04) in hypertonic saline-induced sputum. Furthermore, significant correlations were found between RDR and eosinophil numbers (r = 0.71, p = 0.001), level of ECP (r = 0.72, p = 0.001), IL-8 (r = 0.57, p = 0.015) and MPO (r = 0.64, p = 0.007) in sputum collected after mannitol challenge. ROC-curves showed 60% sensitivity and 100% specificity of RDR for >2.5% eosinophils in mannitol-induced sputum.

Conclusions

In mild-moderate COPD mannitol hyperresponsiveness is associated with biomarkers of airway inflammation. The high specificity of mannitol challenge suggests that the test is particularly suitable to exclude eosinophilic airways inflammation, which may facilitate individualized treatment in COPD.

Trial registration

Netherlands Trial Register (NTR): NTR1283