Table 1.

Summary of the clinical trials and long-term follow-up of BT in asthma

Study	Study design	Number of patients	Inclusion criteria	Exclusion criteria	Endpoints	Outcomes improved	Outcomes unchanged	Key findings
Safety study30	Prospective, non-randomized	16 BT	≥18 years, mild to moderate asthma, Stable symptoms for preceding 6 weeks	Respiratory infection in preceding 6 weeks, ≥2 LRTI requiring antibiotics in previous year, >4 puffs of SABA in 24 hours	Safety; not powered for efficacy outcomes; PFTs, PEF, symptom-free days, AHR, rescue medication use reported	Morning PEF (12 weeks); Evening PEF (12 weeks); Symptom-free days (12 weeks) AHR	FEV1 Rescue SABA use	No major adverse events Improved AHR and symptom-free days No structural abnormalities on CT chest
AIR trial31	Randomized controlled trial	56 control 56 BT	Age 18–65, moderate to severe persistent asthma, FEV1 60%–85% pred, Methacholine PC20 <8 mg/mL, Stable symptoms for preceding 6 weeks, Worsening asthma symptoms upon LABA withdrawal	Respiratory infection in preceding 6 weeks, ≥3 LRTI requiring antibiotics in previous year	Primary: frequency of mild exacerbations Secondary: PFTs, PEF, AHR, rescue medication use, asthma symptom scores	Frequency of mild exacerbations Morning PEF Rescue medication use ACQ score AQLQ score Symptom-free days	FEV1 AHR	Reduced mild exacerbation frequency Improved ACQ, AQLQ scores
RISA trial32	Randomized controlled trial	17 control 15 BT	Age 18–65, Severe persistent asthma, FEV1 ≥50% pred, Airway hyperresponsiveness		Primary: safety Secondary: change in OCS and ICS, rescue medication use, PEF, FEV1, methacholine PC20, asthma symptom scores	Steroid stable phase: SABA use preBD FEV1 ACQ and AQLQ scores Post-steroid wean: SABA use ACQ and AQLQ score	Steroid stable phase: OCS and ICS dosing PEF Symptom-free days PC20 Post-steroid wean: OCS and ICS dosing PEF Symptom-free days PC20 FEV1	Improved FEV1 post-BT during steroid stable phase Increased respiratory adverse events noted during the treatment period No difference in adverse events in the post-treatment period Procedure is safe in severe asthma
AIR-2 trial33	Randomized, double-blind, sham controlled trial	101 control 196 BT	Age 18–65, Severe persistent asthma, FEV1 ≥60% pred, Airway hyperresponsiveness (PC20 <8 mg/mL), AQLQ ≤6.25	Life-threatening asthma, Chronic sinus disease, Use of immunosuppressants, β-adrenergic blocking agents, or anticoagulants, ≥3 hospitalizations for asthma in previous year, ≥3 LRTI in previous year, ≥4 OCS pulses for asthma in previous year	Primary: change in AQLQ Secondary: symptom scores, symptom-free days, PEF, rescue medication use, FEV1, severe exacerbations, emergency department visits, hospitalizations, days missed from work/school	AQLQ score Severe exacerbations Days lost from school/work	PEF Symptom-free days ACQ score Rescue medication use Hospitalizations	Improved AQLQ scores 32% reduction in severe exacerbations 84% reduction in ED visits 66% reduction in days lost work/school
AIR trial 5-year follow-up34		24 control 45 BT	See AIR above	See AIR above		Improved AHR out to 3 years		No increase in respiratory events Stable FEV1 and FVC over 5 years
RISA trial 5-year follow-up35		14 BT	See RISA above	See RISA above		Persistent decrease in hospitalizations and ED visits		No increase in respiratory events Stable FEV1 and FVC over 5 years
AIR-2 trial 5-year follow-up36		162 BT	See AIR-2 above	See AIR-2 above		Sustained reduction in exacerbations and ED visits over 5 years		No increase in respiratory events Stable FEV1 and FVC over 5 years

Abbreviations: BT, bronchial thermoplasty; LRTI, lower respiratory tract infection; SABA, short-acting beta agonist; PFT, pulmonary function testing; PEF, peak expiratory flow; AHR, airway hyperresponsiveness; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; AIR, asthma intervention research; pred, predicted; PC₂₀, provocative concentration causing a 20% decline in FEV₁; LABA, long-acting beta agonist; ACQ, asthma control questionnaire; AQLQ, asthma quality of life questionnaire; RISA, research in severe asthma; OCS, oral corticosteroid; ICS, inhaled corticosteroid; preBD, prebronchodilator; AIR-2, asthma intervention research-2; ED, emergency department.