When is bronchial thermoplasty (BT) indicated?

Updated: Mar 30, 2021
  • Author: Said A Chaaban, MD; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Answer

Candidates for BT include adults with severe persistent asthma who require regular maintenance medications of inhaled corticosteroids (>1000 µg/day of beclomethasone or the equivalent) and a long-acting beta agonist (≥100 µg/day of salmeterol or the equivalent). These patients would have received add-on therapies such as leukotriene modifiers, omalizumab, or oral corticosteroids (≤10 mg/day).

These patients should be on stable maintenance asthma medications according to accepted guidelines, [16]  should have a prebronchodilator forced expiratory volume in 1 second (FEV1) of 60% or more of predicted, and should have a stable asthma status (FEV1 within 10% of the best value, no current respiratory tract infection, and no severe asthma exacerbation within the preceding 4 weeks).

Patients are usually selected on the basis of the AIR 2 trial. The patient should be stable in terms of asthma status, defined as a postbronchodilator FEV1 within 15% of baseline values with no respiratory tract infection or asthma exacerbations within the preceding 14 days. [13]

Asthma exists in multiple phenotypes, and current selection criteria for BT are based on severity rather than on phenotype. The use of biomarkers to predict response to BT has been studied. Histology has also been used to help identify different asthma phenotypes and thereby facilitate the identification of those who may respond to various different medical therapies. Phenotype-guided treatment may be expected to yield better treatment outcomes. [17]

One study looked into the role of endobronchial biopsy as part of the initial evaluation and as a postprocedural measure to evaluate for response. However, performing biopsies is not practical or safe enough to be considered part of the overall evaluation. Drawbacks include the risk of associated complications and the possibility of obtaining a nonrepresentative sample. [6, 9]

Gordon et al established a standardized histologic grading system that assessed both the structural and the inflammatory components on endobronchial biopsy. This system may prove helpful in offering a guide to patient selection and the choice of targeted anti-inflammatory medications or BT. [18]

Other modalities with the potential to replace biopsy in this setting are optical coherence tomography (OCT) and confocal microscopy (CFM) with or without high-resolution radial balloon-based endobronchial ultrasonography (US). OCT allows real-time microscopic evaluation of the mucosae and submucosae during bronchoscopy. Radial endobronchial US (EBUS) has also been used to evaluate changes in wall thickness and wall remodeling. Both of those modalities seem to be valuable tools, but further evaluation is warranted.

Checklists and validation tools have been developed and discussed in international meetings but require further study. [10, 19]


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