Endobronchial biopsy: a guide for asthma therapy selection in the era of bronchial thermoplasty

Bronchial Asthma, Airway Remodeling and Lung Fibrosis as Successive Steps of One Process

Bronchial asthma is a heterogeneous disease characterized by persistent respiratory system inflammation, airway hyperreactivity, and airflow obstruction. Airway remodeling, defined as changes in airway wall structure such as extensive epithelial damage, airway smooth muscle hypertrophy, collagen deposition, and subepithelial fibrosis, is a key feature of asthma. Lung fibrosis is a common occurrence in the pathogenesis of fatal and long-term asthma, and it is associated with disease severity and resistance to therapy. It can thus be regarded as an irreversible consequence of asthma-induced airway inflammation and remodeling. Asthma heterogeneity presents several diagnostic challenges, particularly in distinguishing between chronic asthma and other pulmonary diseases characterized by disruption of normal lung architecture and functions, such as chronic obstructive pulmonary disease. The search for instruments that can predict the development of irreversible structural changes in the lungs, such as chronic components of airway remodeling and fibrosis, is particularly difficult. To overcome these challenges, significant efforts are being directed toward the discovery and investigation of molecular characteristics and biomarkers capable of distinguishing between different types of asthma as well as between asthma and other pulmonary disorders with similar structural characteristics. The main features of bronchial asthma etiology, pathogenesis, and morphological characteristics as well as asthma-associated airway remodeling and lung fibrosis as successive stages of one process will be discussed in this review. The most common murine models and biomarkers of asthma progression and post-asthmatic fibrosis will also be covered. The molecular mechanisms and key cellular players of the asthmatic process described and systematized in this review are intended to help in the search for new molecular markers and promising therapeutic targets for asthma prediction and therapy.

Validation of a Pathological Score for the Assessment of Bronchial Biopsies in Severe Uncontrolled Asthma: Beyond Blood Eosinophils

BACKGROUND

Blood eosinophil count (BEC) is currently used as a surrogate marker of T2 inflammation in severe asthma but its relationship with tissue T2-related changes is elusive. Bronchial biopsy could add reliable information but lacks standardization.

OBJECTIVES

To validate a systematic assessment of the bronchial biopsy for the evaluation of severe uncontrolled asthma (SUA) by standardizing a pathological score.

METHODS

A systematic assessment of submucosal inflammation, tissue eosinophilic count/field (TEC), goblet cells hyperplasia, epithelial changes, basement membrane thickening, prominent airway smooth muscle and submucosal mucous glands was initially agreed and validated in representative bronchial biopsies of 12 patients with SUA by 8 independent pathologists. In a second phase, 62 patients with SUA who were divided according to BEC≥300cells/mm³ or less underwent bronchoscopy with bronchial biopsies and the correlations between the pathological findings and the clinical characteristics were investigated.

RESULTS

The score yielded good agreement among pathologists regarding submucosal eosinophilia, TEC, goblet cells hyperplasia and mucosal glands (ICC=0.85, 0.81, 0.85 and 0.87 respectively). There was a statistically significant correlation between BEC and TEC (r=0.393, p=0.005) that disappeared after correction by oral corticosteroids (OCS) use (r=0.170, p=0.307). However, there was statistically significant correlation between FeNO and TEC (r=0.481, p=0.006) that was maintained after correction to OCS use (r=0.419, p=0.021). 82.4% of low-BEC had submucosal eosinophilia, 50% of them moderate to severe.

CONCLUSION

A standardized assessment of endobronchial biopsy is feasible and could be useful for a better phenotyping of SUA especially in those receiving OCS.

Bronchial Rheoplasty for Treatment of Chronic Bronchitis. Twelve-Month Results from a Multicenter Clinical Trial

Rationale: Chronic bronchitis (CB) is characterized by productive cough with excessive mucus production, resulting in quality-of-life impairment and increased exacerbation risk. Bronchial rheoplasty uses an endobronchial catheter to apply nonthermal pulsed electrical fields to the airways. Preclinical studies have demonstrated epithelial ablation followed by regeneration of normalized epithelium.Objectives: To evaluate the feasibility, safety, and initial outcomes of bronchial rheoplasty in patients with CB.Methods: Pooled analysis of two separate studies enrolling 30 patients undergoing bilateral bronchial rheoplasty was conducted. Follow-up through 6 months (primary outcome) and 12 months included assessment of adverse events, airway histology, and changes in symptoms using the Chronic Obstructive Pulmonary Disease (COPD) Assessment Test and St. George's Respiratory Questionnaire (SGRQ).Measurements and Main Results: Bronchial rheoplasty was performed in all 30 patients (63% male; mean [SD] age, 67 [7.4]; mean [SD] postbronchodilator FEV1, 65% [21%]; mean [SD] COPD Assessment Test score 25.6 [7.1]; mean [SD] SGRQ score, 59.6 [15.3]). There were no device-related and four procedure-related serious adverse events through 6 months, and there were none thereafter through 12 months. The most frequent nonserious, device- and/or procedure-related event through 6 months was mild hemoptysis in 47% (14 of 30) patients. Histologically, the mean goblet cell hyperplasia score was reduced by a statistically significant amount (P < 0.001). Significant changes from baseline to 6 months in COPD Assessment Test (mean, -7.9; median, -8.0; P = 0.0002) and SGRQ (mean, -14.6; median, -7.2; P = 0.0002) scores were observed, with similar observations through 12 months.Conclusions: This study provides the first clinical evidence of the feasibility, safety, and initial outcomes of bronchial rheoplasty in symptomatic patients with CB.Clinical trial registered with www.anzctr.org.au (ACTRN 12617000330347) and clinicaltrials.gov (NCT03107494).

Relationship between opiates and asthma in the determination of death

Several studies have shown an association between asthma and opiate abuse. This retrospective study aims to analyse the demographic, toxicological, and seasonal differences in asthmatic and non-asthmatic subjects who died of opiates. In addition, the relationship between toxicological levels of opiates and histologic grade of lung inflammation is examined. Deaths from 2013 to 2018 involving opiates as the primary cause of death in Cook County, Illinois (USA) were reviewed. Twenty-six cases of opiate deaths of individuals with a history of asthma and lung histology slides available were identified. In comparison, 40 cases of deaths due to opiates only were analysed. A check-list system for the evaluation of the grade of microscopic inflammation in asthma was developed. We found statistically significant differences between the asthmatics and the non-asthmatics regarding demography (age and race) and toxicology (6-MAM presence). In particular, the "opiate and asthma group" was mainly composed of African-American subjects, in contrast with the "opiate group", consisting mostly of Caucasian. The mean age was significantly higher in the "opiate and asthma group" compared with the "opiate group". A greater presence of 6-MAM was detected in the "opiate group" compared with the "opiate and asthma group". While we expected to find that low opiate levels would lead to deaths in asthmatics and, in particular, that lower opiate concentrations would cause deaths in subjects with higher grades of histologic inflammation, our study suggests that the quantity of drug and the level of inflammation are not statistically significant in the determination of death. We, therefore, recommend histologic examination of the lungs to evaluate for asthma, particularly in suspected low-level opiate-related deaths, to help further clarify any relationship between asthma and opiate use.

Recent Developments In Bronchial Thermoplasty For Severe Asthma

PURPOSE

Bronchial thermoplasty is approved in many countries worldwide as a non-pharmacological treatment for severe asthma. This review summarizes recent publications on the selection of patients with severe asthma for bronchial thermoplasty, predictors of a beneficial response and developments in the procedure and discusses specific issues about bronchial thermoplasty including effectiveness in clinical practice, mechanism of action, cost-effectiveness, and place in management.

RESULTS

Bronchial thermoplasty is a treatment option for patients with severe asthma after assessment and management of causes of difficult-to-control asthma, such as nonadherence, poor inhaler technique, comorbidities, under treatment, and other behavioral factors. Patients treated with bronchial thermoplasty in clinical practice have worse baseline characteristics and comparable clinical outcomes to clinical trial data. Bronchial thermoplasty causes a reduction in airway smooth muscle mass although it is uncertain whether this effect explains its efficacy since other mechanisms of action may be relevant, such as alterations in airway epithelial, gland, and/or nerve function; improvements in small airway function; or a placebo effect. The cost-effectiveness of bronchial thermoplasty is greater in countries where the costs of hospitalization and emergency department are high. The place of bronchial thermoplasty in the management of severe asthma is not certain, although some experts propose that bronchial thermoplasty should be considered for patients with severe asthma associated with non-type 2 inflammation or who fail to respond favorably to biologic therapies targeting type 2 inflammation.

CONCLUSION

Bronchial thermoplasty is a modestly effective treatment for severe asthma after assessment and management of causes of difficult-to-control asthma. Asthma morbidity increases during and shortly after treatment. Follow-up studies provide reassurance on the long-term safety of the procedure. Uncertainties remain about predictors of response, mechanism(s) of action, and place in management of severe asthma.

The Impact of Bronchial Thermoplasty on Asthma-Related Quality of Life and Controller Medication Use

BACKGROUND

Despite an improved understanding of the pathophysiology of asthma, severe asthma sufferers continue to experience a poor quality of life (QOL). Bronchial thermoplasty (BT) utilizes thermal energy to reduce airway smooth muscle. In industry-sponsored trials, BT improves QOL and reduces severe exacerbations; however, the impact of BT on asthma-related QOL and medication use in non-industry-sponsored trials is less clear.

OBJECTIVE

The aim of this study was to determine the impact of BT on asthma QOL measures (mini-AQLQ) and asthma controller medication use during the year following treatment with BT.

METHODS

We performed a prospective study of the impact of BT in 25 patients with severe persistent asthma. Our primary outcome was change in asthma-related QOL score (mini-AQLQ) 1 year after BT treatment. Our secondary outcome was change in asthma medication use 1 year after BT.

RESULTS

BT led to an improvement in mini-AQLQ score from a baseline of 3.6 ± 0.3 before therapy to 5.6 ± 0.3 1 year after the final BT procedure. Overall, 88% percent of patients showed a clinically significant improvement in mini-AQLQ at 1 year. Patients treated with BT showed a reduction in the use of montelukast and omalizumab 1 year after BT.

CONCLUSION

In patients with severe persistent asthma and low asthma-related QOL scores, BT leads to an improvement in asthma-related QOL and a decrease in asthma medication use when measured 1 year after the final BT treatment.

Airway smooth muscle as an underutilised biomarker: a case report

Background

Severe asthma and chronic obstructive pulmonary disease (COPD) can be challenging to manage, particularly when the clinical features may be similar. With the increased availability of advanced therapies for both entities, it is more important than ever to diagnose and phenotype accurately to inform appropriate treatment decisions. This case highlights the use of endobronchial biopsies to allow for histological evaluation of airways disease, and in particular the role of airway smooth muscle mass as an additional biomarker that could facilitate the diagnostic process.

Case presentation

A 65 year old woman presented with a diagnosis of severe COPD on the background of previous smoking and mild childhood asthma. Despite taking maximal inhaled pharmacotherapy, she had frequent exacerbations requiring corticosteroids and remained dyspnoeic on mild exertion. Lung function tests showed severe obstruction on spirometry (forced expiratory ratio 43%, forced expiratory volume in 1 s 47% predicted), and single breath Diffusing Capacity for Carbon Monoxide was moderately reduced at 45% predicted. Computed tomography revealed hyperinflation without marked emphysema. Quantitative CT for emphysema distribution demonstrated a relatively small lung fraction of 9.35% with <− 950 Hounsfield units. Bronchoscopy with endobronchial biopsy was undertaken to further determine the underlying pathology, and airway mucosa histology was consistent with typical findings of asthma. The patient was treated with bronchial thermoplasty as she did not meet prescribing criteria for monoclonal antibodies. Six months post treatment, she had a significant improvement in symptom control and medication usage, without any exacerbations.

Conclusions

Airway smooth muscle histology is an underutilised biomarker that has a valuable role in phenotyping airways disease in the era of individualised medicine.

Horses With Pasture Asthma Have Airway Remodeling That Is Characteristic of Human Asthma

Severe equine asthma, formerly recurrent airway obstruction (RAO), is the horse counterpart of human asthma, affecting horses maintained indoors in continental climates. Equine pasture asthma, formerly summer pasture RAO, is clinically similar but affects grazing horses during hot, humid conditions in the southeastern United States and United Kingdom. To advance translational relevance of equine pasture asthma to human asthma, histologic features of airway remodeling in human asthma were scored in lung lobes from 15 pasture asthma-affected and 9 control horses of mixed breeds. All noncartilaginous airways were scored using a standardized grading rubric (0-3) in hematoxylin and eosin (HE) and Movat's pentachrome-stained sections; 15 airways were chosen randomly from each lobe for analysis. Logistic regression identified disease, age, and lobe effects on probability of histologic outcomes. Airway smooth muscle (odds ratio [OR] = 2.5, P < .001), goblet cell hyperplasia/metaplasia (OR = 37.6, P < .0001), peribronchiolar elastic system fibers (OR = 4.2, P < .001), peribronchiolar fibrosis (OR = 3.8, P = .01), airway occlusion by mucus/inflammation (OR = 4.2, P = .04), and airway adventitial inflammation (OR = 3.0, P = .01) were significantly greater in diseased airways. A novel complex tissue disorganization, designated terminal bronchiolar remodeling, was overrepresented in diseased airways (OR = 3.7, P < .0001). Distribution of terminal bronchiolar remodeling corresponded to putative sites of air trapping in human asthma, at secondary pulmonary lobules. Age (>15 years) was an independent risk factor for increased peribronchiolar fibrosis, elastic system fibers, and terminal bronchiolar remodeling. Remodeling differed significantly between lung lobes, congruent with nonhomogeneous remodeling in human asthma. Equine pasture asthma recapitulates airway remodeling in human asthma in a manner not achieved in induced animal asthma models, endorsing its translational relevance for human asthma investigation.

Bronchial thermoplasty as a treatment for severe asthma: controversies, progress and uncertainties

INTRODUCTION

Bronchial thermoplasty is a licensed non-pharmacological treatment for severe asthma. Area covered: This article considers evidence for the efficacy and safety of bronchial thermoplasty from clinical trials and observational studies in clinical practice. Its place in the management of severe asthma, predictors of response and mechanisms of action are reviewed. Expert commentary: Bronchial thermoplasty improves quality of life and reduces exacerbations in moderate to severe asthma. Morbidity from asthma is increased during treatment. Overall, patients treated in clinical practice have worse baseline characteristics and comparable clinical outcomes to trial data. Follow-up studies provide reassurance on long-term safety. Despite some progress, future research needs to investigate uncertainties about predictors of response, mechanism of action and place in management of asthma.

Nerve ablation after bronchial thermoplasty and sustained improvement in severe asthma

BACKGROUND

Bronchial thermoplasty (BT) is a non-pharmacological intervention for severe asthma whose mechanism of action is not completely explained by a reduction of airway smooth muscle (ASM). In this study we analyzed the effect of BT on nerve fibers and inflammatory components in the bronchial mucosa at 1 year.

METHODS

Endobronchial biopsies were obtained from 12 subjects (mean age 47 ± 11.3 years, 50% male) with severe asthma. Biopsies were performed at baseline (T0) and after 1 (T1), 2 (T2) and 12 (T12) months post-BT, and studied with immunocytochemistry and microscopy methods. Clinical data including Asthma Quality of Life Questionnaire (AQLQ) and Asthma Control Questionnaire (ACQ) scores, exacerbations, hospitalizations, oral corticosteroids use were also collected at the same time points.

RESULTS

A statistically significant reduction at T1, T2 and T12 of nerve fibers was observed in the submucosa and in ASM compared to T0. Among inflammatory cells, only CD68 showed significant changes at all time points. Improvement of all clinical outcomes was documented and persisted at the end of follow up.

CONCLUSIONS

A reduction of nerve fibers in epithelium and in ASM occurs earlier and persists at one year after BT. We propose that nerve ablation may contribute to mediate the beneficial effects of BT in severe asthma.

TRIAL REGISTRATION

Registered on April 2, 2013 at ClinicalTrials.gov Identifier: NCT01839591 .

Bronchial Thermoplasty: A Nonpharmacologic Therapy for Severe Asthma

Bronchial thermoplasty is an innovative treatment for patients with severe asthma and chronic airflow obstruction with an established long-term efficacy and safety profile. This review focuses on the role of bronchial thermoplasty in severe asthma, its mechanism of action, appropriate patient selection, current evidence, and recent developments of this therapy.

Airway Inflammation after Bronchial Thermoplasty for Severe Asthma

RATIONALE

Bronchial thermoplasty is an alternative treatment for patients with severe, uncontrolled asthma in which the airway smooth muscle is eliminated using radioablation. Although this emerging therapy shows promising outcomes, little is known about its effects on airway inflammation.

OBJECTIVES

We examined the presence of bronchoalveolar lavage cytokines and expression of smooth muscle actin in patients with severe asthma before and in the weeks after bronchial thermoplasty.

METHODS

Endobronchial biopsies and bronchoalveolar lavage samples from 11 patients with severe asthma were collected from the right lower lobe before and 3 and 6 weeks after initial bronchial thermoplasty. Samples were analyzed for cell proportions and cytokine concentrations in bronchoalveolar lavage and for the presence of α-SMA in endobronchial biopsies.

MEASUREMENTS AND MAIN RESULTS

α-SMA expression was decreased in endobronchial biopsies of 7 of 11 subjects by Week 6. In bronchoalveolar lavage fluid, both transforming growth factor-β1 and regulated upon activation, normal T-cell expressed and secreted (RANTES)/CCL5 were substantially decreased 3 and 6 weeks post bronchial thermoplasty in all patients. The cytokine tumor-necrosis-factor-related apoptosis-inducing ligand (TRAIL), which induces apoptosis in several cell types, was increased in concentration both 3 and 6 weeks post bronchial thermoplasty.

CONCLUSIONS

Clinical improvement and reduction in α-SMA after bronchial thermoplasty in severe, uncontrolled asthma is associated with substantial changes in key mediators of inflammation. These data confirm the substantial elimination of airway smooth muscle post thermoplasty in the human asthmatic airway and represent the first characterization of significant changes in airway inflammation in the first weeks after thermoplasty.

Advances in Bronchial Thermoplasty

Bronchial thermoplasty (BT) is a therapeutic intervention that delivers targeted thermal energy to the airway walls with the goal of ablating the smooth muscle in patients with severe persistent asthma. Since the publication of the original preclinical studies, three large randomized clinical trials evaluating its impact on asthma control have been performed. These trials have shown improvements in asthma-related quality of life and a reduction in asthma exacerbations following treatment with BT. However, there remains significant controversy regarding the true efficacy of BT and the interpretation of these studies, particularly the Asthma Intervention Research 2 trial. In this article, we will discuss these controversies and present the latest evidence on the use of BT in asthma, specifically the 5-year longitudinal evaluation of patients. In addition, we will discuss new insights into the histopathologic changes that occur in the airways following BT, as well as the feasibility of performing the procedure in patients with very severe asthma. We also will discuss the ongoing translational and clinical investigations regarding the underlying mechanism of action and methods to improve patient selection for this procedure.

Should lung biopsies be performed in patients with severe asthma?

Asthma, and severe asthma, in particular, is increasingly recognised as a heterogeneous disease. Identifying these different phenotypes of asthma and assigning patients to phenotype-specific treatments is one of the current conundrums in respiratory medicine. Any diagnostic procedure in severe asthma (or any disease) should have two aims: 1) better understanding or identifying the diagnosis, and 2) providing information on the heterogeneity of asthma phenotypes to guide therapy with the objective of improving outcomes. Lung biopsies can target the large and small airways as well as the lung parenchyma. All compartments are affected in severe asthma; however, knowledge on the distal lung is limited. At this point, it remains uncertain whether lung specimens routinely add diagnostic information that is unable to be obtained otherwise. Indeed, whether a lung biopsy is indicated in the workup of a patient with severe asthma remains an individual decision. It is hoped this review will support rational decision-making and provide a detailed synopsis of the varied histopathological features seen in biopsies of patients with a diagnosis of severe asthma. Due to limited data on this topic this review is primarily based on opinion with recommendations arising primarily from the personal experience of the authors.

Asthma therapy and its effect on airway remodelling

Asthma remains a major health problem with significant morbidity, mortality and economic costs. In asthma, airway remodelling, which refers to all the microscopic structural changes seen in the airway tissue, has been recognised for many decades and remains one of the defining characteristics of the disease; however, it is still poorly understood. The detrimental pathophysiological consequences of some features of remodelling, like increased airway smooth muscle mass and subepithelial fibrosis, are well documented. However, whether targeting these by therapy would be beneficial is unknown. Although the prevailing thinking is that remodelling is an abnormal response to persistent airway inflammation, recent evidence, especially from studies of remodelling in asthmatic children, suggests that the two processes occur in parallel. The effects of asthma therapy on airway remodelling have not been studied extensively due to the challenges of obtaining airway tissue in the context of clinical trials. Corticosteroids remain the cornerstone of asthma therapy, and their effects on remodelling have been better studied than other drugs. Bronchial thermoplasty is the only asthma therapy to primarily target remodelling, although how it results in the apparent clinical benefits seen is not exactly clear. In this article we discuss the mechanisms of airway remodelling in asthma and review the effects of conventional and novel asthma therapies on the process.

Pathobiology of severe asthma

Severe asthma (SA) afflicts a heterogeneous group of asthma patients who exhibit poor responses to traditional asthma medications. SA patients likely represent 5-10% of all asthma patients; however, they have a higher economic burden when compared with milder asthmatics. Considerable research has been performed on pathological pathways and structural changes associated with SA. Although limitations of the pathological approaches, ranging from sampling, to quantitative assessments, to heterogeneity of disease, have prevented a more definitive understanding of the underlying pathobiology, studies linking pathology to molecular markers to targeted therapies are beginning to solidify the identification of select molecular phenotypes. This review addresses the pathobiology of SA and discusses the current limitations of studies, the inflammatory cells and pathways linked to emerging phenotypes, and the structural and remodeling changes associated with severe disease. In all cases, an effort is made to link pathological findings to specific clinical/molecular phenotypes.

Bronchial thermoplasty for moderate or severe persistent asthma in adults

BACKGROUND

Bronchial thermoplasty is a procedure that consists of the delivery of controlled radiofrequency-generated heat via a catheter inserted into the bronchial tree of the lungs through a flexible bronchoscope. It has been suggested that bronchial thermoplasty works by reducing airway smooth muscle, thereby reducing the ability of the smooth muscle to bronchoconstrict. This treatment could then reduce asthma symptoms and exacerbations, resulting in improved asthma control and quality of life.

OBJECTIVES

To determine the efficacy and safety of bronchial thermoplasty in adults with bronchial asthma.

SEARCH METHODS

We searched the Cochrane Airways Group Specialised Register of Trials (CAGR) up to January 2014.

SELECTION CRITERIA

We included randomised controlled clinical trials that compared bronchial thermoplasty versus any active control in adults with moderate or severe persistent asthma. Our primary outcomes were quality of life, asthma exacerbations and adverse events.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed risk of bias.

MAIN RESULTS

We included three trials (429 participants) with differences regarding their design (two trials compared bronchial thermoplasty vs medical management and the other compared bronchial thermoplasty vs a sham intervention) and participant characteristics; one of the studies included participants with more symptomatic asthma compared with the others.The pooled analysis showed improvement in quality of life at 12 months in participants who received bronchial thermoplasty that did not reach the threshold for clinical significance (3 trials, 429 participants; mean difference (MD) in Asthma Quality of Life Questionnaire (AQLQ) scores 0.28, 95% confidence interval (CI) 0.07 to 0.50; moderate-quality evidence). Measures of symptom control showed no significant differences (3 trials, 429 participants; MD in Asthma Control Questionnaire (ACQ) scores -0.15, 95% CI -0.40 to 0.10; moderate-quality evidence). The risk of bias for these outcomes was high because two of the studies did not have a sham intervention for the control group.The results from two trials showed a lower rate of exacerbation after 12 months of treatment for participants who underwent bronchial thermoplasty. The trial with sham intervention showed a significant reduction in the proportion of participants visiting the emergency department for respiratory symptoms, from 15.3% on sham treatment to 8.4% over 12 months following thermoplasty. The trials showed no significant improvement in pulmonary function parameters (with the exception of a greater increase in morning peak expiratory flow (PEF) in one trial). Treated participants who underwent bronchial thermoplasty had a greater risk of hospitalisation for respiratory adverse events during the treatment period (3 trials, 429 participants; risk ratio 3.50, 95% CI 1.26 to 9.68; high-quality evidence), which represents an absolute increase from 2% to 8% (95% CI 3% to 23%) over the treatment period. This means that six of 100 participants treated with thermoplasty (95% CI 1 to 21) would require an additional hospitalisation over the treatment period. No significant difference in the risk of hospitalisation was noted at the end of the treatment period.Bronchial thermoplasty was associated with an increase in respiratory adverse events, mainly during the treatment period. Most of these events were mild or moderate, appeared in the 24-hour post-treatment period, and were resolved within a week.

AUTHORS' CONCLUSIONS

Bronchial thermoplasty for patients with moderate to severe asthma provides a modest clinical benefit in quality of life and lower rates of asthma exacerbation, but no significant difference in asthma control scores. The quality of life findings are at risk of bias, as the main benefits were seen in the two studies that did not include a sham treatment arm. This procedure increases the risk of adverse events during treatment but has a reasonable safety profile after completion of the bronchoscopies. The overall quality of evidence regarding this procedure is moderate. For clinical practice, it would be advisable to collect data from patients systematically in independent clinical registries. Further research should provide better understanding of the mechanisms of action of bronchial thermoplasty, as well as its effect in different asthma phenotypes or in patients with worse lung function.

Bronchial thermoplasty: interventional therapy in asthma

Bronchial thermoplasty is a new treatment option for patients with severe bronchial asthma who remain symptomatic despite maximal medical therapy. The aim of this interventional therapy option is the reduction of smooth muscle in the central and peripheral airways in order to reduce symptomatic bronchoconstriction via the application of heat. A full treatment with bronchial thermoplasty is divided into three bronchoscopies. Randomized, controlled clinical trials have shown an increase in quality of life, a reduction in severe exacerbations, and decreases in emergency department visits as well as days lost from school or work. The trials did not show a reduction in hyperresponsiveness or improvement in forced expiratory volume in 1 s. Short-term adverse effects include an increase in exacerbation rate, an increase in respiratory infections and an increase in hospitalizations. In the 5-year follow up of the studies available there was evidence of clinical and functional stability of the treated patients. Further studies are necessary to identify an asthma phenotype that responds well to this treatment.