Bronchial Thermoplasty: A Hot Approach to Asthma Treatment?

Bronchial thermoplasty is performed with the Alair® System, which includes a single-use catheter device and a controller to deliver radiofrequency energy.

Image courtesy of Asthmatx, Inc.

An investigational procedure, termed bronchial thermoplasty, may help adults with severe asthma whose symptoms are not well controlled with conventional drug therapy.

Bronchial thermoplasty may reduce airway hyper-responsiveness ― the tendency for airways to narrow rapidly and excessively in individuals with asthma.

The Procedure

A flexible tube called a bronchoscope is inserted into the airways through the mouth or nose. The tip of the Alair catheter is then inserted through the bronchoscope and opened to allow four electrodes to make contact with the airway wall.[1] The Alair radiofrequency controller subsequently delivers controlled thermal energy to heat smooth muscle in the airway wall. The heat reduces smooth muscle tissue, which may decrease the ability of airways to narrow and cause asthma symptoms. While general anesthesia may be used,[2] patients typically receive an intravenous sedative and remain conscious during the procedure, which takes less than an hour. Three sessions are usually required, at a minimum of three-week intervals, to treat all accessible airways in both lungs.[1]

Who Might Benefit

Asthma affects more than two million Canadians and is a common reason for hospitalization. Between 1998 and 2001, close to 80,000 people (mostly young children and seniors) were admitted to hospital due to asthma-related illness. In 2001, almost 300 Canadians died from complications associated with asthma.[3]

Regulatory Status

The Alair® System, manufactured by Asthmatx, Inc. (Mountain View, CA), is not currently licensed by any regulatory body. In Canada and the US, the device is limited to investigational use in an ongoing trial.

Cost

The cost of the Alair System is currently unknown.

Evidence

A randomized controlled trial involving 112 adults with moderate or severe asthma reported improved asthma control in those treated with bronchial thermoplasty in addition to drug therapy, compared with those who received drug therapy alone.[2] After 12 months, there were approximately 10 fewer mild exacerbations reported per patient, per year, in the treatment group, compared with the control group. Significant improvements over baseline were reported in the percentage of symptom-free days (40.7 versus 17.1, p=0.005), morning peak expiratory flow (39.3 L/min versus 8.5 L/min, p=0.003), and doses of rescue medication required (-8.9 versus -1.2, p=0.04). However, the number of severe exacerbations from baseline did not differ significantly between the two groups, nor did changes in airway hyper-responsiveness or forced expiratory volume in one second. Adverse events – mainly worsening of asthma symptoms ― were more common in the bronchial thermoplasty group immediately following treatment, but were similar to rates in the control group after the treatment period had ended.

A multi-centre trial is underway to compare the long-term safety and efficacy of bronchial thermoplasty with conventional therapy in patients with severe asthma.[4]

References

[1] Asthmatx. About Bronchial Thermoplasty. In: Air2Trial: Asthma Intervention Research 2 Trial. Mountain View (CA): Asthmatx; 2006. Available: http://www.asthmatx.com/worldwide/patients/bronchial-thermoplasty-for-asthma.html

[2] Cox G, et al. N Engl J Med 2007;356(13):1327-37.

[3] Chen Y, et al. Health Rep 2005;16(2):43-6. Available: http://www.statcan.ca/english/freepub/82-003-XIE/0020482-003-XIE.pdf

[4] Asthma Intervention Research 2 (AIR2) Trial. In: ClinicalTrials.gov. [database online]. Bethesda (MD): National Institutes of Health; 2006. NCT00231114. Available: http://clinicaltrials.gov/ct/show/NCT00231114