Bronchial Thermoplasty (Alair System) for Treating Adult Patients with Severe Symptomatic Asthma
October 15, 2014 | Emerging Technology Reports
Proprietary names: Alair™ Bronchial Thermoplasty System, Alair Catheter Model ATS 2-5, Alair RF Controller Model ATS 200
Bronchial thermoplasty (BT) involves delivery of controlled thermal energy to accessible airway walls during a series of bronchoscopy procedures. It has emerged as a treatment option for some adult patients with severe symptomatic asthma whose disease is not sufficiently controlled by maximal standard medical treatment.1
Asthma, a chronic inflammatory disorder of the respiratory system, is characterized by airway inflammation, airway narrowing, and bronchial hyperresponsiveness.2,3 Individuals with asthma experience recurrent episodes of wheezing, breathlessness, chest tightness, and coughing.4 Inflammation leads to airway edema and mucus secretion, which contribute to airflow obstruction and bronchial reactivity.4 Smooth muscle hyperplasia and airway remodeling may also be present.4 Chronic asthma is also characterized by bronchoconstriction, which occurs when hypertrophic airway smooth muscle contracts.4 Contraction of the airway smooth muscle, which is contained within the lung's airway walls, is a main cause of airway constriction.5 Severe asthma also contributes to increased airway smooth muscle mass.1,6 Together, airway inflammation and muscle thickening increase airflow resistance and decrease the inside diameter of the airways.4 The degree of airway hyperresponsiveness generally correlates with the clinical severity of asthma.7 Clinicians classify asthma severity into four categories by symptom prevalence and pulmonary function testing: mild intermittent, mild persistent, moderate persistent, and severe persistent.8 According to the National Asthma Education and Prevention Program Expert Panel 3, severe persistent asthma is defined by continuous daytime symptoms, frequent nighttime awakenings (often seven times per week), use of a short-acting beta-agonist for symptom control several times a day, frequent exacerbations, physical activities extremely limited by asthma symptoms, and reduced function on spirometry (i.e., forced expiratory volume <60% of predicted value, forced expiratory volume in one second (FEV1)/forced vital capacity reduced >5%).8
Management of asthma involves establishing environmental controls of allergens and irritants, avoiding risk factors that trigger symptoms (e.g., exposure to cat and dog allergens, dust mites, cockroaches, and fungi), and adhering to comprehensive pharmacologic therapy to reduce inflammation and dilate the bronchi by relaxing smooth muscle.5,7 Available asthma medications aim to provide quick relief of acute asthma exacerbations or long-term control.8 Quick-relief medications (i.e., rescue medications) include anticholinergics (i.e., ipratropium bromide), short-acting beta-agonists (i.e., albuterol, levalbuterol, pirbuterol), and systemic corticosteroids.8 Long-term control medications (i.e., controller medications) include corticosteroids, cromolyn sodium and nedocromil, immunomodulators (i.e., omalizumab), leukotriene modifiers, long-acting beta2-agonists (LABAs) (i.e., salmeterol, formoterol), and methylxanthines (i.e., theophylline).8
The Global Initiative for Asthma recommends a stepwise approach for controlling asthma symptoms.2 See Table 1. We refer to Step 4 as maximal standard care (SC) and Step 5 as add-on options for patients whose asthma remains uncontrolled despite maximal SC.
Table**1**. Global Initiative for Asthma 2014: Stepwise Approach to Asthma Care
Despite pharmacologic treatment, 5% to 10% of patients with asthma experience persistent symptoms and frequent exacerbations, which lead to frequent emergency department (ED) visits, lost work productivity, and increased mortality risk.1,9 Due to the complexity of care and the need for ongoing care, treating patients with persistent severe asthma who remain uncontrolled despite SC generates high healthcare costs (See Cost Considerations section below).1 Thus, new therapies are needed for this patient population.
According to the U.S. Centers for Disease Control and Prevention (CDC), 18.7 million noninstitutionalized adults have asthma, which accounts for about 8% of the U.S. adult population.10 The proportion of U.S. patients with the most severe asthma is estimated at 10%, and these patients constitute the majority of asthma-related healthcare burden.11 CDC reported that in 2009 asthma resulted in 10.6 million physician office visits, 2.1 million emergency visits, 479,300 hospitalizations, and 3,388 deaths.12
The World Health Organization estimates that 235 million people worldwide have asthma.13 Worldwide trends suggest an increase in both the prevalence and morbidity of asthma.14 Implicating factors include urbanization, air pollution, passive smoking, and changes in exposure to environmental allergens.14
According to Boston Scientific, more than 1 million patients worldwide may be candidates for BT.15
BT involves delivery of controlled thermal energy to accessible proximal airway walls (those between 3 and 10 mm in diameter and distal to main stem bronchi).5 BT's intent is to decrease the number of severe asthma exacerbations on a long-term basis by reducing, debulking, or partially...