Airway Zapper Helps Severe Asthma
Bronchial Thermoplasty Zaps Airway Muscles, Cuts Asthma Symptoms
March 28, 2007 -- A device that zaps the airway with radio waves cuts moderate-to-severe asthma symptoms, a clinical study shows.
The device, the Alair System from Asthmatx Inc., is a radio-wave generator attached to a specially designed probe. During three procedures -- called bronchial thermoplasty -- the device is inserted into the airway. It zaps the smooth muscle of the airway, making it harder for the airway to spasm and close.
In a trial sponsored by the manufacturer, Gerard Cox, MB, of Canada's McMaster University, and colleagues enrolled 112 people suffering from moderate-to-severe asthma. All the participants were using asthma inhalers that included both an inhaled corticosteroid (such as Qvar) and a long-acting beta agonist (such as Serevent); all had asthma symptoms whenever they stopped using their long-acting beta agonist inhaler.
Half the patients underwent bronchial thermoplasty, and half did not. All agreed to stop using their long-acting beta agonist inhaler for two-week periods, at three, six, and 12 months after the study began.
- Bronchial thermoplasty gave people 86 extra symptom-free days a year.
- Patients who got bronchial thermoplasty had 10 fewer asthma exacerbations per year.
- Patients who got bronchial thermoplasty needed fewer puffs of asthma rescue medications.
The results lasted for at least one year. Preliminary, uncontrolled studies suggest that the treatment may last for at least two years.
The study has one major drawback: Patients knew whether they got the procedure. That could have resulted in a placebo effect that biased the study findings.
But now that there is strong evidence that the procedure is a true benefit, Cox and colleagues say they're ready for the next step. That would be a placebo-controlled study in which some patients agree to undergo sham bronchial thermoplasty.
The findings appear in the March 29 issue of The New England Journal of Medicine. An editorial by Julian Solway, MD, of the University of Chicago and Charles G. Irvin, PhD, of the University of Vermont, accompanies the Cox team's report.
Solway and Irvin note that it's not entirely clear why the Alair System works. The airways of people with asthma thicken over time, and the procedure obviously reduces smooth-muscle mass in the airway. But the procedure may also affect other airway properties.
If that's the case, the editorial suggests, it's possible that the success of bronchial thermoplasty will lead to new, less invasive asthma treatments.