use bronchial thermoplasty to treat severe asthma
- related: Asthma reactive airway disease
- tags: #literature #pulmonary
Links to this note
Clinical trials have shown bronchial thermoplasty (BT) to be a safe add-on treatment for selected patients with severe asthma in stable condition and on optimal medical therapy consisting at least of high-dose inhaled steroids and a long-acting beta agonist, with evidence of poor asthma control (choice D is correct). These trials excluded patients under the age of 18 or those with three or more exacerbations per year (choice A is incorrect), an FEV1 <60% of predicted (choice B is incorrect), and those with chronic sinus disease, so the safety and efficacy of BT in these patient populations are unknown. The Chinese consensus statement on BT lists absolute contraindications that includes the presence of an active implantable electronic device, acute myocardial infarction in the prior 6 weeks, sensitivity to anesthetics required to perform bronchoscopy, coagulation dysfunction, and patients previously treated with BT (choice C is incorrect). It is important to state that prior to referral, all patients should be evaluated for medical adherence, inhaler technique, and alternative diagnoses or comorbid conditions.
BT treatment involves delivering radiofrequency-generated heat to medium-sized and large airways via a bronchoscope, with the primary goal of reducing smooth muscle mass, which is commonly enlarged in patients were severe asthma.
Other potential mechanisms of action have also been proposed including altered immune modulation and neurogenic function. A typical treatment course consists of three separate bronchoscopies, usually 3 to 4 weeks apart, starting with the right lower lobe then the left lower lobe and, lastly, both upper lobes. The right middle lobe is not treated based on the theoretical risk of right middle lobe syndrome (RMLS) due to airway obstruction.
In a double blinded, sham–controlled trial, patients underwent bronchoscopy with BT catheter placement and were randomized to either receive or not receive thermal energy, with the primary outcome of change in asthma quality of life questionnaire (AQLQ) score. While a significant increase in the AQLQ score of the BT group was found, patients treated with sham bronchoscopy also demonstrated an increase in the AQLQ score. As a result, there was a small absolute difference between groups that was below that which is considered clinically meaningful. More BT patients experienced asthma worsening immediately post procedure with greater asthma exacerbations and need for hospital admission, than those in the sham bronchoscopy group. However, in the posttreatment period (6–52 weeks after BT), there was a reduction in the number of severe exacerbations and ED visits in patients treated with BT compared with the sham group. A 5-year follow-up study of this group showed a decrease in hospitalizations and ED visits compared with the period prior to study enrollment. Another trial with similar patients, though with poorer asthma control prior to enrollment; it showed similar results, with an increase in severe exacerbations during the treatment phase but fewer exacerbations, ED visits, and hospitalizations upon follow up at 3-year post-BT. Long-term studies have failed to show adverse events, such as bronchiectasis or airway stenosis, and high-resolution CT imaging has not revealed significant structural changes. Most studies have not shown improvement in FEV1 following BT, though follow-up studies have not demonstrated deterioration in lung function.
Additional controlled studies are needed to determine if bronchial thermoplasty is safe and effective in broader asthma populations to guide patient selection.1